- GCN/BACODINE POSITION NOTICE
TITLE: GCN/SWIFT NOTICE
NOTICE_DATE: Wed 24 Oct 12 02:56:47 UT
NOTICE_TYPE: Swift-BAT GRB Position
TRIGGER_NUM: 536580, Seg_Num: 0
GRB_RA: 70.467d {+04h 41m 52s} (J2000),
70.617d {+04h 42m 28s} (current),
69.884d {+04h 39m 32s} (1950)
GRB_DEC: -12.269d {-12d 16' 06"} (J2000),
-12.245d {-12d 14' 41"} (current),
-12.363d {-12d 21' 46"} (1950)
GRB_ERROR: 3.00 [arcmin radius, statistical only]
GRB_INTEN: 6161 [cnts] Image_Peak=248 [image_cnts]
TRIGGER_DUR: 1.408 [sec]
TRIGGER_INDEX: 472 E_range: 25-100 keV
BKG_INTEN: 52617 [cnts]
BKG_TIME: 10550.20 SOD {02:55:50.20} UT
BKG_DUR: 16 [sec]
GRB_DATE: 16224 TJD; 298 DOY; 12/10/24
GRB_TIME: 10572.47 SOD {02:56:12.47} UT
GRB_PHI: 112.33 [deg]
GRB_THETA: 25.90 [deg]
SOLN_STATUS: 0x3
RATE_SIGNIF: 21.93 [sigma]
IMAGE_SIGNIF: 9.16 [sigma]
MERIT_PARAMS: +1 +0 +0 +0 +2 +0 +0 +0 +67 +0
SUN_POSTN: 208.97d {+13h 55m 52s} -11.86d {-11d 51' 23"}
SUN_DIST: 132.15 [deg] Sun_angle= 9.2 [hr] (West of Sun)
MOON_POSTN: 326.16d {+21h 44m 38s} -7.97d {-07d 58' 28"}
MOON_DIST: 102.25 [deg]
MOON_ILLUM: 71 [%]
GAL_COORDS: 209.49,-34.25 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS: 66.75,-34.14 [deg] ecliptic lon,lat of the burst (or transient)
COMMENTS: SWIFT-BAT GRB Coordinates.
COMMENTS: This is a rate 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 = 29.11,16.49 [deg].
- red DSS finding chart
ps-file
- GCN NOTICE
TITLE: GCN/SWIFT NOTICE
NOTICE_DATE: Wed 24 Oct 12 02:58:20 UT
NOTICE_TYPE: Swift-XRT Position
TRIGGER_NUM: 536580, Seg_Num: 0
GRB_RA: 70.4715d {+04h 41m 53.16s} (J2000),
70.6210d {+04h 42m 29.04s} (current),
69.8883d {+04h 39m 33.18s} (1950)
GRB_DEC: -12.2904d {-12d 17' 25.4"} (J2000),
-12.2666d {-12d 15' 59.9"} (current),
-12.3848d {-12d 23' 05.2"} (1950)
GRB_ERROR: 5.5 [arcsec radius, statistical plus systematic, 90% containment]
GRB_INTEN: 1.10e-09 [erg/cm2/sec]
GRB_SIGNIF: 6.92 [sigma]
IMG_START_DATE: 16224 TJD; 298 DOY; 12/10/24
IMG_START_TIME: 10665.50 SOD {02:57:45.50} UT, 93.0 [sec] since BAT Trigger Time
TAM[0-3]: 327.63 237.26 261.51 243.75
AMPLIFIER: 2
WAVEFORM: 134
SUN_POSTN: 208.97d {+13h 55m 52s} -11.86d {-11d 51' 25"}
SUN_DIST: 132.14 [deg] Sun_angle= 9.2 [hr] (West of Sun)
MOON_POSTN: 326.17d {+21h 44m 41s} -7.97d {-07d 58' 11"}
MOON_DIST: 102.24 [deg]
MOON_ILLUM: 71 [%]
GAL_COORDS: 209.52,-34.25 [deg] galactic lon,lat of the burst
ECL_COORDS: 66.75,-34.17 [deg] ecliptic lon,lat of the burst
COMMENTS: SWIFT-XRT Coordinates.
COMMENTS: The XRT position is 1.33 arcmin from the BAT position.
- GCN NOTICE
TITLE: GCN/SWIFT NOTICE
NOTICE_DATE: Wed 24 Oct 12 02:58:31 UT
NOTICE_TYPE: Swift-XRT Image
TRIGGER_NUM: 536580, Seg_Num: 0
GRB_RA: 70.4715d {+04h 41m 53.1s} (J2000),
70.6210d {+04h 42m 29.0s} (current),
69.8883d {+04h 39m 33.1s} (1950)
GRB_DEC: -12.2904d {-12d 17' 25.4"} (J2000),
-12.2666d {-12d 15' 59.9"} (current),
-12.3848d {-12d 23' 05.2"} (1950)
GRB_ERROR: 5.4 [arcsec, radius, statistical plus systematic]
GRB_INTEN: 48 [cnts]
IMG_START_DATE: 16224 TJD; 298 DOY; 12/10/24
IMG_START_TIME: 10665.50 SOD {02:57:45.50} UT, 93.0 [sec] since BAT Trigger Time
CENTROID_X: 313.93, raw= 314 [pixels]
CENTROID_Y: 277.30, raw= 277 [pixels]
ROLL: 118.79 [deg]
GAIN: 1
MODE: 3, Long Image mode
WAVEFORM: 134
EXPO_TIME: 2.50 [sec]
GRB_POS_XRT_Y: -48.77
GRB_POS_XRT_Z: 24.12
IMAGE_URL: sw00536580000msxps_rw.img
SUN_POSTN: 208.97d {+13h 55m 52s} -11.86d {-11d 51' 25"}
SUN_DIST: 132.14 [deg] Sun_angle= 9.2 [hr] (West of Sun)
MOON_POSTN: 326.17d {+21h 44m 42s} -7.97d {-07d 58' 09"}
MOON_DIST: 102.24 [deg]
MOON_ILLUM: 71 [%]
GAL_COORDS: 209.52,-34.25 [deg] galactic lon,lat of the burst
ECL_COORDS: 66.75,-34.17 [deg] ecliptic lon,lat of the burst
COMMENTS: SWIFT-XRT Image.
- GCN NOTICE
TITLE: GCN/SWIFT NOTICE
NOTICE_DATE: Wed 24 Oct 12 02:58:37 UT
NOTICE_TYPE: Swift-XRT Processed Image
TRIGGER_NUM: 536580, Seg_Num: 0
GRB_RA: 70.4715d {+04h 41m 53.1s} (J2000),
70.6210d {+04h 42m 29.0s} (current),
69.8883d {+04h 39m 33.1s} (1950)
GRB_DEC: -12.2904d {-12d 17' 25.4"} (J2000),
-12.2666d {-12d 15' 59.9"} (current),
-12.3848d {-12d 23' 05.2"} (1950)
GRB_ERROR: 5.4 [arcsec, radius, statistical plus systematic]
GRB_INTEN: 48 [cnts]
IMG_START_DATE: 16224 TJD; 298 DOY; 12/10/24
IMG_START_TIME: 10665.50 SOD {02:57:45.50} UT, 93.0 [sec] since BAT Trigger Time
CENTROID_X: 313.93, raw= 314 [pixels]
CENTROID_Y: 277.30, raw= 277 [pixels]
ROLL: 118.79 [deg]
GAIN: 1
MODE: 3, Long Image mode
WAVEFORM: 134
EXPO_TIME: 2.50 [sec]
GRB_POS_XRT_Y: -48.77
GRB_POS_XRT_Z: 24.12
IMAGE_URL: sw00536580000msxps_rw.img
SUN_POSTN: 208.97d {+13h 55m 52s} -11.86d {-11d 51' 25"}
SUN_DIST: 132.14 [deg] Sun_angle= 9.2 [hr] (West of Sun)
MOON_POSTN: 326.18d {+21h 44m 42s} -7.97d {-07d 58' 08"}
MOON_DIST: 102.24 [deg]
MOON_ILLUM: 71 [%]
GAL_COORDS: 209.52,-34.25 [deg] galactic lon,lat of the burst
ECL_COORDS: 66.75,-34.17 [deg] ecliptic lon,lat of the burst
COMMENTS: SWIFT-XRT Processed Image.
- GCN NOTICE
TITLE: GCN/SWIFT NOTICE
NOTICE_DATE: Wed 24 Oct 12 03:00:11 UT
NOTICE_TYPE: Swift-BAT GRB Lightcurve
TRIGGER_NUM: 536580, Seg_Num: 0
GRB_RA: 70.467d {+04h 41m 52s} (J2000),
70.617d {+04h 42m 28s} (current),
69.884d {+04h 39m 32s} (1950)
GRB_DEC: -12.269d {-12d 16' 06"} (J2000),
-12.245d {-12d 14' 41"} (current),
-12.363d {-12d 21' 46"} (1950)
GRB_DATE: 16224 TJD; 298 DOY; 12/10/24
GRB_TIME: 10572.47 SOD {02:56:12.47} UT
TRIGGER_INDEX: 472
GRB_PHI: 112.33 [deg]
GRB_THETA: 25.90 [deg]
DELTA_TIME: 12.00 [sec]
TRIGGER_DUR: 1.408 [sec]
SOLN_STATUS: 0x3
RATE_SIGNIF: 21.93 [sigma]
IMAGE_SIGNIF: 9.16 [sigma]
LC_URL: sw00536580000msb.lc
SUN_POSTN: 208.97d {+13h 55m 52s} -11.86d {-11d 51' 26"}
SUN_DIST: 132.15 [deg] Sun_angle= 9.2 [hr] (West of Sun)
MOON_POSTN: 326.19d {+21h 44m 45s} -7.96d {-07d 57' 51"}
MOON_DIST: 102.23 [deg]
MOON_ILLUM: 71 [%]
GAL_COORDS: 209.49,-34.25 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS: 66.75,-34.14 [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 a rate 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 = 29.11,16.49 [deg].
- GCN NOTICE
TITLE: GCN/SWIFT NOTICE
NOTICE_DATE: Wed 24 Oct 12 03:06:25 UT
NOTICE_TYPE: Swift-UVOT Source List
TRIGGER_NUM: 536580, Seg_Num: 0
POINT_RA: 70.484d {+04h 41m 56s} (J2000)
POINT_DEC: -12.284d {-12d 17' 00"} (J2000)
POINT_ROLL: 118.792d
IMG_START_DATE: 16224 TJD; 298 DOY; 12/10/24
IMG_START_TIME: 10730.50 SOD {02:58:50.50} UT, 158.0 [sec] since BAT Trigger Time
FILTER: 7, U
BKG_MEAN: 0.333
N_STARS: 88
X_OFFSET: 0 [pixels]
Y_OFFSET: 0 [pixels]
X_MAX: 2047 [pixels]
Y_MAX: 2047 [pixels]
DET_THRESH: 6
PHOTO_THRESH: 2
SL_URL: sw00536580000msufc0158.fits
SUN_POSTN: 208.97d {+13h 55m 53s} -11.86d {-11d 51' 32"}
SUN_DIST: 132.13 [deg] Sun_angle= 9.2 [hr] (West of Sun)
MOON_POSTN: 326.24d {+21h 44m 58s} -7.95d {-07d 56' 43"}
MOON_DIST: 102.19 [deg]
MOON_ILLUM: 71 [%]
GAL_COORDS: 209.52,-34.24 [deg] galactic lon,lat of the pointing direction
ECL_COORDS: 66.77,-34.16 [deg] ecliptic lon,lat of the pointing direction
COMMENTS: SWIFT-UVOT Source List.
- GCN NOTICE
TITLE: GCN/SWIFT NOTICE
NOTICE_DATE: Wed 24 Oct 12 03:06:59 UT
NOTICE_TYPE: Swift-UVOT Processed Source List
TRIGGER_NUM: 536580, Seg_Num: 0
POINT_RA: 70.484d {+04h 41m 56s} (J2000)
POINT_DEC: -12.284d {-12d 17' 00"} (J2000)
POINT_ROLL: 118.792d
IMG_START_DATE: 16224 TJD; 298 DOY; 12/10/24
IMG_START_TIME: 10730.50 SOD {02:58:50.50} UT, 158.0 [sec] since BAT Trigger Time
FILTER: 7, U
BKG_MEAN: 0.333
N_STARS: 88
X_OFFSET: 0 [pixels]
Y_OFFSET: 0 [pixels]
X_MAX: 2047 [pixels]
Y_MAX: 2047 [pixels]
DET_THRESH: 6
PHOTO_THRESH: 2
SL_URL: sw00536580000msufc0158.fits
SUN_POSTN: 208.97d {+13h 55m 53s} -11.86d {-11d 51' 32"}
SUN_DIST: 132.13 [deg] Sun_angle= 9.2 [hr] (West of Sun)
MOON_POSTN: 326.25d {+21h 44m 59s} -7.94d {-07d 56' 36"}
MOON_DIST: 102.19 [deg]
MOON_ILLUM: 71 [%]
GAL_COORDS: 209.52,-34.24 [deg] galactic lon,lat of the pointing direction
ECL_COORDS: 66.77,-34.16 [deg] ecliptic lon,lat of the pointing direction
COMMENTS: SWIFT-UVOT Processed Source List.
COMMENTS: All 4 attachments are included.
- GCN NOTICE
TITLE: GCN/SWIFT NOTICE
NOTICE_DATE: Wed 24 Oct 12 03:07:45 UT
NOTICE_TYPE: Swift-UVOT Image
TRIGGER_NUM: 536580, Seg_Num: 0
POINT_RA: 70.484d {+04h 41m 56s} (J2000)
POINT_DEC: -12.284d {-12d 17' 00"} (J2000)
ROLL: 118.792d
IMG_START_DATE: 16224 TJD; 298 DOY; 12/10/24
IMG_START_TIME: 10730.50 SOD {02:58:50.50} UT, 158.0 [sec] since BAT Trigger Time
FILTER: 7, U
EXPOSURE_ID: 372740340
X_OFFSET: 792 [pixels]
Y_OFFSET: 977 [pixels]
WIDTH: 160 [pixels]
HEIGHT: 160 [pixels]
X_GRB_POS: 952
Y_GRB_POS: 1137
BINNING_INDEX: 1
IM_URL: sw00536580000msuni0168.fits
SUN_POSTN: 208.97d {+13h 55m 54s} -11.86d {-11d 51' 33"}
SUN_DIST: 132.13 [deg] Sun_angle= 9.2 [hr] (West of Sun)
MOON_POSTN: 326.25d {+21h 45m 01s} -7.94d {-07d 56' 28"}
MOON_DIST: 102.18 [deg]
MOON_ILLUM: 71 [%]
GAL_COORDS: 209.52,-34.24 [deg] galactic lon,lat of the pointing direction
ECL_COORDS: 66.77,-34.16 [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: Wed 24 Oct 12 03:08:05 UT
NOTICE_TYPE: Swift-UVOT Processed Image
TRIGGER_NUM: 536580, Seg_Num: 0
POINT_RA: 70.484d {+04h 41m 56s} (J2000)
POINT_DEC: -12.284d {-12d 17' 00"} (J2000)
ROLL: 118.792d
IMG_START_DATE: 16224 TJD; 298 DOY; 12/10/24
IMG_START_TIME: 10730.50 SOD {02:58:50.50} UT, 158.0 [sec] since BAT Trigger Time
FILTER: 7, U
EXPOSURE_ID: 372740340
X_OFFSET: 792 [pixels]
Y_OFFSET: 977 [pixels]
WIDTH: 160 [pixels]
HEIGHT: 160 [pixels]
X_GRB_POS: 952
Y_GRB_POS: 1137
BINNING_INDEX: 1
IM_URL: sw00536580000msuni0168.fits
SUN_POSTN: 208.97d {+13h 55m 54s} -11.86d {-11d 51' 33"}
SUN_DIST: 132.13 [deg] Sun_angle= 9.2 [hr] (West of Sun)
MOON_POSTN: 326.26d {+21h 45m 02s} -7.94d {-07d 56' 24"}
MOON_DIST: 102.18 [deg]
MOON_ILLUM: 71 [%]
GAL_COORDS: 209.52,-34.24 [deg] galactic lon,lat of the pointing direction
ECL_COORDS: 66.77,-34.16 [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: All 4 attachments are included.
- GCN NOTICE
TITLE: GCN/SWIFT NOTICE
NOTICE_DATE: Wed 24 Oct 12 03:10:48 UT
NOTICE_TYPE: Swift-UVOT Position
TRIGGER_NUM: 536580, Seg_Num: 0
GRB_RA: 70.4720d {+04h 41m 53.27s} (J2000),
70.6215d {+04h 42m 29.16s} (current),
69.8888d {+04h 39m 33.30s} (1950)
GRB_DEC: -12.2907d {-12d 17' 26.5"} (J2000),
-12.2669d {-12d 16' 01.0"} (current),
-12.3851d {-12d 23' 06.3"} (1950)
GRB_ERROR: 0.8 [arcsec radius, statistical only]
GRB_MAG: 18.37 +/- 0.16 [mag]
FILTER: 7, U
IMG_START_DATE: 16224 TJD; 298 DOY; 12/10/24
IMG_START_TIME: 10730.00 SOD {02:58:50.00} UT, 157.5 [sec] since BAT Trigger Time
SUN_POSTN: 208.98d {+13h 55m 54s} -11.86d {-11d 51' 36"}
SUN_DIST: 132.14 [deg] Sun_angle= 9.2 [hr] (West of Sun)
MOON_POSTN: 326.28d {+21h 45m 07s} -7.93d {-07d 55' 55"}
MOON_DIST: 102.15 [deg]
MOON_ILLUM: 71 [%]
GAL_COORDS: 209.52,-34.25 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS: 66.75,-34.17 [deg] ecliptic lon,lat of the burst (or transient)
COMMENTS: SWIFT UVOT Position Notice.
COMMENTS: This Notice was ground-generated -- not flight-generated.
COMMENTS: The UVOT position is 1.8 arcsec from the XRT position.
COMMENTS: Result based on Genie data.
COMMENTS: Notice generated automatically.
- GCN Circular #13886
C. Pagani (U Leicester), S. D. Barthelmy (GSFC),
W. H. Baumgartner (GSFC/UMBC), C. Gronwall (PSU), J. A. Kennea (PSU),
C. B. Markwardt (NASA/GSFC), F. E. Marshall (NASA/GSFC),
K. L. Page (U Leicester), D. M. Palmer (LANL), T. Sakamoto (AGU),
B. Sbarufatti (INAF-OAB/PSU), M. H. Siegel (PSU) and
T. N. Ukwatta (MSU) report on behalf of the Swift Team:
At 02:56:12 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 121024A (trigger=536580). Swift slewed immediately to the burst.
The BAT on-board calculated location is
RA, Dec 70.467, -12.269 which is
RA(J2000) = 04h 41m 52s
Dec(J2000) = -12d 16' 06"
with an uncertainty of 3 arcmin (radius, 90% containment, including
systematic uncertainty). The BAT light curve shows a few overlapping peaks
with a duration of about 15 sec. The peak count rate
was ~3500 counts/sec (15-350 keV), at ~1 sec after the trigger.
The XRT began observing the field at 02:57:45.5 UT, 93.0 seconds after
the BAT trigger. XRT found a bright, uncatalogued X-ray source located
at RA, Dec 70.4715, -12.2904 which is equivalent to:
RA(J2000) = +04h 41m 53.16s
Dec(J2000) = -12d 17' 25.4"
with an uncertainty of 5.5 arcseconds (radius, 90% containment). This
location is 78 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.
The initial flux in the 2.5 s image was 1.10e-09 erg cm^-2 s^-1 (0.2-10
keV).
UVOT took a finding chart exposure of 250 seconds with the U filter starting
158 seconds after the BAT trigger. There is a candidate afterglow in the
rapidly available 2.7'x2.7' sub-image at
RA(J2000) = 04:41:53.28 = 70.47201
DEC(J2000) = -12:17:26.8 = -12.29079
with a 90%-confidence error radius of about 0.78 arc sec. This position is 2.3
arc sec. from the center of the XRT error circle. The estimated magnitude is
18.38 with a 1-sigma error of about 0.16. No correction has been made for the
expected extinction corresponding to E(B-V) of 0.10.
Burst Advocate for this burst is C. Pagani (cp232 AT star.le.ac.uk).
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 #13887
Klotz A. (IRAP-CNRS-OMP), Gendre B. (ASDC/INAF-OAR),
Boer M. (UNS-CNRS-OCA), Atteia J.L. (IRAP-CNRS-OMP) report:
We imaged the field of GRB 121024A detected by SWIFT
(trigger 536580) with the TAROT robotic telescope (D=25cm)
located at the Calern observatory, France.
The observations started 45.0s after the GRB trigger
(13.9s after the notice). The elevation of the field decreased from
32 degrees above horizon and weather conditions
were good.
The first image is trailed with a duration of 60.0s
(see the description in Klotz et al., 2006, A&A 451, L39).
We detect a new fading source in the error box given by SWIFT
We detected the candidate couterpart mentioned by XXX et al. (GCNC XXXX)
at the following position (+/- 1 arcsec):
RA(J2000.0) = 04h 41m 53.41s
DEC(J2000.0) -12d 17' 26.9"
OT was R~13.3 betwenn 45.0s and 60s after GRB.
Then the flux decreases.
Observations are continuing.
Magnitudes were estimated with the nearby NOMAD1 stars
and are not corrected for galactic dust extinction.
N.B. Galactic coordinates are lon=209.4933 lat=-34.2488
and the galactic extinction in R band is about 0.1 magnitude
estimated from D. Schlegel et al. 1998ApJ...500..525S.
This message may be cited.
- GCN NOTICE
TITLE: GCN/SWIFT NOTICE
NOTICE_DATE: Wed 24 Oct 12 03:23:06 UT
NOTICE_TYPE: Swift-XRT Position UPDATE
TRIGGER_NUM: 536580, Seg_Num: 0
GRB_RA: 70.4712d {+04h 41m 53.08s} (J2000),
70.6207d {+04h 42m 28.97s} (current),
69.8880d {+04h 39m 33.11s} (1950)
GRB_DEC: -12.2911d {-12d 17' 27.9"} (J2000),
-12.2673d {-12d 16' 02.4"} (current),
-12.3855d {-12d 23' 07.7"} (1950)
GRB_ERROR: 3.7 [arcsec radius, statistical plus systematic, 90% containment]
GRB_INTEN: 1.00e-10 [erg/cm2/sec]
GRB_SIGNIF: 10.00 [sigma]
IMG_START_DATE: 16224 TJD; 298 DOY; 12/10/24
IMG_START_TIME: 10991.00 SOD {03:03:11.00} UT, 418.5 [sec] since BAT Trigger Time
TAM[0-3]: 100.00 100.00 100.00 100.00
AMPLIFIER: 1
WAVEFORM: 31
SUN_POSTN: 208.98d {+13h 55m 56s} -11.86d {-11d 51' 46"}
SUN_DIST: 132.15 [deg] Sun_angle= 9.2 [hr] (West of Sun)
MOON_POSTN: 326.39d {+21h 45m 33s} -7.89d {-07d 53' 41"}
MOON_DIST: 102.05 [deg]
MOON_ILLUM: 71 [%]
GAL_COORDS: 209.52,-34.25 [deg] galactic lon,lat of the burst
ECL_COORDS: 66.75,-34.17 [deg] ecliptic lon,lat of the burst
COMMENTS: SWIFT-XRT Coordinates.
COMMENTS: This Notice was ground-generated -- not flight-generated.
COMMENTS: This is an Update Notice -- the RA,Dec values herein supersede the previous XRT_POS Notice.
COMMENTS: TAM values, flux and significance fields are not valid.
COMMENTS: This position was automatically generated on the ground using
COMMENTS: Photon Counting data telemetered via TDRSS (SPER data).
COMMENTS: See http://www.swift.ac.uk/sper/docs.php for details.
COMMENTS: The probability that this is a serendipitous source in the
COMMENTS: SPER window is 0.11% < P(seren) < 0.58%.
- GCN Circular #13888
Martin Jelinek, Alberto J. Castro-Tirado and Javier Gorosabel
(IAA-CSIC Granada) on behalf of a larger collaboration
report:
"The 0.3m BOOTES-1B robotic telescope located in Huelva
(Spain), observed the optical afterglow of GRB 121024A
(Pagani et al., GCNC 13886; Klotz et al., GCNC 13887).
The observations started 40 minutes after the GRB trigger.
The sum of 20 minutes of unfiltered images with a mean
integration time 54 minutes after the GRB shows the OT
with magnitude roughly 18.2+-0.5."
- GCN Circular #13889
A. LaCluyze, J. Haislip, K. Ivarsen, D. Reichart, J. Moore, H. T.
Cromartie, R. Egger, A. Foster, N. Frank, M. Nysewander, A. Oza, E.
Speckhard, A.Trotter, and J. A. Crain report:
Skynet observed the field of GRB121024A (GCN 13886, Swift trigger #536580)
with the PROMPT telescopes located at CTIO in Chile and the 16" Dolomites
Astronomical Observatory telescope (DAO) in Italy beginning ~1 minute after
the burst trigger. We detect the fading optical source reported by Klotz
et al. (GCN #13887) in all observed filters (g',r',i',z' and BRI.)
Further observations are ongoing.
- GCN Circular #13890
N. R. Tanvir (U. Leicester), J. P. U. Fynbo (DARK/NBI), A. Melandri (INAF-OAB),
A. J. Levan (U. Warwick), D. Xu (WIS), V. D'Elia (ASDC) report on behalf of
the X-shooter GTO collaboration:
We observed the afterglow of GRB 121024A (Pagani et al. GCN 13886) with the
X-shooter spectrograph at the VLT. Observations began at 04:45 UT, approximately
1.8 hours after the initial detection of the burst. The afterglow is well detected in
the acquisition image, and in the resulting spectrum we see a strong, broad
damped-Lya absorption feature at ~4000A, combined with numerous narrow metal
lines of CIV, SiII, SiIV, FeII, SII and AlII, as well as fine-structure lines associated
with SiII*. These point to a common redshift of z=2.298 for GRB 121024A.
We thank Maja Vuckovic, Giovanni Carraro, Marcelo Lopez and Felipe Gaete
for their assistance in obtaining these observations, and Gianni Marconi
and Gerry Gilmore for kindly allowing the ToO to be performed during their
visitor mode run.
- GCN Circular #13891
F. Knust, P. Schady and J. Greiner (all MPE Garching) report on behalf
of the GROND team
We observed the field of GRB 121024A (Pagani et al., GCN 13886)
simultaneously in g'r'i'z' with GROND (Greiner et al. 2008, PASP, 120,
405) mounted on the 2.2 m MPG/ESO telescope at La Silla Observatory
(Chile).
Due to clouds, observations only started at 05:53 UT no 24th October,
3 hours after the GRB trigger, and continued until the end of the
night, 3.8 hours later. They were performed at an average seeing of
1.4" and at an average airmass of 1.1.
We find a single point source within the 0.8 arcsec Swift/UVOT error
circle reported by Pagani et al. (GCN 13886) at
RA (J2000.0) = 04:41:53.30
Dec (J2000.0) = -12:17:26.5
with an uncertainty of 0.4" in each coordinate.
Based on the first 142 sec integration in g'r'i'z' and 240 sec
integration in JHK taken at a mid-time of 05:58 UT and 05:54 UT in the
optical and NIR respectively, we estimate preliminary magnitudes (all
in AB system) of
g' = 21.0 +/- 0.2 mag
r' = 20.1 +/- 0.2 mag
i' = 19.8 +/- 0.2 mag
z' = 19.5 +/- 0.2 mag
J = 18.7 +/- 0.1 mag
H = 18.4 +/- 0.1 mag
K = 17.9 +/- 0.1 mag
Given magnitudes are calibrated against GROND zeropoints in the
optical, and 2MASS field stars in the NIR, and are not corrected for
the expected Galactic foreground extinction corresponding to a
reddening of E(B-V) = 0.1 mag in the direction of the burst (Schlegel
et al. 1998).
- GCN Circular #13892
K.L. Page (U. Leicester), A. Maselli (INAF-IASFPA), V. Mangano
(INAF-IASFPA), A. Melandri (INAF-OAB), M.C. Stroh (PSU), D.N. Burrows
(PSU), J.A. Kennea (PSU), A.P. Beardmore (U. Leicester) and C. Pagani
report on behalf of the Swift-XRT team:
We have analysed 7.0 ks of XRT data for GRB 121024A (Pagani et al. GCN
Circ. 13886), from 82 s to 23.5 ks after the BAT trigger. The data
comprise 242 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 = 70.47078, -12.29099 which
is equivalent to:
RA (J2000): 04 41 52.99
Dec(J2000): -12 17 27.6
with an uncertainty of 3.5 arcsec (radius, 90% confidence).
The late-time light curve (from T0+3.9 ks) can be modelled with a
power-law decay with a decay index of alpha=0.89 (+/-0.13).
A spectrum formed from the WT mode data can be fitted with an absorbed
power-law with a photon spectral index of 2.15 (+/-0.08). The
best-fitting absorption column is 8.0 (+2.1, -2.0) x 10^21 cm^-2, at a
redshift of 2.298, in addition to the Galactic value of 5.4 x 10^20
cm^-2 (Kalberla et al. 2005). The PC mode spectrum has a photon index
of 1.96 (+/-0.13) and a best-fitting absorption column of 7.1 (+4.0,
-3.6) x 10^21 cm^-2. The counts to observed (unabsorbed) 0.3-10 keV
flux conversion factor deduced from this spectrum is 3.7 x 10^-11 (4.7
x 10^-11) erg cm^-2 count^-1.
A summary of the PC-mode spectrum is thus:
Galactic foreground: 5.4 x 10^20 cm^-2
Intrinsic column: 7.1 (+4.0, -3.6) x 10^21 cm^-2 at z=2.298
Photon index: 1.96 (+/-0.13)
If the light curve continues to decay with a power-law decay index of
0.89, the count rate at T+24 hours will be 0.016 count s^-1,
corresponding to an observed (unabsorbed) 0.3-10 keV flux of 5.8 x
10^-13 (7.3 x 10^-13) erg cm^-2 s^-1.
The results of the XRT-team automatic analysis are available at
http://www.swift.ac.uk/xrt_products/00536580.
This circular is an official product of the Swift-XRT team.
- GCN Circular #13893
A. N. Morgan, and J. S. Bloom (UC Berkeley) report:
We observed the field of GRB 121024A (Pagani et al., GCN 13886) with
the 1.3m PAIRITEL located at Mt. Hopkins, Arizona. Observations began
at 2012-Oct-24 07h31m47s UT, ~4.6 hours after the Swift Trigger. In
mosaics (effective exposure time of 0.46 hours) taken simultaneously
in the J, H, and K filters, we detect a source at the optical
afterglow location (Pagani et al., GCN 13886; Klotz et al., GCN 13887;
Jelinek et al., GCN 13888; LaCluyze et al., GCN 13889; Knust et al.
GCN 13891).
The preliminary photometry yields:
post burst
t_mid (hr) exp.(hr) filt mag m_err
6.06 0.46 J >18.4 3sig
6.06 0.46 H 17.1 0.2
6.06 0.46 Ks >16.2 3sig
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 #13894
J.P. Osborne, A.P. Beardmore, P.A. Evans and M.R. Goad (U. Leicester)
report on behalf of the Swift-XRT team.
Using 7610 s of XRT Photon Counting mode data and 6 UVOT
images for GRB 121024A, we find an astrometrically corrected X-ray
position (using the XRT-UVOT alignment and matching UVOT field sources
to the USNO-B1 catalogue): RA, Dec = 70.47208, -12.29052 which is equivalent
to:
RA (J2000): 04h 41m 53.30s
Dec (J2000): -12d 17' 25.9"
with an uncertainty of 1.4 arcsec (radius, 90% confidence).
This position may be improved as more data are received. The latest
position can be viewed at http://www.swift.ac.uk/xrt_positions. Position
enhancement is described by Goad et al. (2007, A&A, 476, 1401) and Evans
et al. (2009, MNRAS, 397, 1177).
This circular was automatically generated, and is an official product of the
Swift-XRT team.
- GCN Circular #13896
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 121024A (Pagani et al., GCNC 13886)
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 2012-10-24 13:51:59 UT (~10.9 h after the burst)
We did not find any new point source within the enhanced XRT circle
(Osborne et al., GCNC 13894) in all the three bands.
We also could not detect the previously reported afterglow
(Klotz et al., GCNC 13887).
Three sigma upper limits of the OT are listed below. We used
GSC2.3 catalog for flux calibration.
T0+[day] MID-UT T-EXP[sec] g' Rc Ic
------------------------------------------------------
0.55338 16:13:04 7740.0 >20.1 >20.0 >19.3
------------------------------------------------------
T0+ : Elapsed time after the burst [day]
T-EXP: Total Exposure time [sec]
- GCN Circular #13897
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 121024A (Pagani et al., GCNC 13886)
with the optical three color (g', Rc and Ic) CCD camera attached
to the Murikabushi 1m telescope of Ishigakijima Astronomical Observatory.
The observation started on 2012-10-24 14:30:52 UT (~11.6 h after the burst)
We did not find any new point source within the enhanced XRT circle
(Osborne et al., GCNC 13894) in all the three bands.
We also could not detect the previously reported afterglow
(Klotz et al., GCNC 13887).
Three sigma upper limits of the OT are listed below. We used
GSC2.3 catalog for flux calibration.
T0+[day] MID-UT T-EXP[sec] g' Rc Ic
------------------------------------------------------
0.52401 15:30:47 6060.0 >21.7 >21.4 >20.6
------------------------------------------------------
T0+ : Elapsed time after the burst [day]
T-EXP: Total Exposure time [sec]
- GCN Circular #13898
X.-H. Zhao (YNAO), J.-R. Mao (KASI/YNAO), J.-M. Bai
(YNAO) report on behalf of a larger collaboration:
We observed the field of GRB 121024A (Pagani et al., GCN 13886) with 2.4m Gao-Mei-Gu (GMG) telescope. Observations
started at 16:30:00 UT on 2012-10-24 (i.e., 13.6 hrs after the burst) and 2x900s R-band images were obtained. The optical afterglow of this burst was clearly detected. The results are as follows:
mid time from trigger (hr) Mag. Err. Exposure time (second)
13.69 20.88 0.1 900
13.81 20.81 0.1 900
We thank the GMG staff, especially Fang Wang, De-Qing Wang and Jian-Duo He for
performing these observations.
- GCN Circular #13899
S. D. Barthelmy (GSFC), T. Sakamoto (AGU), W. H. Baumgartner (GSFC/UMBC),
J. R. Cummings (GSFC/UMBC), E. E. Fenimore (LANL), N. Gehrels (GSFC),
H. A. Krimm (GSFC/USRA), C. B. Markwardt (GSFC), C. Pagani (U Leicester),
D. M. Palmer (LANL), 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-239 to T+963 sec from the recent telemetry downlink,
we report further analysis of BAT GRB 121024A (trigger #536580)
(Pagani, et al., GCN Circ. 13886). The BAT ground-calculated position is
RA, Dec = 70.481, -12.255 deg, which is
RA(J2000) = 04h 41m 55.5s
Dec(J2000) = -12d 15' 19.1"
with an uncertainty of 1.7 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 50%.
The mask-weighted light curve shows two overlapping peaks starting
at ~T-9 sec, peaking at ~T-7 and ~T+2 sec, and ending at ~T+6 sec
with a long low tail out to ~T+70 sec (and possibly out to ~T+130 sec).
T90 (15-350 keV) is 69 +- 32 sec (estimated error including systematics).
The time-averaged spectrum from T-8.27 to T+75.73 sec is best fit by a simple
power-law model. The power law index of the time-averaged spectrum is
1.41 +- 0.22. The fluence in the 15-150 keV band is 1.1 +- 0.1 x 10^-6 erg/cm2.
The 1-sec peak photon flux measured from T+0.73 sec in the 15-150 keV band
is 1.3 +- 0.2 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/536580/BA/
- GCN Circular #13900
B. Zauderer, T. Laskar and E. Berger (Harvard) report on behalf of the
CARMA Key Project "A Millimeter View of the Transient Universe":
"We observed the position of GRB 121024A (Pagani et al; GCN 13886) with
the Combined Array for Research in Millimeter Astronomy beginning 2012
Oct 25.5 (dt=1.4 d after the burst). At a mean frequency of ~85 GHz, we
detect a radio counterpart with a preliminary flux of ~1 mJy within the
enhanced Swft/XRT error circle (Osborne et al; GCN 13894) and consistent
with the optical afterglow (e.g. Knust et al.; GCN 13891).
We thank the CARMA observers and staff for their support. Followup
observations are planned."
- GCN Circular #13901
S. T. Holland (STScI) and C. Pagani (U Leicester)
report on behalf of the Swift/UVOT team:
The Swift/UVOT began settled observations of the field of GRB
121024A starting 158 s after the BAT trigger (Pagani et al., 2012,
GCNC 13886). We continued to detect the optical afterglow until
approximately 10 ks after the BAT trigger. Preliminary UVOT
photometry, and 3-sigma upper limits, for the afterglow is presented
below.
-----------------------------------------------------
Filter TSTART TSTOP Exp Time Mag Err
-----------------------------------------------------
u (fc) 158 408 246 18.43 0.10
-----------------------------------------------------
v 464 483 19 >18.1
b 413 433 19 18.44 0.25
u 538 557 19 >18.5
uvw1 513 533 19 >18.1
uvm2 488 508 19 >17.6
uvw2 439 459 19 >18.1
-----------------------------------------------------
The quoted magnitudes and upper limits have not been corrected for
the Galactic extinction along the line of sight to this burst of
E_{B-V} = 0.09 mag (Schlafly et al. 2011, ApJS, 737, 103). The
photometry is in the UVOT photometric system (Breeveld et al. 2011,
AIP Conf. Proc. 1358, 373).
- GCN Circular #13903
T. Laskar, A. Zauderer, and E. Berger (Harvard) report:
"We observed the position of GRB 121024A (Pagani et al; GCN 13886) with the
EVLA beginning on 2012 Oct 25.3 UT (1.2 days after the burst). At a mean
frequency of 22 GHz, we detect a radio counterpart with a preliminary flux
density of ~ 0.1 mJy consistent with the enhanced Swft/XRT position
(Osborne et al; GCN 13894), the optical position (e.g. Knust et al.; GCN
13891) and the CARMA 3 mm position (Zauderer et al; GCN 13900). Follow-up
observations are planned."
- GCN Circular #13904
S. B. Pandey and Brajesh Kuamr (ARIES Nainital India,
on behalf of larger Indian GRB collaboration).
We observed the GRB 121024A field (Pagani et al., GCN 13886) using
1.04m telescope at ARIES Nainital, starting ~16.9 hours after the
burst (19:49:49 UT, 2012-10-24). Several frames in R_c and I_c
pass-bands were acquired in high air-mass conditions.
In our co-added image (6x300 sec) of R_c band, the optical afterglow
candidate (Knust et al., GCN 13891) is clearly detected. The preliminary
photometry of the co-added frame (calibrated against nearby USNO stars)
estimates the magnitude of the optical afterglow to be 21.1 +- 0.1 mag.
This massage may be cited.
- GCN Circular #13928
B. E. Cobb (GWU), reports:
Using the ANDICAM instrument on the 1.3m telescope at CTIO, we obtained
optical/IR imaging of the error region of GRB 121024A (GCN 13886,
Pagani et al.) over several epochs (with mid-exposure times of
2012-10-24 03:51 UT, 06:10 UT, 08:12 UT and 2012-10-25 06:53 UT).
For each epoch, several dithered images were obtained with
total summed exposure times of 15 min in V and I and 12 min in
J and K. For the final epoch, total exposure times were
36 min in I and 30 min in J.
The fading afterglow of GRB 121024A (e.g. GCN 13887, Klotz et al.; GCN
13888, Jelinek et al.; GCN 13891, Knust et al.) was detected with the
following magnitudes (or 3-sigma limits):
mid-exposure
time
(hours) I mag J mag K mag
0.90722 18.0 +/- 0.1 16.7 +/- 0.1 15.2 +/- 0.2
3.23611 19.4 +/- 0.1 17.9 +/- 0.1 16.3 +/- 0.2
5.27333 19.8 +/- 0.1 > 18.0 > 16.4
27.95278 > 21.9 > 19.3 ...
(Optical photometry is calibrated against USNO-B1.0 stars
and IR photometry is calibrated against 2MASS stars in the field.)
- GCN Circular #13931
M. Jang, M. Im (SNU), and Y. Urata (NCU), on behalf of a larger collaboration
We observed GRB 121024A in RIzY-bands starting at UT 10:52:00, 2012-10-24,
~ 9 hrs after the BAT trigger (Baumgartner et al, GCN 10484),
using the 1.0m telescope at Mt.Lemmon in Arizona, U.S.
We do not detect the GRB afterglow in all bands within the error circle
of the enhanced XRT position (Evans et al.,GCN 13892).
We estimate the 3-sigma limiting magnitude of the afterglow to be
R ~ 20.0 at the midpoint time (~T0+9.3 hrs)
by calibrating it against seven USNO-B1 stars with R2 magnitudes
without the galactic extinction correction.
We thank the LOAO operator, J. Yoon, for performing the observation.
- 1409.6315 from 24 Sep 14
M. Friis et al.: The warm, the excited, and the molecular gas: GRB 121024A shining through its star-forming galaxy
We present the first reported case of the simultaneous metallicity determination of a gamma-ray burst (GRB) host galaxy, from both afterglow
absorption lines as well as strong emission-line diagnostics. Using spectroscopic and imaging observations of the afterglow and host of the
long-duration GRB121024A at z = 2.30, we give one of the most complete views of a GRB host/environment to date. We observe a strong damped
Ly-alpha absorber (DLA) with a hydrogen column density of log N(HI) = 21.80+/-0.15, H_2 absorption in the Lyman-Werner bands (molecular
fraction of log(f) ~ -1.4; fourth solid detection of molecular hydrogen in a GRB-DLA), the nebular emission lines H-alpha, H-beta, [OII],
[OIII] and [NII], as well as a large variety of metal absorption lines. We find a GRB host galaxy that is highly star-forming (SFR ~ 40
Msolar/yr), with a dust-corrected metallicity along the line of sight of [Zn/H]corr = -0.5+/-0.2 ([O/H] ~ -0.3 from emission lines), and a
depletion factor of refractory elements of [Zn/Fe] = 0.85+/-0.04. The molecular gas is separated by 400 km/s from the gas that is excited by
the GRB (implying a fairly massive host, in agreement with the derived stellar mass of log(Mstellar/Msolar) = 9.9+/-0.2). Including emission
line analysis, we isolate and characterise three different gas-phases within the star-forming host galaxy. Our main result is that the
metallicity determinations from both absorption and emission lines are consistent, which is encouraging for the comparison of GRB host
metallicities at different redshifts.
- 1410.0489 from 3 Oct 14
K. Wiersema et al.: Circular polarization in the optical afterglow of GRB 121024A
Gamma-ray bursts (GRBs) are most probably powered by collimated relativistic outflows (jets) from accreting black holes at cosmological
distances. Bright afterglows are produced when the outflow collides with the ambient medium. Afterglow polarization directly probes the
magnetic properties of the jet, when measured minutes after the burst, and the geometric properties of the jet and the ambient medium when
measured hours to days after the burst. High values of optical polarization detected minutes after burst in GRB 120308A indicate the presence
of large-scale ordered magnetic fields originating from the central engine (the power source of the GRB). Theoretical models predict low
degrees of linear polarization and negligable circular polarization at late times, when the energy in the original ejecta is quickly
transferred to the ambient medium and propagates farther into the medium as a blastwave. Here we report the detection of circularly polarized
optical light in the afterglow of GRB 121024A, measured 0.15 days after the burst. We show that the circular polarization is intrinsic to the
afterglow and unlikely to be produced by dust scattering or plasma propagation effects. A possible explanation is to invoke anisotropic (rather
than the commonly assumed isotropic) electron pitch angle distributions, and we suggest that new models are required to produce the complex
microphysics of realistic shocks in relativistic jets.
- 1503.07513 from 26 Mar 15
K. Varela et al.: Microphysics and dynamics of the Gamma-Ray Burst GRB 121024A
Using multi-epoch broad-band observations of the GRB 121024A afterglow, we measure the three characteristic break frequencies of the
synchrotron spectrum. We use 6 epochs of combined XRT and GROND data to constrain the temporal slope, the dust extinction and the spectral
slope with high accuracy. Two further epochs of combined data from XRT, GROND, APEX, CARMA and EVLA are used to set constraints on the break
frequencies and therefore on the micro-physical and dynamical parameters. The XRT and GROND light curves show a simultaneous break at around 42
ks. No spectral evolution is observed between the afterglow SEDs before and after the break. As a result, the crossing of the synchrotron
cooling break is not suitable as an explanation for the break in the light curve. The multi-wavelength data give us a unique opportunity to
discern between two plausible scenarios explaining the break: the end of energy injection and a jet break. The observations are explained by
two possible scenarios, a jet break and an energy injection model. The jet break model has been suggested by previous analysis of the observed
linear and circular polarisation although it requires a flat electron spectrum, a very low cooling break and a non-spreading jet. The energy
injection avoids an extremely flat spectrum for the shock-accelerated electrons, the very low cooling break frequency and the extreme prompt
emission efficiency. However some atypical values for the micro-physics of particle acceleration arise in this model. It is consistent with the
correlation between luminosity and end-time of the plateau in the light curve, reported from large sample studies of XRT data.
- 1503.08991 from 1 Apr 15
Lara Nava et al.: Linear and circular polarization in GRB afterglows
A certain degree of linear polarization has been measured in several GRB afterglows. More surprisingly, circular polarization has been recently
measured in GRB121024A. For synchrotron emission, the polarization level depends on: (i) the local magnetic field orientation (ii) the geometry
of the emitting region with respect to the line of sight and (iii) the electron pitch-angle distribution. For this reason, polarization
measurements are a valuable tool to probe afterglow micro-physics. We present numerical estimates of linear and circular polarization for
different configurations (i.e., magnetic fields, geometries and pitch-angle distributions). For each different scenario, we study the
conditions for reaching the maximum and minimum linear and circular polarization and provide their values. We discuss the implication of our
results to the micro-physics of GRB afterglows in view of recent polarization measurements.
- 1509.02525 from 10 Sep 15
Lara Nava et al.: Linear and Circular polarization in ultra-relativistic synchrotron sources - implications to GRB afterglows
Polarization measurements from relativistic outflows are a valuable tool to probe the geometry of the emission region and the microphysics of
the particle distribution. Indeed, the polarization level depends on: (i) the local magnetic field orientation, (ii) the geometry of the
emitting region with respect to the line of sight, and (iii) the electron pitch-angle distribution. Here we consider optically thin synchrotron
emission and we extend the theory of circular polarization from a point source to an extended radially expanding relativistic jet. We present
numerical estimates for both linear and circular polarization in such systems. We consider different configurations of the magnetic field,
spherical and jetted outflows, isotropic and anisotropic pitch-angle distributions, and outline the difficulty in obtaining the reported high
level of circular polarization observed in the afterglow of GRB 121024A. We conclude that the origin of the observed polarization cannot be
intrinsic to an optically thin synchrotron process, even when the electron pitch-angle distribution is extremely anisotropic.
- 1512.03205 from 11 Dec 15
Mette Friis: Exploring Gamma-Ray Bursts, Their Immediate Environment and Host Galaxies
Lasting anywhere from a few milliseconds to several minutes, GRBs shine hundreds of times brighter than a typical supernova, making them
briefly the brightest source of cosmic gamma-ray photons in the observable Universe. This thesis focuses on 3 different aspects of GRBs: (1)
The radiative mechanism of GRBs and their afterglows, i.e. the occurrence of thermal emission and the physical parameters we can determine
through this emission. (2) Their host galaxies, using results from observations of GRB 121024A as a case study. (3) How they can be used to
answer some of the larger astrophysical questions, more specifically in this case, to study interstellar dust and grey extinction.