- GCN/BACODINE POSITION NOTICE
TITLE: GCN/SWIFT NOTICE
NOTICE_DATE: Sat 27 Apr 13 07:49:14 UT
NOTICE_TYPE: Swift-BAT GRB Position
TRIGGER_NUM: 554620, Seg_Num: 0
GRB_RA: 173.139d {+11h 32m 33s} (J2000),
173.314d {+11h 33m 15s} (current),
172.480d {+11h 29m 55s} (1950)
GRB_DEC: +27.692d {+27d 41' 29"} (J2000),
+27.618d {+27d 37' 04"} (current),
+27.968d {+27d 58' 04"} (1950)
GRB_ERROR: 3.00 [arcmin radius, statistical only]
GRB_INTEN: 0 [cnts] Image_Peak=7320 [image_cnts]
TRIGGER_DUR: 64.000 [sec]
TRIGGER_INDEX: 20000 E_range: 15-50 keV
BKG_INTEN: 0 [cnts]
BKG_TIME: 0.00 SOD {00:00:00.00} UT
BKG_DUR: 0 [sec]
GRB_DATE: 16409 TJD; 117 DOY; 13/04/27
GRB_TIME: 28077.51 SOD {07:47:57.51} UT
GRB_PHI: -76.18 [deg]
GRB_THETA: 39.09 [deg]
SOLN_STATUS: 0x20000013
RATE_SIGNIF: 0.00 [sigma]
IMAGE_SIGNIF: 23.81 [sigma]
MERIT_PARAMS: +1 +0 +0 +6 +1 +8 +0 +0 +53 +0
SUN_POSTN: 34.87d {+02h 19m 30s} +13.92d {+13d 55' 16"}
SUN_DIST: 122.14 [deg] Sun_angle= -9.2 [hr] (East of Sun)
MOON_POSTN: 235.69d {+15h 42m 45s} -18.77d {-18d 46' 27"}
MOON_DIST: 76.12 [deg]
MOON_ILLUM: 97 [%]
GAL_COORDS: 206.53, 72.50 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS: 162.22, 22.60 [deg] ecliptic lon,lat of the burst (or transient)
COMMENTS: SWIFT-BAT GRB Coordinates.
COMMENTS: This is an image trigger. (The RATE_SIGNIF & BKG_{INTEN, TIME, DUR} are undefined.)
COMMENTS: A point_source was found.
COMMENTS: This does not match any source in the on-board catalog.
COMMENTS: This does not match any source in the ground catalog.
COMMENTS: This is a GRB.
COMMENTS: This trigger occurred at longitude,latitude = 162.17,-20.22 [deg].
COMMENTS:
COMMENTS: NOTE: This BAT event is temporally(51.0<100sec) coincident with the FERMI_GBM event (trignum=388741629).
- red DSS finding chart
ps-file
- GCN NOTICE
TITLE: GCN/FERMI NOTICE
NOTICE_DATE: Sat 27 Apr 13 07:47:32 UT
NOTICE_TYPE: Fermi-GBM Flight Position
RECORD_NUM: 48
TRIGGER_NUM: 388741629
GRB_RA: 170.550d {+11h 22m 12s} (J2000),
170.734d {+11h 22m 56s} (current),
169.857d {+11h 19m 26s} (1950)
GRB_DEC: +47.717d {+47d 43' 00"} (J2000),
+47.644d {+47d 38' 37"} (current),
+47.991d {+47d 59' 28"} (1950)
GRB_ERROR: 3.35 [deg radius, statistical plus systematic]
GRB_INTEN: 8093 [cnts/sec]
DATA_SIGNIF: 375.70 [sigma]
INTEG_TIME: 1.024 [sec]
GRB_DATE: 16409 TJD; 117 DOY; 13/04/27
GRB_TIME: 28026.42 SOD {07:47:06.42} UT
GRB_PHI: 110.00 [deg]
GRB_THETA: 30.00 [deg]
DATA_TIME_SCALE: 1.0240 [sec]
HARD_RATIO: 0.48
LOC_ALGORITHM: 3 (version number of)
MOST_LIKELY: 95% GRB
2nd_MOST_LIKELY: 4% Generic Transient
DETECTORS: 0,0,0, 0,0,0, 1,0,0, 1,1,1, 0,0,
SUN_POSTN: 34.87d {+02h 19m 29s} +13.92d {+13d 55' 15"}
SUN_DIST: 106.95 [deg] Sun_angle= -9.1 [hr] (East of Sun)
MOON_POSTN: 235.67d {+15h 42m 40s} -18.77d {-18d 46' 18"}
MOON_DIST: 88.14 [deg]
MOON_ILLUM: 97 [%]
GAL_COORDS: 157.22, 63.04 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS: 149.20, 39.41 [deg] ecliptic lon,lat of the burst (or transient)
COMMENTS: Fermi-GBM Flight-calculated Coordinates.
COMMENTS: This trigger occurred at longitude,latitude = 271.82,21.57 [deg].
- GCN NOTICE
TITLE: GCN/FERMI NOTICE
NOTICE_DATE: Sat 27 Apr 13 07:47:45 UT
NOTICE_TYPE: Fermi-GBM Ground Position
RECORD_NUM: 58
TRIGGER_NUM: 388741629
GRB_RA: 175.100d {+11h 40m 24s} (J2000),
175.274d {+11h 41m 06s} (current),
174.446d {+11h 37m 47s} (1950)
GRB_DEC: +27.530d {+27d 31' 48"} (J2000),
+27.456d {+27d 27' 22"} (current),
+27.807d {+27d 48' 26"} (1950)
GRB_ERROR: 1.00 [deg radius, statistical only]
DATA_SIGNIF: 500.30 [sigma]
DATA_INTERVAL: 2.048 [sec]
GRB_DATE: 16409 TJD; 117 DOY; 13/04/27
GRB_TIME: 28026.42 SOD {07:47:06.42} UT
GRB_PHI: 129.00 [deg]
GRB_THETA: 47.00 [deg]
E_RANGE: 44.032 - 279.965 [keV]
LOC_ALGORITHM: 4143 (Gnd S/W Version number)
SUN_POSTN: 34.87d {+02h 19m 29s} +13.92d {+13d 55' 15"}
SUN_DIST: 123.55 [deg] Sun_angle= -9.4 [hr] (East of Sun)
MOON_POSTN: 235.67d {+15h 42m 41s} -18.77d {-18d 46' 19"}
MOON_DIST: 74.53 [deg]
MOON_ILLUM: 97 [%]
GAL_COORDS: 207.38, 74.23 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS: 164.00, 23.20 [deg] ecliptic lon,lat of the burst (or transient)
COMMENTS: Fermi-GBM Ground-calculated Coordinates.
COMMENTS: In the LAT Field-of-view.
COMMENTS: Bright hard burst in the GBM.
COMMENTS: This Notice was ground-generated -- not flight-generated.
- GCN NOTICE
TITLE: GCN/FERMI NOTICE
NOTICE_DATE: Sat 27 Apr 13 07:47:42 UT
NOTICE_TYPE: Fermi-GBM Flight Position
RECORD_NUM: 59
TRIGGER_NUM: 388741629
GRB_RA: 170.667d {+11h 22m 40s} (J2000),
170.851d {+11h 23m 24s} (current),
169.974d {+11h 19m 54s} (1950)
GRB_DEC: +48.050d {+48d 02' 60"} (J2000),
+47.977d {+47d 58' 37"} (current),
+48.324d {+48d 19' 28"} (1950)
GRB_ERROR: 3.22 [deg radius, statistical plus systematic]
GRB_INTEN: 52874 [cnts/sec]
DATA_SIGNIF: 5014.30 [sigma]
INTEG_TIME: 4.096 [sec]
GRB_DATE: 16409 TJD; 117 DOY; 13/04/27
GRB_TIME: 28026.42 SOD {07:47:06.42} UT
GRB_PHI: 110.00 [deg]
GRB_THETA: 30.00 [deg]
DATA_TIME_SCALE: 4.0960 [sec]
HARD_RATIO: 0.32
LOC_ALGORITHM: 3 (version number of)
MOST_LIKELY: 96% GRB
2nd_MOST_LIKELY: 3% Generic Transient
DETECTORS: 0,0,0, 0,0,0, 1,0,0, 1,1,1, 0,0,
SUN_POSTN: 34.87d {+02h 19m 29s} +13.92d {+13d 55' 15"}
SUN_DIST: 106.77 [deg] Sun_angle= -9.1 [hr] (East of Sun)
MOON_POSTN: 235.67d {+15h 42m 41s} -18.77d {-18d 46' 19"}
MOON_DIST: 88.25 [deg]
MOON_ILLUM: 97 [%]
GAL_COORDS: 156.56, 62.87 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS: 149.07, 39.73 [deg] ecliptic lon,lat of the burst (or transient)
COMMENTS: Fermi-GBM Flight-calculated Coordinates.
COMMENTS: This trigger occurred at longitude,latitude = 271.82,21.57 [deg].
- GCN NOTICE
TITLE: GCN/SWIFT NOTICE
NOTICE_DATE: Sat 27 Apr 13 07:50:50 UT
NOTICE_TYPE: Swift-XRT Position
TRIGGER_NUM: 554620, Seg_Num: 0
GRB_RA: 173.1362d {+11h 32m 32.68s} (J2000),
173.3114d {+11h 33m 14.74s} (current),
172.4773d {+11h 29m 54.54s} (1950)
GRB_DEC: +27.7129d {+27d 42' 46.4"} (J2000),
+27.6393d {+27d 38' 21.3"} (current),
+27.9891d {+27d 59' 20.8"} (1950)
GRB_ERROR: 4.7 [arcsec radius, statistical plus systematic, 90% containment]
GRB_INTEN: 4.38e-07 [erg/cm2/sec]
GRB_SIGNIF: 17.69 [sigma]
IMG_START_DATE: 16409 TJD; 117 DOY; 13/04/27
IMG_START_TIME: 28217.70 SOD {07:50:17.70} UT, 140.2 [sec] since BAT Trigger Time
TAM[0-3]: 327.61 237.22 261.54 243.67
AMPLIFIER: 2
WAVEFORM: 134
SUN_POSTN: 34.87d {+02h 19m 30s} +13.92d {+13d 55' 18"}
SUN_DIST: 122.12 [deg] Sun_angle= -9.2 [hr] (East of Sun)
MOON_POSTN: 235.70d {+15h 42m 49s} -18.78d {-18d 46' 35"}
MOON_DIST: 76.15 [deg]
MOON_ILLUM: 97 [%]
GAL_COORDS: 206.46, 72.50 [deg] galactic lon,lat of the burst
ECL_COORDS: 162.21, 22.62 [deg] ecliptic lon,lat of the burst
COMMENTS: SWIFT-XRT Coordinates.
COMMENTS: The XRT position is 1.29 arcmin from the BAT position.
COMMENTS: The object found at this position is either a very bright burst or a cosmic ray hit.
COMMENTS: Examine the XRT Image to differentiate (CRs are much more compact); see examples at:
COMMENTS: http://www.swift.psu.edu/xrt/XRT_Postage_Stamp_Image_Photo_Gallery.htm .
- GCN NOTICE
TITLE: GCN/SWIFT NOTICE
NOTICE_DATE: Sat 27 Apr 13 07:51:00 UT
NOTICE_TYPE: Swift-XRT Image
TRIGGER_NUM: 554620, Seg_Num: 0
GRB_RA: 173.1362d {+11h 32m 32.6s} (J2000),
173.3114d {+11h 33m 14.7s} (current),
172.4773d {+11h 29m 54.5s} (1950)
GRB_DEC: +27.7129d {+27d 42' 46.4"} (J2000),
+27.6393d {+27d 38' 21.3"} (current),
+27.9891d {+27d 59' 20.8"} (1950)
GRB_ERROR: 4.3 [arcsec, radius, statistical plus systematic]
GRB_INTEN: 313 [cnts]
IMG_START_DATE: 16409 TJD; 117 DOY; 13/04/27
IMG_START_TIME: 28217.70 SOD {07:50:17.70} UT, 140.2 [sec] since BAT Trigger Time
CENTROID_X: 268.46, raw= 268 [pixels]
CENTROID_Y: 276.68, raw= 277 [pixels]
ROLL: 310.40 [deg]
GAIN: 8
MODE: 2, Short Image mode
WAVEFORM: 134
EXPO_TIME: 0.10 [sec]
GRB_POS_XRT_Y: -50.24
GRB_POS_XRT_Z: -83.05
IMAGE_URL: sw00554620000msxps_rw.img
SUN_POSTN: 34.87d {+02h 19m 30s} +13.92d {+13d 55' 18"}
SUN_DIST: 122.12 [deg] Sun_angle= -9.2 [hr] (East of Sun)
MOON_POSTN: 235.71d {+15h 42m 49s} -18.78d {-18d 46' 36"}
MOON_DIST: 76.15 [deg]
MOON_ILLUM: 97 [%]
GAL_COORDS: 206.46, 72.50 [deg] galactic lon,lat of the burst
ECL_COORDS: 162.21, 22.62 [deg] ecliptic lon,lat of the burst
COMMENTS: SWIFT-XRT Image.
COMMENTS: The object found at this position is either a very bright burst or a cosmic ray hit.
COMMENTS: Examine the XRT Image to differentiate (CRs are much more compact); see examples at:
COMMENTS: http://www.swift.psu.edu/xrt/XRT_Postage_Stamp_Image_Photo_Gallery.htm .
- GCN NOTICE
TITLE: GCN/SWIFT NOTICE
NOTICE_DATE: Sat 27 Apr 13 07:51:07 UT
NOTICE_TYPE: Swift-XRT Processed Image
TRIGGER_NUM: 554620, Seg_Num: 0
GRB_RA: 173.1362d {+11h 32m 32.6s} (J2000),
173.3114d {+11h 33m 14.7s} (current),
172.4773d {+11h 29m 54.5s} (1950)
GRB_DEC: +27.7129d {+27d 42' 46.4"} (J2000),
+27.6393d {+27d 38' 21.3"} (current),
+27.9891d {+27d 59' 20.8"} (1950)
GRB_ERROR: 4.3 [arcsec, radius, statistical plus systematic]
GRB_INTEN: 313 [cnts]
IMG_START_DATE: 16409 TJD; 117 DOY; 13/04/27
IMG_START_TIME: 28217.70 SOD {07:50:17.70} UT, 140.2 [sec] since BAT Trigger Time
CENTROID_X: 268.46, raw= 268 [pixels]
CENTROID_Y: 276.68, raw= 277 [pixels]
ROLL: 310.40 [deg]
GAIN: 8
MODE: 2, Short Image mode
WAVEFORM: 134
EXPO_TIME: 0.10 [sec]
GRB_POS_XRT_Y: -50.24
GRB_POS_XRT_Z: -83.05
IMAGE_URL: sw00554620000msxps_rw.img
SUN_POSTN: 34.87d {+02h 19m 30s} +13.92d {+13d 55' 18"}
SUN_DIST: 122.12 [deg] Sun_angle= -9.2 [hr] (East of Sun)
MOON_POSTN: 235.71d {+15h 42m 50s} -18.78d {-18d 46' 37"}
MOON_DIST: 76.15 [deg]
MOON_ILLUM: 97 [%]
GAL_COORDS: 206.46, 72.50 [deg] galactic lon,lat of the burst
ECL_COORDS: 162.21, 22.62 [deg] ecliptic lon,lat of the burst
COMMENTS: SWIFT-XRT Processed Image.
COMMENTS: The object found at this position is either a very bright burst or a cosmic ray hit.
COMMENTS: Examine the XRT Image to differentiate (CRs are much more compact); see examples at:
COMMENTS: http://www.swift.psu.edu/xrt/XRT_Postage_Stamp_Image_Photo_Gallery.htm .
- GCN NOTICE
TITLE: GCN/SWIFT NOTICE
NOTICE_DATE: Sat 27 Apr 13 07:52:04 UT
NOTICE_TYPE: Swift-BAT GRB Lightcurve
TRIGGER_NUM: 554620, Seg_Num: 0
GRB_RA: 173.139d {+11h 32m 33s} (J2000),
173.314d {+11h 33m 15s} (current),
172.480d {+11h 29m 55s} (1950)
GRB_DEC: +27.692d {+27d 41' 29"} (J2000),
+27.618d {+27d 37' 04"} (current),
+27.968d {+27d 58' 04"} (1950)
GRB_DATE: 16409 TJD; 117 DOY; 13/04/27
GRB_TIME: 28077.51 SOD {07:47:57.51} UT
TRIGGER_INDEX: 20000
GRB_PHI: -76.18 [deg]
GRB_THETA: 39.09 [deg]
DELTA_TIME: 0.00 [sec]
TRIGGER_DUR: 64.000 [sec]
SOLN_STATUS: 0x13
RATE_SIGNIF: 0.00 [sigma]
IMAGE_SIGNIF: 23.81 [sigma]
LC_URL: sw00554620000msb.lc
SUN_POSTN: 34.87d {+02h 19m 30s} +13.92d {+13d 55' 19"}
SUN_DIST: 122.14 [deg] Sun_angle= -9.2 [hr] (East of Sun)
MOON_POSTN: 235.72d {+15h 42m 52s} -18.78d {-18d 46' 41"}
MOON_DIST: 76.15 [deg]
MOON_ILLUM: 97 [%]
GAL_COORDS: 206.53, 72.50 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS: 162.22, 22.60 [deg] ecliptic lon,lat of the burst (or transient)
COMMENTS: SWIFT-BAT GRB Lightcurve.
COMMENTS:
COMMENTS: The next comments were copied from the BAT_POS Notice:
COMMENTS: This is an image trigger.
COMMENTS: A point_source was found.
COMMENTS: This does not match any source in the on-board catalog.
COMMENTS: This does not match any source in the ground catalog.
COMMENTS: This is a GRB.
COMMENTS: This trigger occurred at longitude,latitude = 162.17,-20.22 [deg].
- GCN NOTICE
TITLE: GCN/SWIFT NOTICE
NOTICE_DATE: Sat 27 Apr 13 07:53:24 UT
NOTICE_TYPE: Swift-UVOT Source List
TRIGGER_NUM: 554620, Seg_Num: 0
POINT_RA: 173.143d {+11h 32m 34s} (J2000)
POINT_DEC: +27.689d {+27d 41' 21"} (J2000)
POINT_ROLL: 310.394d
IMG_START_DATE: 16409 TJD; 117 DOY; 13/04/27
IMG_START_TIME: 28225.19 SOD {07:50:25.19} UT, 147.7 [sec] since BAT Trigger Time
FILTER: 10, White
BKG_MEAN: 2.155
N_STARS: 92
X_OFFSET: 520 [pixels]
Y_OFFSET: 528 [pixels]
X_MAX: 1479 [pixels]
Y_MAX: 1487 [pixels]
DET_THRESH: 12
PHOTO_THRESH: 6
SL_URL: sw00554620000msufc0147.fits
SUN_POSTN: 34.88d {+02h 19m 30s} +13.92d {+13d 55' 20"}
SUN_DIST: 122.14 [deg] Sun_angle= -9.2 [hr] (East of Sun)
MOON_POSTN: 235.73d {+15h 42m 56s} -18.78d {-18d 46' 48"}
MOON_DIST: 76.16 [deg]
MOON_ILLUM: 97 [%]
GAL_COORDS: 206.54, 72.51 [deg] galactic lon,lat of the pointing direction
ECL_COORDS: 162.23, 22.60 [deg] ecliptic lon,lat of the pointing direction
COMMENTS: SWIFT-UVOT Source List.
- GCN NOTICE
TITLE: GCN/SWIFT NOTICE
NOTICE_DATE: Sat 27 Apr 13 07:53:49 UT
NOTICE_TYPE: Swift-UVOT Processed Source List
TRIGGER_NUM: 554620, Seg_Num: 0
POINT_RA: 173.143d {+11h 32m 34s} (J2000)
POINT_DEC: +27.689d {+27d 41' 21"} (J2000)
POINT_ROLL: 310.394d
IMG_START_DATE: 16409 TJD; 117 DOY; 13/04/27
IMG_START_TIME: 28225.19 SOD {07:50:25.19} UT, 147.7 [sec] since BAT Trigger Time
FILTER: 10, White
BKG_MEAN: 2.155
N_STARS: 92
X_OFFSET: 520 [pixels]
Y_OFFSET: 528 [pixels]
X_MAX: 1479 [pixels]
Y_MAX: 1487 [pixels]
DET_THRESH: 12
PHOTO_THRESH: 6
SL_URL: sw00554620000msufc0147.fits
SUN_POSTN: 34.88d {+02h 19m 30s} +13.92d {+13d 55' 20"}
SUN_DIST: 122.14 [deg] Sun_angle= -9.2 [hr] (East of Sun)
MOON_POSTN: 235.74d {+15h 42m 57s} -18.78d {-18d 46' 50"}
MOON_DIST: 76.16 [deg]
MOON_ILLUM: 97 [%]
GAL_COORDS: 206.54, 72.51 [deg] galactic lon,lat of the pointing direction
ECL_COORDS: 162.23, 22.60 [deg] ecliptic lon,lat of the pointing direction
COMMENTS: SWIFT-UVOT Processed Source List.
COMMENTS: If you have elected to receive attachments:
COMMENTS: The uvot_catalog_srclist.fits.gz file does not exist; skipping the attachment.
- GCN NOTICE
TITLE: GCN/SWIFT NOTICE
NOTICE_DATE: Sat 27 Apr 13 07:54:49 UT
NOTICE_TYPE: Swift-UVOT Image
TRIGGER_NUM: 554620, Seg_Num: 0
POINT_RA: 173.143d {+11h 32m 34s} (J2000)
POINT_DEC: +27.689d {+27d 41' 21"} (J2000)
ROLL: 310.394d
IMG_START_DATE: 16409 TJD; 117 DOY; 13/04/27
IMG_START_TIME: 28225.19 SOD {07:50:25.19} UT, 147.7 [sec] since BAT Trigger Time
FILTER: 10, White
EXPOSURE_ID: 388741835
X_OFFSET: 991 [pixels]
Y_OFFSET: 884 [pixels]
WIDTH: 160 [pixels]
HEIGHT: 160 [pixels]
X_GRB_POS: 1151
Y_GRB_POS: 1044
BINNING_INDEX: 1
IM_URL: sw00554620000msuni0158.fits
SUN_POSTN: 34.88d {+02h 19m 30s} +13.92d {+13d 55' 21"}
SUN_DIST: 122.14 [deg] Sun_angle= -9.2 [hr] (East of Sun)
MOON_POSTN: 235.75d {+15h 42m 59s} -18.78d {-18d 46' 55"}
MOON_DIST: 76.17 [deg]
MOON_ILLUM: 97 [%]
GAL_COORDS: 206.54, 72.51 [deg] galactic lon,lat of the pointing direction
ECL_COORDS: 162.23, 22.60 [deg] ecliptic lon,lat of the pointing direction
COMMENTS: SWIFT-UVOT Image.
COMMENTS: The GRB Position came from the XRT Position Command.
COMMENTS: The image has 2x2 binning (compression).
- GCN NOTICE
TITLE: GCN/SWIFT NOTICE
NOTICE_DATE: Sat 27 Apr 13 07:55:05 UT
NOTICE_TYPE: Swift-UVOT Processed Image
TRIGGER_NUM: 554620, Seg_Num: 0
POINT_RA: 173.143d {+11h 32m 34s} (J2000)
POINT_DEC: +27.689d {+27d 41' 21"} (J2000)
ROLL: 310.394d
IMG_START_DATE: 16409 TJD; 117 DOY; 13/04/27
IMG_START_TIME: 28225.19 SOD {07:50:25.19} UT, 147.7 [sec] since BAT Trigger Time
FILTER: 10, White
EXPOSURE_ID: 388741835
X_OFFSET: 991 [pixels]
Y_OFFSET: 884 [pixels]
WIDTH: 160 [pixels]
HEIGHT: 160 [pixels]
X_GRB_POS: 1151
Y_GRB_POS: 1044
BINNING_INDEX: 1
IM_URL: sw00554620000msuni0158.fits
SUN_POSTN: 34.88d {+02h 19m 30s} +13.92d {+13d 55' 21"}
SUN_DIST: 122.14 [deg] Sun_angle= -9.2 [hr] (East of Sun)
MOON_POSTN: 235.75d {+15h 43m 00s} -18.78d {-18d 46' 57"}
MOON_DIST: 76.17 [deg]
MOON_ILLUM: 97 [%]
GAL_COORDS: 206.54, 72.51 [deg] galactic lon,lat of the pointing direction
ECL_COORDS: 162.23, 22.60 [deg] ecliptic lon,lat of the pointing direction
COMMENTS: SWIFT-UVOT Processed Image.
COMMENTS: The GRB Position came from the XRT Position Command.
COMMENTS: The image has 2x2 binning (compression).
COMMENTS: If you have elected to receive attachments:
COMMENTS: The uvot_catalog_image.fits.gz file does not exist; skipping the attachment.
- GCN NOTICE
TITLE: GCN/SWIFT NOTICE
NOTICE_DATE: Sat 27 Apr 13 08:05:28 UT
NOTICE_TYPE: Swift-UVOT Source List
TRIGGER_NUM: 554620, Seg_Num: 0
POINT_RA: 173.146d {+11h 32m 35s} (J2000)
POINT_DEC: +27.687d {+27d 41' 15"} (J2000)
POINT_ROLL: 310.396d
IMG_START_DATE: 16409 TJD; 117 DOY; 13/04/27
IMG_START_TIME: 28950.86 SOD {08:02:30.86} UT, 873.4 [sec] since BAT Trigger Time
FILTER: 10, White
BKG_MEAN: 2.001
N_STARS: 53
X_OFFSET: 431 [pixels]
Y_OFFSET: 324 [pixels]
X_MAX: 1870 [pixels]
Y_MAX: 1763 [pixels]
DET_THRESH: 12
PHOTO_THRESH: 6
SL_URL: sw00554620000msufc0873.fits
SUN_POSTN: 34.88d {+02h 19m 32s} +13.92d {+13d 55' 29"}
SUN_DIST: 122.14 [deg] Sun_angle= -9.2 [hr] (East of Sun)
MOON_POSTN: 235.86d {+15h 43m 27s} -18.80d {-18d 47' 49"}
MOON_DIST: 76.26 [deg]
MOON_ILLUM: 97 [%]
GAL_COORDS: 206.55, 72.51 [deg] galactic lon,lat of the pointing direction
ECL_COORDS: 162.23, 22.60 [deg] ecliptic lon,lat of the pointing direction
COMMENTS: SWIFT-UVOT Source List.
- GCN NOTICE
TITLE: GCN/SWIFT NOTICE
NOTICE_DATE: Sat 27 Apr 13 08:05:45 UT
NOTICE_TYPE: Swift-UVOT Processed Source List
TRIGGER_NUM: 554620, Seg_Num: 0
POINT_RA: 173.146d {+11h 32m 35s} (J2000)
POINT_DEC: +27.687d {+27d 41' 15"} (J2000)
POINT_ROLL: 310.396d
IMG_START_DATE: 16409 TJD; 117 DOY; 13/04/27
IMG_START_TIME: 28950.86 SOD {08:02:30.86} UT, 873.4 [sec] since BAT Trigger Time
FILTER: 10, White
BKG_MEAN: 2.001
N_STARS: 53
X_OFFSET: 431 [pixels]
Y_OFFSET: 324 [pixels]
X_MAX: 1870 [pixels]
Y_MAX: 1763 [pixels]
DET_THRESH: 12
PHOTO_THRESH: 6
SL_URL: sw00554620000msufc0873.fits
SUN_POSTN: 34.88d {+02h 19m 32s} +13.92d {+13d 55' 30"}
SUN_DIST: 122.14 [deg] Sun_angle= -9.2 [hr] (East of Sun)
MOON_POSTN: 235.86d {+15h 43m 27s} -18.80d {-18d 47' 50"}
MOON_DIST: 76.27 [deg]
MOON_ILLUM: 97 [%]
GAL_COORDS: 206.55, 72.51 [deg] galactic lon,lat of the pointing direction
ECL_COORDS: 162.23, 22.60 [deg] ecliptic lon,lat of the pointing direction
COMMENTS: SWIFT-UVOT Processed Source List.
COMMENTS: If you have elected to receive attachments:
COMMENTS: The uvot_catalog_srclist.fits.gz file does not exist; skipping the attachment.
- GCN NOTICE
TITLE: GCN/SWIFT NOTICE
NOTICE_DATE: Sat 27 Apr 13 08:06:49 UT
NOTICE_TYPE: Swift-UVOT Image
TRIGGER_NUM: 554620, Seg_Num: 0
POINT_RA: 173.146d {+11h 32m 35s} (J2000)
POINT_DEC: +27.687d {+27d 41' 15"} (J2000)
ROLL: 310.396d
IMG_START_DATE: 16409 TJD; 117 DOY; 13/04/27
IMG_START_TIME: 28950.86 SOD {08:02:30.86} UT, 873.4 [sec] since BAT Trigger Time
FILTER: 10, White
EXPOSURE_ID: 388742561
X_OFFSET: 990 [pixels]
Y_OFFSET: 883 [pixels]
WIDTH: 160 [pixels]
HEIGHT: 160 [pixels]
X_GRB_POS: 1150
Y_GRB_POS: 1043
BINNING_INDEX: 1
IM_URL: sw00554620000msuni0884.fits
SUN_POSTN: 34.88d {+02h 19m 32s} +13.93d {+13d 55' 30"}
SUN_DIST: 122.14 [deg] Sun_angle= -9.2 [hr] (East of Sun)
MOON_POSTN: 235.88d {+15h 43m 30s} -18.80d {-18d 47' 56"}
MOON_DIST: 76.28 [deg]
MOON_ILLUM: 97 [%]
GAL_COORDS: 206.55, 72.51 [deg] galactic lon,lat of the pointing direction
ECL_COORDS: 162.23, 22.60 [deg] ecliptic lon,lat of the pointing direction
COMMENTS: SWIFT-UVOT Image.
COMMENTS: The GRB Position came from the Window Position in the Mode Command.
COMMENTS: The image has 2x2 binning (compression).
- GCN NOTICE
TITLE: GCN/SWIFT NOTICE
NOTICE_DATE: Sat 27 Apr 13 08:07:04 UT
NOTICE_TYPE: Swift-UVOT Processed Image
TRIGGER_NUM: 554620, Seg_Num: 0
POINT_RA: 173.146d {+11h 32m 35s} (J2000)
POINT_DEC: +27.687d {+27d 41' 15"} (J2000)
ROLL: 310.396d
IMG_START_DATE: 16409 TJD; 117 DOY; 13/04/27
IMG_START_TIME: 28950.86 SOD {08:02:30.86} UT, 873.4 [sec] since BAT Trigger Time
FILTER: 10, White
EXPOSURE_ID: 388742561
X_OFFSET: 990 [pixels]
Y_OFFSET: 883 [pixels]
WIDTH: 160 [pixels]
HEIGHT: 160 [pixels]
X_GRB_POS: 1150
Y_GRB_POS: 1043
BINNING_INDEX: 1
IM_URL: sw00554620000msuni0884.fits
SUN_POSTN: 34.88d {+02h 19m 32s} +13.93d {+13d 55' 31"}
SUN_DIST: 122.14 [deg] Sun_angle= -9.2 [hr] (East of Sun)
MOON_POSTN: 235.88d {+15h 43m 31s} -18.80d {-18d 47' 57"}
MOON_DIST: 76.28 [deg]
MOON_ILLUM: 97 [%]
GAL_COORDS: 206.55, 72.51 [deg] galactic lon,lat of the pointing direction
ECL_COORDS: 162.23, 22.60 [deg] ecliptic lon,lat of the pointing direction
COMMENTS: SWIFT-UVOT Processed Image.
COMMENTS: The GRB Position came from the Window Position in the Mode Command.
COMMENTS: The image has 2x2 binning (compression).
COMMENTS: If you have elected to receive attachments:
COMMENTS: The uvot_catalog_image.fits.gz file does not exist; skipping the attachment.
- GCN Circular #14448
A. Maselli (INAF-IASFPA), A. P. Beardmore (U Leicester),
A. Y. Lien (NASA/GSFC/ORAU), V. Mangano (INAF-IASFPA),
C. J. Mountford (U Leicester), K. L. Page (U Leicester),
D. M. Palmer (LANL) and M. H. Siegel (PSU) report on behalf of the
Swift Team:
At 07:47:57 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 130427A (trigger=554620). Swift slewed immediately to the burst.
The BAT on-board calculated location is
RA, Dec 173.139, +27.692 which is
RA(J2000) = 11h 32m 33s
Dec(J2000) = +27d 41' 29"
with an uncertainty of 3 arcmin (radius, 90% containment, including
systematic uncertainty). The BAT light curve shows an extremely bright
complex peak about 20 seconds long starting at T-50, while Swift was
slewing from the previous pre-planned target, followed by a smaller
peak during the slew to the burst with emission through at least T+200.
The peak count rate was ~ 100,000 counts/sec (15-350 keV),
at T-40 sec, before the trigger.
The XRT began observing the field at 07:50:17.7 UT, 140.2 seconds after
the BAT trigger. XRT found a bright, uncatalogued X-ray source located
at RA, Dec 173.1362, 27.7129 which is equivalent to:
RA(J2000) = +11h 32m 32.69s
Dec(J2000) = +27d 42' 46.4"
with an uncertainty of 4.7 arcseconds (radius, 90% containment). This
location is 75 arcseconds from the BAT onboard position, within the BAT
error circle. No event data are yet available to determine the column
density using X-ray spectroscopy.
UVOT took a finding chart exposure of 150 seconds with the White filter
starting 147 seconds after the BAT trigger. A blurred bright source
appears to be located near the XRT position in the initial 2.7'x2.7'
sub-image. However, the lack of reference stars and lack of star tracker
lock prevents a definitive identification and the measurement of a position
or magnitude.
This is an extremely bright burst in all three instruments,
and it was also seen by Fermi/GBM.
After the slew to the burst, the star trackers had trouble
locking on to give a spacecraft attitude, so the XRT position
may be inaccurate at the arcminute level.
The apparent optical counterpart appears extremely blurred,
possibly due to the lack of star tracker lock, but more likely to be
due to instrumental effects on a very bright optical counterpart.
Further follow-up is warranted for all ground-based observatories.
Burst Advocate for this burst is A. Maselli (maselli AT ifc.inaf.it).
Please contact the BA by email if you require additional information
regarding Swift followup of this burst. In extremely urgent cases, after
trying the Burst Advocate, you can contact the Swift PI by phone (see
Swift TOO web site for information: http://www.swift.psu.edu/too.html.)
- GCN Circular #14449
D. A. Perley (Caltech) reports on behalf of a larger collaboration:
The Palomar 60-inch telescope automatically responded to GRB 130427A
(Maselli et al., GCN 14448) and began taking observations at 07:52:22 UT
(4.42 minutes after the BAT trigger). A series of 60-second images were
taken in r, i, and z filters; observations are still ongoing. Inspection
of individual frames shows no detection of an optical transient
consistent with the XRT position to approximately r > 20.6 mag, i > 20.7
mag, z > 19.7 mag.
Nondetection of an afterglow in rapidly-triggered P60 observations is
unusual (Cenko et al. 2009, ApJ 693, 1484), especially in the presence
of an very bright GRB and early XRT afterglow. This is suggestive of a
highly extinguished (or possibly high-redshift) burst, and may indicate
that the possible UVOT source reported by Maselli et al. was spurious.
Further observations, especially in the NIR, are strongly encouraged.
- GCN Circular #14450
L. Elenin (KIAM), A. Volnova ( IKI), V. Savanevych (KNURE), A.
Bryukhovetskiy (NSFCTC), I. Molotov (KIAM), A. Pozanenko (IKI) report on
behalf of larger GRB follow-up collaboration:
We started observation of the field of the Swift GRB 130427A (Maselli et
al., GCN 14448) with 0.45-m telescope of ISON-NM observatory on Apr. 27
(UT) 07:50:17.
On the first images of 30 s exposure we identified very bright optical
counterpart of GRB 130427A (Maselli et al., GCN 14448) at about 12m in the
intitial images.
The coordinates of the counterpart are (J2000) 11 32 32.84 +27 41 56.2 with
uncertainties of about 1".
Observations are continuing.
- GCN Circular #14451
D. A. Perley (Caltech) reports on behalf of a larger collaboration:
Upon further inspection of the P60 images, we identify a very bright
optical source separated by about 51 arcseconds from the XRT afterglow
location but consistent with the optical afterglow location reported by
Elenin et al. (GCN 14450) The source is saturated in the early images.
Further observations are ongoing.
We also note that there is an SDSS galaxy at this position, suggesting a
low-redshift event.
- GCN Circular #14452
A. Melandri (INAF-OAB), C. Guidorzi (U. Ferrara), A. Gomboc,
J. Japelj (U. Ljubljana), C.G. Mundell (LJMU) report on
behalf of a larger collaboration:
The 2-m Faulkes Telescope North robotically followed up GRB130427A
(SWIFT trigger 554620, Maselli et al. GCN 14448 ) starting 4.3 min
after the GRB trigger time. We detect a bright fading source
at the position reported by Elenin et al. (GCN 14450), Perley
(GCN 14451) with R ~11.5 mag.
We note also a faint, 21-mag, underlying source visible in SDSS
images that may suggest this GRB is nearby with a bright host galaxy.
Observations are ongoing.
- GCN/MAXI Notice
TITLE: GCN/MAXI NOTICE
NOTICE_DATE: Sat 27 Apr 13 09:23:11 UT
NOTICE_TYPE: MAXI Unknown Source Position
EVENT_ID_NUM: 409851159
EVENT_RA: 173.14d {+11h 32m 33s} (J2000),
173.31d {+11h 33m 15s} (current),
172.48d {+11h 29m 55s} (1950)
EVENT_DEC: +27.69d {+27d 41' 31"} (J2000),
+27.62d {+27d 37' 06"} (current),
+27.97d {+27d 58' 06"} (1950)
EVENT_ERROR: 1.0 [deg radius, stat+sys, 90% containment]
EVENT_FLUX: 128.0 +- 0.0 [mCrab]
EVENT_DATE: 16409 TJD; 117 DOY; 13/04/27
EVENT_TIME: 31293.00 SOD {08:41:33.00} UT
EVENT_TSCALE: 1s
EVENT_EBAND: Low, 2-4 keV
SUN_POSTN: 34.93d {+02h 19m 44s} +13.94d {+13d 56' 31"}
SUN_DIST: 122.08 [deg]
MOON_POSTN: 236.70d {+15h 46m 47s} -18.90d {-18d 54' 13"}
MOON_DIST: 76.98 [deg]
MOON_ILLUM: 97 [%]
GAL_COORDS: 206.53, 72.50 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS: 162.22, 22.60 [deg] ecliptic lon,lat of the burst (or transient)
COMMENTS: MAXI Unknown Source Position. GRB or unknown X-ray Transient.
- GCN Circular #14453
A. N. Morgan (UC Berkeley) reports:
We observed the field of GRB 130427A (Maselli et al., GCN 14448) with the
1.3m PAIRITEL located at Mt. Hopkins, Arizona. Observations began at
2013-Apr-27 07h59m24s UT, 11.45 minutes after the Swift Trigger. In
preliminary mosaics (consisting of 75 ~8 second images for a total
effective exposure time of 9.75 minutes) taken simultaneously in the J, H,
and Ks filters, we detect the optical afterglow (Elenin et al., GCN 14450;
Perley, GCN 14451; Melandri et al., GCN 14452).
The preliminary photometry yields:
post burst
t_mid (hr) exp.(m) filt mag m_err
0.36 9.75 J 12.13 0.03
0.36 9.75 H 11.75 0.04
0.36 9.75 Ks 11.02 0.08
Observations continued until the source passed beyond telescope limits. All
magnitudes are given in the Vega system, calibrated to 2MASS. No correction
for Galactic extinction has been made to the above reported values.
- GCN Circular #14454
Y. Yatsu, Y. Yano, R. Usui, Y. Tachibana, K. Ito, T. Yoshii,
S. Kurita, Y. Saito, and N. Kawai (Tokyo Tech)
report on behalf of the MITSuME collaboration:
We observed GRB 130427A (Maselli et al., GCNC 14448) with an
optical tri-color (g, Rc, and Ic) camera attached to the MITSuME
50 cm telescope of Akeno Observatory, Yamanashi, Japan.
The observation started on 2013-04-27 10:06:09.60 UT (8293 sec after the
trigger).
And we found the optical counterpart reported in the twilight sky.
The measured magnitudes were listed below.
MID-MJD T-EXP[sec] g' Rc Ic
-------------------------------------------------------------------------------------------
56409.4231929 360 15.66+/-0.10 15.03+/-0.07 14.71+/-0.09
-------------------------------------------------------------------------------------------
T-EXP: Total Exposure time [sec]
(The photon flux were calibrated against GSC2.3 catalog.)
- GCN Circular #14455
A.J. Levan (U. Warwick), S.B. Cenko (U.C. Berkeley), D.A. Perley
(Caltech) and N.R. Tanvir (U. Leicester) report for a larger
collaboration:
We obtained spectroscopy of the afterglow of GRB 130427A (Maselli
et al. GCN 14448, Elenin et al. GCN 14450, Perley et al. GCN 14451)
with Gemini-North / GMOS, begininnig at 09:19 UT roughly 1.5 hours
after the burst. Two different central wavelengths were observed
giving a coverage from ~3100-6700 A. The resulting spectra are of
very high signal to noise given the brightness of the afterglow.
In these spectra we identify absorption lines due to Ca H and K,
Mg I as well as the Mg II doublet at a common redshift of z=0.34.
We suggest this to be the redshift of GRB 130427A.
We do not see evidence for emission lines from an underlying host,
although given the brightness of the afterglow this is not surprising.
The absolute magnitude of object in SDSS, if at z=0.34 is M_R ~
-19.7, relatively bright for a GRB host.
We thank the Gemini-staff for their help in rapidly obtaining these
observations.
- GCN Circular #14456
D. A. Perley (Caltech) and S. B. Cenko (UC Berkeley) report:
We have continued observations of the afterglow of GRB130427A (Maselli et
al., GCN 14448) with the Palomar 60-inch telescope until the field set.
Relative to SDSS reference stars in the field, in some select recent
images we estimate afterglow magnitudes of:
r' = 14.86 mag (t = 1.40 hours)
r' = 15.32 mag (t = 2.31 hours)
r' = 15.55 mag (t = 3.10 hours)
This is brighter (by about 1 mag) than any other Swift burst as measured
at similar epoch (as of 2010; Kann et al. ApJ 720:1513), though still
significantly fainter than GRB 030329 which reached approximately 13 mag
at 0.1 day. The rate of fading corresponds to a relatively shallow decay
index of approximately alpha~-0.85, suggesting that this afterglow will
remain bright for an extended period. Worldwide small-telescope follow-up
(including by amateurs) is strongly encouraged.
- GCN Circular #14457
Veli-Pekka Hentunen, Markku Nissinen and Tuomo Salmi (Taurus Hill
Observatory, Varkaus, Finland) report:
We have detected GRB 130427A optical afterglow at iTelescope
observatory T11 (Mayhill, New Mexico) 0.50-m/6.8 astrograph and FLI
ProLine PL11002M CCD. Three unfiltered and three photometric V filter
images with 120 sec exposure time were made.
The afterglow was detected at following position RA 11:32:32.83
and DEC +27:41:56.4
The following magnitudes were obtained from the observations using
NOMAD1 1176-0248446 (R=13.520, V=13.120) as the comparison:
Tmid(sec)+T0 Filter Exp. time Mag Mag err.
4597 unfiltered 120 15.02CR 0.04
4743 unfiltered 120 15.09CR 0.05
4887 unfiltered 120 15.11CR 0.05
5438 V 120 14.89V 0.04
5582 V 120 14.89V 0.04
5726 V 120 14.86V 0.04
- GCN Circular #14458
D. Xu (DARK/NBI), C. Cao, S.-M. Hu, C.-M. Zhang (SDU) report:
We observed the field of GRB 130427A (Maselli et al., GCN 14448) with
the 1m telescope located in Weihai, Shandong Province, China. A series
of I-, R-, V-, and B-band frames were obtained, and observations are
still ongoing.
Although under quite much cloud, at the afterglow position (Elenin et
al., GCN 14450; Perley, GCN 14451) we detect the optical counterpart
with R=15.5 mag, with a median time of 4.178 hr after the BAT trigger
and calibrated with nearby USNO B1 stars.
- GCN Circular #14459
Nat Butler (ASU), Alan M. Watson (UNAM), Alexander Kutyrev (GSFC), Willia=
m
H. Lee (UNAM), Michael G. Richer (UNAM), Chris Klein (UCB), Ori Fox (UCB)
J. Xavier Prochaska (UCSC), Josh Bloom (UCB), Antonino Cucchiara (UCSC),
Eleonora Troja (GSFC), Owen Littlejohns (ASU), Enrico Ramirez-Ruiz (UCSC)=
,
Jos=E9 A. de Diego (UNAM), Leonid Georgiev (UNAM), Jes=FAs Gonz=E1lez (UN=
AM),
Carlos Rom=E1n-Z=FA=F1iga (UNAM), Neil Gehrels (GSFC), and Harvey Moseley=
(GSFC)
report:
We observed the field of GRB 130427A (Maselli, et al., GCN 14448) with th=
e
Reionization and Transients Infrared Camera (RATIR; www.ratir.org) on the
1.5m Harold Johnson Telescope at the Observatorio Astron=F3mico Nacional =
on
Sierra San Pedro M=E1rtir from 2013/04 27.34 to 2013/04 27.39 UTC (0.25 t=
o
1.67 hours after the BAT trigger), obtaining a total of 1.07 hours exposu=
re
in the r' and i' bands and 0.45 hours exposure in the Z, Y, J, and H band=
s.
For a source at afterglow location reported by Elenin et al. (GCN 14450),
in comparison with SDSS DR8 and 2MASS, we obtain the following detections=
:
i' 14.46 +/- 0.01
Z 14.13 +/- 0.03
Y 14.02 +/- 0.03
J 14.05 +/- 0.02
H 13.77 +/- 0.03
These magnitudes are not corrected for Galactic extinction in the direction
of the GRB.
We thank the staff of the Observatorio Astron=F3mico Nacional in San Pedro
M=E1rtir.
- GCN Circular #14462
T. Kawamuro, M. Shidatsu (Kyoto U.), S. Nakahira (JAXA), H. Negoro (Nihon U.),
S. Ueno, H. Tomida, M. Kimura, M. Ishikawa (JAXA),
T. Mihara, M. Sugizaki, M. Serino, M. Morii, T. Yamamoto, J. Sugimoto, T. Takagi, M. Matsuoka (RIKEN),
N. Kawai, R. Usui, K. Ishikawa, T. Yoshii (Tokyo Tech),
A. Yoshida, T. Sakamoto, Y. Nakano (AGU),
H. Tsunemi, M. Sasaki (Osaka U.),
M. Nakajima, T. Onodera, K. Fukushima, K. Suzuki (Nihon U.),
Y. Ueda, M. Shidatsu (Kyoto U.),
Y. Ueda (Kyoto U.),
Y. Tsuboi, M. Higa (Chuo U.),
M. Yamauchi, K. Yoshidome, Y. Ogawa, H. Yamada (Miyazaki U.),
K. Yamaoka (Nagoya U.) report on behalf of the MAXI team
MAXI/GSC detected the bright GRB 130427A in the scan transit
at 2013-04-27T08:42 UT, about 50 min after the trigger by Swift-BAT (Maselli et al. GCN 14448).
The one-scan averaged 2-10 keV fluxes were 71 +- 19 mCrab and 23 +- 13 mCrab in the scan transits
at 2013-04-27T08:42 and 2013-04-27T10:13, respectively.
There were no significant excess fluxes in the previous scan transit at 07:12 UT and
in the transit at 11:46 with an upper limit of 30 mCrab for each.
- GCN Circular #14463
T. Kawamuro, M. Shidatsu (Kyoto U.), S. Nakahira (JAXA), H. Negoro (Nihon U.),
S. Ueno, H. Tomida, M. Kimura, M. Ishikawa (JAXA),
T. Mihara, M. Sugizaki, M. Serino, M. Morii, T. Yamamoto, J. Sugimoto, T. Takagi, M. Matsuoka (RIKEN),
N. Kawai, R. Usui, K. Ishikawa, T. Yoshii (Tokyo Tech),
A. Yoshida, T. Sakamoto, Y. Nakano (AGU),
H. Tsunemi, M. Sasaki (Osaka U.),
M. Nakajima, T. Onodera, K. Fukushima, K. Suzuki (Nihon U.),
Y. Ueda, M. Shidatsu (Kyoto U.),
Y. Ueda (Kyoto U.),
Y. Tsuboi, M. Higa (Chuo U.),
M. Yamauchi, K. Yoshidome, Y. Ogawa, H. Yamada (Miyazaki U.),
K. Yamaoka (Nagoya U.) report on behalf of the MAXI team
MAXI/GSC detected the bright GRB 130427A in the scan transit
at 2013-04-27T08:42 UT, about 50 min after the trigger by Swift-BAT (Maselli et al. GCN 14448).
The one-scan averaged 2-10 keV fluxes were 71 +- 19 mCrab and 23 +- 13 mCrab in the scan transits
at 2013-04-27T08:42 and 2013-04-27T10:13, respectively.
There were no significant excess fluxes in the previous scan transit at 07:12 UT and
in the transit at 11:46 with an upper limit of 30 mCrab for each.
- GCN Circular #14464
M. Im (CEOU/SNU) on behalf of a larger collaboration
We observed GRB 130427A (Maselli et al., GCN 14448)
in BVRI filters using T30 telescope (0.5m) of the iTelescope
network (AAO, Australia), and also are conducting
follow-up imaging observations using facilities in Korea.
The T30 observation started at about 4 hours after the BAT alert,
and other observations starting at a similar epoch. We clearly
identify the fading afterglow in T30 images, at the location
reported earlier (Elenin et al. GCN 14450).
Preliminary BRI magnitudes of the afterglow in one of the epochs,
calibrated against a USNO B-1 star in the vicinity of the afterglow,
are given below:
T(mid, UT) Mag
04-27 11:42:56 I=14.86 +- 0.12
04-27 11:45:29 R=15.60 +- 0.10
04-27 11:50:29 B=16.10 +- 0.15
Follow-up observations are still ongoing.
- GCN Circular #14465
D. Kuroda, K. Yanagisawa, Y. Shimizu, H. Toda (OAO, NAOJ),
S. Nagayama (NAOJ), M. Yoshida (Hiroshima), K. Ohta (Kyoto)
and N. Kawai(Tokyo Tech)
report on behalf of the MITSuME collaboration:
We observed the field of GRB 130427A (Masell et al., GCNC 14448)
with the optical three color (g', Rc and Ic) CCD camera attached
to the MITSuME 50cm telescope of Okayama Astrophysical Observatory.
The observation started on 013-04-27 10:57:02 UT (~3.2 h after the burst).
We detected the previously reported afterglow (Elenin et al., GCNC 14450)
in all the three bands.
Photometric results of the OT are listed below.
We used SDSS catalog for flux calibration.
#T0+[day] MID-UT T-EXP[sec] g' g'_err Rc Rc_err Ic Ic_err
-----------------------------------------------------------------------
0.13478 11:02:01 540.0 15.82 0.03 15.48 0.02 15.04 0.03
0.30675 15:09:39 540.0 16.45 0.06 16.27 0.03 15.87 0.04
------------------------------------------------------------------------
T0+ : Elapsed time after the burst [day]
T-EXP: Total Exposure time [sec]
- GCN Circular #14466
X.-H. Zhao (YNAO and PSU), J. Mao (RIKEN and YNAO), Y. X. Xin(YNAO), J.-M. Bai
(YNAO) report on behalf of a larger collaboration:
We observed the field of GRB 130427A (Maselli et al., GCN 14448) with 2.4m Gao-Mei-Gu (GMG) telescope. Observation
was started at 13:25:18 UT on 2013-04-27 (i.e., 5.6 hrs after the burst) under a bad weather condition. The sloan filters of g', r',i' and z' were used. The afterglow is very bright in every band with magnitudes of g'~16.36, r'~16.1, i'~15.9 and z'~15.8. The observations are ongoing.
We thank the GMG staff, especially Hong-Yan Gao and Jian-Duo He for
performing these observations.
- GCN Circular #14468
B. Gendre, A. Klotz (IRAP-CNRS-OMP), D. Macpherson (UWA/ICRAR),
D. Coward (UWA), M. Boer, K. Siellez, H. Dereli ,
O. Bardho (UNS-CNRS-ARTEMIS-OCA), A. Williams (PO-UWA),
R. Martin (PO-UWA) report:
We imaged the field of GRB 130427A detected by SWIFT
(trigger 554620) with the Zadko robotic telescope (D=100cm)
located at the observatory - Gingin, Australia.
The observations started 3.44h after the GRB trigger
(the event occured during the local afternoon).
The elevation of the field increased from
23 degrees above horizon and weather conditions
were good.
We detect the optical couterpart discovered by
Elenin et al. (GCNC 14450). The unfiltered images
are analyzed regarding the R magnitude of star
catalogues. The preliminary light curve is:
Tstart Tstop Rmag 1sig
(mins) (mins)
207 219 15.50 0.1
220 232 15.54 0.1
238 250 15.37 0.1
252 264 15.56 0.1
265 277 15.51 0.1
304 319 15.58 0.1
447 450 16.27 0.2
Magnitudes are not corrected for galactic dust extinction.
This message may be cited.
- GCN Circular #14470
S. D. Barthelmy (GSFC), W. H. Baumgartner (GSFC/UMBC), J. R. Cummings (GSFC/UMBC),
E. E. Fenimore (LANL), N. Gehrels (GSFC), H. A. Krimm (GSFC/USRA),
A. Y. Lien (NASA/GSFC/ORAU), C. B. Markwardt (GSFC), A. Maselli (INAF-IASFPA),
D. M. Palmer (LANL), T. Sakamoto (AGU), G. Sato (ISAS),
M. Stamatikos (OSU), J. Tueller (GSFC), T. N. Ukwatta (MSU)
(i.e. the Swift-BAT team):
Using the data set from T-60 to T+243 sec from recent telemetry downlinks,
we report further analysis of BAT GRB 130427A (trigger #554620)
(Maselli, et al., GCN Circ. 14448). The BAT ground-calculated position is
RA, Dec = 173.150, 27.706 deg which is
RA(J2000) = 11h 32m 36.1s
Dec(J2000) = +27d 42' 20.3"
with an uncertainty of 1.0 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 14%.
The mask-weighted light curve shows the main emission occuring during a
pre-planned slew. The burst location came into the BAT FoV at ~T-52 sec.
The first recorded peak started at ~T-51 sec and ending at ~T-50 sec.
The main, large peak started at ~T-50 sec, peaked at ~T-42 sec (~310 cnts/cm2/sec),
and ended at ~T-10 sec. The spacecraft settled at T+0, and then BAT triggered
(a 64-sec image trigger) at the beginning a long slow peak starting at ~T+0 sec,
peaking at ~T+90 sec, and returning to baseline ~T+2000 sec.
T90 (15-350 keV) is 162.83 +- 1.36 sec (estimated error including systematics).
We note that (a) there is a possibility that there was emission from this burst
before it came into the BAT FoV at ~T-52 sec, and (b) that Fermi-GBM triggered
on this burst at 07:47:06.42 (T_bat-51 sec) [GCN/FERMI_GBM_FLIGHT_POSITION Notice,
TrigNum=388741629].
The time-averaged spectrum from T-51.05 to T+223.50 sec is best fit by a simple
power-law model. The power law index of the time-averaged spectrum is
1.21 +- 0.02. The fluence in the 15-150 keV band is 3.1 +- 0.03 x 10^-4 erg/cm2.
The 1-sec peak photon flux measured from T-44.25 sec in the 15-150 keV band
is 331.0 +- 4.6 ph/cm2/sec. All the quoted errors are at the 90% confidence
level.
The results of the batgrbproduct analysis are available at
http://gcn.gsfc.nasa.gov/notices_s/554620/BA/
- GCN Circular #14471
S. Zhu, J. Racusin, D. Kocevski, J. McEnery (NASA/GSFC), F. Longo (Univ of Trieste and INFN), J. Chiang (SLAC), G. Vianello (Stanford) report on behalf of the Fermi-LAT team:
At 07:47:15 UT on 27 April 2013, Fermi LAT detected high energy emission from GRB 130427A, which was also detected by Fermi-GBM (trigger 388741629/130427324) and by Swift (Maselli et al. GCN 14448). The GBM detection triggered an autonomous repoint of the spacecraft.
The LAT on-ground location is consistent with the optical position reported in Elenin et al. (GCN 14450). The burst was about 47 deg from the LAT boresight at the time of the trigger and within the LAT field of view for the next 700 seconds.
The data from the Fermi LAT show a multi-peaked light curve consistent with the GBM trigger. More than 200 photons above 100 MeV are observed within 100 seconds with a TS of >1000. Using the non-standard LAT Low Energy (LLE) data selection, thousands of counts above background were detected within a 100 s interval coinciding with the time of the GBM emission, with a significance of ~40 sigma. The highest energy LAT photon has an energy of 94 GeV.
A GBM circular is forthcoming.
The Fermi LAT point of contact for this burst is Sylvia Zhu (s.jc.zhu@gmail.com).
The Fermi LAT is a pair conversion telescope designed to cover the energy band from 20 MeV to greater than 300 GeV. It is the product of an international collaboration between NASA and DOE in the U.S. and many scientific institutions across France, Italy, Japan and Sweden.
- GCN Circular #14472
T. Pritchard (PSU), A. Maselli (INAF-IASFPA), N. P. M. Kuin (MSSL),
S. R. Oates (MSSL-UCL), M. De Pasquale (MSSL-UCL),
and M. H. Siegel (PSU), report on behalf of the Swift/UVOT team:
Further to Maselli et al., GCN Circ. 14448 we have performed manual
stacking and aspect corrections on the initial UVOT image. These
resulting images still retain some instrumental effects due to the
brightness of the object and loss of star tracking lock.
Preliminary 3-sigma detections using the UVOT photometric system
(Breeveld et al. 2011, AIP Conf. Proc. 1358, 373) for the UVOT
observations are:
Filter T_start(s) T_stop(s) Exp(s) Mag
wh 1522 1542 19.5 13.8=B11.1
v 382 401 19.5 12.1=B10.04
b 480 500 19.5 12.6=B11.09
u 456 475 19.5 11.8=B11.09
w1 430 450 19.5 11.2=B10.04
m2 406 426 19.5 11.2=B10.04
w2 358 377 19.5 11.2=B10.04
The magnitudes in the table are not corrected for the Galactic extinction
due to the reddening of E(B-V) =3D 0.24 in the direction of the burst
(Schlegel et al. 1998).
- GCN Circular #14473
A. von Kienlin (MPE) reports on behalf of the Fermi GBM Team:
"At 07:47:06.42 UT on 27 April 2013, the Fermi Gamma-Ray Burst Monitor
triggered and located GRB 130427A (trigger 388741629/130427324) which
was also detected by the Swift/BAT and Fermi/LAT (Maselli et al. 2013,
GCN 14448 and S. Zhu et al., GCN 14471) The GBM on-ground location is
consistent with the Swift position.
The angle from the Fermi LAT boresight is 48 degrees.
Based on hard and intense emission in a GBM BGO detector, GBM
initiated an Autonomous Report Request. This request caused Fermi
to reorient towards this GRB (GBM flight location).
The GBM light curve consists of a bright structured peak followed
at ~T0+120 s by a FRED-like pulse. The overall duration (T90)
is about 138s s (50-300 keV).
Owing to the brightness of the burst, systematic effects are very large
and no single model gives an adequate fit in this preliminary analysis.
A Band function fit in the interval from T0+0.002 s to T0+18.432 s yields
the following parameters Epeak = 830 +/- 5 keV, alpha = -0.789 +/- 0.003,
and beta = -3.06 +/- 0.02.
The event fluence (10-1000 keV) in this time interval is
(1.975 +/- 0.003)E-03 erg/cm^2. The 1.024 sec peak photon flux measured
starting from T0+7.48808 s in the 8-1000 keV band
is 1052 +/- 2 ph/s/cm^2, making this the most intense and fluent GRB
detected by Fermi GBM.
Further analysis is being performed"
- GCN Circular #14474
A. Volnova ( IKI), D. Shakhovskoy (CrAO), V. Rumyantsev (CrAO), A.
Pozanenko (IKI) report on behalf of larger GRB follow-up collaboration:
We started observation of the field of the Swift GRB 130427A (Maselli et
al., GCN 14448) with AZT-11 telescope of CrAO observatory on Apr. 27 (UT)
18:21:45 in VRI filters. We clearly detect still bright optical counterpart
of GRB 130427A (Maselli et al., GCN 14448, Elenin et al. GCN 14450, Perley
GCN 14451). Preliminary photometry is following
filter tstart (UT) exp,s T-t0,d OT +/- err
R 18:21:45 120 0,76580 16,71 +/- 0,06
R 18:27:52 120 0,77005 16,87 +/- 0,06
R 18:34:00 120 0,77431 16,83 +/- 0,07
R 18:40:07 120 0,77855 16,81 +/- 0,06
Observation is continuing.
- GCN Circular #14475
E. Sonbas (Adiyaman Univ.), T. Guver (Sabanci Univ.), E. Gogus (Sabanci
Univ.), H. Kirbiyik (TUG) report on behalf of a larger collaboration
We observed the field of Swift GRB 130427A (Maselli et al. GCN#14448)
with the 1.0 meter T100 telescope (TUBITAK National Observatory,
Antalya - Turkey), starting April, 27, 20:39:28 UT (~ 13 hours after
the trigger). Observations were carried out in the R filter under good
weather conditions. The afterglow is clearly detected in 60 s R band
images at a position that is consistent with Elenin et al. GCN#14450
Using USNO-B1 star USNO-B1 1177-0254824 (RA= 11:32:31.23, Dec=
+27:42:23.02 ) in the field, the magnitudes of the OT were estimated as
follows;
t-t0 (hr) exp.(s) filt mag err (+/-)
12.850 60 R 16.2 0.05
12.871 60 R 16.6 0.03
12.874 60 R 16.3 0.03
12.877 60 R 16.5 0.01
Further observations using the same filter are ongoing.
We are grateful to the TUBITAK National Observatory staff for promptly
scheduling the observations and their technical support.
- GCN Circular #14476
J. Wren, W.T. Vestrand, P. Wozniak, and H. Davis,
of Los Alamos National Laboratory report:
Three RAPTOR full-sky persistent monitors at Maui, HI, and Los Alamos, NM,
independently detected bright optical emission at the location of the
Swift trigger 554620 (Maselli, et al., GCN 14448). Starting at 07:47:07.28
UT (50.2 seconds before the Swift trigger) we detect a brightening counterpart
which peaks at magnitude R~7.4. After the peak, the source fades to below
10th magnitude at approximately the Swift trigger time. The unfiltered images
from all three monitors are calibrated to the Tycho-2 V-band catalog.
- GCN Circular #14478
D. Xu (DARK/NBI), A. de Ugarte Postigo (IAA-CSIC, DARK/NBI), S.
Schulze (PUC and MCSS), J. Jessen-Hansen (AU), G. Leloudas (OKC,
Stockholm), T. Kruehler, J.P.U. Fynbo (DARK/NBI), P. Jakobsson (U.
Iceland) report on behalf of a larger collaboration:
We observed the field of GRB 130427A (Maselli et al., GCN 14448) with
the 2.5m Nordic Optical Telescope (NOT) equipped with the ALFOSC
camera. Observations started at 20:39:12 UT on 2013-04-27 (i.e., 12.85
hr after the BAT trigger).
We first obtained a series of frames in the sloan u-, g-, r-, i-, and
z-band filters. The optical afterglow (ref., Elenin et al., GCN 14450)
is clearly detected in the stacked images in each of these filters.
Preliminary analysis gives the following magnitudes
u=17.70+/-0.03
g=17.34+/-0.03
r=17.07+/-0.03
i=16.94+/-0.03
z=16.88+/-0.03
at a mean time of 12.96 hr post-trigger, calibrated with nearby stars
in the SDSS field.
We also carried out a 1800s spectroscopic exposure. The spectrum
covers 3200 - 9100 AA at a resolution of ~700 and has a high S/N. We
detect prominent absorption lines of the MgII doublet, MgI and CaII K
& H as well as weak emission lines of the [OII] doublet and H-beta,
all at a common redshift of z=0.338+/-0.002, consistent with the
redshift reported by Levan et al. (GCN 14455).
- GCN Circular #14480
B. A. Zauderer, E. Berger, S. Chakraborti, and A. Soderberg (Harvard)
report on behalf of a larger collaboration:
"We observed the position of GRB 130427A (Maselli et al.; GCN 14448)
beginning 2013 Apr 27.99 (dt = 0.67 d) with the Very Large Array in its
D configuration (synthesized beam ~18'' x 11''). At a mean frequency of
~5.8 GHz, we detect a source with a flux of ~1 mJy +/- 20 uJy at a
position consistent with the optical afterglow (e.g. Elenin et al.,
Perley et al.; GCNs 14450, 14451). Followup observations are planned for
this nearby z~0.34 GRB (Levan et al., Xu et al; GCNs 14455, 14478).
We thank the VLA observatory staff for their support of these observations."
- GCN Circular #14481
M. Im, C. Choi (CEOU/SNU), H.-I. Sung, Y.-B. Jeon (KASI),
and Y. Urata (NCU) on behalf of a larger collaboration
We continued our follow-up imaging observation of
GRB 130427A (Maselli et al., GCN 14448) in BVRI filters at
Seoul National University Observatory (SNUO, 0.6m), Sobaeksan
Optical Astoronomy Observatory (SOAO, 0.6m), and Bohyunsan
Optical Astronomy Observatory (BOAO), all located in Korea.
The observations span the time period of about 4 hrs
between 04-27 11:28 and 04-27 15:48 UT. The GRB afterglow
(e.g., Elenin et al. GCN 14450; Im GCN 14464) is identified
in the observed frames at magnitudes of ~16-17 mag
Further analysis of the data is ongoing, and additional follow-up
observation with these and other facilities is ongoing and planned.
We thank the staffs of SOAO for performing the ToO observation.
- GCN Circular #14482
B. A. Zauderer, E. Berger, S. Chakraborti, and A. M. Soderberg (Harvard)
report on behalf of the CARMA Key Project "A Millimeter View of the
Transient Universe":
"We began observing the field of GRB 130427A (Maselli et al.; GCN 14448)
with the Combined Array for Research in Millimeter Astronomy on 2013 Apr
28.13 UT (dt ~ 0.8 d). In 45 minutes integration on source at a mean
frequency of 85 GHz, we detect a radio counterpart with a preliminary
flux of ~3 mJy (>10-sigma) at a position consistent with the reported
optical afterglow (Elenin et al., Perley et al.; GCNs 14450, 14451) and
our VLA 5 GHz detection (Zauderer et al.; GCN 14480). Observations are
ongoing.
We thank the CARMA observers and the observatory staff for their support."
- GCN Circular #14483
Nat Butler (ASU), Alan M. Watson (UNAM), Alexander Kutyrev (GSFC), Willia=
m
H. Lee (UNAM), Michael G. Richer (UNAM), Chris Klein (UCB), Ori Fox (UCB)
J. Xavier Prochaska (UCSC), Josh Bloom (UCB), Antonino Cucchiara (UCSC),
Eleonora Troja (GSFC), Owen Littlejohns (ASU), Enrico Ramirez-Ruiz (UCSC)=
,
Jos=E9 A. de Diego (UNAM), Leonid Georgiev (UNAM), Jes=FAs Gonz=E1lez (UN=
AM),
Carlos Rom=E1n-Z=FA=F1iga (UNAM), Neil Gehrels (GSFC), and Harvey Moseley=
(GSFC)
report:
We again observed the field of GRB 130427A (Maselli, et al., GCN 14448)
with the Reionization and Transients Infrared Camera (RATIR; www.ratir.or=
g)
on the 1.5m Harold Johnson Telescope at the Observatorio Astron=F3mico
Nacional on Sierra San Pedro M=E1rtir from 2013/04 28.14 to 2013/04 28.20=
UTC
(19.62 to 20.99 hours after the BAT trigger), obtaining a total of 1.07
hours exposure in the r' and i' bands and 0.45 hours exposure in the Z, Y=
,
J, and H bands.
We continue to detect the optical/NIR afterglow (Elenin et al; GCN 14450)
in all bands. In comparison with SDSS DR8 and 2MASS, we find:
r' 17.68 +/- 0.01
i' 17.52 +/- 0.01
Z 17.26 +/- 0.04
Y 17.12 +/- 0.02
J 17.21 +/- 0.02
H 17.01 +/- 0.03
These magnitudes are in the AB system and not corrected for Galactic
extinction in the direction of the GRB. Uncertaints are 1-sigma. The
source has faded by about 3 magnitudes in all bands as compared to our
measurements last night (Butler et al. 2013; GCN 14459).
We thank the staff of the Observatorio Astron=F3mico Nacional in San Pedr=
o
M=E1rtir.
- GCN Circular #14484
A. Pozanenko (IKI), P. Minaev (IKI), A. Volnova (IKI) report:
The SPI-ACS detector (> 80 keV) of INTEGRAL observatory was triggered by the
Swift GRB 130427A (Maselli et al., GCN 14448) on (UT) T0=07:47:06.36. Light
curve of the GRB 130427A
(http://www.isdc.unige.ch/integral/ibas/cgi-bin/ibas_acs_web.cgi) consists
of the first peak of ~ 1 s duration which coincides with bright optical
emission detected by RAPTOR (Wren et al., GCN 14476). This peak is also
clearly visible in the BAT light curve at ~T0_BAT-51 s (
http://gcn.gsfc.nasa.gov/notices_s/554620/BA/ ). Following the first peak
extremely intense emission was detected coinciding with BAT/Swift and
Fermi-LAT detection (Zhu et al., GCN 14471). The emission in SPI-ACS
detector is significantly detectable at least up to 100 s after T0.
The SPI-ACS light curve can be also found at
http://grb.rssi.ru/GRB130427A/GRB130427A_SPI-ACS.png
- GCN Circular #14485
J.A. Kennea (PSU), M.C. Stroh (PSU), D.N. Burrows (PSU), J.P. Osborne
(U. Leicester), K.L. Page (U. Leicester), C. Pagani (U. Leicester), A.
Melandri (INAF-OAB), B. Sbarufatti (INAF-OAB/PSU), G. Stratta (ASDC)
and A. Maselli report on behalf of the Swift-XRT team:
We have analysed 2.4 ks of XRT data for GRB 130427A (Maselli et al.
GCN Circ. 14448), from 130 s to 48.1 ks after the BAT trigger. The
data comprise 84 s in Windowed Timing (WT) mode (the first 9 s were
taken while Swift was slewing) with the remainder in Photon Counting
(PC) mode. The refined XRT position is RA, Dec = 173.13594, +27.69769
which is equivalent to:
RA (J2000): 11 32 32.63
Dec(J2000): +27 41 51.7
with an uncertainty of 3.5 arcsec (radius, 90% confidence).
The light curve can be modelled with an initial power-law decay with an
index of alpha=7.9980 (+0.0021, -1.0800), followed by a break at T+252
s to an alpha of 0.61 (+/-0.10).
A spectrum formed from the PC mode data can be fitted with an absorbed
power-law with a photon spectral index of 1.79 (+0.17, -0.16). The
best-fitting absorption column is 9.9 (+6.4, -6.0) x 10^20 cm^-2, at a
redshift of 0.34, in addition to the Galactic value of 1.8 x 10^20
cm^-2 (Kalberla et al. 2005). The counts to observed (unabsorbed)
0.3-10 keV flux conversion factor deduced from this spectrum is 4.0 x
10^-11 (4.7 x 10^-11) erg cm^-2 count^-1.
A summary of the PC-mode spectrum is thus:
Galactic foreground: 1.8 x 10^20 cm^-2
Intrinsic column: 9.9 (+6.4, -6.0) x 10^20 cm^-2 at z=0.34
Photon index: 1.79 (+0.17, -0.16)
If the light curve continues to decay with a power-law decay index of
0.61, the count rate at T+24 hours will be 2.3 count s^-1,
corresponding to an observed (unabsorbed) 0.3-10 keV flux of 9.4 x
10^-11 (1.1 x 10^-10) erg cm^-2 s^-1.
The results of the XRT-team automatic analysis are available at
http://www.swift.ac.uk/xrt_products/00554620.
This circular is an official product of the Swift-XRT team.
- GCN Circular #14486
R. Itoh, K. Kawaguchi, Y. Moritani, K. Takaki, K. S. Kawabata, M. Ohno,
H. Takahashi, Y. Tanaka, and M. Yoshida (Hiroshima Univ.) report on behalf
of Kanata team:
We performed a series of optical imaging polarimetry for the optical
afterglow of GRB 130427A (Elenin et al., GCN 14450) from 3.87 hr through
10.04 hr after the Swift/BAT trigger (Maselli et al., GCN 14448) with HOWPol
attached to the 1.5-m Kanata telescope at Higashi-Hiroshima Observatory, Japan.
Our quick-look analysis indicates that the R-band magnitude of the optical
afterglow was 15.9 at the beginning of our observation, and then smoothly
declined. Its decline rate between 3.87 hr and 10.04 hr can be approximated by
a single power-low decay with an index -1.0. The polarization seems not so
large (<~3%) in that period. Further analysis is ongoing.
- GCN Circular #14487
S. Golenetskii, R.Aptekar, D. Frederiks, E. Mazets, V. Pal'shin,
P. Oleynik, M. Ulanov, D. Svinkin, and T. Cline on behalf
of the Konus-Wind team, report:
The long extremely intense GRB 130427A (Swift-BAT trigger #554620:
Maselli et al., GCN 14448; Barthelmy et al., GCN 14470;
Fermi-LAT detection: Zhu et al., GCN 14471;
Fermi-GBM observation: von Kienlin, GCN 14473;
SPI-ACS/INTEGRAL observations: Pozanenko et al., GCN 14484)
triggered Konus-Wind (K-W) at T0=3D28029.501s UT (07:47:09.501)
~50 s before the BAT trigger.
The K-W light curve shows a huge mult-peaked emission complex
started at ~T0, peaked at ~T0+8 s, and having a duration of ~20 s.
The emission is seen up to ~12 Mev.
This extremely bright phase of the event passes into a weaker decaying
tail out to ~T0+120s, when the second emission episode started.
It shows a FRED-like pulse, ~100 times weaker in a peak count
rate than the initial complex.
The decaying emission is detectable by K-W in the 20-1200 keV band
out to ~T0+250s, when the instrument switched into the data readout mode.
The Konus-Wind light curve of this GRB is available at
http://www.ioffe.ru/LEA/GRBs/GRB130427_T28029/
As observed by Konus-Wind, the main phase of the burst had
a fluence of (2.68 =B1 0.01)x10^-3 erg/cm2 and a 16-ms peak flux,
measured from T0+7.774 s, of (6.9 =B1 0.1)x10^-4 erg/cm2/s
(both in the 20 - 1200 keV energy range).
The fluence of GRB 130427A is the highest observed by K-W
for ~18 years of GRB observations and its peak flux
is only ~30% lower than measured by K-W for the
ultra-luminous GRB 110918A.
The time-averaged spectrum of the main phase of the burst
(measured from T0 to T0+18.688 s) is best fit in the 20 keV-15 MeV range
by the GRB (Band) function with the following model parameters:
the low-energy photon index alpha =3D -0.958 =B1 0.006,
the high energy photon index beta =3D -4.17 =B1 0.16,
the peak energy Ep =3D 1028 =B1 8 keV,
chi2 =3D 124/96 dof.
The spectrum at the maximum count rate (measured from T0+7.680 to T0+7.93=
6 s)
is best fit in the 20 keV - 15 MeV range
by a power law with exponential cutoff model, for which:
the photon index alpha =3D -0.57 =B1 0.02, and
the peak energy Ep =3D 1213 =B1 31 keV,
chi2 =3D 63/84 dof.
Modelling the 3-channel time-averaged spectrum
of the second emission episode (from T0+120 s to T0+250 s)
by a power law with exponential cutoff model
yiels the photon index alpha~-1.6 and
the peak energy Ep ~ 240 keV.
The 20-1200 keV energy fluence measured at this
phase of the event is ~9x10^-5 erg/cm2.
Assuming z=3D0.34 (Levan et al., GCN 14455; Xu et al. GCN 14478)
and a standard cosmology model with H_0 =3D 70 km/s/Mpc,
Omega_M =3D 0.27, and Omega_Lambda =3D 0.73,
the isotropic energy release E_iso is ~8.5x10^53 erg,
and the peak luminosity (L_iso)_max is ~2.7x10^53 erg/s.
All the quoted errors are estimated at the 1 sigma confidence level.
- GCN Circular #14488
Veli-Pekka Hentunen, Markku Nissinen and Tuomo Salmi (Taurus Hill
Observatory, Varkaus, Finland) report:
We have continued observing GRB 130427A optical afterglow at iTelescope
observatory T21 (Mayhill, New Mexico) 0.43-m/6.8 astrograph and
FLI-PL6303E CCD. Two unfiltered, two photometric R filter and two
photometric V filter images with 600 sec exposure time were made.
The following magnitudes were obtained from the observations using
NOMAD1 1176-0248446 (R=13.520, V=13.120) as the comparison:
Tmid(h)+T0 Filter Exp. time Mag Mag err.
22.67 V 600 17.73V 0.11
22.85 V 600 17.72V 0.11
23.10 unfiltered 600 18.01CR 0.07
23.27 unfiltered 600 18.22CR 0.09
23.56 R 600 18.18R 0.12
23.74 R 600 18.36R 0.14
- GCN Circular #14489
S. B. Pandey and Brajesh Kumar (ARIES Nainital India, on behalf of larger
Indian GRB collaboration)
We observed Swift GRB 130427A field (Maselli et al., GCN 14448) using 1.04m
telescope at ARIES Nainital on 2013-04-27 starting at 14:25:16 UT in
UBV(RI)_c filters. Several frames were obtained in average sky conditions.
We clearly detect the bright optical counterpart of GRB 130427A (Maselli et
al. GCN 14448, Elenin et al. GCN 14450) in each individual exposures.
The preliminary photometry is as following:
(UT)Start filter exp(sec) mag
14:25:16 B 300 16.61 +/- 0.06
14:53:36 I 200 14.83 +/- 0.05
The photometry was performed in comparison to nearby USNO- B1 stars. Our
observations seem to follow the power-law decay exponent ~ -0.9 as noticed
by Perley and Cenko GCN 14456.
Further observations are going on. This massage may be cited.
- GCN Circular #14490
Patrick Wiggins (Stansbury Park, Utah, United States) reports the following
optical observations of the error box of GRB 130427A (GCN Circ #14448,
Maselli et al.) to the AAVSO International High Energy Network:
P. Wiggins reports three hours of time-series photometry of the bright GRB
130427A (Maselli et al., GCN Circ. #14448; Elenin et al., GCN Circ. #
14450). Wiggins used a 0.35-m C-14 f/5.5 telescope with an SBIG ST-10XME
camera and clear filter located in Stansbury Park, Utah. Observations
commenced 2013 April 27 08:05:12 UT -- less than 20 minutes post trigger
-- and continued through 11:10:06 UT. The first four observations were
made with 60-second exposure times, which were found to be close to
saturation; subsequent exposure times were 30 seconds. The transient was
detected by visual inspection of the first frame, and found to be very
bright. Time-series observations were begun immediately.
Thirty-three images of the field were taken, and the resulting light curve
is as follows. All magnitudes are taken with respect to the comparison
star GSC 01984-00021, which has an r-magnitude of 12.553 (APASS DR7,
http://www.aavso.org/apass ); the resulting magnitudes should be
interpreted as through a clear filter with r'-band zero point. Note that
the first four magnitudes with integration times of 60 seconds may be
saturated. All times are given as the mid-point of the exposure, UT on
2013 April 27, and T(0)+h is hours since trigger (07:47:57 UT):
Obs. UT T(0)+h Exp. time magn. mag.err.
08:05:41.529 0.296 60.00 13.108 0.006
08:06:57.779 0.317 60.00 13.194 0.007
08:14:16.467 0.439 60.00 13.557 0.009
08:27:07.951 0.653 60.00 13.995 0.013
08:40:35.701 0.877 30.00 14.304 0.024
08:46:36.857 0.978 30.00 14.413 0.027
08:50:51.998 1.049 30.00 14.47 0.029
08:55:17.311 1.122 30.00 14.546 0.030
09:00:52.545 1.215 30.00 14.623 0.033
09:06:26.014 1.308 30.00 14.684 0.035
09:11:59.514 1.401 30.00 14.731 0.038
09:17:33.139 1.493 30.00 14.792 0.041
09:23:06.748 1.586 30.00 14.829 0.043
09:28:40.357 1.679 30.00 14.969 0.050
09:34:18.373 1.773 30.00 14.957 0.050
09:39:51.873 1.865 30.00 14.911 0.050
09:45:25.545 1.958 30.00 15.025 0.055
09:50:59.404 2.051 30.00 15.158 0.064
09:56:32.982 2.143 30.00 15.104 0.064
10:02:06.529 2.236 30.00 15.22 0.073
10:07:40.154 2.329 30.00 15.138 0.071
10:13:13.732 2.421 30.00 15.249 0.080
10:15:01.029 2.451 30.00 15.219 0.078
10:20:47.498 2.547 30.00 15.302 0.088
10:26:21.123 2.64 30.00 15.424 0.099
10:31:54.732 2.733 30.00 15.387 0.100
10:37:28.451 2.825 30.00 15.247 0.091
10:43:02.248 2.918 30.00 15.512 0.123
10:48:35.811 3.011 30.00 15.496 0.124
10:54:09.561 3.103 30.00 15.517 0.128
10:59:43.279 3.196 30.00 15.633 0.150
11:05:19.092 3.289 30.00 15.555 0.150
11:10:20.982 3.373 30.00 15.48 0.153
The AAVSO International High Energy Network is supported through the
AAVSO Endowment Fund. We thank the Charles Curry Foundation and
NASA for past support.
- GCN Circular #14491
GRB 130427A: VLT/X-shooter redshift confirmation
H. Flores (Obs. de Paris), S. Covino (INAF), D. Xu, T. Kruehler,
J. Fynbo, B. Milvang-Jensen(DARK/NBI), A. de Ugarte Postigo (IAA-CSIC,
DARK/NBI), L. Kaper (UVA) and K. Wiersema (U. Leicester) report on behalf
of the X-shooter GRB collaboration:
VLT/X-shooter observed the afterglow of GRB 130427A (Maselli et al.,
GCN 14448; Elenin et al., GCN 14450), starting on 2013-04-28 at UT
00:23. The observation consisted of 2x600s exposures.
In the spectra we detect the continuum in the complete range from 3000
to 24800 A. We find several absorption features including FeII, MnII,
MgII, MgI, TiII, CaII, NaI, and emission lines such as H-alpha,
H-beta, [OIII], and [OII], all at a common redshift of z=0.3399 +/- 0.0002,
consistent with the measurement in Levan et al. (GCN 14455) and
Xu et al. (GCN 14478).
We thank the Paranal staff for excellent support, in particular Andrea
Mehner and Christophe Martayan.
- GCN Circular #14492
L.P. Xin, J. Y. Wei, Y. L. Qiu, J. Wang,
J. S. Deng, C. Wu, X.H. Han report on behalf of EAFON team:
We began to observe the field of GRB 130427A (Maselli, et al., GCN 14448)
using 80cm TNT telescope located at Xinglong observatory, China
at 12:52:38 UT on 2013-04-28. We obtained several B, V, R-band images.
The optical counterpart is detected in all images. The prelinary analysis shows that
its brightness is about R=18.3 mag, calibrated with USNO B2 stars,
at the mean time of 29.08 h after the trigger time.
This message may be cited.
- GCN Circular #14494
D. A. Perley (Caltech) reports on behalf of a larger collaboration:
We observed the position of GRB 130427A (Maselli et al.; GCN 14448) with
the Combined Array for Research in Millimeter Astronomy on two epochs on
2013-04-28 (UT), between 01:45 and 02:46 and again between 07:22 and
08:14, at a frequency of 93 GHz (3 mm). The afterglow is well-detected
in both epochs. Preliminary reduction gives fluxes of:
3.7 +/- 0.4 mJy (t_mid = 0.769 day)
2.6 +/- 0.4 mJy (t_mid = 1.000 day)
These values are consistent with the flux reported by Zauderer et al.
(GCN 14482) as also measured by CARMA at a time intermediate between
these epochs.
The source location is:
RA = 11:32:32.82
Dec = +27:41:56.06
(J2000, uncertainty 0.4 arcsec)
Further observations are planned.
We thank the CARMA staff for their support in executing these observations.
- GCN Circular #14495
J. Takahashi, K. Morihana, S. Honda and Y. Takagi (Univ. of Hyogo)
report on behalf of Nayuta team:
We observed the field of GRB 130427A (Masell et al., GCNC 14448)
in near-infared three bands (J, H and Ks) with NIC attached to the
Nayuta 2-m telescope at the Nishi-Harima Astronomical Observatory.
The observations were conducted from 2013-04-27 12:26 UT to 2013-04-27
17:25 UT (from ~4.7 h to ~9.6 h after the burst).
We detected the previously reported afterglow (Elenin et al., GCNC 14450)
in all the three bands.
Photometric results of our observations are listed below.
We used 2MASS 11323755+2743196 as the reference star for flux calibration.
# MID-UT T-EXP[sec] J J_err H H_err Ks Ks_err
-----------------------------------------------------------------------
12:26:56 150 14.7 0.2 13.5 0.2 13.5 0.2
13:27:59 150 14.7 0.2 14.2 0.2 13.2 0.3
14:39:42 150 14.7 0.3 14.3 0.2 13.4 0.3
17:17:31 150 --* --* 14.8 0.2 14.6 0.2
17:24:52 300 15.2 0.2 14.8 0.2 14.0 0.2
------------------------------------------------------------------------
T-EXP: Total Exposure time [sec]
* Photometry was not possible because the signal from the reference star
was too low.
- GCN Circular #14497
A. Trotter, D. Reichart, J. Haislip, A. LaCluyze, T. Berger, H. T.
Cromartie, R. Egger, A. Foster, N. Frank, K. Ivarsen, M. Maples, J.
Moore, M. Nysewander, E. Speckhard, and J. A. Crain report:
Skynet observed the Swift/XRT localization of GRB 130427A (Maselli et
al., GCN 14448, Swift trigger #554620) with four 16" telescopes of the
PROMPT array at CTIO, Chile, starting at 2013-04-27, 23:28 UT, and
continuing until 04-28, 05:30 UT (t=15.69h-21.67h post-trigger). It took
~124 160-s exposures, simultaneously in each of the BVRI bands. We
performed photometry on each exposure, calibrated to two SDSS stars in
the field. We detect a fading afterglow in BVRI at the position reported
by Elenin et al. (GCN 14450), which is ~50" south of the initial XRT
localization.
A preliminary light curve of the first night's data is at:
http://skynet.unc.edu/grb/grb130427a.png
Further Skynet observations are ongoing.
- GCN Circular #14498
D. Kuroda, (OAO, NAOJ), H. Hanayama (IAO, NAOJ), K. Yanagisawa,
Y. Shimizu, H. Toda (OAO, NAOJ), T. Miyaji J. Watanabe, (IAO, NAOJ),
S.Nagayama (NAOJ), M. Yoshida (Hiroshima), K. Ohta (Kyoto)
and N. Kawai(Tokyo Tech) report on behalf of the MITSuME collaboration:
We observed the field of GRB 130427A (Masell et al., GCNC 14448)
with the optical three color (g', Rc and Ic) CCD camera attached
to the MITSuME 50cm telescope of Okayama Astrophysical Observatory
and the Murikabushi 1m telescope of Ishigakijima Astronomical
Observatory.
We detected the previously reported afterglow (Elenin et al., GCNC 14450)
in all the three bands. Photometric results of the OT are listed below.
We used SDSS catalog for flux calibration.
Okayama Astrophysical Observatory:
The observation started on 2013-04-28 11:29:25 UT (~1.15 days after the burst).
#T0+[day] MID-UT T-EXP[sec] g' g'_err Rc Rc_err Ic Ic_err
-----------------------------------------------------------------------
1.16123 11:40:06 1440.0 18.4 0.2 17.9 0.1 17.7 0.1
------------------------------------------------------------------------
T0+ : Elapsed time after the burst [day]
T-EXP: Total Exposure time [sec]
Ishigakijima Astronomical Observatory:
The observation started on 2013-04-28 14:02:08 UT (~1.26 days after the burst).
#T0+[day] MID-UT T-EXP[sec] g' g'_err Rc Rc_err Ic Ic_err
-----------------------------------------------------------------------
1.31290 15:18:30 1020.0 18.61 0.06 18.22 0.04 17.37 0.05
------------------------------------------------------------------------
T0+ : Elapsed time after the burst [day]
T-EXP: Total Exposure time [sec]
- GCN Circular #14502
P.A. Evans, K.L. Page (U. Leicester), A. Maselli, V. Mangano, M. Capalbi
(INAF-IASFPA), D.N. Burrows (PSU) report on behalf of the Swift-XRT team:
We have reanalysed the XRT data for GRB 130427A (Maselli et al. GCN
Circ. 14448) from 144 s to 141 ks after the BAT trigger. The data
comprise 1.9 ks of Windowed Timing (WT) mode data, with the rest taken
in Photon Counting (PC) mode.
The star trackers on Swift failed to find a correct aspect solution
during the first 1.9 ks of exposure (when the WT mode data were
collected; see GCN Circ. 14448), and the GRB is seen to be drifting on
the XRT detector. We have fitted this drift as a linear function, which
is a good representation to the data. We have then rebuilt the GRB light
curve and spectrum using this information. However, the time-tag of
individual photon events may be incorrect by up to 1 second, and the
method that we have used to correct the attitude may introduce low-level
fluctuations. It is therefore inappropriate to perform any detailed
timing or periodicity analysis with the current XRT data. We are working
to rectify this situation.
The light curve can be modelled as a broken power-law with an initial
decay index of 2.81 (+/- 0.04) with a break at T+421 s to a slope of
alpha=1.17 (+/-0.01). This then breaks again at T+53.4ks to a final
slope of 1.79 (+0.5, -0.05).
A spectrum formed from the WT mode data can be fitted with an absorbed
power-law with a photon spectral index of 1.91 (+/-0.11). The best
fitting absorption column is 2.8 (+/-0.05) x 10^21 cm^-2 at a redshift
of 0.34, in addition to the Galactic value of 1.8 x 10^20 cm^-2
(Kalberla et al. 2005). The counts to observed (unabsorbed) 0.3-10 keV
flux conversion factor deduced from this spectrum is 3.8 x 10^-11 (5.2
x 10^-11) erg cm^-2 count^-1.
If the light curve continues to decay with a power-law decay index of
1.79, the count rate at T+3 days will be 0.14 count/sec, corresponding
to an observed (unabsorbed) 0.3-10 keV flux of 5.3 x 10^-12 (7.3 x
10^-12) erg cm^-2 s^-1.
The automated light curve of this GRB is online at
http://www.swift.ac.uk/xrt_curves/00554620/
This circular is an official product of the Swift-XRT team.
- GCN Circular #14503
L. Amati (INAF - IASF Bologna, Italy), S. Dichiara, F. Frontera, C.
Guidorzi (University of Ferrara, Italy), report:
Based on the preliminary values of fluence and spectral parameters
reported by the Fermi/GBM (Kienlin et al., GCN 14473) and Konus-Wind
(Golenetskii et al., GCN 14487) teams, and by assuming a redshift of 0.34
(Levan et al., CGN 14455; Flores et al., GCN 14491) and a standard
Lambda_CDM cosmology with H_0 = 70 km/s/Mpc, Omega_M = 0.27, Omega_Lambda
= 0.73, we estimate for GRB 130427A an intrinsic spectral peak energy Ep,i
of 1250+/-150 keV and an isotropic-equivalent radiated energy of
(1.05+/-0.15)x10^54 erg (1-10000 keV cosmological rest-frame).
These values are fully consistent with the best-fit power-law of the
Ep,i-Eiso correlation holding for all long-bright cosmological GRBs (as
determined, e.g., by Amati et al. 2009, A&A 508, 173). This is further
evidence that the prompt emission properties of GRB 130427A, the most
energetic GRB detected at z < 1, are the same as those of very bright,
high-redshift events. Hence, its relatively low redshift makes it a unique
case for investigating wether this class of events is associated to SNe
with properties similar to those associated to "local" sub-luminous GRBs.
- GCN Circular #14505
A. Volvach (CrAO), L. Volvach (CrAO), A. Pozanenko (IKI) on behalf of=20
larger collaboration report:
We observed the field of GRB 130427A (Maselli et al., GCN 14448) on Apr.=20
28 between (UT) 16:22-18:41 with 22-m radio telescope RT-22 of
Crimean Astrophysical Observatory at mean frequency of 36 GHz. At the=20
position of the optical (Elenin et al., GCN 14450; Perley et al., GCN=20
14451) and radio afterglow (Zauderer et al., GCN 14480; Zauderer et al.,=20
GCN 14482; Perley, GCN 14494) we detected a source with a flux 1.9 =C2=B1=
0.4=20
mJy at T_mid =3D 1.405 days after burst trigger.
- GCN Circular #14506
Nat Butler (ASU), Alan M. Watson (UNAM), Alexander Kutyrev (GSFC), Willia=
m
H. Lee (UNAM), Michael G. Richer (UNAM), Chris Klein (UCB), Ori Fox (UCB)
J. Xavier Prochaska (UCSC), Josh Bloom (UCB), Antonino Cucchiara (UCSC),
Eleonora Troja (GSFC), Owen Littlejohns (ASU), Enrico Ramirez-Ruiz (UCSC)=
,
Jos=E9 A. de Diego (UNAM), Leonid Georgiev (UNAM), Jes=FAs Gonz=E1lez (UN=
AM),
Carlos Rom=E1n-Z=FA=F1iga (UNAM), Neil Gehrels (GSFC), and Harvey Moseley=
(GSFC)
report:
We again observed the field of GRB 130427A (Maselli, et al., GCN 14448)
with the Reionization and Transients Infrared Camera (RATIR; www.ratir.or=
g)
on the 1.5m Harold Johnson Telescope at the Observatorio Astron=F3mico
Nacional on Sierra San Pedro M=E1rtir from 2013/04 29.14 to 2013/04 29.27=
UTC
(43.64 to 46.60 hours after the BAT trigger), obtaining a total of 3.02
hours exposure in the r' and i' bands and 1.57 hours exposure in the Z, Y=
,
J, and H bands.
We continue to detect the optical/NIR afterglow (Elenin et al; GCN 14450)
in all bands. In comparison with SDSS DR8 and 2MASS, we find:
r' 18.90 +/- 0.01
i' 18.67 +/- 0.01
Z 18.38 +/- 0.03
Y 18.19 +/- 0.02
J 18.29 +/- 0.02
H 18.01 +/- 0.02
These magnitudes are in the AB system and not corrected for Galactic
extinction in the direction of the GRB. Uncertaints are 1-sigma. The
source has faded by about 1 magnitude in all bands as compared to our
measurements on the previous night (Butler et al. 2013; GCN 14483).
We thank the staff of the Observatorio Astron=F3mico Nacional in San Pedr=
o
M=E1rtir.
- GCN Circular #14507
William C. Keel (U. of Alabama, Tuscaloosa), Dieter Hartmann and Aman Kaur
(Clemson University) report:
We observed the field of GRB 130427A (Maselli, et al., GCN 14448) with the
SARA 0.9m telescope at KPNO (http://saraobservatory.org) from 0350-0420 UT
on April 29, obtaining a total of 30 min exposure in the B,V, and R band.
We detect the optical afterglow (Elenin et al; GCN14450) in all bands.
In comparison with Landolt (PG 0942) standard stars we find
B = 19.32
V = 19.00
R = 18.53
These magnitudes are not corrected for Galactic extinction, but include
KPNO airmass corrections at the time of observation.
This message may be cited
- GCN Circular #14508
S. Zhu, J. Racusin (NASA/GSFC), J. Chiang (SLAC), G. Vianello (Stanford) report on behalf of the Fermi LAT team:
Using LAT source class events >100 MeV between T0+0 and 700 seconds after the GBM trigger, we find a LAT localization of RA = 173.148, Dec = +27.709, with a 68% containment radius of 0.068 degrees (statistical only). This localization is consistent with other reported positions.
The >100 MeV emission spectrum during the GBM T90 (T0+0 to 138 seconds) is fit by a power law with an index of -1.96 +/- 0.07. The fluence during this time is (1.1 +/- 0.1)E-4 erg/cm^2, making this the highest fluence LAT-detected burst in the LAT energy range (Fermi LAT Collaboration, arXiv:1303.2908). The >100 MeV peak flux, measured from 11.52 to 37.33 seconds, is (1.4 +/- 0.2)E-3 ph/cm^2/s.
The LAT Low Energy (LLE) emission during the bright structured peak (0 to 20 seconds) is roughly correlated with the GBM emission. A spike at T0+0 seconds is coincident in both LAT and LLE, but precedes the onset of the GBM emission. There are peaks in the LAT light curve at approximately 13 and 22 seconds; neither peak is coincident with the LLE or GBM.
Significant emission >100 MeV was detected throughout the first orbit until ~735 seconds, at which point the burst became occulted by the Earth. The LAT emission was still significantly detected when the burst emerged from occultation at ~3000 seconds, and remained detectable for about a day. The extended emission light curve can be fit by a broken power-law that has a power-law index = -0.89 +/- 0.04 at early times, and at late times, it has an index in the range -1.3 to -1.5; the temporal break occurs around 550-800 seconds after the GBM trigger.
We clarify that the Swift-BAT trigger time (Barthelmy et al., GCN 14470) is ~51 seconds after the GBM trigger, so the emission detected by RAPTOR beginning ~50 seconds before the Swift trigger with a peak magnitude of R~7.4 (Wren et al., GCN 14476) is therefore coincident with the GBM and LAT emission onset.
The Fermi LAT point of contact for this burst is Sylvia Zhu (s.jc.zhu@gmail.com).
The Fermi LAT is a pair conversion telescope designed to cover the energy band from 20 MeV to greater than 300 GeV. It is the product of an international collaboration between NASA and DOE in the U.S. and many scientific institutions across France, Italy, Japan and Sweden.
- GCN Circular #14509
X.-H. Zhao (YNAO and PSU), J. Mao (RIKEN and YNAO), J. G. Wang(YNAO), J.-M. Bai
(YNAO) report on behalf of a larger collaboration:
We further observed the afterglow of GRB 130427A (Maselli et al., GCN 14448) with 2.4m Gao-Mei-Gu (GMG) telescope on Apr 28 and Apr 29.
The sloan filter of r' was used. The magnitudes of the afterglow are
r'~18.2 31.16 hrs after trigger
r'~18.9 53.37 hrs after trigger
We thank the GMG staff, especially Hong-Yan Gao, Jian-Duo He and Gui-Hua He for performing these observations.
- GCN Circular #14510
A. Trotter, D. Reichart, J. Haislip, A. LaCluyze, T. Berger, H. T.
Cromartie, R. Egger, A. Foster, N. Frank, K. Ivarsen, M. Maples, J.
Moore, M. Nysewander, E. Speckhard, and J. A. Crain report:
Skynet continued observing the Swift/XRT localization of GRB 130427A
(Maselli et al., GCN 14448, Swift trigger #554620) with four 16"
telescopes of the PROMPT array at CTIO, Chile, starting at 2013-04-28,
23:06 UT, and continuing until 04-29, 3:51 UT (t=39.28h-44.03h
post-trigger). It took ~110 160-s exposures, simultaneously in each of
the BVRI bands. We performed photometry on each exposure, calibrated to
two SDSS stars in the field. B-band photometry was performed on stacks
of 3-4 images in order to provide at least 3sigma detections.
A preliminary light curve of the second's data is at:
http://skynet.unc.edu/grb/grb130427a_2.png
A light curve of both the first and second nights' data is at:
http://skynet.unc.edu/grb/grb130427a_1_2.png
See Trotter et al. (GCN 14497) for a description of the first night's
observations. Further Skynet observations are ongoing.
- GCN Circular #14511
Jay Norris, Daryl Macomb (Boise State U.) report:
We observed GRB 130427A with the Challis Observatory's 0.4-m telescope
(114.33 deg W, 44.5 deg N, 2165 m elevation) on April 29, 05:58 to 06:22 UT.
Using seventeen 10-second frames in the R filter acquired in a clear sky,
centered at ~ 06:06 UT, 22.3 hours after the Swift/BAT trigger (GCN 14448),
we clearly detected the optical afterglow.
Comparison with six stars in the field of view (R = 15.5 to 16.8 mag)
yielded an estimate of R = 17.6 mag for the afterglow with uncertainty
of ~ 0.15 mag. Further observations were interrupted by clouds.
- GCN Circular #14513
D. Kuroda (OAO, NAOJ), H. Hanayama, T. Miyaji, J. Watanabe (IAO, NAOJ),
K. Yanagisawa (OAO, NAOJ), S.Nagayama (NAOJ), M. Yoshida (Hiroshima),
K. Ohta (Kyoto) and N. Kawai(Tokyo Tech)
report on behalf of the MITSuME collaboration:
We observed the field of GRB 130427A (Masell et al., GCNC 14448)
with the optical three color (g', Rc and Ic) CCD camera attached
to the Murikabushi 1m telescope of Ishigakijima Astronomical
Observatory.
We detected the previously reported afterglow (Elenin et al., GCNC 14450)
in all the three bands. The observation started on 2013-04-29 15:02:55 UT (~2.30
days after the burst).
Photometric results of the OT are listed below.
We used SDSS catalog for flux calibration.
#T0+[day] MID-UT T-EXP[sec] g' g'_err Rc Rc_err Ic Ic_err
-----------------------------------------------------------------------
2.31262 15:18:06 1500.0 19.19 0.05 18.87 0.04 18.65 0.09
2.33383 15:48:38 1440.0 19.29 0.06 18.90 0.05 18.76 0.11
------------------------------------------------------------------------
T0+ : Elapsed time after the burst [day]
T-EXP: Total Exposure time [sec]
- GCN Circular #14514
Nat Butler (ASU), Alan M. Watson (UNAM), Alexander Kutyrev (GSFC), Willia=
m
H. Lee (UNAM), Michael G. Richer (UNAM), Chris Klein (UCB), Ori Fox (UCB)
J. Xavier Prochaska (UCSC), Josh Bloom (UCB), Antonino Cucchiara (UCSC),
Eleonora Troja (GSFC), Owen Littlejohns (ASU), Enrico Ramirez-Ruiz (UCSC)=
,
Jos=E9 A. de Diego (UNAM), Leonid Georgiev (UNAM), Jes=FAs Gonz=E1lez (UN=
AM),
Carlos Rom=E1n-Z=FA=F1iga (UNAM), Neil Gehrels (GSFC), and Harvey Moseley=
(GSFC)
report:
We again observed the field of GRB 130427A (Maselli, et al., GCN 14448)
with the Reionization and Transients Infrared Camera (RATIR; www.ratir.or=
g)
on the 1.5m Harold Johnson Telescope at the Observatorio Astron=F3mico
Nacional on Sierra San Pedro M=E1rtir from 2013/04 30.14 to 2013/04 30.37=
UTC
(67.58 to 73.15 hours after the BAT trigger), obtaining a total of 3.91
hours exposure in the r' and i' bands and 1.64 hours exposure in the Z, Y=
,
J, and H bands.
We continue to detect the optical/NIR afterglow (Elenin et al; GCN 14450)
in all bands. In comparison with SDSS DR8 and 2MASS, we find:
r' 19.39 +/- 0.01
i' 19.31 +/- 0.01
Z 18.89 +/- 0.03
Y 18.75 +/- 0.03
J 18.87 +/- 0.02
H 18.56 +/- 0.03
These magnitudes are in the AB system and not corrected for Galactic
extinction in the direction of the GRB. Uncertaints are 1-sigma. The
source has faded by about 0.5 magnitude in all bands as compared to our
measurements on the previous night (Butler et al. 2013; GCN 14506).
We thank the staff of the Observatorio Astron=F3mico Nacional in San Pedr=
o
M=E1rtir.
- GCN Circular #14515
F. Verrecchia, C. Pittori (ASDC and INAF/OAR), A. Giuliani (INAF/IASF-Mi),
M. Marisaldi (INAF/IASF-Bo), F. Longo (University of Trieste and INFN
Trieste), F. Lucarelli (ASDC and INAF/OAR), E. Del Monte, F. Lazzarotto, I.
Donnarumma, Y. Evangelista, M. Feroci, L. Pacciani, P. Soffitta, E. Costa,
I. Lapshov, M. Rapisarda (INAF/IAPS Rome), G. Barbiellini, (INFN Trieste),
A. Bulgarelli, F. Gianotti, M. Trifoglio, G. Di Cocco, C. Labanti, V.
Fioretti, F. Fuschino, M. Galli (INAF/IASF-Bo), A. Chen, S. Mereghetti,
F. Perotti, P. Caraveo (INAF/IASF-Mi), M. Cardillo, E. Striani, M. Tavani
(INAF/IAPS Rome, and Univ. Roma Tor Vergata), A. Argan, G. Piano, S.
Sabatini, V. Vittorini (INAF/IAPS Rome), G. Pucella (ENEA Frascati), A.
Pellizzoni, A. Trois (INAF/OA Cagliari), M. Pilia (ASTRON), S. Vercellone
(INAF/IASF-Pa), P. W. Cattaneo, A. Rappoldi (INFN Pavia), A. Morselli, P.
Picozza (INFN Roma-2), M. Prest, E. Vallazza (Universita`
dell'Insubria), P.
Lipari, D. Zanello (INFN Roma-1), P. Giommi (ASI), and G. Valentini (ASI),
on behalf of the AGILE Team, report:
The AGILE Gamma Ray Imaging Detector (GRID) detected high energy emission
from GRB 130427A (A. Maselli et al., GCN 14448), also reported
by Fermi-LAT (S. Zhu et al., GCN 14471).
A preliminary analysis of the AGILE-GRID data in temporal coincidence with
the GRB shows a significant excess of gamma-ray photons above 50 MeV at the
location of the event. The emission detected by the AGILE-GRID mostly
occurred between ~ t0 + 180 sec and t0 + 700 sec where t0 is 27 April 2013
at 07:47:15 UT. During this interval, the burst position was inside the
instrument FOV.
A maximum likelihood analysis of the AGILE-GRID data integrating over 12
hours, from 2013-04-27 05:00 UT to 2013-04-27 17:00 UT, using the standard
parameters used by AGILE quick look to detect persistent gamma-ray sources,
yields a detection at a significance level larger than 6 sigma, and a mean
flux F = (8.0+/-2.7) 10-6 ph/cm2/s (E > 100 MeV).
The preliminary photon spectral index obtained with this integration is
1.55 +/- 0.30.
Due to the exceptionally high fluence above 100 MeV of this burst, it is
possible for the first time to derive its properties using the maximum
likelihood techniques routinely used in the standard data analysis of
AGILE-GRID point sources.
The GRB also triggered the AGILE Minicalorimeter (MCAL), sensitive to
gamma-rays above 350 keV, at the time 07:47:06 UT.
According to the MCAL light curve, the emission lasts for about 20 s
divided
into three main episodes. Although the large initial off-axis angle (more
than 120 degrees) prevents an accurate spectral analysis of MCAL data,
significant emission above 15 MeV is detected.
This measurement was obtained with AGILE observing a large portion of the
sky in spinning mode.
This message may be cited.
- GCN Circular #14516
A. Vonova (IKI), L. Elenin (KIAM), A. Pozanenko (IKI)
We have investigated photo-z of possible host galaxy (Melandri et al., GCN
14452, Levan et al., 14455). Using LePhare sw (Arnouts et al. 1999, MNRAS,
310, 540; Ilbert et al. 2006, A&A, 457, 841) and SDSS magnitudes we
estimated a redshift of the galaxy z = 0.49 (+0.12,-0.24). This photo-z
value is compatible with a spectroscopy redshift (Levan et al., GCN 14455;
Xu et al., GCN 14478; Flores et al., 14491) and confirms the SDSS galaxy
as the host.
- GCN Circular #14517
A. Arai, J. Takahashi, K. Morihana, S. Honda and Y. Takagi (Univ. of Hyogo)
report on behalf of Nayuta team:
We performed low resolution ( R ~ 500) optical spectroscopic observations
of a source on the position of GRB 130427A (Masell et al., GCNC 14448)
with MALLS attached to the Nayuta 2-m telescope at the Nishi-Harima
Astronomical Observatory.
The observations were conducted from 2013-04-27 12:48 UT to 2013-04-27
22 : 09 UT (from ~5.1 h to ~ 5.4 h after the burst).
The resulting spectrum ( S/N ~ 5) shows a feature less continuum light
without any emission nor absorption line features in the wavelength
range between 450 nm and 680 nm.
- GCN Circular #14518
X.-H. Zhao (YNAO and PSU), J. Mao (RIKEN and YNAO), L. Chang (YNAO), J.-M. Bai
(YNAO) report on behalf of a larger collaboration:
We again observed the afterglow of GRB 130427A (Maselli et al., GCN 14448) with 2.4m Gao-Mei-Gu (GMG) telescope from 15:46:37 UT on 2013-04-30.
We used the sloan filter of r' and obtained two images with the exposure time of 900s each image. The GRB afterglow decayed to r'~19.4 with a middle time of
80.2 hrs post-burst.
We thank the GMG staff, especially Jian-Duo He and Gui-Hua He for performing these observations.
- GCN Circular #14519
Poonam Chandra (NCRA-TIFR) reports on behalf of a larger team:
We carried out Giant Metrewave Radio Telescope (GMRT) observations of
GRB 130427A at 1390 GHz band on 2013 Apr 30.57 UT. In our preliminary
analysis we detect the GRB with a flux density of 500+/-94 uJy at
RA, Decl (J200) of 11 32 32.81, +27 41 56.00 which is consistent with
optical position reported by Elenin et al. (GCN 14450) within error bars.
We thank GMRT staff for making these observations possible. More
observations are planned.
- GCN Circular #14520
Search for high-energy neutrinos in coincidence with GRB 130427A
The IceCube collaboration (icecube.wisc.edu) reports:
We used the data from IceCube to perform several searches for high-energy=
neutrinos in spatial and temporal=20
coincidence with GRB 130427A (A. Maselli et al., GCN 14485).=20
The first analysis is an automated online search for muon neutrino multip=
lets of two or more neutrinos in coincidence
within 100 seconds and 3.5 degrees. The search has a threshold of ~1 TeV =
and does not depend on an external GRB
trigger. No such multiplet was found.=20
A second offline analysis is a likelihood based search for muon neutrinos=
with energies ~1 TeV and higher, with a primary=20
background of atmospheric neutrinos and atmospheric muons. Data was scann=
ed in the T90=3D162.83 s window reported by Swift BAT (S. D.=20
Barthelmy et al., GCN 14470), and found no neutrinos. We also performed =
a series of rolling time-window searches=20
covering a window of interest of +/- 1 hour relative to the burst time an=
d again found no neutrinos.
A final search focused on neutrinos of all flavors with energies ~100 Te=
V and higher that have interaction vertices that fall within the detector=
in a window=20
of interest of +-1 day. Because the intrinsic background for this search =
is very low only temporal information was used=20
in this search. No neutrinos were found in this search.
Implications with respect to neutrino fluence for this GRB will be report
ed elsewhere.
IceCube is a kilometer cubed neutrino telescope located at the geographic
South Pole sensitive to neutrinos above=20
~100 GeV. Previous limits on the emission of neutrinos by GRBs have been
presented in R. Abbasi et al., Nature 484,
351=96354 (2012). A description of the multiplet search is found in R. Abbasi et al., A&A 539, A60 (2012). Funding
acknowledgement and author list for IceCube are listed
[http://icecube.wisc.edu/collaboration/authors/current here]
- GCN Circular #14521
I. van de Stadt (AWSV Metius, the Netherlands), K. Wiersema (U. of Leicester),
T. Bekkers (AWSV Metius), M. Seynen (AWSV Metius) and
F. Nieuwenhout (AWSV Metius) report:
We observed the afterglow of GRB 130427A with the ABT, a 10-inch remote controlled observatory in Alkmaar,
The Netherlands. In a series of V band exposures the afterglow is detected with
V=18.70 +/- 0.13 mag at midtime 1.633 days after burst.
- GCN Circular #14522
A. Corsi (GWU) reports on behalf of a larger collaboration:
We imaged the position of GRB 130427A (Maselli et al., GCN 14448) with
the Very Large Array in the 20-22 GHz frequency band, starting at about
1.9 days after the burst. A provisional reduction shows a source consistent
with the location of the GRB optical (e.g., Elenin et al., GCN 14450; Perley et al.,
GCN 14451) and radio (e.g., Zauderer et al., GCN 14480) afterglow. At this time
and frequency (~21 GHz), we estimate a preliminary flux of about 1.3 mJy.
Further observations are planned.
We thank the VLA staff for their support.
- GCN Circular #14523
Aman Kaur, Dieter Hartmann (Clemson University), and William C. Keel (U.
of Alabama, Tuscaloosa), report:
We continued our observations of GRB 130427A (Maselli, et al., GCN 14448)
with the SARA 0.9m telescope at KPNO (http://saraobservatory.org)
starting on April 29. We obtained a total of 190 min exposure in the R
band, with a sequence of 36 five min exposures, and one ten min
exposure.
We detect the optical afterglow (Elenin et al; GCN14450) decay between R
= 19.2 and R = 19.4
during that sequence, which implies a temporal power law decay of the flux
density with a slope of
alpha ~ 0.8
Magnitudes are not corrected for Galactic extinction.
This message may be cited
- GCN Circular #14525
WeiKang Zheng, S. Bradley Cenko, Alexei V. Filippenko and Adam Morgan
(UC Berkeley) report on behalf of the KAIT GRB team:
We observed the afterglow of GRB 130427A (e.g., Maselli et al., GCN
14448; Elenin et al., GCN 14450; Perley, GCN 14451) with the 0.76-m
Katzman Automatic Imaging Telescope (KAIT) located at Lick Observatory
on Apr. 28, 29, 30, and May 1 UT. Observations were carried out in the
B, V, R, and I filters. A series of images, lasting for about an hour,
was taken on each night. The afterglow is well detected in all filters,
and the estimated R-band magnitudes (calibrated to SDSS, transformed to
R) are as follows, with times relative to the BAT trigger:
t_mid(hr) exp(s) R(mag) err
20.2 60.0 17.4 +/- 0.1
45.1 60.0 18.5 +/- 0.1
69.1 360.0 19.1 +/- 0.1
93.1 600.0 19.6 +/- 0.2
A power-law fit to the data shows the afterglow continues to decay with
an index of roughly -1.0 (Itoh et al., GCN 14486).
Further observations are planned.
- GCN Circular #14526
R. Ruffini, C.L. Bianco, M. Enderli, M. Muccino, A.V. Penacchioni, G.B. Pisani, J.A. Rueda, N. Sahakyan, Y. Wang, L. Izzo report:
The late x ray observations of GRB 130427A by Swift-XRT clearly evidence a pattern typical of a family of GRBs associated to supernova (SN) following the Induce Gravitational Collapse (IGC) paradigm (Rueda & Ruffini 2012; Pisani et al. 2013). We assume that the luminosity of the possible SN associated to GRB 130427A would be the one of 1998bw, as found in the IGC sample described in Pisani et al. 2013. Assuming the intergalactic absorption in the I-band (which corresponds to the R-band rest-frame) and the intrinsic one, assuming a Milky Way type for the host galaxy, we obtain a magnitude expected for the peak of the SN of I = 22 - 23 occurring 13-15 days after the GRB trigger, namely between the 10th and the 12th of May 2013.
Further optical and radio observations are encouraged.
- GCN Circular #14534
D. Kuroda (OAO, NAOJ), H. Hanayama, T. Miyaji, J. Watanabe (IAO, NAOJ),
K. Yanagisawa (OAO, NAOJ), S.Nagayama (NAOJ), M. Yoshida (Hiroshima),
K. Ohta (Kyoto) and N. Kawai(Tokyo Tech)
report on behalf of the MITSuME collaboration:
We observed the field of GRB 130427A (Masell et al., GCNC 14448)
with the optical three color (g', Rc and Ic) CCD camera attached
to the Murikabushi 1m telescope of Ishigakijima Astronomical
Observatory.
We detected the previously reported afterglow (Elenin et al., GCNC 14450)
in only Rc-band. The observation started on 2013-05-02 13:08:42 UT
(~5.2 days after the burst).
Photometric result and three sigma upper limits of the OT are listed below.
We used SDSS catalog for flux calibration.
#T0+[day] MID-UT T-EXP[sec] g' Rc Rc_err Ic
---------------------------------------------------------
5.25248 13:51:30 540.0 >20.7 20.3 0.3 >19.1
---------------------------------------------------------
T0+ : Elapsed time after the burst [day]
T-EXP: Total Exposure time [sec]
- GCN Circular #14538
H. Flewelling, A. Schultz, N. Primak, K. C. Chambers, E. A. Magnier, W.
Sweeney, C. Z. Waters, S. Chastel, M. E. Huber, I. Smith, report on behalf
of Pan-STARRS 1:
Pan-STARRS 1, a 1.8 m survey telescope located at Haleakala, Hawaii,
observed GRB 130427A (Masell et al., GCNC 14448) a total of 4 times in the
z and y filters using the 1.4 Gigapixel camera, in the course of normal
survey operations. PS1 detected the afterglow (Elenin et al., GCNC 14450),
and the observations were calibrated with the "ubercal" technique (Schafly
et al 2011) and the PS1 reference catalog (Magnier et al 2012). The results
are:
t_mid(hr) exp(s) filter mag
108.18 80.0 y 19.52 +/- 0.10
108.21 80.0 y 19.66 +/- 0.09
111.35 60.0 z 19.84 +/- 0.07
111.37 60.0 z 19.81 +/- 0.06
Note the host galaxy pre-outburst has been observed in the PS1 3pi survey
and thus photometry of the host galaxy is available.
This discovery was made possible by the PS1 system operated by the
PS1 Science Consortium and its member institutions (
http://www.ps1sc.org/PS1_System_GCN.shtml ). We thank the telescope
operators of the PS1 telescope for their support.
- GCN Circular #14549
D. Lennarz, I. Taboada (Georgia Tech) report on behalf of the HAWC
collaboration (http://www.hawc-observatory.org/collaboration/):
We used data from the partially built HAWC detector to perform a search
for VHE emission in temporal coincidence with GRB 130427A (A. Maselli et
al., GCN 14448). This search was conducted using the scaler data
acquisition only, as the main data acquisition was not operational at
the time. At the time of the GBM trigger, the elevation of the burst in
HAWC's field of view, was only 33.13 degrees and setting. The
sensitivity of HAWC at this elevation is more than 2 orders of magnitude
poorer than near the zenith. Furthermore, while near zenith the nominal
threshold of the scaler system is a few GeV, towards the horizon the
nominal threshold is much higher.
We used six search windows with respect to the GBM trigger time: one in
the range 0 s to 20 s, which covers the bright structured peak seen by
Fermi-GBM that seems to be correlated with the Fermi-LAT emission (S.
Zhu et al., GCN 14508), an extended window from -5 s to 55 s and a
window from -5 s to 145 s, which is slightly larger than the T90
reported by GBM. We also searched around the second peak in the GBM
light curve (120 s to 300 s), -10 s to 10 s around the time of the
highest energy LAT photon and in an extended window from -10 s to 290 s.
We find a deviation of +38960 / -77884 / -337877 / -165991 / -519485 /
-1036 of the global PMT count with respect to a moving average in the
six time windows mentioned above. The p-value for these deviations
assuming background hypothesis are 17 % / 78 % / 95 % / 71 % / 90 % and
50 % respectively. Our observations are consistent with background only.
The implications of this non-detection with respect to the VHE fluence
of this GRB will be reported elsewhere.
HAWC is a gamma-ray detector under construction in Central Mexico. It
currently consists of 29 operational Water Cherenkov Detectors out of
300 planned. A detailed description of the sensitivity of HAWC to GRBs
can be found in A.U. Abeysekara et al., Astroparticle Physics 35,
641-=C2=96650 (2012).
- GCN Circular #14579
D. Frederiks, on behalf of the Konus-Wind team, reports:
We have also found a typo in our GCN Circ. 14487 "Konus-Wind observation of GRB 130427A":
the correct energy range for the total K-W energy fluence and the peak flux estimations
for GRB 130427A is 20-10000 keV, not "20 - 1200 keV", as mentioned.
The 20-10000 keV range is a standard for K-W estimations of GRB energetics
in the observer frame.
We thank D.A.Kann for his help in clearing this issue and sorry again for the inconvenience.
- GCN Circular #14582
V. Rumyantsev (CrAO), K.Antoniuk (CrAO), D. Shakhovskoy (CrAO), A.
Pozanenko (IKI) report on behalf of larger GRB follow-up collaboration:
We continue observation of the Swift GRB 130427A (Maselli et al., GCN
14448) with AZT-11 telescope of CrAO observatory. Preliminary
photometry the optical afterglow of GRB 130427A (Maselli et al., GCN
14448, Elenin et al. GCN 14450, Perley GCN 14451) is following
T_start (UT) T0+ Filter Exp. OT
mid,days s mag
2013-05-02T19:34:45.35 5.5618 R 6120 19.75 +/- 0.15
2013-05-03T20:41:27.17 6.5581 R 3600 20.30 +/- 0.25
2013-05-04T18:26:22.25 7.4747 R 5400 20.20 +/- 0.18
Photometry is based on SDSS star
SDSS id B eB V eV R eR I eI
J113220,11+274133,5 17,421 0,020 16,911 0,020 16,561 0,015 16,124 0,016
- GCN Circular #14590
David M. Smith (UC Santa Cruz), Andre Csillaghy (Fachhochschule Nordwestschweiz),
Kevin Hurley (UC Berkeley), Hugh Hudson (UC Berkeley, U. Glasgow), Steven Boggs
(UC Berkeley), and Andrew Inglis (NASA Goddard/CUA) report:
The Reuven Ramaty High-Energy Solar Spectroscopic Imager (RHESSI)
satellite observed the prompt emission of GRB 130427A (Maselli et
al. , GCN 14448), with usable data over the approximate range 50 keV to
15 MeV, and a time resolution of 1us on each photon recorded.
Absolute timing accuracy is ~1ms. Since the GRB was 122 degrees from
the Sun, the photons entered through the rear of the spectrometer.
The lightcurve of the main outburst in three energy bands is shown binned to 25ms
resolution at:
http://scipp.ucsc.edu/~dsmith/rhessi/grb/130427a_longplot.gif
The black, red, and orange lightcurves represent the energy ranges 50 keV to 1 MeV,
1-5 MeV, and 5-15 MeV, respectively.
The lightcurve of the slower, fainter peak of the GRB, about two minutes after
the primary outburst, is shown here:
http://scipp.ucsc.edu/~dsmith/rhessi/grb/130427a_lateplot.gif
The black, red, and orange lightcurves in this case represent the energy ranges
50-200 keV, 200-500 keV, and 500 keV to 1 MeV, respectively.
RHESSI data are publicly available. We invite anyone intending to use the RHESSI
data to consult with us about instrumental issues associated with the observation.
- GCN Circular #14592
D. A. Kann, B. Stecklum, and F. Ludwig (TLS Tautenburg) report:
We observed the optical afterglow (Elenin et al., GCN 14450) of the nearby
(Levan et al., GCN 14455), extremely bright GRB 130427A (Maselli et al.,
GCN 14448; Zhu et al., GCN 14471; von Kienlin, GCN 14473; Golenetskii et
al., GCN 14487) with the 1.34m Schmidt telescope of the Thueringer
Landessternwarte Tautenburg equipped with a 4k CCD camera under good
weather conditions. We obtained 3 x 600 sec frames in the Rc band. The
afterglow is detected in each frame.
Using the nearby star given in Rumyantsev et al. (GCN 14582), we derive a
preliminary magnitude of Rc = 20.27 +/- 0.07 at 8.55173 days after the
GRB.
This value is in good agreement with detections from the last few days
(Kuroda et al., GCN 14534; Rumyantsev et al., GCN 14582). The afterglow
does not yet show clear signs of flattening associated with either a
rising supernova component or a significant contribution from the
underlying host galaxy.
This message may be cited.
- 1305.1261 from 7 May 13
Yi-Zhong Fan et al.: High energy emission of GRB 130427A: evidence for inverse Compton radiation
A nearby super-luminous burst GRB 130427A was simultaneously detected by five $\gamma$-ray space telescopes ({\it Swift}, Fermi-GBM/LAT,
Konus-Wind, SPI-ACS/INTEGRAL and AGILE) and by three RAPTOR full-sky persistent monitors. The isotropic $\gamma-$ray energy release is of $\sim
10^{54}$ erg and the absence of a jet break in the X-ray afterglow lightcurve up to $t>7$ days suggests an intrinsic energy release of $>
10^{52}$ erg, rendering it the most powerful explosion among the GRBs with a redshift $z\leq 0.5$. The emission above 100 MeV lasted about one
day and four photons are at energies greater than 40 GeV. We show that the count rate of 100 MeV-100 GeV emission may be mainly accounted for
by the forward shock synchrotron radiation and the inverse Compton radiation likely dominates at GeV-TeV energies. In particular, an inverse
Compton radiation origin is established for the $\sim (95.3,~47.3,~41.4)$ GeV photons arriving at $t\sim (243,~256.3,~610.6)$ s after the
trigger of Fermi-GBM. Interestingly, the external-inverse-Compton-scattering of the prompt emission (the second episode, i.e., $t\sim 120-260$
s) by the forward-shock-accelerated electrons is expected to produce a few $\gamma-$rays with a typical energy $\sim 10$ GeV, while five
photons above 10 GeV were detected in the same time interval. A possible unified model for the prompt soft $\gamma-$ray, optical and GeV
emission of GRB 130427A, GRB 080319B and GRB 090902B is outlined. Implication of the null detection of $>1$ TeV neutrinos from GRB 130427A by
IceCube is discussed.
- GCN Circular #14596
L. Hermansson, P. Holmstr=F6m, M. Johansson (Sandvreten Observatory, Sweden)
We observed the field of GRB 130427A (Maselli et al., GCN 14448; Elenin et
al., GCN 14450) with the 0.45 m f/4.5 Newton located at Sandvreten
Observatory, Sweden.
Observations were obtained between 2013-Apr-27 22:29:03 and 23:48:43 UT.
Two
images each were obtained in each of B, V, Rc and Ic bands with Sch=FCler
Johnson-Cousins photometric filters and an SBIG ST-7E CCD.
The following magnitudes were obtained from the observations with Maxim DL
software using four SDSS comparison stars transformed to the BVRI system
using Lupton (2005). Magnitudes are not corrected for extinction.
Filter Tmid (T0+day) Exp (s) Mag Err
B 0.65231 2x600 17.74 0.06
V 0.63317 2x300 17.38 0.03
Rc 0.61726 2x300 16.99 0.03
Ic 0.66821 2x300 16.78 0.05
We wish to thank D. A. Kann and the Cosmoquest forum for alerting us to GRB
130427A. We are also grateful for the guidance D.A. Kann provided during
the preparation of this report.
- GCN Circular #14597
D. Xu (DARK/NBI), A. de Ugarte Postigo (IAA-CSIC, DARK/NBI), T.
Kruehler, D. Malesani (DARK/NBI), G. Leloudas (OKC, Stockholm and
DARK/NBI), J.P.U. Fynbo, J. Hjorth, (DARK/NBI), S. Schulze (PUC and
MCSS), P. Jakobsson, Z. Cano (U. Iceland), J. Gorosabel
(IAA-CSIC/UPV-EHU), report:
We have been monitoring the optical counterpart of GRB 130427A
(Maselli et al., GCN 14448; Elenin et al., 14450) starting 12.85 hr
after the GRB trigger (Xu et al., GCN 14478), mainly using the 2.5
Nordic Optical Telescope (NOT) equipped with the ALFOSC camera.
Observations were carried out using the SDSS filters.
The light curve between ~1.0 and 5.0 days after the trigger (observer
frame) is well fit by a power law with decay index 1.3. Starting from
day 5.0, however, the light curve gradually flattens. The flattening,
albeit reduced, is still evident after subtracting the (known) flux
contribution of the host galaxy. In particular, clear flux in excess
of the afterglow and host contribution is apparent on May 5 and 6,
that is 8.6 and 9.6 days after the GRB.
Photometry in the Sloan griz filters was secured during the night of
May 6. After subtracting from the observed flux the host contribution,
and correcting for the (small) Galactic extinction, the SED clearly
deviates from a power-law, in sharp contrast with our earlier
measurements and the typical spectrum of GRB afterglows. Instead, the
griz SED shows a broad hump peaking in the i and r bands, which is
roughly consistent with the spectrum of other broad-lined SNe
associated with GRBs at comparable epochs (e.g., SN 1998bw: Patat et
al. ApJ, 555 900; SN 2006aj: Pian et al., Nat. 442,1011).
The flattening in the decay, the change of the spectral shape, and the
overall flux level are all consistent with the emergence of a SN,
though detailed spectroscopy and long-term monitoring will be required
to fully assess the nature of the flux excess.
- GCN Circular #14598
Martin Topinka, Lorraine Hanlon, Pete Tisdall, Seamus Meehan, Antonio Mar=
tin-Carrillo (UCD, Dublin) and Petr Kub=C3=A1nek (FZ=C3=9A AV=C4=8CR, Pra=
ha) on behalf of the Watcher telescope team, report:
We followed the Swift detection of GRB 130427A (Maselli et al., GCN 14448=
, Swift trigger 554620) with the Watcher robotic telescope (D=3D40cm) loc=
ated at Boyden Observatory, near Bloemfontein in South Africa.
We started imaging the field at 16:43:55 UT on 2013-04-27 (i.e. 8.9 hr af=
ter the BAT trigger) taking 2 minute exposures in the clear filter using =
an Andor CCD camera.
The optical afterglow (Elenin et al., GCN 14450) is clearly detected. Pre=
liminary analysis of some of the initial images gives a magnitude for the=
optical afterglow of 16.59+/-0.04 @ 17:00:35 UT and 16.79+/-0.07 @ 18:59=
:13 UT.
Magnitudes were estimated using several nearby USNO-B1 stars as reference=
s and are not corrected for galactic dust extinction. Further analysis of=
these images is on-going. The field continues to be regularly observed w=
ith Watcher.
This message is quotable in publications.
- GCN Circular #14605
P. Garnavich (Notre Dame) reports:
A spectrum of the GRB 130427A afterglow was obtained with the
Large Binocular Telescope (LBT+MODS1 instrument) on 2013 May 7.15 (UT),
9.8 days after the burst. The spectrum covers 340 nm to 950 nm and
is dominated by a power-law continuum. Narrow Balmer, [OII], [OIII]
emission lines, and MgII and MgI absorption lines from the host
galaxy are present at a redshift of 0.340.
The LBT spectrum shows no obvious undulations characteristic of a
broad-lined type Ic supernova such as SN 1998bw. In contrast,
a 98bw-like supernova was detectable from GRB 030329 around
seven days after its burst (Stanek et al. 2003, ApJ, 591, L17).
This early detection was primarily due to the prominent peak
seen around 500 nm (rest frame) in broad-lined type Ic events.
Adding a pre-maximum spectrum of SN 1998bw
(Patat et al. 2001, ApJ, 555, 900) to a power-law continuum
suggests that any 98bw-like supernova is at least an R-band
magnitude fainter than the afterglow 10 days after the
GRB 130427A burst.
I thank Rick Pogge, Paul Martini and Scott Adams for help in
obtaining the spectra.
The LBT is an international collaboration among institutions in the
United States, Italy and Germany. LBT Corporation partners are:
The University of Arizona on behalf of the Arizona university system;
Istituto Nazionale di Astrofisica, Italy; LBT Beteiligungsgesellschaft,
Germany, representing the Max-Planck Society, the Astrophysical
Institute Potsdam, and Heidelberg University; The Ohio State University,
and The Research Corporation, on behalf of The University of Notre Dame,
University of Minnesota and University of Virginia.
- GCN Circular #14606
Alan M. Watson (UNAM), Nat Butler (ASU), Alexander Kutyrev (GSFC),
William H. Lee (UNAM), Michael G. Richer (UNAM), Chris Klein (UCB), Ori
Fox (UCB) J. Xavier Prochaska (UCSC), Josh Bloom (UCB), Antonino
Cucchiara (UCSC), Eleonora Troja (GSFC), Owen Littlejohns (ASU), Enrico
Ramirez-Ruiz (UCSC), Jos=E9 A. de Diego (UNAM), Leonid Georgiev (UNAM),
Jes=FAs Gonz=E1lez (UNAM), Carlos Rom=E1n-Z=FA=F1iga (UNAM), Neil Gehrels
(GSFC),
and Harvey Moseley (GSFC) report:
We have been monitoring GRB 130427A with the Reionization and
Transients Infrared Camera (RATIR; www.ratir.org) on the 1.5m Harold
Johnson Telescope at the Observatorio Astron=F3mico Nacional on Sierra San
Pedro M=E1rtir. We have precise and homogeneous photometry for all nights
except 2013 May 6.
During the first night the optical afterglow is well-fitted by a power
law with an index of -1. However, around 1 day after the burst there is
a break, and the power law steepens.
Our photometry in gri from 2 to 11 days is well-fitted by a power law
with an index very close to -1.5 plus a constant contribution with i =
21.23 =B1 0.05, g-i =3D 0.74 =B1 0.12, and r-i =3D 0.05 =B1 0.05, consistent
with the SDSS DR9 photometry of the presumed host galaxy.
We see no evidence for an additional component such as the one mentioned
by Xu et al. (GCN Circular 14597).
Further observations are planned.
We thank the staff of the Observatorio Astron=F3mico Nacional in San Pedro
M=E1rtir.
- GCN Circular #14608
A. Trotter, D. Reichart, J. Haislip, A. LaCluyze, K. McLin, L. Cominsky,
T. Berger, H. T. Cromartie, R. Egger, A. Foster, N. Frank, K. Ivarsen,
M. Maples, J. Moore, M. Nysewander, E. Speckhard, and J. A. Crain report:
Skynet continued observing the Swift/XRT localization of GRB 130427A
(Maselli et al., GCN 14448, Swift trigger #554620) with four 16"
telescopes of the PROMPT array at CTIO, Chile (BVRI bands), and with the
14" GLAST Optical Robotic Telescope (GORT) at the Hume Observatory in
California (RcIc bands). Our observations span 10 nights, from t=0.65 to
10.8 days post-trigger. Skynet has taken 2684 160-second exposures on
the 4 PROMPT telescopes, and 360 160-second exposures on GORT, or a
total of over 135 hours on source. We performed photometry on each
exposure, calibrated to two SDSS stars in the field. We stacked
exposures to improve sensitivity, in groups ranging from 3 exposures on
night 1, to 60 exposures on night 10.
We detect a fading afterglow in BVRI at the position reported by Elenin
et al. (GCN 14450), which is ~50" south of the initial XRT localization.
From night 2 onwards, the light curves fade with an approximate power
law index alpha=-1 (with no corrections for the known host galaxy flux).
We see some evidence for flattening of the I-band light curve beginning
at t~8 days, and of the R-band curve at t~10 days, though it is not
clear whether this is due to host galaxy contamination or to an
intrinsic re-brightening.
A preliminary light curve including all Skynet observations through
t=10.8 days is at:
http://skynet.unc.edu/grb/grb130427a_10.png
See Trotter et al. (GCN 14497, GCN 14510) for descriptions and light
curves of the first and second nights' observations. Further Skynet
observations are ongoing.
- GCN Circular #14615
D. A. Perley and S. Tang (Caltech) report:
On the night of 2013-05-09 UT we observed the location of GRB 130427A
with the Low Resolution Imaging Spectrometer (LRIS) on the Keck I 10m
telescope, during excellent weather conditions (clear skies and 0.7
arcsecond seeing).
In a pair of 90 second g-band images we clearly detect the transient
superimposed on a faint, extended source that we identify as the host
galaxy. While blended with the light of the transient, the diameter of
this extended emission is approximately 3 arcseconds, corresponding to a
physical size of ~14 kpc at a redshift of z=0.34. The magnitude of the
transient at this time (within a 1" aperture centered on the optical
position) is:
g = 21.23 +/- 0.04 mag (t = 12.00 days)
This is consistent (within uncertainties) with the rate of decay seen in
recent P60 observations between 1-8 days post-GRB after subtraction of
the host galaxy.
We also acquired a deep sequence of spectroscopic observations (2000 sec
total integration) with LRIS, covering a wavelength range from
approximately 3250 to 10300 Angstroms. We observe no broad features or
other evidence of contribution of a supernova to the spectrum at this
time, similar to as reported from LBT observations two nights previously
(Garnavich et al., GCN 14605.)
We thank and S. R. Kulkarni and the PTF collaboration for these
observations.
- GCN Circular #14617
K. Wiersema (U. of Leicester), O. Vaduvescu (ING), N. Tanvir (U. of Leicester),
A. Levan (Warwick) and O. Hartoog (U. of Amsterdam) report:
We observed the position of GRB 130427A with the 4.2m William Herschel telescope,
using the PFIP camera, on April 8th, under good seeing conditions (0.7 arcseconds).
Exposures of 4x600 seconds were obtained using a narrowband filter covering
the [O II] emission line doublet (3728 A) at the redshift of the
GRB (z=0.3399; Levan et al., Xu et al. and Flores et al.; GCN 14455, 14478, 14491).
We used this filter to obtain the best visibility of the host galaxy against the bright afterglow
and possible supernova contribution.
The resulting data show a clear detection of the host galaxy. The GRB is located near, but
somewhat offset from, a brighter patch in the host. The host is an irregular galaxy, with
a broadly elliptical shape. The GRB is located North-West of the
majority of extended, smooth, host emission - a convenient choice in spectrograph slit
position angle may minimize host contamination and aid in identification of SN signatures.
The long axis of the host is approximately oriented along 70 degrees position angle (where
North=0, East = 90 degrees), and is approximately 3.4 arcseconds in length.
A jpg finder chart of the [OII] imaging can be found here:
http://www.star.le.ac.uk/~kw113/grb130427A/hostgalaxy_130427a.jpg
- GCN Circular #14631
D. A. Kann, B. Stecklum, and C. Hoegner (TLS Tautenburg) report:
We observed the optical afterglow position (Elenin et al., GCN 14450) of
GRB 130427A (Maselli et al., GCN 14448) with the 1.34m Schmidt telescope
of the Thueringer Landessternwarte Tautenburg equipped with the 2k CCD
camera under good weather conditions. We obtained 3 x 600 sec frames in
the Rc band. The afterglow is detected in each frame.
Using the nearby star given in Rumyantsev et al. (GCN 14582) and also used
in our first epoch observations (Kann et al., GCN 14592), we derive a
preliminary magnitude of Rc = 20.37 +/- 0.07 at 15.54806 days after the
GRB.
This magnitude is only insignificantly fainter than the one we derived in
the first epoch, evidencing a clear flattening (see also Xu et al., GCN
14597). The host galaxy is expected to have about 21st magnitude in Rc
(Vega) following r' = 21.26 from SDSS (see, e.g., Watson et al., GCN
14606). Subtracting this magnitude from our detection yields a magnitude
for the optical transient of ~ 21.2 +/- 0.2. This value agrees well with
an extrapolation of the earlier slope, implying that no further break has
occurred in the optical light curve (in agreement with the X-ray decay,
which shows a very similar slope). This implies either that the post-jet
break decay is among the most shallow known, or that a jet break has still
not occurred, pushing GRB 130427A further into the territory of hyper-
luminous events (Fan et al., arXiv:1305.1261, though see Laskar et al.,
arXiv:1305.2453).
The situation concerning a rising supernova is still unclear. Xu et al.
(GCN 14597) claimed a host-independent flattening and spectral change,
which was afterwards disputed on photometric (Watson et al., GCN 14606;
Perley & Tang, GCN 14615) and spectroscopic (Garnavich, GCN 14605; Perley
& Tang, GCN 14615) grounds. Our measurement offers no solution to this
conundrum, but it is possible that the SN, even if as luminous as SN
1998bw, will peak at a magnitude significantly fainter than the host
galaxy and afterglow (Ruffini et al., GCN 14526), making detection more
difficult than even in the case of GRB 030329/SN 2003dh.
We wish to thank T. Kruehler for discussions relating to the host galaxy.
This message may be cited.
- 1305.2453 from 14 May 13
T. Laskar et al.: A Reverse Shock in GRB 130427A
We present extensive radio and millimeter observations of the unusually bright GRB 130427A at z=0.340, spanning 0.67 to 12 days after the
burst. Taken in conjunction with detailed multi-band UV, optical, NIR, and X-ray observations we find that the broad-band afterglow emission is
composed of distinct reverse shock and forward shock contributions. The reverse shock emission dominates in the radio/millimeter and at <0.1
days in the UV/optical/NIR, while the forward shock emission dominates in the X-rays and at >0.1 days in the UV/optical/NIR. We further find
that the optical and X-ray data require a Wind circumburst environment, pointing to a massive star progenitor. Using the combined forward and
reverse shock emission we find that the parameters of the burst are an isotropic kinetic energy of E_Kiso~2e53 erg, a mass loss rate of
Mdot~3e-8 Msun/yr (for a wind velocity of 1,000 km/s), and a Lorentz factor at the deceleration time of Gamma(200s)~130. Due to the low density
and large isotropic energy, the absence of a jet break to ~15 days places only a weak constraint on the opening angle of theta_j>2.5 deg, and
therefore a total energy of E_gamma+E_K>1.2e51 erg, similar to other GRBs. The reverse shock emission is detectable in this burst due to the
low circumburst density, which leads to a slow cooling shock. We speculate that this is a required property for the detectability of reverse
shocks in the radio and millimeter bands. Following on GRB 130427A as a benchmark event, observations of future GRBs with the exquisite
sensitivity of VLA and ALMA, coupled with detailed modeling of the reverse and forward shock contributions will test this hypothesis.
- 1305.2626 from 14 May 13
Giovanni Amelino-Camelia et al.: Quantum-spacetime scenarios and soft spectral lags of the remarkable GRB130427A
We process the Fermi LAT data on GRB130427A using the Fermi Science Tools, and we summarize some of the key facts that render this observation
truly remarkable, especially concerning the quality of information on high-energy emission by GRBs. We then exploit this richness for a search
of spectral lags, of the type that has been recently of interest for its relevance in quantum-spacetime research. We do find some evidence of
systematic soft spectral lags: when confining the analysis to photons of energies greater than 5 GeV there is an early hard development of
minibursts within this long burst. The effect turns out to be well characterized quantitatively by a linear dependence, within such a
miniburst, of the detection time on energy. With the guidance of our findings for GRB130427A we can then recognize that some support for these
features is noticeable also in earlier Fermi-LAT GRBs, particularly for the presence of hard minibursts whose onset is marked by the
highest-energy photon observed for the GRB. A comparison of these features for GRBs at different redshifts provides some encouragement for a
redshift dependence of the effects of the type expected for a quantum-spacetime interpretation, but other aspects of the analysis appear to
invite the interpretation as intrinsic properties of GRBs.
- GCN Circular #14645
A. Volnova (IKI), I. Korobtsev (ISTP), E. Klunko (ISTP), A. Pozanenko
(IKI) on behalf of larger GRB follow-up collaboration:
We continue observation of the Swift GRB 130427A (Maselli et al., GCN
14448) with AZT-33IK telescope of Sayan observatory (Mondy). The
afterglow (Elenin et al. GCN 14450, Perley GCN 14451) is clearly
detected. The brightness of the afterglow+host is following:
UT start, t-t0 Filter Exp. OT
(mid, days) (s) (mag.)
2013-05-13T15:20:00 16.3346 R 3600 20.66 +/- 0.06
2013-05-14T14:24:35 17.2968 R 3600 20.63 +/- 0.07
The photometry is based on the same star reported by Rumyantsev et al.
(GCN 14582). After subtraction of a suggested brightness (R, Vega)of
the host galaxy (e.g. Watson et al., GCN 14606; Kann et al., GCN 14631)
from our photometric values, our light curve can be approximated (in
general) by a single power law starting at ~ 0.6 days after burst
trigger. Indeed our early observations suggest some flattening between
6.5 - 13 days (Xu et al., GCN 14597; Kann et al., GCN 14631). It could
be due to a SN or due to a wide bump analogous to bumps observed early
in the light curve. However photometry is still preliminary and more
detailed calibration/intercalibration is necessary.
- GCN Circular #14646
A. de Ugarte Postigo (IAA-CSIC, DARK/NBI), D. Xu (DARK/NBI),
G. Leloudas (OKC, Stockholm, DARK/NBI), T. Kruehler,
D. Malesani (DARK/NBI), J. Gorosabel (IAA-CSIC, UPV/EHU),
C.C. Thoene, R. Sanchez-Ramirez (IAA-CSIC), S. Schulze (PUC and MCSS),
J.P.U. Fynbo, J. Hjorth (DARK/NBI), P. Jakobsson (U. Iceland) and
A. Cabrera-Lavers (IAC-ULL) report on behalf of a larger collaboration:
We obtained spectroscopy of the optical counterpart and host galaxy of
GRB 130427A (Maselli et al., GCN 14448; Elenin et al., GCN 14450) with the
10.4m GTC telescope, 16.7 days after the GRB onset. This is 12.5 days in the
host galaxy rest-frame (z = 0.34; Levan et al. GCN 14455, Xu et al. GCN 14478
and Flores et al. GCN 1449). Observations consisted of 4x1200s with the
R500R grism, covering the range between 4800 and 10000 AA with a
resolution of ~600. The slit was oriented to cover both the afterglow and the
host galaxy centre.
The spectrum has a strong contribution from the host galaxy. To overcome this,
we built a synthetic host galaxy spectrum based on the SDSS (DR9) photometry
using LePhare (version 2.2, Arnouts et al. 1999, MNRAS, 310, 540; Ilbert et al.
2006, A&A, 457, 841). We then subtracted this host galaxy template from the
GTC spectrum to obtain a "clean" spectrum of the counterpart associated to GRB
130427A.
The resulting spectrum is that of a broad-lined Ic SN, with a prominent bump at
~6800 A observer frame. In particular, we obtain an excellent match with the
spectrum of SN 2010bh at 12.7 (rest-frame) days after GRB 100316D
(Bufano et al. 2012, ApJ 753, 67).
We stress that this conclusion is independent of the host galaxy model
adopted. By running SNID (Blondin & Tonry 2007, ApJ, 666, 1024) on the
original spectrum (i.e. including host contamination), we still obtain good
matches with a series of broad-lined Type Ic SNe, including SNe 1998bw,
1997ef, 2002ap and 2006aj, albeit at a lower redshift. The fact that SNID
suggests a lower redshift is explained by the fact that SN 2010bh had high
expansion velocities, reaching ~34000 km/s at similar phases (Bufano et al.
2012, ApJ 753, 67), which we suggest is also the case for the SN associated
with GRB 130427A.
A figure of our preliminary analysis can be seen at:
http://www.iaa.es/~deugarte/GRBs/130427A/130427A_GTC.jpg
We acknowledge excellent support from the GTC staff.
- 1305.3217 from 15 May 13
Pak-Hin Thomas Tam et al.: Discovery of an extra hard spectral component in the high-energy afterglow emission of GRB 130427A
The extended high-energy gamma-ray (>100 MeV) emission occurred after the prompt gamma-ray bursts is usually characterized by a single
power-law spectrum, which has been explained as the afterglow synchrotron radiation. The afterglow inverse-Compton emission has long been
predicted to be able to produce a high-energy component as well, but previous observations have not revealed such a signature clearly, probably
due to the small number of >10 GeV photons even for the brightest GRBs known so far. In this Letter, we report on the Fermi Large Area
Telescope (LAT) observations of the >100 MeV emission from the very bright and nearby GRB 130427A. We characterize the time-resolved spectra of
the GeV emission from the GRB onset to the afterglow phase. Based on detection of about a dozen >10 GeV photons from GRB 130427A, we found a
strong evidence of an extra hard spectral component that exists in the extended high-energy emission of this GRB. We argue that this hard
component may arise from the afterglow inverse Compton emission.
- GCN Circular #14662
A. Trotter, D. Reichart, J. Haislip, A. LaCluyze, K. McLin, L. Cominsky,
A. Smith, D. Caton, L. Hawkins, B. Holmes, T. Linder, T. Berger, H. T.
Cromartie, R. Egger, A. Foster, N. Frank, K. Ivarsen, M. Maples, J.
Moore, M. Nysewander, E. Speckhard, and J. A. Crain report:
Skynet has continued observing the Swift/XRT localization of GRB 130427A
(Maselli et al., GCN 14448, Swift trigger #554620) with: four 16"
telescopes of the PROMPT array at CTIO, Chile (BVRI bands); the 14"
GLAST Optical Robotic Telescope (GORT) at the Hume Observatory in
California (RcIc bands); the 14" Deep Sky Observatory (DSO-14) telescope
at Pisgah National Forest, NC; and the 30" telescope at the Astronomical
Research Observatory (ARO-30) in Westfield, IL. Our observations now
span 18 nights, from t=0.65 to 17.6 days post-trigger. Skynet has taken
3420 160-second exposures on the 4 PROMPT telescopes, 420 160-second
exposures on GORT, 91 160s exposures on DSO-14 and 133 60-160s exposures
on ARO-30, or a total of over 178 hours on source. We performed
photometry on each exposure, calibrated to two SDSS stars in the field.
We stacked exposures to improve sensitivity, in groups ranging from 3
exposures on night 1, to 60 exposures on night 18.
In Trotter et al. (GCN 14608) we reported a flattening of the light
curve at t~10 days. That flattening has continued, with possible
chromatic bumps in V, R and I bands at ~14d, 11d and 10d, respectively.
Our most recent observations, at t=17.8d, show a rebrightening in V, R
and I bands; we speculate that this may be the onset of the classical
supernova, which was detected spectroscopically by de Ugarte Postigo et
al. (GCN 14646) at t=16.7 days.
A preliminary light curve including all Skynet observations through
t=17.8 days is at:
http://skynet.unc.edu/grb/grb130427a_17.png
Further observations are scheduled.
- GCN Circular #14666
Alan M. Watson (UNAM), Nat Butler (ASU), Alexander Kutyrev (GSFC),
William H. Lee (UNAM), Michael G. Richer (UNAM), Chris Klein (UCB), Ori
Fox (UCB), J. Xavier Prochaska (UCSC), Josh Bloom (UCB), Antonino
Cucchiara (UCSC), Eleonora Troja (GSFC), Owen Littlejohns (ASU), Enrico
Ramirez-Ruiz (UCSC), Jos=E9 A. de Diego (UNAM), Leonid Georgiev (UNAM),
Jes=FAs Gonz=E1lez (UNAM), Carlos Rom=E1n-Z=FA=F1iga (UNAM), Neil Gehrels=
(GSFC),
and Harvey Moseley (GSFC) report:
We have continued to monitor GRB 130427A with the Reionization and
Transients Infrared Camera (RATIR; www.ratir.org) on the 1.5m Harold
Johnson Telescope at the Observatorio Astron=F3mico Nacional on Sierra Sa=
n
Pedro M=E1rtir, obtaining homogenous photometry in griZYJH. We have
photometry for every night except 2013 May 6. On most nights our
photometric uncertainties in gri are about 2%.
As we reported earlier in Watson et al. (GCN Circular 14606), the
optical afterglow during the first day is well-fitted by a power law
with a temporal index of -1. However, around T+1d there is a break, and
the power law steepens. From T+2.5d to T+14.9d our gri photometry is
well-fitted by a power law with a temporal index close to -1.5 plus a
constant component consistent with the presumed SDSS host galaxy.
However, our observations at T+15.9d, T+16.9d, and T+17.9d are
systematically brighter than this fit. Adding a new component starting
at T+15.5d with zero colors and constant magnitude significantly
improves the fit (with a confidence level of better than 99.5%). The
constant component has
g =3D r =3D i =3D 24.53 =B1 0.25.
We do not mean to suggest that the new component actually has zero color
or constant magnitude. However, at this moment our data cannot usefully
constrain anything other than a characteristic brightness.
Our data, model, and residuals are shown at
https://dl.dropboxusercontent.com/u/528672/GCN/2013-05-16-GRB-130427A.pdf
Assuming a distance modulus of 41.26, the new component corresponds to
an absolute magnitude of -16.7 =B1 0.25. If the new component is a Type 1=
c
supernova, as suggested by de Ugarte Postigo et al. (GCN Circular
14646), we might expect the peak extinction-corrected absolute magnitude =
to be
around -18 (Drout et al. 2011, ApJ, 741, 97). Thus, depending on the
host galaxy extinction, we might be seeing this possible supernova at or =
just
before its peak.
We caution that the new component is currently about 2 magnitudes
fainter than the afterglow component, which at 18.0 days is predicted to
have
i =3D 22.21 =B1 0.04
and even fainter then the galaxy, which is predicted to have
i =3D 21.23 =B1 0.03.
The relative brightnesses of the new component, the fading afterglow,
and the host galaxy also have significant implications for unveiling the
spectrum of the possible supernova.
We further caution that from our data alone we cannot exclude the
possibility that the new component might simply be a significant
flattening of the late afterglow component.
The largest residuals of our observations from the model (with or
without the new component) are at the level of 0.05 magnitudes. We do
not see the large variations reported by Trotter et al. (GCN Circular
14662).
Further observations are planned.
We thank the staff of the Observatorio Astron=F3mico Nacional in San Pedr=
o
M=E1rtir.
- GCN Circular #14669
Vladimir V. Sokolov (SAO-RAS), Alberto J. Castro-Tirado (IAA-CSIC),
Alexander S. Moskvitin, Elena A. Barsukova, Viktoria N. Komarova, Nikolaj
V. Borisov, Azamat F. Valeev, Tatyana N. Sokolova (SAO-RAS) and Vitaly P.
Goranskij (SAI-MSU, SAO-RAS), report:
"We have obtained 3 epochs of spectroscopy for the GRB 130427A optical
afterglow (Maselli et al. GCNC 14448, Elenin et al. GCNC 14450) with the
6-meter BTA equipped with Scorpio. The spectra (with exposure times of
4 x 900 s, 5 x 900 s and 4 x 1200 s) were taken on May 2/3, 5/6 and
10/11 respectively. We used the VPHG 550G grating which covers the
3700-7900 A spectral range and provides a 13 A spectral resolution.
Narrow host galaxy lines such as 3727 A [OII], [OIII] 4959 A, 5007 A and
Balmer lines are noticeable in all spectra. The measured redshift is 0.3393,
in good agreement with the previously reported values (Levan et al. GCNC
14455; Xu et al. GCNC 14478; Flores et al. GCNC 14491; Garnavich GCNC 14605
and Perley & Tang, GCNC 14615). Particularly, we detect marginal excess
emission in the range 6000-7000 A on the later spectrum obtained on May
10/11, which can be interpreted as evidence of the underlying SN (de
Ugarte Postigo et al., GCNC 14646), what is also supported by the
long-term photometric observations (Trotter et al., GCNC 14662; Watson et
al., GCNC 14666).
Our preliminary flux-calibrated spectra can be seen at:
http://www.sao.ru/hq/grb/GRB130427A/GRB130427A_BTA_May2-10.jpg
We thanks S.N. Fabrika, O.P. Zhelenkova, Yu.Yu. Balega, V.V. Vlasyuk and
A.S. Moiseev for their help in obtaining the observations."
- GCN Circular #14672
J. Kelemen (kelemen at konkoly.hu) on behalf of the GRB OT observing program
at the Konkoly Observatory.
Starting on the evening of 15/05/2013 we observed the field of GRB 130427A
(Maselli et al., GCN 14448) 18.5435 days after the burst, using a 60/90/180 cm
Schmidt telescope located at the Mountain Station of the Konkoly
Observatory equipped with an Apogee CCD camera through R filter. On the coadded
R images (total exp.time 1120 sec) we detected the OT and the host galaxy as
well.
Based on the nearby UCAC-4 stars we provide 20.90 +/- 0.05 magnitude in the R
band for the OT. The brightness of the host galaxy was not subtracted.
time from GRB exp filter Mag.
18.5435 1120 s R 20.9 +/-0.05
- GCN Circular #14673
A. Melandri (INAF-OAB), V. D'Elia (ASDC), P. D'Avanzo (INAF-OAB), M.
Della Valle (INAF-OAC), E. Pian (INAF-OAT/SNS), G. Tagliaferri (INAF-
OAB) on behalf of a larger collaboration report:
We have observed the field of GRB 130427A (Maselli et al., GCN 14448)
for 9 epochs from t-t0=6.7 to t-t0=18.8 days after the burst event.
The preliminary light curve in BVR and I bands does not show any
evidence of a bump related to a SN, and it is marginally consistent
with a SN component, which should be at least 2 mag fainter than 98bw
at maximum.
The spectrum (2x1800s) of 13 May, after comparison with SN2010bh
template, is suggestive, in the range 5000A-7500A of broad GRB-SN
features, but altogether, we don't find the good similarity that the
GTC finds (de Ugarte-Postigo et al., CBET 3529). The spectrum of the
transient (after subtraction of a galaxy template) is available at:
http://www.brera.inaf.it/utenti/davanzo/grb/GRB130427A/GRB130427A.png
Observations have been taken in the framework of the ESO-Program
091.D-0291 (PI E. Pian).
- GCN Circular #14686
A.J. Levan (U. Warwick), A.S. Fruchter, J. Graham (STScI), N.R. Tanvir (U. Leicester), Jens Hjorth, Johan Fynbo (Dark Cosmology Centre, Copenhagen), D. Perley (Caltech), S.B. Cenko (U.C. Berkeley), E. Pian (Trieste), Z. Cano (U. Iceland) A. Pe'er (Cork), R. Hounsell (STScI), K. Mishra (ARIES, India), C. Kouveliotou (MSFC) report:
We observed the optical/NIR counterpart of GRB 130427A (Maselli et al. GCN 14448) with the Hubble Space Telescope beginning at 02:23 UT on 20 May 2013. The afterglow is well detected in our multi-band observations in the UV (F336W), optical (F606W) and NIR (F160W) and is offset approximately 0.8" from the optical centroid of its host. The host itself also contains additional star forming complexes including a bright UV source approximately 0.25" from the GRB position.
In the three bands we measure preliminary magnitudes of the afterglow + supernova of
F336W=23.10 +/- 0.02
F606W=21.85 +/- 0.02
F160W=21.34 +/- 0.03
These magnitudes show significant curvature in the optical likely due to the underlying supernova SN 2013cq (de Ugarte Postigo CBET 3529; Xu et al. GCN 14597). If the optical light were entirely dominated by supernova emission the absolute magnitude at z=0.34 would be M_B~ -19.1 at 17 rest-frame days post burst. However, SNe are weaker UV and IR emitters and so under the naive assumption that the UV and IR bands are dominated by power-law afterglow emission with minimal supernova contribution the inferred magnitude of the supernova in the V-band (rest frame B-band) is V~23. This corresponds to an absolute magnitude of M_B ~ -17.9, approximately a magnitude fainter than the B-band peak of SN 1998bw (which occurred at a comparable epoch of 15 days post burst). However, the SN could contribute as much as one half of the flux we are seeing in the NIR and UV and there may be substantial host emission underneath the object in the optical and UV. Thus the SN magnitude shou!
ld be considered very approximate.
Images of the field are posted at
http://www.star.le.ac.uk/~anl/GRB130427A
We thank the staff of STScI for their work in rapidly scheduling these observations.
- 1306.5207 from 24 Jun 13
Ruo-Yu Liu et al.: Interpretation of the unprecedentedly long-lived high-energy emission of GRB 130427A
High energy photons (>100 MeV) are detected by the Fermi/LAT from GRB 130427A up to almost one day after the burst, with an extra hard spectral
component being discovered in the high-energy afterglow. We show that this hard spectral component arises from afterglow synchrotron-self
Compton emission. This scenario can explain the origin of >10 GeV photons detected up to ~30000s after the burst, which would be difficult to
be explained by synchrotron radiation due to the limited maximum synchrotron photon energy. The lower energy multi-wavelength afterglow data
can be fitted simultaneously by the afterglow synchrotron emission. The implication of detecting the SSC emission for the circumburst
environment is discussed.
- 1307.4401 from 18 Jul 13
D. A. Perley et al.: The Afterglow of GRB 130427A from 1 to 10^16 GHz
We present multiwavelength observations of the afterglow of GRB 130427A, the brightest (in total fluence) gamma-ray burst of the past 29 years.
Optical spectroscopy from Gemini-North reveals the redshift of the GRB to be z=0.340, indicating that its unprecedented brightness is primarily
the result of its relatively close proximity to Earth; the intrinsic luminosities of both the GRB and its afterglow are not extreme in
comparison to other bright GRBs. We present a large suite of multiwavelength observations spanning from 300 s to 60 d after the burst and
demonstrate that the afterglow shows relatively simple, smooth evolution at all frequencies with no significant late-time flaring or
rebrightening activity. The entire dataset from 1 GHz to 0.1 TeV can be modeled as synchrotron emission from a combination of reverse and
forward shocks in good agreement with the standard afterglow model, providing strong support to the applicability of the underlying theory and
clarifying the nature of the GeV emission observed to last for minutes to hours following other very bright GRBs. A tenuous, wind-stratified
circumburst density profile is required by the observations, suggesting a massive-star progenitor with a low mass-loss rate, perhaps due to low
metallicity. GRBs similar in nature to GRB 130427A, inhabiting low-density media and exhibiting strong reverse shocks, are probably not
uncommon but may have been difficult to recognize in the past due to their relatively faint late-time radio emission; more such events should
be found in abundance by the new generation of sensitive radio and millimeter instruments.
- 1307.5338 from 23 Jul 13
A.J. Levan et al.: Hubble Space Telescope observations of the afterglow, supernova and host galaxy associated with the extremely bright GRB 130427A
We present Hubble Space Telescope observations of the exceptionally bright and luminous Swift gamma-ray burst, GRB 130427A. At z=0.34 this
burst affords an excellent opportunity to study the supernova associated with an intrinsically extremely luminous burst (E_iso >10^54 erg),
much more luminous than almost all previous GRBs with spectroscopically associated supernovae. We use the combination of the image quality and
UV capability of HST to provide the best possible separation of the afterglow, host and supernova contributions to the observed light ~17
rest-frame days after the burst. We find that the burst originated ~4 kpc from the nucleus of a moderately star forming (1 Msol/yr), possibly
interacting disc galaxy. ACS grism observations show that the associated supernova, SN 2013cq, is well fit in the red by an SN 1998bw-like
supernovae of similar luminosity and velocity (v~15,000 km/s). The positions of the bluer features are better matched by the higher velocity SN
2010bh (v~30,000 km/s), but this SN fails to reproduce the overall spectral shape, perhaps indicative of velocity structure in the ejecta. The
similarity of supernovae from both the most luminous and least luminous GRBs suggests broadly similar progenitor stars can create GRBs across
six orders of magnitude in isotropic energy.
- 1311.5245 from 22 Nov 13
C. Kouveliotou et al.: NuSTAR Observations of GRB130427A establish a single component synchrotron afterglow origin for the late optical to multi-GeV emission
C. D. Dermer, N. Gehrels, C. J. Hailey, F. A. Harrison, A. Melandri, J. E. McEnery, C. G. Mundell, D. K. Stern, G. Tagliaferri, W. W. Zhang
GRB 130427A occurred in a relatively nearby galaxy; its prompt emission had the largest GRB fluence ever recorded. The afterglow of GRB 130427A
was bright enough for the Nuclear Spectroscopic Telescope ARray (NuSTAR) to observe it in the 3-79 keV energy range long after its prompt
emission (~1.5 and 5 days). This range, where afterglow observations were previously not possible, bridges an important spectral gap. Combined
with Swift, Fermi and ground-based optical data, NuSTAR observations unambiguously establish a single afterglow spectral component from optical
to multi-GeV energies a day after the event, which is almost certainly synchrotron radiation. Such an origin of the late-time Fermi/LAT > 10
GeV photons requires revisions in our understanding of collisionless relativistic shock physics.
- 1311.5254 from 22 Nov 13
A. Maselli et al.: GRB 130427A: a Nearby Ordinary Monster
Cummings (7), G. Cusumano (1), P. A. Evans (8), G. Ghirlanda (2), G. Ghisellini (2), C. Guidorzi (9), S. Kobayashi (4), P. Kuin (10), V. La
Parola (1), V. Mangano (1 and 11), S. Oates (10), T. Sakamoto (12), M. Serino (6), F. Virgili (4), B. -B. Zhang (11), S. Barthelmy (13), A.
Beardmore (8), M. G. Bernardini (2), D. Bersier (4), D. Burrows (11), G. Calderone (2 and 14), M. Capalbi (1), J. Chiang (15), P. D'Avanzo (2),
V. D'Elia (16 and 17), M. De Pasquale (10), D. Fugazza (2), N. Gehrels (13), A. Gomboc (18 and 19), R. Harrison (4), H. Hanayama (20), J.
not shown)
Long-duration Gamma-Ray Bursts (GRBs) are an extremely rare outcome of the collapse of massive stars, and are typically found in the distant
Universe. Because of its intrinsic luminosity ($L\sim 3 \times 10^{53}$ erg s$^{-1}$) and its relative proximity ($z=0.34$), GRB 130427A was a
unique event that reached the highest fluence observed in the gamma-ray band. Here we present a comprehensive multiwavelength view of GRB
130427A with Swift, the 2-m Liverpool and Faulkes telescopes and by other ground-based facilities, highlighting the evolution of the burst
emission from the prompt to the afterglow phase. The properties of GRB 130427A are similar to those of the most luminous, high-redshift GRBs,
suggesting that a common central engine is responsible for producing GRBs in both the contemporary and the early Universe and over the full
range of GRB isotropic energies.
- 1311.5489 from 22 Nov 13
W. T. Vestrand et al.: The Bright Optical flash and Afterglow from the Gamma-Ray Burst GRB 130427A
Rosing
The optical light that is generated simultaneously with the x-rays and gamma-rays during a gamma-ray burst (GRB) provides clues about the
nature of the explosions that occur as massive stars collapse to form black holes. We report on the bright optical flash and fading afterglow
from the powerful burst GRB 130427A and present a comparison with the properties of the gamma-ray emission that show correlation of the optical
and >100 MeV photon flux light curves during the first 7,000 seconds. We attribute this correlation to co-generation in an external shock. The
simultaneous, multi-color, optical observations are best explained at early times by reverse shock emission generated in the relativistic burst
ejecta as it collides with surrounding material and at late times by a forward shock traversing the circumburst environment. The link between
optical afterglow and >100 MeV emission suggests that nearby early peaked afterglows will be the best candidates for studying GRB emission at
GeV/TeV energies.
- 1311.5581 from 25 Nov 13
R. Preece et al.: The First Pulse of the Extremely Bright GRB 130427A: A Test Lab for Synchrotron Shocks
Connaughton, A. Diekmann, G. Fitzpatrick, S. Foley, M. Gibby, M. Giles, A. Goldstein, J. Greiner, D. Gruber, P. Jenke, R. M. Kippen, C.
Kouveliotou, S. McBreen, C. Meegan, W. S. Paciesas, V. Pelassa, D. Tierney, A. J. van der Horst, C. Wilson-Hodge, S. Xiong, G. Younes, H.-F.
Yu, M. Ackermann, M. Ajello, M. Axelsson, L. Baldini, G. Barbiellini, M. G. Baring, D. Bastieri, R. Bellazzini, E. Bissaldi, E. Bonamente, J.
Bregeon, M. Brigida, P. Bruel, R. Buehler, S. Buson, G. A. Caliandro, R. A. Cameron, P. A. Caraveo, C. Cecchi, E. Charles, A. Chekhtman, J.
not shown)
Gamma-ray burst (GRB) 130427A is one of the most energetic GRBs ever observed. The initial pulse up to 2.5 s is possibly the brightest
well-isolated pulse observed to date. A fine time resolution spectral analysis shows power-law decays of the peak energy from the onset of the
pulse, consistent with models of internal synchrotron shock pulses. However, a strongly correlated power-law behavior is observed between the
luminosity and the spectral peak energy that is inconsistent with curvature effects arising in the relativistic outflow. It is difficult for
any of the existing models to account for all of the observed spectral and temporal behaviors simultaneously.
- 1311.5623 from 25 Nov 13
Sylvia Zhu et al.: Fermi-LAT Observations of the Gamma-ray Burst GRB 130427A
The observations of the exceptionally bright gamma-ray burst (GRB) 130427A by the Large Area Telescope aboard the Fermi Gamma-ray Space
Telescope provide constraints on the nature of such unique astrophysical sources. GRB 130427A had the largest fluence, highest-energy photon
(95 GeV), longest $\gamma$-ray duration (20 hours), and one of the largest isotropic energy releases ever observed from a GRB. Temporal and
spectral analyses of GRB 130427A challenge the widely accepted model that the non-thermal high-energy emission in the afterglow phase of GRBs
is synchrotron emission radiated by electrons accelerated at an external shock.
- 1311.5867 from 25 Nov 13
A. Panaitescu et al.: An external-shock model for GRB afterglow 130427A
The complex multiwavelength emission of GRB afterglow 130427A (monitored in the radio up to 10 days, in the optical and X-ray until 50 days,
and at GeV energies until 1 day) can be accounted for by a hybrid reverse-forward shock synchrotron model, with inverse-Compton emerging only
above a few GeV. The high ratio of the early optical to late radio flux requires that the ambient medium is a wind and that the forward-shock
synchrotron spectrum peaks in the optical at about 10 ks. The latter has two consequences: the wind must be very tenuous and the optical
emission before 10 ks must arise from the reverse-shock, as suggested also by the bright optical flash that Raptor has monitored during the
prompt emission phase (<100 s). The VLA radio emission is from the reverse-shock, the Swift X-ray emission is mostly from the forward-shock,
but the both shocks give comparable contributions to the Fermi GeV emission. The weak wind implies a large blast-wave radius (8 t_{day}^{1/2}
pc), which requires a very tenuous circumstellar medium, suggesting that the massive stellar progenitor of GRB 130427A resided in a
super-bubble.
- 1401.1733 from 9 Jan 14
Pak-Hin Thomas Tam: The Very Bright and Nearby GRB 130427A: The Extra Hard Spectral Component and Implications for Very High-energy Gamma-ray Observations
of Gamma-ray Bursts
The extended high-energy gamma-ray (>100 MeV) emission occurring after the prompt gamma-ray bursts (GRBs) is usually characterized by a single
power-law spectrum, which has been explained as the afterglow synchrotron radiation. We report on the Fermi Large Area Telescope (LAT)
observations of the >100 MeV emission from the very bright and nearby GRB 130427A, up to ~100 GeV. By performing time-resolved spectral fits of
GRB 130427A, we found a strong evidence of an extra hard spectral component above a few GeV that exists in the extended high-energy emission of
this GRB. This extra spectral component may represent the first clear evidence of the long sought-after afterglow inverse Compton emission.
Prospects for observations at the very high-energy gamma-rays, i.e., above 100 GeV, are described.
- 1402.2595 from 12 Feb 14
Indrek Vurm et al.: Pair-dominated GeV-optical flash in GRB 130427A
We show that the light curve of the double GeV+optical flash in GRB 130427A is consistent with radiation from the blast wave in a wind-type
medium with density parameter $A=\rho r^2\sim 5\times 10^{10}$ g cm$^{-1}$. The peak of the flash is emitted by copious $e^\pm$ pairs created
and heated in the blast wave; our first-principle calculation determines the pair-loading factor and temperature of the shocked plasma. Using
detailed radiative transfer simulations we reconstruct the observed double flash. The optical flash is dominated by synchrotron emission from
the thermal plasma behind the forward shock, and the GeV flash is produced via inverse Compton (IC) scattering by the same plasma. The seed
photons for IC scattering are dominated by the prompt MeV radiation during the first tens of seconds, and by the optical to X-ray afterglow
thereafter. IC cooling of the thermal plasma behind the forward shock reproduces all GeV data from a few seconds to $\sim 1$ day. We find that
the blast-wave Lorentz factor at the peak of the flash is $\Gamma\approx 200$, and the forward shock magnetization is $\epsilon_B\sim 3\times
10^{-4}$. An additional source is required by the data in the optical and X-ray bands at times $>10^2$ s; we speculate that this additional
source may be a long-lived reverse shock in the explosion ejecta.
- 1403.2217 from 11 Mar 14
G. E. Anderson et al.: Probing the Bright Radio Flare and Afterglow of GRB 130427A with the Arcminute Microkelvin Imager
We present one of the best sampled early time light curves of a gamma-ray burst (GRB) at radio wavelengths. Using the Arcminute Mircrokelvin
Imager (AMI) we observed GRB 130427A at the central frequency of 15.7 GHz between 0.36 and 59.32 days post-burst. These results yield one of
the earliest radio detections of a GRB and demonstrate a clear rise in flux less than one day after the gamma-ray trigger followed by a rapid
decline. This early time radio emission probably originates in the GRB reverse shock so our AMI light curve reveals the first ever confirmed
detection of a reverse shock peak in the radio domain. At later times (about 3.2 days post-burst) the rate of decline decreases, indicating
that the forward shock component has begun to dominate the light-curve. Comparisons of the AMI light curve with modelling conducted by Perley
et al. show that the most likely explanation of the early time 15.7 GHz peak is caused by the self-absorption turn-over frequency, rather than
the peak frequency, of the reverse shock moving through the observing bands.
- 1405.5723 from
R. Ruffini et al.: GRB 130427A and SN 2013cq: A Multi-wavelength Analysis of An Induced Gravitational Collapse Event
GRB 130427A, one of the most energetic gamma-ray bursts (GRBs) ever observed, has the largest \u03b3-ray fluence and the longest lasting simultaneous optical, X-ray, \u03b3-ray and GeV observations in the past 40 years. We apply to GRB 130427A the induced gravitational collapse (IGC) paradigm for GRBs associated to supernovae (SNe). On May 2, 2013, we predicted (GCN 14526) the forthcoming emergence of a supernova associated with GRB 130427A on the ground of a first look at Episode 3. Later, SN 2013cq was successfully detected on May 13. Here, we use the simultaneous observations by Swift, NuStar and Fermi satellites to probe our IGC paradigm in the "terra incognita" of this most energetic GRB. First, we verified that GRB 130427A is indeed an IGC event by identifying the expected scaling laws and power-law behavior of Episode 3 X-ray (0.3-10~keV) emission. Then, we turn to the optical, \u03b3-ray and high energy light curves finding, unexpectedly, a power-law behavior similar to the soft X-ray one. Also Episode 3 spectrum, stretching 10 orders of magnitude from optical to GeV, is consistent with a power-law. It is clear that all these features in Episode 3 of the IGC system point to a common phenomena carried by the supernova ejecta or in accretion processes onto the newly born black hole. These results extend the predicting power of the IGC paradigm to the strongest energy sources (Eiso\u22431054~ergs) and offer new challenges and opportunities for the theoretical understanding of GRBs and SNe.
- 1410.1536 from 8 Oct 14
A. U. Abeysekara et al.: Search for gamma-rays from the unusually bright GRB 130427A with the HAWC Gamma-ray Observatory
The long gamma-ray burst (GRB) 130427A was the most powerful burst ever detected with a redshift $z\lesssim0.5$, featuring the highest energy
photon so far detected from a GRB and the longest lasting emission above 100 MeV. The HAWC Gamma-ray Observatory is a new extensive air shower
detector currently under construction in central Mexico. It features two data acquisition (DAQ) systems - one designed to readout full
air-shower events (main DAQ) and the other one counting the signals in each photomultiplier tube (scaler DAQ). The burst occurred at a zenith
angle of $57^\circ$, when HAWC was running 10% of the final detector and collecting data with the scaler DAQ only. Based on the observed light
curve at MeV-GeV energies, 8 different time periods have been searched for prompt and delayed emission from this GRB. In all cases, no
statistically significant excess of counts has been found and upper limits have been placed. It is shown that a similar GRB close to zenith
would be easily detected by the full HAWC detector, which will be completed soon. A detection could provide evidence for a synchrotron
energy range could be the signature of gamma-ray absorption, either in the GRB or along the line of sight due to the extragalactic background
light.
- 1410.5367 from 21 Oct 14
E. Aliu et al.: Constraints on Very High Energy Emission from GRB 130427A
Cerruti, X. Chen, L. Ciupik, V. Connaughton, W. Cui, H. J. Dickinson, J. D. Eisch, M. Errando, A. Falcone, S. Federici, Q. Feng, J. P. Finley,
H. Fleischhack, P. Fortin, L. Fortson, A. Furniss, N. Galante, G. H. Gillanders, S. Griffin, S. T. Griffiths, J. Grube, G. Gyuk, N. Håkansson,
D. Hanna, J. Holder, G. Hughes, T. B. Humensky, C. A. Johnson, P. Kaaret, P. Kar, M. Kertzman, Y. Khassen, D. Kieda, H. Krawczynski, F.
Krennrich, M. J. Lang, A. S. Madhavan, G. Maier, S. McArthur, A. McCann, K. Meagher, J. Millis, P. Moriarty, R. Mukherjee, D. Nieto, A.
Prompt emission from the very fluent and nearby (z=0.34) gamma-ray burst GRB 130427A was detected by several orbiting telescopes and by
ground-based, wide-field-of-view optical transient monitors. Apart from the intensity and proximity of this GRB, it is exceptional due to the
extremely long-lived high-energy (100 MeV to 100 GeV) gamma-ray emission, which was detected by the Large Area Telescope on the Fermi Gamma-ray
Space Telescope for ~70 ks after the initial burst. The persistent, hard-spectrum, high-energy emission suggests that the highest-energy gamma
rays may have been produced via synchrotron self-Compton processes though there is also evidence that the high-energy emission may instead be
an extension of the synchrotron spectrum. VERITAS, a ground-based imaging atmospheric Cherenkov telescope array, began follow-up observations
of GRB 130427A ~71 ks (~20 hr) after the onset of the burst. The GRB was not detected with VERITAS; however, the high elevation of the
observations, coupled with the low redshift of the GRB, make VERITAS a very sensitive probe of the emission from GRB 130427A for E > 100 GeV.
The non-detection and consequent upper limit derived place constraints on the synchrotron self-Compton model of high-energy gamma-ray emission
from this burst.
- 1504.06369 from 27 Apr 15
Romain Hascoët et al.: Measuring Ambient Densities and Lorentz Factors of Gamma-Ray Bursts from GeV and Optical Observations
Fermi satellite discovered that cosmological gamma-ray bursts (GRBs) are accompanied by long GeV flashes. In two GRBs, an optical counterpart
of the GeV flash has been detected. Recent work suggests that the GeV+optical flash is emitted by the external blast wave from the explosion in
a medium loaded with copious $e^\pm$ pairs. The full light curve of the flash is predicted by a first-principle radiative transfer simulation
and can be tested against observations. Here we examine a sample of 7 bursts with best GeV+optical data and test the model. We find that the
observed light curves are in agreement with the theoretical predictions and allow us to measure three parameters for each burst: the Lorentz
factor of the explosion, its isotropic kinetic energy, and the external density. With one possible exception of GRB 090510 (which is the only
short burst in the sample) the ambient medium is consistent with a wind from a Wolf-Rayet progenitor. The wind density parameter $A=\rho r^2$
varies in the sample around $10^{11}$g/cm. The initial Lorentz factor of the blast wave varies from 200 to 540 and correlates with the burst
luminosity. Radiative efficiency of the prompt emission in the sample is between 0.1 and 0.8. For the two bursts with detected optical flash,
GRB 120711A and GRB 130427A, we also estimate the magnetization of the external blast wave. Remarkably, the model reproduces the entire optical
light curve of GRB 120711A (with its sharp peak, fast decay, plateau, and break) as well as the GeV data. The spectrum of GeV flashes is
predicted to extend above 0.1 TeV, where they can be detected by ground-based Cherenkov telescopes.
- 1512.02434 from 9 Dec 15
Jagdish C. Joshi et al.: Photodisintegrated gamma rays and neutrinos from heavy nuclei in the gamma-ray burst jet of GRB 130427A
Detection of $\sim$ 0.1-70 GeV prompt $\gamma$-ray emission from the exceptionally bright gamma-ray burst (GRB) 130427A by the ${\it
Fermi}$-Large Area Telescope provides an opportunity to explore the physical processes of GeV $\gamma$-ray emission from the GRB jets. In this
work we discuss interactions of Iron and Oxygen nuclei with observed keV-MeV photons in the jet of GRB 130427A in order to explain an
additional, hard spectral component observed during 11.5-33 second after trigger. The photodisintegration time scale for Iron nuclei is
comparable to or shorter than this duration. We find that $\gamma$ rays resulting from the Iron nuclei disintegration can account for the hard
power-law component of the spectra in the $\sim$ 1-70 GeV range, before the $\gamma\gamma \to e^\pm$ pair production with low-energy photons
severely attenuates emission of higher energy photons. Electron antineutrinos from the secondary neutron decay, on the other hand, can be
emitted with energies up to $\sim$ 2 TeV. The flux of these neutrinos is low and consistent with non-detection of GRB~130427A by the IceCube
Neutrino Observatory. The required total energy in the Iron nuclei for this hadronic model for GeV emission is $\lesssim 10$ times the observed
total energy released in the prompt keV-MeV emission.
- 1601.01264 from 7 Jan 16
Nissim Fraija et al.: Modeling the early multiwavelength emission in GRB130427A
One of the most powerful gamma-ray bursts, GRB 130427A was swiftly detected from GeV $\gamma$-rays to optical wavelengths. In the GeV band, the
Large Area Telescope (LAT) on board the Fermi Gamma-Ray Space Telescope observed the highest-energy photon ever recorded of 95 GeV, and a
bright peak in the early phase followed by emission temporally extended for more than 20 hours. In the optical band, a bright flash with a
magnitude of $7.03\pm 0.03$ in the time interval from 9.31 s to 19.31 s after the trigger was reported by RAPTOR in r-band. We study the origin
of the GeV $\gamma$-ray emission, using the multiwavelength observation detected in X-ray and optical bands. The origin of the temporally
extended LAT, X-ray and optical flux is naturally interpreted as synchrotron radiation and the 95-GeV photon and the integral flux upper limits
placed by the HAWC observatory are consistent with synchrotron self-Compton from an adiabatic forward shock propagating into the stellar wind
of its progenitor. The extreme LAT peak and the bright optical flash are explained through synchrotron self-Compton and synchrotron emission
from the reverse shock, respectively, when the ejecta evolves in thick-shell regime and carries a significant magnetic field.
- 1602.04158 from 15 Feb 16
M. De Pasquale et al.: The 80 Ms follow-up of the X-ray afterglow of GRB 130427A challenges the standard forward shock model
GRB 130427A was the brightest gamma-ray burst detected in the last 30 years. With an equivalent isotropic energy output of $8.5\times10^{53}$
erg and redshift $z=0.34$, it uniquely combined very high energetics with a relative proximity to Earth. As a consequence, its X-ray afterglow
has been detected by sensitive X-ray observatories such as XMM-Newton and Chandra for a record-breaking baseline longer than 80 million
seconds. We present the X-ray light-curve of this event over such an interval. The light-curve shows a simple power-law decay with a slope
$\alpha = 1.309 \pm 0.007$ over more than three decades in time (47 ks - 83 Ms). We discuss the consequences of this result for a few models
proposed so far to interpret GRB 130427A, and more in general the significance of this outcome in the context of the standard forward shock
model. We find that this model has difficulty in explaining our data, in both cases of constant density and stellar-wind circumburst media, and
requires far-fetched values for the physical parameters involved.
- 1603.06537 from 22 Mar 16
Shlomo Dado et al.: Critical Test Of Gamma Ray Burst Theories
Long and precise follow-up measurements of the X-ray afterglow (AG) of very intense gamma ray bursts (GRBs) provide a critical test of GRB
afterglow theories. Here we show that the power-law decline with time of X-ray AG of GRB 130427A, the longest measured X-ray AG of an intense
GRB with the Swift, Chandra and XMM Newton satellites, and of all other well measured late-time X-ray afterglow of intense GRBs, is that
predicted by the cannonball (CB) model of GRBs from their measured spectral index, while it disagrees with that predicted by the widely
accepted fireball (FB) models of GRBs.
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