- GCN/BACODINE POSITION NOTICE
TITLE: GCN/SWIFT NOTICE
NOTICE_DATE: Sat 18 Feb 06 03:36:02 UT
NOTICE_TYPE: Swift-BAT GRB Position
TRIGGER_NUM: 191157, Seg_Num: 0
GRB_RA: 50.404d {+03h 21m 37s} (J2000),
50.490d {+03h 21m 58s} (current),
49.699d {+03h 18m 48s} (1950)
GRB_DEC: +16.866d {+16d 51' 58"} (J2000),
+16.888d {+16d 53' 16"} (current),
+16.687d {+16d 41' 14"} (1950)
GRB_ERROR: 3.00 [arcmin radius, statistical only]
GRB_INTEN: 0 [cnts] Image_Peak=2111 [image_cnts]
TRIGGER_DUR: 80.000 [sec]
TRIGGER_INDEX: 20000 E_range: 15-50 keV
BKG_INTEN: 0 [cnts]
BKG_TIME: -1.02 SOD {00:00:-1.-1} UT
BKG_DUR: 0 [sec]
GRB_DATE: 13784 TJD; 49 DOY; 06/02/18
GRB_TIME: 12870.97 SOD {03:34:30.97} UT
GRB_PHI: 178.43 [deg]
GRB_THETA: 25.03 [deg]
SOLN_STATUS: 0x13
RATE_SIGNIF: 0.00 [sigma]
IMAGE_SIGNIF: 7.84 [sigma]
MERIT_PARAMS: +1 +0 +0 +6 +1 -2 +0 +0 -12 +1
SUN_POSTN: 331.46d {+22h 05m 49s} -11.70d {-11d 42' 11"}
SUN_DIST: 83.15 [deg] Sun_angle= -5.3 [hr] (East of Sun)
MOON_POSTN: 200.65d {+13h 22m 37s} -10.52d {-10d 31' 13"}
MOON_DIST: 150.36 [deg]
MOON_ILLUM: 80 [%]
GAL_COORDS: 166.92,-32.89 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS: 52.40, -1.55 [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 = 119.70,17.54 [deg].
- red DSS finding chart
ps-file
- GCN NOTICE
TITLE: GCN/SWIFT NOTICE
NOTICE_DATE: Sat 18 Feb 06 03:37:12 UT
NOTICE_TYPE: Swift-XRT Nack-Position
TRIGGER_NUM: 191157, Seg_Num: 0
POINT_RA: 50.396d {+03h 21m 35s} (J2000)
POINT_DEC: +16.870d {+16d 52' 13"} (J2000)
IMG_START_DATE: 13784 TJD; 49 DOY; 06/02/18
IMG_START_TIME: 13024.05 SOD {03:37:04.05} UT, 153.1 [sec] since BAT Trigger Time
COUNTS: 95 Min_needed= 20
STD_DEV: 47.52 Max_StdDev_for_Good=28.44 [arcsec]
PH2_ITER: 2 Max_iter_allowed= 4
ERROR_CODE: 3
COMMENTS: SWIFT-XRT Nack Position.
COMMENTS: Standard deviation too large.
- GCN NOTICE
TITLE: GCN/SWIFT NOTICE
NOTICE_DATE: Sat 18 Feb 06 03:39:17 UT
NOTICE_TYPE: Swift-BAT GRB Lightcurve
TRIGGER_NUM: 191157, Seg_Num: 0
GRB_RA: 50.404d {+03h 21m 37s} (J2000),
50.490d {+03h 21m 58s} (current),
49.699d {+03h 18m 48s} (1950)
GRB_DEC: +16.866d {+16d 51' 58"} (J2000),
+16.888d {+16d 53' 16"} (current),
+16.687d {+16d 41' 14"} (1950)
GRB_DATE: 13784 TJD; 49 DOY; 06/02/18
GRB_TIME: 12870.97 SOD {03:34:30.97} UT
TRIGGER_INDEX: 20000
GRB_PHI: 178.43 [deg]
GRB_THETA: 25.03 [deg]
DELTA_TIME: 0.00 [sec]
TRIGGER_DUR: 80.000 [sec]
SOLN_STATUS: 0x13
RATE_SIGNIF: 0.00 [sigma]
IMAGE_SIGNIF: 7.84 [sigma]
LC_URL: sw00191157000msb.lc
SUN_POSTN: 331.46d {+22h 05m 50s} -11.70d {-11d 42' 09"}
SUN_DIST: 83.15 [deg] Sun_angle= -5.3 [hr] (East of Sun)
MOON_POSTN: 200.68d {+13h 22m 43s} -10.53d {-10d 31' 57"}
MOON_DIST: 150.38 [deg]
MOON_ILLUM: 80 [%]
GAL_COORDS: 166.92,-32.89 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS: 52.40, -1.55 [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 = 119.70,17.54 [deg].
- GCN NOTICE
TITLE: GCN/SWIFT NOTICE
NOTICE_DATE: Sat 18 Feb 06 03:46:36 UT
NOTICE_TYPE: Swift-UVOT Source List
TRIGGER_NUM: 191157, Seg_Num: 0
POINT_RA: 50.395d {+03h 21m 35s} (J2000)
POINT_DEC: +16.871d {+16d 52' 17"} (J2000)
POINT_ROLL: 255.474d
IMG_START_DATE: 13784 TJD; 49 DOY; 06/02/18
IMG_START_TIME: 13023.36 SOD {03:37:03.36} UT, 152.4 [sec] since BAT Trigger Time
FILTER: 3, V
BKG_MEAN: 2.991
N_STARS: 71
X_OFFSET: 407 [pixels]
Y_OFFSET: 524 [pixels]
X_MAX: 1366 [pixels]
Y_MAX: 1483 [pixels]
DET_THRESH: 14
PHOTO_THRESH: 8
SL_URL: sw00191157000msufc0152.fits
SUN_POSTN: 331.46d {+22h 05m 51s} -11.70d {-11d 42' 02"}
SUN_DIST: 83.13 [deg] Sun_angle= -5.3 [hr] (East of Sun)
MOON_POSTN: 200.73d {+13h 22m 56s} -10.56d {-10d 33' 37"}
MOON_DIST: 150.45 [deg]
MOON_ILLUM: 80 [%]
GAL_COORDS: 166.91,-32.89 [deg] galactic lon,lat of the pointing direction
ECL_COORDS: 52.39, -1.55 [deg] ecliptic lon,lat of the pointing direction
COMMENTS: SWIFT-UVOT Source List.
- GCN NOTICE
TITLE: GCN/SWIFT NOTICE
NOTICE_DATE: Sat 18 Feb 06 03:48:13 UT
NOTICE_TYPE: Swift-UVOT Image
TRIGGER_NUM: 191157, Seg_Num: 0
POINT_RA: 50.395d {+03h 21m 35s} (J2000)
POINT_DEC: +16.871d {+16d 52' 17"} (J2000)
ROLL: 255.474d
IMG_START_DATE: 13784 TJD; 49 DOY; 06/02/18
IMG_START_TIME: 13023.36 SOD {03:37:03.36} UT, 152.4 [sec] since BAT Trigger Time
FILTER: 3, V
EXPOSURE_ID: 161926624
X_OFFSET: 727 [pixels]
Y_OFFSET: 844 [pixels]
WIDTH: 160 [pixels]
HEIGHT: 160 [pixels]
X_GRB_POS: 887
Y_GRB_POS: 1004
BINNING_INDEX: 1
IM_URL: sw00191157000msuni0152.fits
SUN_POSTN: 331.46d {+22h 05m 51s} -11.70d {-11d 42' 01"}
SUN_DIST: 83.13 [deg] Sun_angle= -5.3 [hr] (East of Sun)
MOON_POSTN: 200.75d {+13h 22m 59s} -10.57d {-10d 34' 00"}
MOON_DIST: 150.46 [deg]
MOON_ILLUM: 80 [%]
GAL_COORDS: 166.91,-32.89 [deg] galactic lon,lat of the pointing direction
ECL_COORDS: 52.39, -1.55 [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 18 Feb 06 03:54:47 UT
NOTICE_TYPE: Swift-UVOT Source List
TRIGGER_NUM: 191157, Seg_Num: 0
POINT_RA: 50.395d {+03h 21m 35s} (J2000)
POINT_DEC: +16.872d {+16d 52' 21"} (J2000)
POINT_ROLL: 255.474d
IMG_START_DATE: 13784 TJD; 49 DOY; 06/02/18
IMG_START_TIME: 13229.65 SOD {03:40:29.65} UT, 358.7 [sec] since BAT Trigger Time
FILTER: 9, B
BKG_MEAN: 3.057
N_STARS: 44
X_OFFSET: 407 [pixels]
Y_OFFSET: 524 [pixels]
X_MAX: 1366 [pixels]
Y_MAX: 1483 [pixels]
DET_THRESH: 14
PHOTO_THRESH: 8
SL_URL: sw00191157000msufc0358.fits
SUN_POSTN: 331.47d {+22h 05m 53s} -11.70d {-11d 41' 55"}
SUN_DIST: 83.13 [deg] Sun_angle= -5.3 [hr] (East of Sun)
MOON_POSTN: 200.80d {+13h 23m 11s} -10.59d {-10d 35' 29"}
MOON_DIST: 150.52 [deg]
MOON_ILLUM: 80 [%]
GAL_COORDS: 166.90,-32.89 [deg] galactic lon,lat of the pointing direction
ECL_COORDS: 52.39, -1.55 [deg] ecliptic lon,lat of the pointing direction
COMMENTS: SWIFT-UVOT Source List.
- GCN NOTICE
TITLE: GCN/SWIFT NOTICE
NOTICE_DATE: Sat 18 Feb 06 03:56:07 UT
NOTICE_TYPE: Swift-UVOT Image
TRIGGER_NUM: 191157, Seg_Num: 0
POINT_RA: 50.395d {+03h 21m 35s} (J2000)
POINT_DEC: +16.872d {+16d 52' 21"} (J2000)
ROLL: 255.474d
IMG_START_DATE: 13784 TJD; 49 DOY; 06/02/18
IMG_START_TIME: 13229.65 SOD {03:40:29.65} UT, 358.7 [sec] since BAT Trigger Time
FILTER: 9, B
EXPOSURE_ID: 161926830
X_OFFSET: 727 [pixels]
Y_OFFSET: 844 [pixels]
WIDTH: 160 [pixels]
HEIGHT: 160 [pixels]
X_GRB_POS: 887
Y_GRB_POS: 1004
BINNING_INDEX: 1
IM_URL: sw00191157000msuni0358.fits
SUN_POSTN: 331.47d {+22h 05m 53s} -11.70d {-11d 41' 54"}
SUN_DIST: 83.13 [deg] Sun_angle= -5.3 [hr] (East of Sun)
MOON_POSTN: 200.81d {+13h 23m 13s} -10.60d {-10d 35' 47"}
MOON_DIST: 150.53 [deg]
MOON_ILLUM: 80 [%]
GAL_COORDS: 166.90,-32.89 [deg] galactic lon,lat of the pointing direction
ECL_COORDS: 52.39, -1.55 [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 18 Feb 06 04:30:11 UT
NOTICE_TYPE: Swift-UVOT Source List
TRIGGER_NUM: 191157, Seg_Num: 0
POINT_RA: 50.395d {+03h 21m 35s} (J2000)
POINT_DEC: +16.872d {+16d 52' 21"} (J2000)
POINT_ROLL: 255.474d
IMG_START_DATE: 13784 TJD; 49 DOY; 06/02/18
IMG_START_TIME: 13700.41 SOD {03:48:20.41} UT, 829.4 [sec] since BAT Trigger Time
FILTER: 9, B
BKG_MEAN: 1.676
N_STARS: 46
X_OFFSET: 407 [pixels]
Y_OFFSET: 524 [pixels]
X_MAX: 1366 [pixels]
Y_MAX: 1483 [pixels]
DET_THRESH: 11
PHOTO_THRESH: 5
SL_URL: sw00191157000msufc0829.fits
SUN_POSTN: 331.49d {+22h 05m 58s} -11.69d {-11d 41' 24"}
SUN_DIST: 83.10 [deg] Sun_angle= -5.3 [hr] (East of Sun)
MOON_POSTN: 201.07d {+13h 24m 16s} -10.73d {-10d 43' 33"}
MOON_DIST: 150.81 [deg]
MOON_ILLUM: 79 [%]
GAL_COORDS: 166.90,-32.89 [deg] galactic lon,lat of the pointing direction
ECL_COORDS: 52.39, -1.55 [deg] ecliptic lon,lat of the pointing direction
COMMENTS: SWIFT-UVOT Source List.
- GCN Circular #4775
G. Cusumano (IASF-Pa INAF), S. Barthelmy (GSFC), N. Gehrels (GSFC),
S. Hunsberger (PSU), S. Immler (GSFC), F. Marshall (GSFC),
D. Palmer (LANL), T. Sakamoto (GSFC/ORAU)
on behalf of the Swift team:
At 03:34:30 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 060218 (trigger=191157). Swift slewed immediately to the burst.
The BAT on-board calculated location is RA,Dec 50.404, +16.866 deg
{03h 21m 37s, +16d 51' 58"} (J2000) with an uncertainty of 3 arcmin
(radius, 90% containment, including systematic uncertainty). The TDRSS
lightcurve shows nothing, which is consistent and common for an image trigger.
The XRT began taking data at 03:37:04 UT, 153 seconds after the BAT trigger.
The XRT on-board centroid algorithm did not find a source in the image and
no prompt position is available. We are waiting for down-linked data
to detect and determine a position for the source.
The UVOT began taking data 152 seconds after the BAT trigger.
There is an indication of an afterglow candidate at RA,Dec
03h 21m 39.8s,+16d 52' 06" +/- 1 arcsec with an estimated B magnitude of 19.4.
- GCN NOTICE
TITLE: GCN/SWIFT NOTICE
NOTICE_DATE: Sat 18 Feb 06 04:31:26 UT
NOTICE_TYPE: Swift-UVOT Image
TRIGGER_NUM: 191157, Seg_Num: 0
POINT_RA: 50.395d {+03h 21m 35s} (J2000)
POINT_DEC: +16.872d {+16d 52' 21"} (J2000)
ROLL: 255.474d
IMG_START_DATE: 13784 TJD; 49 DOY; 06/02/18
IMG_START_TIME: 13700.41 SOD {03:48:20.41} UT, 829.4 [sec] since BAT Trigger Time
FILTER: 9, B
EXPOSURE_ID: 161927301
X_OFFSET: 727 [pixels]
Y_OFFSET: 844 [pixels]
WIDTH: 160 [pixels]
HEIGHT: 160 [pixels]
X_GRB_POS: 887
Y_GRB_POS: 1004
BINNING_INDEX: 1
IM_URL: sw00191157000msuni0829.fits
SUN_POSTN: 331.49d {+22h 05m 58s} -11.69d {-11d 41' 23"}
SUN_DIST: 83.10 [deg] Sun_angle= -5.3 [hr] (East of Sun)
MOON_POSTN: 201.07d {+13h 24m 18s} -10.73d {-10d 43' 50"}
MOON_DIST: 150.82 [deg]
MOON_ILLUM: 79 [%]
GAL_COORDS: 166.90,-32.89 [deg] galactic lon,lat of the pointing direction
ECL_COORDS: 52.39, -1.55 [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 18 Feb 06 05:04:32 UT
NOTICE_TYPE: Swift-UVOT Source List
TRIGGER_NUM: 191157, Seg_Num: 0
POINT_RA: 230.419d {+15h 21m 41s} (J2000)
POINT_DEC: -80.012d {-80d 00' 43"} (J2000)
POINT_ROLL: 102.815d
IMG_START_DATE: 13784 TJD; 49 DOY; 06/02/18
IMG_START_TIME: 13906.77 SOD {03:51:46.77} UT, 1035.8 [sec] since BAT Trigger Time
FILTER: 3, V
BKG_MEAN: 1.223
N_STARS: 86
X_OFFSET: 407 [pixels]
Y_OFFSET: 524 [pixels]
X_MAX: 1366 [pixels]
Y_MAX: 1483 [pixels]
DET_THRESH: 9
PHOTO_THRESH: 4
SL_URL: sw00191157000msufc1035.fits
SUN_POSTN: 331.52d {+22h 06m 04s} -11.68d {-11d 40' 53"}
SUN_DIST: 80.36 [deg] Sun_angle= 6.7 [hr] (West of Sun)
MOON_POSTN: 201.33d {+13h 25m 19s} -10.86d {-10d 51' 22"}
MOON_DIST: 70.51 [deg]
MOON_ILLUM: 79 [%]
GAL_COORDS: 309.35,-19.07 [deg] galactic lon,lat of the pointing direction
ECL_COORDS: 257.87,-58.26 [deg] ecliptic lon,lat of the pointing direction
COMMENTS: SWIFT-UVOT Source List.
- GCN NOTICE
TITLE: GCN/SWIFT NOTICE
NOTICE_DATE: Sat 18 Feb 06 05:05:42 UT
NOTICE_TYPE: Swift-UVOT Image
TRIGGER_NUM: 191157, Seg_Num: 0
POINT_RA: 230.419d {+15h 21m 41s} (J2000)
POINT_DEC: -80.012d {-80d 00' 43"} (J2000)
ROLL: 102.815d
IMG_START_DATE: 13784 TJD; 49 DOY; 06/02/18
IMG_START_TIME: 13906.77 SOD {03:51:46.77} UT, 1035.8 [sec] since BAT Trigger Time
FILTER: 3, V
EXPOSURE_ID: 161927507
X_OFFSET: 727 [pixels]
Y_OFFSET: 844 [pixels]
WIDTH: 160 [pixels]
HEIGHT: 160 [pixels]
X_GRB_POS: 887
Y_GRB_POS: 1004
BINNING_INDEX: 1
IM_URL: sw00191157000msuni1035.fits
SUN_POSTN: 331.52d {+22h 06m 04s} -11.68d {-11d 40' 52"}
SUN_DIST: 80.36 [deg] Sun_angle= 6.7 [hr] (West of Sun)
MOON_POSTN: 201.34d {+13h 25m 21s} -10.86d {-10d 51' 38"}
MOON_DIST: 70.50 [deg]
MOON_ILLUM: 79 [%]
GAL_COORDS: 309.35,-19.07 [deg] galactic lon,lat of the pointing direction
ECL_COORDS: 257.87,-58.26 [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 Circular #4776
J. A. Kennea, D. N. Burrows (PSU), G. Cusumano (INAF-Pa), and G.
Tagliaferri (INAF-OAB) report on behalf of the Swift XRT team:
The Swift XRT observed the position of GRB 060218 (Cusumano et al., GCN
4775) beginning at 03:37:04 UT, 153 s after the BAT trigger. The
on-board centroiding algorithm did not find a source. Ground-processing
of the data was delayed, but we have now partially analyzed data from
the first two orbits, using Level 0 data from the MOC. The XRT was in
Windowed Timing mode for the entire first orbit and therefore no
position is available from that orbit. The XRT switched into PC mode
during the second orbit, during which we clearly detect a bright, fading
point source located at:
RA(J2000): 03h 21m 39.7s
Dec(J2000): 16d 52' 01.33"
We estimate the uncertainty to be about 5 arcseconds (90% confidence
radius). This position lies 39 arcseconds from the BAT position reported
in GCN 4775. A full analysis of the XRT data will follow.
This circular is an official product of the Swift XRT Team.
- GCN Circular #4777
Richard J. Cool (Arizona), Daniel J. Eisenstein (Arizona),
David W. Hogg (NYU), Michael R. Blanton (NYU), David
J. Schlegel (LBNL), J. Brinkmann (APO), Donald P. Schneider
(PSU), and Daniel E. Vanden Berk (PSU) report:
The Sloan Digital Sky Survey (SDSS) imaged the field of
burst GRB060218 prior to the burst. As these data should
be useful as a pre-burst comparison and for calibrating
photometry, we are supplying the images and photometry
measurements for this GRB field to the community.
Data from the SDSS, including 5 FITS images, 3 JPGS, and
3 files of photometry and astrometry, are being placed
at http://mizar.as.arizona.edu/~grb/public/GRB060218
We supply FITS images in each of the 5 SDSS bands of a
8'x8' region centered on the GRB position (ra=50.4154
(03:21:39.7), dec=16.8670 (16:52:01.3); GCN 4776),
as well as 3 gri color-composite JPGs (with different
stretches). The units in the FITS images are nanomaggies
per pixel. A pixel is 0.396 arcsec on a side. A nanomaggie
is a flux-density unit equal to 10^-9 of a magnitude
0 source or, to the extent that SDSS is an AB system,
3.631e-6 Jy. The FITS images have WCS astrometric
information.
In the file GRB060218_sdss.calstar.dat, we report
photometry and astrometry of 308 bright stars (r<20.5)
within 15' of the burst location. The magnitudes presented
in this file are asinh magnitudes as are standard in the
SDSS (Lupton 1999, AJ, 118, 1406). Beware that some of
these stars are not well-detected in the u-band; use the
errors and object flags to monitor data quality.
In the files GRB060218_sdss.objects_flux.dat and
GRB060218_sdss.objects_magnitudes.dat, we report photometry
of 947 objects detected within 6' of the GRB position.
We have removed saturated objects and objects with
model magnitudes fainter than 23.0 in the r-band.
The fluxes listed in GRB060218_sdss.objects_flux.dat
are in nanomaggies while the magnitudes listed in
GRB060218_sdss.objects_magnitudes.dat are asinh magnitudes.
All quantities reported are standard SDSS photometry,
meaning that they are very close to AB zeropoints
and magnitudes are quoted in asinh magnitudes.
Photometric zeropoints are known to about 2% rms.
None of the photometry is corrected for dust extinction.
The Schlegel, Finkbeiner, and Davis (1998) predictions
for this region are A_U=0.749 mag, A_g=0.551 mag, A_r =
0.400 mag, A_i=0.303 mag, and A_z=0.215 mag.
There are currently no objects within 6 arcminutes of the
GRB position in the SDSS spectroscopic database.
SDSS astrometry is generally better than 0.1 arcsecond
per coordinate. Users requiring high precision astrometry
should take note that the SDSS astrometric system can
differ from other systems such as those used in other
notices; we have not checked the offsets in this region.
More detailed information pertaining to our SDSS GRB
releases can be found in our initial data release paper
(Cool et al. 2006, astro-ph/0601218). See the SDSS DR4
documentation for more details: http://www.sdss.org/dr4.
These data have been reduced using a slightly different
pipeline than that used for SDSS public data releases.
We cannot guarantee that the values here will exactly match
those in the data release in which these data are included.
In particular, we expect the photometric calibrations to
differ by of order 0.01 mag.
This note may be cited, but please also cite the SDSS data
release paper, Adelman-McCarthy et al. (2006, ApJS, in
press, astro-ph/0507711), when using the data or referring
to the technical documentation.
- GCN Circular #4779
F. Marshall (GSFC), S. Immler (GSFC/USRA) and G. Cusumano (IASF-Pa INAF)
report on behalf of the Swift team:
The UVOT source reported by Cusumano et al. (GCN 4775) is detected in all
four UVOT finding chart exposures ranging from 153s to 1036s
from the burst trigger as shown in the table below. There is marginal
evidence for brightening in the V filter. The revised source position is
03:21:39.71 +16:52:02.6 (J2000) with an estimated 1-sigma error of about 1.0".
This position is within the XRT error circle (Kennea et al. GCN 4776).
We note the existence of a source in the USNO-B1 catalog
at 03:21:39.69 +16:52:02.2 with a B2 magnitude of 20.67
and an R2 magnitude of 20.3. Further UVOT observations
are underway to search for fading of this afterglow candidate.
T_start Exposure Filter Mag Mag. Range (1-sigma)
153 200 V 19.6 19.1 - 20.3
359 155 B 19.4 19.2 - 19.6
830 127 B 19.3 19.1 - 19.5
1036 148 V 18.4 18.2 - 18.6
- GCN Circular #4780
L. Barbier (GSFC), S. Barthelmy (GSFC), J. Cummings (GSFC/NRC),
G. Cusumano (IASF-Pa INAF), E. Fenimore (LANL), N. Gehrels (GSFC),
D. Hullinger (GSFC/UMD), H. Krimm (GSFC/USRA), C. Markwardt (GSFC/UMD),
D. Palmer (LANL), A. Parsons (GSFC), T. Sakamoto (GSFC/NRC),
G. Sato (ISAS), J. Tueller (GSFC)
on behalf of the Swift-BAT team:
Using a partial data set from T-60 to T+116 sec from the recent telemetry
downlink, we report further analysis of BAT GRB 060218 (trigger #191157)
(Cusumano, et al., GCN 4775). The BAT ground-calculated position is
RA,Dec = 50.380,+16.904 deg {03h 21m 31.1s, 16d 54' 14.8"} (J2000)
+- 2.6 arcmin, (radius, sys+stat, 90% containment). The partial coding was 88%.
The mask-weighted lightcurve is weak and flat from T-60 to T+120 sec
(all the data we have so far). Nothing can be said about T90.
Since there is obvious emission prior to T-60 and after T+116,
we are not quoting the usual spectral fit values at this time.
We note that Swift completed a Pre-Planned Slew 8 sec prior to the beginning
of the image trigger integration which resulted in trigger 191157,
and therefore BAT was unable to trigger prior to this slew on this source.
We also note that all the emission is in the 15-50 keV band.
There is also a detection at this location at the same flux level at T+900 sec.
And there is a possible 5.6-sigma detection at the same location on Jan 17, 2006
(a month earlier). While we can rule out that this is a chance fluctuation,
it does call into question the GRB nature of the event (trigger 191157).
At this stage in the analysis, it is equally likely that this trigger
is a GRB or hard x-ray transient. We expect the full data set by Feb 20,
and so will be able make a better assessment.
- GCN Circular #4781
G. Cusumano (IASF-Pa INAF), A. Moretti (INAF-OAB), G. Tagliaferri
(INAF-OAB), J. Kennea (PSU) and D. Burrows (PSU), report on behalf of
the Swift/XRT Team:
We have performed a preliminary analysis of Swift/XRT ground-linked data
associated to the possible burst GRB060218 (trigger=191157; Cusumano et
al., GCN 4775, Kennea et al. 4776). We confirm the presence of a bright
X-ray source at the following location:
RA(J2000): 3h 21m 39.9s
Dec(J2000): 16d 52m 03.7s
with an estimated uncertainty of 7 arcseconds (90% containment). Note
that this position lies 3.7" from the previous XRT position (GCN 4775),
3' from the BAT position reported in GCN 4780 and 2.9" from the UVOT
position. A full analysis of the XRT data will follow.
This circular is an official product of the Swift XRT Team.
- GCN Circular #4782
R. Quimby (U Texas), B. E. Schaefer (Louisiana State), H. Swan (U
Mich), report on behalf of the ROTSE collaboration:
ROTSE-IIIb, located at the McDonald Observatory, Texas, responded to
Swift trigger 191157 (possible GRB 060218A; Cusumano et al. GCN 4775;
Barbier et al. GCN 4780). The first image was taken at 03:36:07.9 UT,
97.0 s after the burst (5.9 s after the GCN notice time). We detect a
source coincident with the refined UVOT position reported by Marshall
et al. (GCN 4779). Intermittent clouds reduced the overall data
quality, and after 80 minutes the clouds rendered the images
unusable. We set the following magnitude limits and detection
calibrated relative to the USNO-B1.0 R2 magnitudes:
tstart(s) tend(s) exp(s) mag emag limmag
--------------------------------------------------------------
96.98 130.61 25 --- -- 15.68
217.71 472.78 180 --- -- 17.60
482.43 681.24 180 --- -- 18.55
690.49 1027.40 300 18.09 0.11 19.00
1036.55 1789.28 660 --- -- 18.44
1868.39 4780.74 1680 --- -- 16.91
These magnitudes show that the optical source was significantly
brighter for a ~5-minute interval starting ~12-minutes after the
burst than either before or after this interval, as is consistent with
the two UVOT V-band magnitudes reported by Marshall et al. (GCN 4779).
- GCN Circular #4783
N. Mirabal (U. Michigan) reports:
"Analysis of the SDSS pre-burst observations of the GRB 060218 field
(Cool et al. GCN #4777) reveals an extended object at 03h21m39.68s
+16:52:01.66 (J2000). Given the proximity of this object to the reported
XRT and UVOT positions for a candidate afterglow (Cusumano et al. GCN
#4775, Marshall et al. GCN #4779), this should be considered a potential
host galaxy of a low-redshift GRB. Further multiwavelength observations
are encouraged to confirm the reality of this trigger (Barbier et al. GCN
#4780), and its possible association with this nearby galaxy. I
acknowledge useful conversations with Richard Cool."
- GCN Circular #4784
N. Mirabal (U. Michigan) reports on behalf of the MDM Observatory GRB
follow-up team:
"I observed the candidate optical afterglow of Swift GRB 060218 detected
by the Swift UVOT (Cusumano et al. GCN #4775, Marshall et al. GCN #4779,
Quimby et al. GCN #4782) with the MDM 2.4m telescope and RETROCAM imager
under partly cloudy conditions. Calibration with SDSS pre-burst
observations (Cool et al. GCN #4777) yields r = 17.55 +/- 0.1 on Feb.
19.1438 UT for the OT. This is brighter than the pre-burst observations
and confirms it as the OT of GRB 060218."
- GCN Circular #4785
F. Marshall (GSFC), S. Immler (GSFC/USRA) and G. Cusumano (IASF-Pa INAF)
report on behalf of the Swift team:
Continuing UVOT observations of the possible GRB 060218 show that
the candidate optical afterglow reported by Cusumano et al. (GCN 4775)
and Marshall et al. (GCN 4779) has brightened by a factor of about 5
in the 10 hours since the BAT trigger. Consequently, this source is unlikely
to be the optical afterglow of a GRB. This brightening, the extended emission
detected with BAT, and the possible BAT detection a month earlier
(Barbier et al. GCN 4780) suggest that the UVOT source is the optical
counterpart of a hard X-ray transient.
- GCN Circular #4786
G. Cusumano (IASF-Pa INAF), A. Moretti (INAF-OAB), G. Tagliaferri=20
(INAF-OAB), J. Kennea (PSU) and D. Burrows (PSU), report on behalf of=20
the Swift/XRT Team:
We analised the first 14 orbits of data (the first orbit is fully in=20
Windowed Timing (WT) mode, the second is in WT mode for the first 84=20
seconds, the rest of the data are all in Photon Counting (PC) mode). The=20
following refined position for the X-ray afterglow was determined:
RA(J2000) =3D 03h 21m 39.7s
Dec(J2000) =3D +16d 52' 01.8"
with an estimated uncertainty of 3.6 arcsec (90% containment). This is=20
3.0 arcmin from the BAT position reported in GCN 4780, 3.4 arcsec from=20
the XRT position given in GCN 4781 and 0.8 arcsec from the UVOT source=20
given in GCN 4779.
The WT light curve starts 159 s after the BAT trigger with a count rate=20
that rises from about 40 counts/s up to about 110 counts/s. The peak=20
occurs around 990 s after the trigger, then the count rate decays and at=20
2770 s after the trigger, when the first observation orbit ends, the=20
count rate is about 50 counts/s. At the beginning of the second orbit=20
(5944 s post-trigger) the count rate has faded to a value of about 1.1=20
cts/s and decays very fast. The light curve after the first orbit is=20
modelled by a broken power law characterized by a decay index of 6.38 =B1=
=20
0.05 up to 9250 =B1 270 s post trigger, followed by an intensity decrease=
=20
with a decay index of 1.15+/- 0.15.=20
The light curve can be seen at=20
http://www.merate.mi.astro.it/~moretti/lc_060218.gif
The spectrum obtained for the first orbit of data (159 - 2770 s=20
post-trigger) can be fitted with a power-law of photon index Gamma =3D=20
1.82 =B1 0.01, with an absorbing column density of (1.9 =B1 0.01)e21 cm^=
-2=20
in excess of the Galactic column of 1.1e21 cm^-2. Over this time span,=20
the mean 0.2-10 keV observed (unabsorbed) flux is 3.6e-9 (5.6e-9) erg=20
cm^-2 s^-1.
The spectrum obtained in the following orbits can be fitted with a=20
power-law of photon index Gamma =3D 3.3 =B1 0.2, with an excess of absorb=
ing=20
column density of (3.2 =B1 0.4)e21 cm^-2. The mean 0.2-10 keV observed=20
(unabsorbed) flux is 1.5e-12 (1.4e-11) erg cm^-2 s^-1.
If the burst continues to decay at the current rate we estimate an XRT=20
count rate of 2.5e-3 counts/s at T+48hr, which corresponds to an=20
unabsorbed 0.2-10 keV flux of 7.6e-13 erg cm^-2 s^-1.
The long, slow flux increase and gradual decrease are unlike any=20
previous GRB prompt or afterglow emission seen by the XRT. Combined=20
with the unusual spectral evolution, this suggests that this source may=20
be an X-ray transient rather than a GRB.
This circular is an official product of the Swift XRT Team.
- GCN Circular #4787
N. Gehrels (NASA-GSFC) on behalf of the Swift team:
We point out that GRB 060218 (Cusumano et al. GCN 4775) is a
strange event. It has
- a gamma-ray light curve that is flat and a soft spectrum
(Barbier et al. GCN 4780)
- an X-ray light curve with a long, slow rise and gradual
decline (Cusumano et al. GCN 4786)
- an optical light curve with brightening after 10 hours
(Marshall et al. GCN 4785).
These characteristics are unlike previous GRBs.
It has properties that are also atypical of a transient:
- it is far off the galactic plane (b = -32.9 deg) and
far away from the bulge (l = 166.9 deg)
- there is a possible association (Mirabel GCN 4783) with
a galaxy in the SDSS pre-burst field (Cool et al. GCN 4777).
Further observations are warranted.
- GCN Circular #4790
A. de Ugarte Postigo, A. J. Castro-Tirado,
S. B. Pandey (IAA-CSIC, Granada), D. Barrado-
Navascu=E9s, B. Montesinos (LAEFF-INTA, Madrid),
K. Mishra (ARIES, Nainital),and S. Dehaes
(Inst. voor Sterrenkunde, K.U. Leuven), on
behalf of a larger collaboration report:
"Following the detection by SWIFT of "GRB" 060218
(Cusumano et al. GCN Circ. 4770, Gehrels et al.
GCN Circ. 4787) we have obtained UBVRIJHK images
with the 1.2m Mercator (+MEROPE) and 3.5m TNG (+NICS)
telescopes at La Palma (Canary Islands), starting on
Feb 19.85 UT (i.e. 40.8 hr after the event).
We detect a near-IR counterpart to the hard energy
source on a stacked 150s image in the K'-band with
K about 17 (with respect to 2MASS catalogue).
Astrometry against USNO-A2.0 yields RA(2000) =3D
03 21 39.71, Dec(2000) =3D +16 52 02.1 (+/-0.5").
This position is fully consistent with the optical
counterpart proposed by Cusumano et al. (op. cit.)
and Marshall et al. (GCN Circ. 4779) and with the
faint object reported by Mirabal (GCN Circ. 4783)
on the SDSS archival data (Cool et al. GCN Circ.
4777). However, we do not find evidence of underlying
extended emission in our K'-band frame (0".7 seeing).
Together with the fact that the colour index of the
source is J-K = 0, unlike GRB afterglow colours
(see fig. 2 of Gorosabel et al. 2002, A&A 384, 11),
it clearly favours a high-energy transient in our
Galaxy."
This Circular might be cited.
- GCN Circular #4792
N. Mirabal (U. Michigan) and J. P. Halpern (Columbia U.) report on behalf
of the MDM Observatory GRB follow-up team:
"We obtained a low-resolution spectrum of the optical afterglow and
host galaxy of GRB 060218 using the MDM 2.4m telescope and Boller &
Chivens (CCDS) Spectrograph on Feb. 20 02:20 UT. Strong, narrow emission
lines of H-beta, [O III] 4959,5007, and H-alpha at z=0.0331 are seen,
superposed on a blue continuum, which is still much brighter than the
SDSS pre-burst magnitudes. The line ratios are typical of a high-excitation
starburst. This confirms the low-redshift, extragalactic nature of this
unusual GRB.
This message may be cited."
- GCN Circular #4794
Alicia M. Soderberg (Caltech) and Dale A. Frail (NRAO) report on behalf
of a large collaboration:
"We observed the field of GRB 060218 (GCN 4775) with the Very Large Array
at 8.46 GHz on February 20.0 UT. We detect a source coincident with the
optical afterglow candidate (GCN 4779) and host galaxy (GCN 4783).
Further observations are planned."
- GCN Circular #4800
F. Marshall (GSFC), P. Brown (PSU), S. Immler (GSFC/USRA), and
G. Cusumano (IASF-Pa INAF) report on behalf of the Swift team:
The optical counterpart of the unusual GRB 060218
(Cusumano et al. (GCN 4775), Marshall et al. (GCN 4779))
is detected in all 6 of the Swift/UVOT broad-band filters
(V, B, U, UVW1, UVM2, UVW2). The filters collectively cover
the wavelength range from 180 to 560 nm. The light curves
for all the filters have similar shapes. The emission steadily
brightens by 1 to 2 magnitudes from the first detection about
150 s. after the burst trigger, peaks in a broad plateau
about 10 hours after the trigger, and then slowly declines for
at least the next 20 hours. Peak magnitudes
are 17.8, 17.7, 16.3, 16.2, 16.1, and 16.0 for the
V, B, U, UVW1, UVM2, and UWW2 filters respectively.
UVOT observations are continuing.
- GCN Circular #4802
W.K. Zheng, M.Zai, Y.L. Qiu, J.Y. Wei,J.Y. Hu and J.S Deng
reports on behalf of the Xinglong GRB follow-up team report:
"We observed the optical counterpart of the GRB 20060218
(Cusumano et al. (GCN 4775)) with the 0.8m and the 1m telescopes
at Xinglong Observatory, National Astronomical Observatories,
Chinese Academy of Sciences. We began observations in R band
7.1953 hours after the trigger. Preliminary analyses show the
object has a R magnitude of 17.79 0.1 on Feb 18.4522 UT
and 18.25 0.1 on Feb 20.4471 UT (reference stars from
USNO-A2.0), which is brighter than the pre-burst counterpart
observed by SDSS(GCN 4777). Further analysis is under processing."
This message may be cited
- GCN Circular #4803
N. Masetti, E. Palazzi (INAF-IASF, Bologna), E. Pian (INAF, OA
Trieste) and F. Patat (ESO), on behalf of the GRACE collaboration, report:
"On 2006 February 21.051 UT we acquired a 30-min spectrum of the optical
transient associated with the possible GRB060218 (Cusumano et al., GCN
4775) with VLT-Antu equipped with FORS2 and low resolution grating
300V+GG435. We confirm the presence of narrow nebular lines at redshift
z = 0.033 (Mirabal & Halpern, GCN 4792). We also note that the spectral
continuum shows an overall shape which resembles that of supernova 1997ef
around maximum (Iwamoto et al., 2000, ApJ, 534, 660).
This may suggest that, if this object is a SN associated with GRB060218,
it is either rapidly evolving or it exploded days before the GRB.
We acknowledge the assistance of the ESO-Paranal staff.
This message may be cited."
- GCN Circular #4804
A. M. Soderberg (Caltech), E. Berger (Carnegie), and B. P. Schmidt (ANU)
report on behalf of a larger collaboration:
"We obtained an optical spectrum of the afterglow of GRB 060218 (GCN 4775)
with GMOS on the Gemini-south telescope starting on 2006 Feb 21.024 UT,
for a total of 1800 sec. We confirm the presence of narrow emission lines
at z=0.033 (GCNs 4792,4803), as well as the presence of broad absorption
features similar to those seen in SN1998bw and other broad-lined
Type Ibc supernovae (GCN 4803).
A plot of our spectrum is available at:
http://www.ociw.edu/~eberger/grb060218_gemini.ps
Further observations are planned."
- GCN Circular #4805
J. Nousek (PSU), G. Cusumano (IASF-Pa INAF), A. Moretti (INAF-OAB), G.
Tagliaferri
(INAF-OAB), S. Campana (INAF-OAB), J. Kennea (PSU), D. Burrows (PSU), P. Roming
(PSU), D. VandenBerk (PSU), P. Brown (PSU), N. Gehrels (GSFC), S. Barthelmy
(GSFC), F. Marshall(GSFC), P. Boyd (GSFC), T. Sakamoto (GSFC), J. Osborne
(U. Leicester), P. O'Brien (U. Leicester), G. Chincarini (Univ.
Milano-Bicocca),
B. Zhang (UNLV) and M. de Pasquale (MSSL)
report on behalf of the Swift Team:
The Swift team now believes that GRB 060218 is most likely an underluminous
GRB. This view is supported by the remarkably long duration of the prompt
emission seen by all three Swift instruments and the probable association
with a
low-z (z=0.033) galaxy (Mirabel GCN 4783; Masetti et al GCN 4803). Although
there are unusual aspects to this event (cf. Gehrels GCN 4787), the high
galactic
latitude seems to make a Galactic X-ray transient origin unlikely. Moreover,
the extremely rapid X-ray decay after T+3000 seconds (3 orders of magnitude
in an hour), followed by a slow power law decay in time (alpha = 1.2), looks
very much like a normal GRB XRT lightcurve.
We also draw attention to the chromatic nature of the Swift light curves.
The BAT emission peaked substantially earlier than the XRT emission,
which preceded the UVOT emission peak. Although the low
luminosity inferred from the low-z might suggest a highly off-axis viewing
angle for this burst, an off-axis burst should show achromatic emission
variation, which is not seen here (see predictions by Kumar, P. & Granot, J.
2003, ApJ, 591, 1075, for example.)
The burst continues to be bright in the UVOT, (V= 18.29 +/- 0.07
at 21:29 UT on 20 Feb 2006), so we suggest additional follow-up observations
that might confirm signatures of a host supernova or other evidence that
might clarify the nature of this highly unusual GRB.
- GCN Circular #4806
S. Barthelmy (GSFC), J. Cummings (GSFC/NRC), T. Sakamoto (GSFC/NRC),
C. Markwardt (GSFC/UMD), N. Gehrels (GSFC)
on behalf of the Swift-BAT team:
Using the data set from T-50 to T+2000 sec from telemetry downlinks,
we report further analysis of BAT GRB 060218 (trigger #191157)
(Cusumano, et al., GCN 4745; Barbier, et al., GCN 4780; Gehrels, GCN 4787).
The BAT ground-calculated position is RA,Dec = 50.379,+16.904 deg
{3h 21m 30.9s, 16d 54' 14.2"} (J2000) +- 2.6 arcmin, (radius, sys+stat,
90% containment). The partial coding was 88%.
Extending the mask-weighted lightcurve beyond T+120 sec (GCN 4780),
it continues the weak, flat, soft emission out to T+280 sec. This flux
is 0.06 +- 0.02 counts/cm2/sec in the 15-50 keV band. At T+290 sec
there is a 10-sec wide spike which is spectrally harder than the
flat emission (all the emission is in the 25-100 keV band).
Starting at ~T+200 the lightcurve starts an approximately
linear increase to a peak flux of 0.1 counts/cm2/sec (15-100 keV),
and then begins a roughly exponential decay out to at least
T+2000 sec.
We note that this is a very long event. It is among the very longest
of GRBs. At this point, using BAT results alone, we can not rule out
a non-GRB nature for this event.
- GCN Circular #4807
D. Fugazza, P. D'Avanzo (INAF/OABr), D. Malesani (SISSA/ISAS), M. Della
Valle (INAF/OAA), N. Masetti, E. Palazzi (INAF/IASF Bo), E. Pian
(INAF/OATs), L.A. Antonelli, V. D'Elia, F. Fiore, S. Piranomonte, L.
Stella (INAF/OAR), S. Campana, G. Chincarini, S. Covino, G. Tagliaferri
(INAF/OABr), L. Di Fabrizio (INAF/TNG) report:
We observed the optical counterpart of GRB 060218 (Moretti et al., GCN
4775; Marshall et al., GCN 4779; Quimby et al., GCN 4782) with the 3.6m
TNG telescope located at the Canary Islands.
Spectroscopy in the range 4000-8000 AA reveals a blue continuum with
prominent star-forming emission features (Mirabal & Halpern, GCN 4792;
Masetti et al., GCN 4803).
A weak, broad bump is seen at ~5000 A, which is consistent with the peak
of a broad-lined SN like SN\1998bw (see also Masetti et al., GCN 4803;
Soderberg et al., GCN 4804). The overall observed shape would imply a
roughly equal contribution from the afterglow and the SN.
This message can be cited.
- GCN Circular #4808
E. Berger (Carnegie), B. P. Schmidt (ANU), and A. M. Soderberg (Caltech)
report on behalf of a larger collaboration:
"As part of our spectroscopic observations with GMOS on Gemini-south (GCN
4804) we obtained a single 30-sec r-band image of the field on 2006, Feb
21.01 UT. Calibration against 9 nearby stars from SDSS (GCN 4777) yields
r = 17.92+/-0.12 mag for the afterglow+SN+host. Subtracting off the
contribution of the host (r = 19.93+/-0.03; GCN 4777) we find that the
afterglow+SN faded by 0.43+/-0.22 mag compared to the measurement by
Mirabal (GCN 4784). This corresponds to a decay rate of -0.4+/-0.2, which
is relatively shallow compared to typical optical afterglows, and
furthermore indicates a turnover in the flux evolution following the
initial period of brightening in the B,V bands observed with UVOT (GCN
4800)."
- GCN Circular #4809
T. A. Fatkhullin, V. V. Sokolov, A. V. Moiseev (SAO-RAS Nizhnij Arkhyz),
S. Guziy and A. J. Castro-Tirado (IAA-CSIC Granada), on behalf
of a larger collaboration, report:
"We have obtained optical spectroscopy of the GRB 060218 optical
counterpart (Cusumano et al. GCNC 4775) with the 6.0m BTA telescope
of SAO-RAS in Zelenchuk, equipped with SCORPIO. First epoch
spectroscopy in the 3500-7500 A range was obtained on Feb 20.65 UT,
confirming z = 0.033 (Mirabal and Halpern GCNC 4792). Second epoch
data was gathered on Feb 21.65 UT. Comparison between the two datasets
clearly reveals continuum variations that we interpret as the emergence
of the underlying type-Ic SN spectrum, strengthening the SN-GRB 060218
relationship first suggested by Masetti et al. (GCNC 4803). In
particular, an "emission peak" at ~4500 A is showing up, possibly as
a result of the blending of the Fe lines redward of this feature,
giving rise to a broad absorption trough, as it was seen in the type
Ic SNe 1997ef (Iwamoto et al. 2000, ApJ 534, 660) and 2002ap (Foley
et al. 2003, PASP 115, 1220). Further spectroscopic observations are
encouraged."
- GCN Circular #4810
P. D'Avanzo (INAF/OABr), D. Malesani (SISSA/ISAS), M. Della Valle
(INAF/OAA), D. Fugazza (INAF/OABr), N. Masetti, E. Palazzi (INAF/IASF
Bo), E. Pian (INAF/OATs), L.A. Antonelli, V. D'Elia, F. Fiore, S.
Piranomonte, L. Stella (INAF/OAR), S. Campana, G. Chincarini, S. Covino,
G. Tagliaferri (INAF/OABr), L. Di Fabrizio (INAF/TNG), report:
We observed again the optical counterpart of GRB 060218 (Moretti et al.
GCN 4775; Marshall et al., GCN 4779) with the TNG telescope. Comparison
between our previous photometry (taken on Feb 20.85 UT) and the new
observations (Feb 21.84 UT) reveals a rebrightening by 0.20+-0.05 mag in
both the V and R filters.
Following the earlier decay (e.g. Marshall et al., GCN 4800; Berger et
al., GCN 4808), this behaviour may mark the emergence of the underlying
SN 2006aj already suggested on spectroscopic grounds (Masetti et al.,
GCN 4803; Soderberg et al., IAUC 8674; Fugazza et al., GCN 4807, CBET
410; Mirabal et al., CBET 409; Fatkhullin et al., GCN 4809). The
rebrightening may also suggest that the SN is still before its maximum.
This message can be cited.
- GCN Circular #4812
Paolo A. Mazzali (MPA, INAF-Ts) and Elena Pian (INAF-Ts) report:
inspection of the VLT-FORS2 spectrum of GRB060218/SN2006aj taken on 21 Feb
2006 (Masetti et al. 2006, GCN 4803), i.e. ~3 days after the GRB event,
indicates that the observed features are similar to those of the energetic
type Ic SN 2002ap at a comparable epoch (Mazzali et al. 2002, Ap. J. 572,
L21, Fig. 2). In particular, broad absorptions near 4800 Ang and 5800 Ang
can be identified as due to FeII and SiII lines, respectively. This
suggests that the SN and the GRB occurred within ~1 day of one another.
The observed luminosity of the optical counterpart of GRB060218 is larger
than that of SN2002ap at the same epoch, and is consistent with the
luminosity of SN1998bw.
If an afterglow is still present, we estimate that it does not contribute
for more than 25% of the total flux. If it has a power-law shape, this is
not bluer than nu^{-2}.
Although spectroscopy of SN1998bw did not begin until day 8 (Galama et al.
1998, Nature 395, 670), and therefore a direct comparison is not yet
possible, it is likely that SN2006aj will evolve to resemble SN1998bw.
- GCN Circular #4816
Jan-Erik Ovaldsen (ITA), Dong Xu (DARK, NBI), Josefine H. Selj (ITA),
Andreas O. Jaunsen (ITA), Chloe Feron, Christina Thoene, Johan
P. U. Fynbo, and Jens Hjorth (DARK, NBI) report:
From observations of GRB060218/SN 2006aj (Cusumano et al., GCN #4775)
with DFOSC on the Danish 1.5m telescope at La Silla/ESO we find that
the optical afterglow + SN 2006aj has brightened by 0.2 (+/- 0.01) mag
in R and 0.1 (+/- 0.02) mag in V from Feb 20.03 UT to Feb 21.03 UT. An
optical brightening is in line with the notion that the underlying SN
2006aj has still to reach its maximum, as noted in previous reports.
- GCN Circular #4817
D. Malesani (SISSA/ISAS), P. D'Avanzo (INAF/OABr), M. Della Valle
(INAF/OAA), L.A. Antonelli, V. D'Elia, F. Fiore, S. Piranomonte, L.
Stella (INAF/OAR), S. Campana, G. Chincarini, S. Covino, G. Tagliaferri
(INAF/OABr), N. Masetti, E. Palazzi (INAF/IASF Bo), E. Pian (INAF/OATs),
M. Pedani (INAF/TNG) report:
We observed the optical counterpart of GRB 060218 (Cusumano et al., GCN
4775, 4781; Marshall et al., GCN 4800) with the TNG telescope under good
observing conditions. Comparison of the new data with our earlier
photometry (D'Avanzo et al., GCN 4810) reveals further brightening of
the source between Feb 21.85 and Feb 22.86 UT. This is consistent with
the underlying supernova being in the rise phase (Masetti et al., GCN
4803; Soderberg et al., IAUC 8674; Fugazza et al., GCN 4807, CBET 410;
Mirabal et al., CBET 409; Fatkhullin et al., GCN 4809; Mazzali & Pian,
GCN 4812).
This message can be cited.
- GCN Circular #4818
Jan-Erik Ovaldsen (ITA) et al. report:
Due to a typo the time of the brightening event was incorrectly
reported in GCN 4816.
The text should read:
"From observations of GRB060218/SN 2006aj (Cusumano et al., GCN #4775)
with DFOSC on the Danish 1.5m telescope at La Silla/ESO we find that
the optical afterglow + SN 2006aj has brightened by 0.2 (+/- 0.01) mag
in R and 0.1 (+/- 0.02) mag in V from Feb 21.03 UT to Feb 22.03 UT. An
optical brightening is in line with the notion that the underlying SN
2006aj has still to reach its maximum, as noted in previous reports."
- GCN Circular #4819
The very recent GRB 060218 long burst, brightening,
decline and rebrightening are puzzling, but consistent
with a model for GRB (and later on for SGR),
made by precessing spinning and blazing gamma
collimated Jets (solid angle about 10^-8 sr). See ref. below.
The GRB is associated to a blazing Jet whose
peak power is like a Supernova one (but apparent as GRB power).
In a very small near-by cosmic volumes as GRB 060218 at z=0.0331
or GRB980425 at z=0.008, it is quite off-axis (a few degree).
The off-axis geometry increase the probability to be found and reduce
its apparent luminosity (underluminous GRB).
The spinning-precessing jet lead to inner fast variability,
rebrightenings and while shining away, the smooth GRB decay.
In analogy, but at much lower power and therefore at nearer distances
later on, comparable and longeve X-Jet-pulsars are blazing as SGR.
The persistent precessing jet offer multi optical rebrightening
and-or permits un-correlation with earlier SN.
Hadron material around the SN make the GRB event a
possible TeV source observable by Milagro or ARGO,Hess and MAGIC,
an UHECR source in Auger and Hires,a UHE neutrino source for AMANDA
and Baikal (see DF and M.G. Nuovo Cim. 28 C.N 4-5.p.813-816.
astro-ph/0505150). The GRB maybe obsevable by its PeVs Glashow
neutrino while inducing air-showers at horizons
or EeV Tau air-showers below the MAGIC horizons
(see astro-ph/0511597).
In conclusion:
The presence (but even the already absence)
in near days of a complete SN rise combined with multi-bumps
(optical and-or radio rebrightening)
will stand for a definitive long live
(but decaying) precessing Jet,
blazing within an earlier SN shell.
Its possible late Jet blaze has been and it maybe
observed in future X flare again (if shining online to us).
On the contrary the rise of an unique dramatic SN bump
a few days later the observed brightening
and rebrightening of the GRB,
will be the clear hint that GRB-SN explosion maybe preceeded
by a persistent SGR Jet activity whose culmination ends into a the
catastrophic SN-GRB most powerfull beamed event. This scenario
may be still marginally coexisting with previous one ,
if a Jet activity may trigger the star collapse
and survive the SN explosion.
see D.F.
ATEL # 31; by DF, 15 Jul 1998;
"On the nature of GRB-SGRs blazing jets" in
Astron. Astrophys. Suppl. Ser. 138, 507-508;
and or more recent astro-ph/0501403 in
D.F. Chin.J.Astron.Astrophys.3,3 (2003) 472-482.
This message may be cited
Daniele Fargion
E_mail: daniele.fargion@roma1.infn.it
Phone: +390649914287
Fax: +39064957697
- GCN Circular #4822
T. Sakamoto (GSFC/ORAU), L. Barbier (GSFC), S. Barthelmy (GSFC),
J. Cummings (GSFC/ORAU), E. Fenimore (LANL), N. Gehrels (GSFC),
D. Hullinger (UMD), H. Krimm (GSFC/USRA), C. Markwardt (GSFC/UMD),
D. Palmer (LANL), A. Parsons (GSFC), G. Sato (ISAS), J. Tueller (GSFC),
on behalf of the Swift-BAT team:
We report further analysis of BAT GRB 060218/SN 2006aj (trigger #191157)
(Cusumano, et al., GCN 4775, Barbier, et al., GCN 4780,
Nousek, et al., GCN 4805).
The time-averaged spectrum from T-8 to T+2732 is best fit by
a simple power-law model. The power law index of the time-averaged
spectrum is 2.5 +- 0.1. The fluence in the 15-150 keV band is
6.8 +- 0.4 x 10^-6 erg/cm2. The peak energy flux in 1.6 sec time
interval starting from T+455.2 sec in the 15-150 keV band is
2.0 +- 1.1 x 10^-8 erg/cm2/sec.
Using the redshift of z=0.033 (Soderberg, et al., GCN 4804), the
isotropic equivalent energy, Eiso, is 1.9 +- 0.1 x 10^49 erg,
and the peak luminosity, Liso, is 6 +- 3 x 10^46 erg/s in
15.5 keV - 154.8 keV at the GRB rest frame. This Eiso is
comparable to that of the one of the softest X-ray flash XRF 020903
observed by HETE-2 (Sakamoto et al., ApJ, 602, 875, Soderberg et al.,
ApJ, 606, 994). The Liso is comparable to that of GRB 980425/SN 1998bw
(Galama et al., Nature, 395, 670). Note that the BAT Eiso and Liso
of GRB 060218 are not bolometric values due to its narrow energy band.
All the quoted errors are at the 90% confidence level. We use
Omega_M = 0.3, Omega_lamda = 0.7, and H0 = 65 in the calculation
of the luminosity distance.
- GCN Circular #4828
Alicia M. Soderberg (Caltech) and Dale A. Frail (NRAO) report on
behalf of a larger collaboration:
"Using additional data we have been able to obtain a flux calibration
of the radio afterglow detected with the VLA on February 20.01 UT
(GCN 4794). At 8.46 GHz the peak flux density was 453 +/- 77 microJy at
a position (epoch J2000) of R.A.=03:21:39.683, dec.+16:52:01.82, with
conservative errors of +/-0.06 arcsec. Further observations are planned.
The National Radio Astronomy Observatory is a facility of the National
Science
Foundation operated under cooperative agreement by Associated
Universities, Inc."
- GCN Circular #4830
C. Rodgers (U of Wyoming), D. Allen (U of Wyoming), Marc Herman (U of
Wyoming), R. Rodgers (ACSD#1), R. Canterna (U of Wyoming) report on behalf
of the Red Buttes Observatory (0.6m) GRB Team as part of the FUN GRB
Collaboration.
We responded to the rebrightening of GRB 060218/SN 2006aj at the position
reported by Kennea et al. (GCN 4776) at 2006/02/25 01:47:07 UT. We took
10 minute exposures in BVRI over 4 different epochs. The data are presented
below in magnitudes with a S/N > 14.0. Each of the BRI magnitudes were
obtained using the USNO B1.0 catalog, and the V magntudes were determined
from Cool et al. (GCN 4777) SDSS g and r data by using Smith et al. (2002)
transformation equations.
B V R I UT (B)
18.140 17.116 17.240 16.369 01:47:07
18.134 17.294 17.214 16.248 02:46:14
18.188 17.312 17.243 16.301 03:46:55
18.054 17.288 17.212 16.128 04:30:42
This message may be cited.
- GCN Circular #4831
C. Rodgers, D. Allen, B. Barlow, C. Garcia, M. Pierce, R. Canterna (U of
Wyoming) report on behalf of the Wyoming Infra-Red Observatory (2.3m) GRB
Team as part of the FUN GRB Collaboration.
GRB 060218/SN 2006aj was observed at the postion reported by Kennea et al.
(GCN 4776) at 2006/02/25 02:03:49 UT in Johnson B. The following B
magnitudes were determined using the USNO B1.0 catalog with a S/N ~ 180.
B (mag) B err (mag) UT
18.250 0.007 02:03:49
18.281 0.006 02:09:48
18.276 0.006 02:33:12
18.295 0.006 02:51:45
18.282 0.007 02:57:13
18.259 0.006 03:14:08
18.245 0.006 03:19:32
18.293 0.011 04:52:09
18.245 0.010 04:57:32
This message may be cited.
- GCN Circular #4832
Atish Kamble (Raman Research Institute [RRI], Bangalore, India),
C. H. Ishwara Chandra (NCRA, Pune, India) and D. Bhattacharya (RRI)
report on behalf of a larger GRB collaboration :
The Giant Meterwave Radio Telescope (GMRT), India observed the field of
GRB 060218 (GCN 4775, GCN 4776, GCN 4779) on 20 Feb. 2006
(between 14.0 UT to 17.0 UT) at 1280 MHz using a bandwidth of 32 MHz.
We do not detect any source coincident with the position of optical
afterglow (GCN 4779). The 3-sigma upper limit achieved is ~ 0.45 mJy.
We thank GMRT and the National Centre for Radio Astrophysics (NCRA) staff.
This TOO was done under the GMRT Director's Discretionary Time.
GMRT is run by NCRA-TIFR, Pune (INDIA).
This messege may be cited.
- GCN Circular #4833
S. Covino, D. Malesani, E. Molinari, G. Chincarini, F.M. Zerbi, V.
Testa, G. Tosti, F. Vitali, L.A. Antonelli, P. Conconi, G. Cutispoto, G.
Malaspina, L. Nicastro, E. Palazzi, E. Meurs, P. Goldoni, on behalf of
the REM/ROSS team, report:
We imaged the field of GRB 060218 (Cusumano et al., GCNs 4775, 4781)
with the robotic 60-cm REM telescope located at La Silla, Chile.
Observations were performed on 2006 Feb 25 from 00:16 to 00:30 UT under
mediocre conditions just after the La Silla sunset with the R and J
filters. REM is equipped with the REMIR near-infrared camera (10x10
arcmin^2 FoV, JHK filters) and the ROSS optical spectrograph/imager
(10x10 arcmin^2 FoV, VRI filters and AMICI prism).
The optical counterpart (Cusumano et al., GCN 4775; Marshall et al., GCN
4779; Mirabal et al., GCN 4784) was detected in both bands with magnitudes:
R = 17.05 +- 0.17
J = 16.90 +- 0.20
Calibration was based on the SDSS and 2MASS catalogs for the optical and
near-infrared observations, respectively.
This message is citeable.
- GCN Circular #4834
K. Wiersema (University of Amsterdam) and F. Nieuwenhout report on
behalf of the AWSV "Metius" ABT collaboration:
"We observed GRB060218/SN 2006aj (Cusumano et al., GCN 4775)
with the amateur 0.25m ABT telescope, from Alkmaar, The Netherlands,
under moderate observing conditions.
Starting from Feb 24 17:58 UT, a series of 1 minute exposures in
V band were acquired, ending at 18:38 UT. 28 exposures were combined.
The object is detected and we measure V = 17.37 +/- 0.21, using
SDSS g' and r' data from Cool et al. (GCN 4777) and the transformation
equations by Smith et al. (2002).
We like to point out the suitability of this supernova for intensive
amateur follow-up.
The ABT telescope is an internet-controlled 0.25m telescope
located in Alkmaar, The Netherlands, built and operated by members of
local amateur astronomy club "Metius".
This detection of GRB060218/SN 2006aj is the first reported
detection of an optical GRB afterglow/SN from Dutch soil.
We acknowledge the assistance of E. Rol and R. Wijers in making the
ABT GRB follow-up program possible."
- GCN Circular #4836
V. Larionov and L.Larionova from St.Petersburg University (Russia)
, report:
We imaged GRB20060218 with 70-cm telescope of Crimean Astrophysical
observatory (Ukraine) and ST-7 camera of St.Petersburg University
in photometric and polarimetric mode. Observations were made in R band from
February 20.17 to February 23.18. The rate of brightening in this period was
0.18 mag/day. The polarization reached maximum of 6% on February 21
and decreased to 3% on February 23. The positional angle remained
practically unchanged, 110+\-5 deg. The high and variable polarization
gives evidence of strongly aspherical or non-thermal component in
GRB20060218/SN2006aj radiation.
This message is citeable.
- GCN Circular #4837
B. E. Cobb and C. D. Bailyn (Yale), part of the larger SMARTS
consortium, report:
Using the ANDICAM instrument on the 1.3m telescope at CTIO, we
obtained optical/IR imaging of the position of GRB 060218/SN 2006aj
(GCN 4775, Cusumano et al.) over 5 nights. Total summed exposure time
on each night amounted to 36 minutes in I and 30 minutes in J.
The object shows continued brightening over our images. The preliminary
I magnitude of the object on 2006-02-22 is calculated based
on contemporaneous observations of Landolt RU149. The preliminary J
magnitude on the same day is calculated in comparison to 2MASS
stars in the field.
Mid-Exposure
UT Date and Time
2006-02-22 00:35 I = 17.58 +/- 0.05 J = 17.31 +/- 0.05
I mag relative to 1st epoch J mag relative to 1st epoch
2006-02-23 00:27 -0.18 +/- 0.02 -0.11 +/- 0.05
2006-02-24 00:20 -0.29 +/- 0.02 -0.24 +/- 0.05
2006-02-25 00:16 -0.39 +/- 0.02 -0.28 +/- 0.05
2006-02-26 00:18 -0.46 +/- 0.02 -0.38 +/- 0.05
- GCN Circular #4838
Elena Pavlenko(CrAO, Crimea), Alex Shlyapnikov (CrAO,Crimea),
Sergey Guziy (IAA-CSIC, Granada) , on behalf of a larger collaboration,
report:
"We imaged the field of GRB 060218 (Cusumano et al., GCNs 4775, 4781)
with the K-380 Cassegrain telescope of the Crimean Astrophysical
Observatory.
Observations of the afterglow have been carried out on 2006 Feb 20 -
Feb 23.
A series of 2-minute exposures in R(Johnson) band were acquired.
Calibration was
based on the SDSS catalog. On Feb 20 19:18 - 20:00 UT for 20 combined
images,
afterglow has magnitude R = 18.00 +/- 0.06 and displayed the brightening
of 0.15 mag/day.
Further observations are planned."
This message may be cited.
- GCN Circular #4840
Atish Kamble (Raman Research Institute [RRI], Bangalore, India),
C. H. Ishwara Chandra (NCRA, Pune, India) and D. Bhattacharya (RRI)
report on behalf of a larger GRB collaboration :
The date of GMRT observation of GRB 060218 reported in GCN 4832
has a typo. The correct date of observation was 21 Feb 2006 and
not 20 Feb 2006.
Our apologies for the inconvenience it might have caused.
With further analysis of the data (same observation) we could
improve the upper limits on the radio afterglow flux
of GRB 060218. We now put a 3 sigma upper limit of ~ 0.3 mJy.
This messege may be cited.
- GCN Circular #4842
E. Pavlenko, Yu. Efimov, A. Shlyapnikov, V.Rumyantsev (CrAO), A.Pozanenko
(IKI) on behalf of a larger collaboration report:
We observed GRB 060218/SN 2006aj (Cusumano et al. GCN 4775) with CrAO Shajn
2.6m telescope on Feb. 23. A series of BVRI 30 s exposures were taken
starting (UT) 19:27.
Using SDSS pre-burst observations (Cool et al. GCN 4777) we estimate
brightness of the optical afterglow + SN in R:
Mid time, exp., R mag
(UT) (s)
Feb.23 19:32 8x30 s 17.40 +/- 0.01
Feb.23 19:58 8x30 s 17.41 +/- 0.01
The values is compatible with the brightening rate ~0.2 per day between Feb.
20 and Feb. 23 reported earlier (Ovaldsen et al, GCN 4818, Pavlenko et al,
GCN 4838).
- GCN Circular #4843
M. Andreev (Institute of Astronomy), E. Pavlenko (CrAO), A. Pozanenko
(IKI) on behalf of larger GRB follow up collaboration report:
We observed GRB 060218/SN 2006aj (Cusumano et al. GCN 4775) in V-band with
the 60 cm telescope of peak Terskol observatory on Feb. 22 and Feb. 23. A
series of 60 s exposures were taken in both epochs.
Using SDSS pre-burst observations (Cool et al. GCN 4777) we estimate
brightness of the optical afterglow + SN:
Mid time, exp., V mag
(UT) (s)
Feb.22 17:08 147x60 s 18.00 +/- 0.01
Feb.23 18:20 12x60 s 17.82 +/- 0.03
The brightening rate in V between Feb. 22 and Feb. 23 is 0.16m per day.
- GCN Circular #4845
R. Novak (N. Copernicus Observatory in Brno, Czech Republic),
report:
We have observed filed of GRB060218 (sn 2006aj) for 133 min during night
24./25.2.2006 with the 40cmreflector at N. Copernicus Observatory
equipped with ST-7 CCD (R band
filter) camera. we have detected source as R aprox. 18mag close to the
limit of the combined dframe beacuse of very bad weather conditions (high
altitude clouds, wind). More precise photometry may be available in
future.
This message may be cited.
- GCN Circular #4846
L. Amati (INAF-IASF Bologna), F. Frontera (Ferrara University and
INAF-IASF Bologna), C. Guidorzi (Liverpool JM University) and E. Montanari
(Ferrara University) report:
"Based on the photon index measured by Swift/BAT (2.5+/-0.1 in 15-150 keV,
Sakamoto et al., GCN #4822) and Swift/XRT during the prompt emission
(1.82+/-0.01 in 0.2-10 keV, Cusumano et al., GCN #4786), it can be inferred
that the intrinsic peak energy Ep,i of GRB060218/SN2006aj (at the suggested
redshift z=0.03) is < 10 keV and lies probably towards the low energy bound of
XRT (i.e. a few keV at most). This information, when combined with the Eiso
(1-10000 keV) value of about (5 - 8)x10^(49) erg, as derived on the basis of
the preliminary BAT and XRT (first orbit) fluxes and spectra, shows that
GRB060218 is likely consistent with the Ep,i - Eiso (Amati) correlation. This
behaviour, if confirmed by more refined analysis, is at odds with that of
GRB980425/SN1998bw and of the other possibly sub-energetic event
GRB031203/SN2003lw, which showed Ep,i and Eiso values completely inconsistent
with the correlation (see e.g. Amati, 2006, astro-ph/0601553 for a discussion).
Given that one of the most popular explanations of the inconsistency of
GRB980425 and GRB031203 with the Ep,i-Eiso correlation is that they were
'normal' GRBs seen at very high off-axis angles (e.g. Yamazaki, Yonetoku &
Nakamura, 2003, ApJ 594 L79 , Ramirez-Ruiz et al., 2005, ApJ, 625 L91), this
evidence shows that GRB060218 may not be an off-axis event, as also
suggested by Nousek et al. (GGN #4805) based on the 'chromatic' behaviour of
afterglow light curves measured by Swift."
This message may be cited.
- GCN Circular #4847
R. Burenin, A. Mescheryakov, M. Pavlinsky, R. Sunyaev (IKI),
I. Khamitov, Z. Aslan (TUG), U. Kiziloglu (METU), E. Gogus (Sabanci Uni.),
I. Bikmaev, N. Sakhibullin (KSU/AST)
report:
We observed GRB 060218/SN 2006aj (Cusumano et al., GCN 4775) with
Russian-Turkish 1.5-m telescope (RTT150, Bakirlitepe, TUBITAK National
Observatory, Turkey) over 3 nights in BVRI. The magnitudes of the object
are:
Time (UT) B V R I
Feb 21.84 18.49 - 17.82 17.53
Feb 22.75 18.20 17.80 17.62 17.40
Feb 25.75 17.98 17.57 17.30 16.89
The photometry is preliminary and is based on our observations of Landolt
stars in these and previous nights.
This message may be cited.
- GCN Circular #4853
Andrea De Luca (INAF/IASF, Milano) on behalf
of a larger collaboration reports:
We have analyzed the XMM-Newton observation
of the field of GRB060218, discovered by
Swift/BAT on 2006, February 18 at 03:34:30 UT
(GCN4775, Cusumano et al.)
The XMM-Newton observation started on 2006,
February 20 at 17:21:45 UT (~61.8 hours after
the GRB trigger) and lasted for 14 ks.
The observation is affected by a high
particle background, which hampers a detailed
temporal and spectral analysis of the faint X-ray
afterglow.
We report here on data collected by the EPIC/pn camera.
spanning the time range 223.9-234.9 ks after the trigger.
The afterglow of GRB060218 is detected at the
following coordinates:
RA(J2000): 03h 21m 39.63s, Dec(J2000): 16d 52' 03.4"
with an uncertainty of 1.2 arcsec (1sigma),
fully consistent with the coordinates of the
optical (GCN4779, Marshall et al.) and radio
(GCN4828, Soderberg & Frail) afterglow, as well as
with the Swift/XRT position (GCN4786, Cusumano et al.).
Extracting source events from a circle of 10 arcsec
radius (containing ~50% of the total counts) the pn
time-averaged, background-subtracted count rate in the
0.5-8 keV range is of 0.017+/-0.002 cts/s.
No significant fading of the X-ray flux is detected along
the XMM-Newton observation.
The time-integrated X-ray spectrum is well fit
(reduced chi2=0.98, 14 d.o.f.) by a steep power
law absorbed by the Galactic column (NH=1.1e21 cm^-2,
Dickey & Lockman, 1990), with a photon index Gamma=3.3+/-0.6
(90% conf. level for a single parameter).
The observed flux (0.5-10 keV) is of 5.7x10^-14 erg
cm^-2 s^-1, corresponding to an unabsorbed flux of
8.4x10^-14 erg cm^-2 s^-1.
- GCN Circular #4863
E. W. Guenther, S. Klose, Thueringer Landessternwarte Tautenburg,
P. Vreeswijk, University of Chile/ESO,
E. Pian, INAF-OA Trieste, and
J. Greiner, MPE Garching, on behalf of the GRACE collaboration
report:
ESO's VLT-Kueyen (UT 2) observed SN 2006aj (GRB 060218) around the
time of maximum light on March 3/4, 2006. Observations were performed
using the Ultraviolet and Visual Echelle Spectrograph (UVES) at a
spectral resolution of 46 000. The signal-to-noise ratio of the
spectrum (2100 sec exposure time) is about 30 per resolution element,
which is sufficient to measure the equivalent width (EW) of the Na I D
lines along the line of sight.
For the Na I D2 component (lambda 5889.95) produced in our Galaxy we
find EW = (0.321 +/- 0.008) Angstrom. Using the empirical relation
between the equivalent width of the 5889.95 line and the interstellar
reddening (Munari & Zwitter A&A 318, 269, 1997), this corresponds to
a Galactic reddening of E(B-V) = (0.127 +/- 0.005) mag. Assuming a
ratio of total-to-selective extinction of R_V = 3.1, we obtain a
Galactic visual extinction along the line of sight of A_V = (0.39 +/-
0.02) mag. This is slightly less than what follows from the COBE
maps (Schlegel, Finkbeiner, & Davis 1998).
In the GRB host galaxy we identify two redshift systems at a
heliocentric velocity of 10008.1 km/s and 10032.3 km/s (Na I D2) with
the following equivalent widths in the observer frame: system I:
EW(D2) = (0.084 +/- 0.008) Angstrom, system II: EW(D2) = (0.072 +/-
0.008) Angstrom. Assuming that the aforementioned empirical relation
is also representative for the interstellar medium in the GRB host
galaxy, and correcting EW for a factor of 1/(1+z) for the host frame, we
arrive at a combined reddening of E(B-V) = (0.042 +/- 0.003) mag. If
again R_V = 3.1, we obtain a host extinction along the line of sight
of A_V = (0.13 +/- 0.01) mag.
We finally note that the tiny error bars should not be overinterpreted.
They just include the measurement errors but not the systematic error
of the method itself, which we cannot quantify.
We thank the ESO staff, in particular Dominique Naef, for performing
the observations and Alain Smette, ESO, for valuable comments.
This message may be quoted.
- GCN Circular #4866
A.L. Homewood, C.A. Riddle, K.V. Garimella, M.R. Troutman, D.H. Hartmann
(Clemson University) and G.D. Henson (ETSU) report on behalf of the
Clemson GRB Follow-Up Team:
We have imaged the field of GRB060218 (GCN 4775, 4776) beginning
approximately 4 days after the trigger notice with the SARA 0.9-m at Kitt
Peak, under good weather conditions. We obtained 9 300-seconds exposures
in V filter and 7 300-second exposures in B filter. We detect the
supernova in each exposure and have carried out the following data
analysis:
Observations in V began at UT Feb. 22.0923958 and ended at 22.1539931. We
observe magnitudes ranging from V=17.3 to 17.7 +/- 0.2 mag during that
time period.
Similiarly, observations in B began at UT Feb. 22.096088 and ended at
22.1504167. We observed magnitudes ranging from B=18.2 to 18.7 +/-0.2
mag.
These values correspond to single 300-second exposures, and quoted errors
are 1-sigma. Further analyses of observations from additional nights are
in progress.
The Clemson Unversity GRB Response Site may be found at:
http://people.clemson.edu/~kgarime/burst/index.php
The SARA Homepage can be found at:
http://saraobservatory.org
This message may be cited.
- astro-ph/0603279 from 11 Mar 2006
Campana: The shock break-out of GRB 060218/SN 2006aj
Supernovae (SNe) share with Gamma Ray Bursts (GRBs) the property of being the
most powerful explosions in the Universe after the Big Bang. The link between
GRBs and exploding massive stars has been established on the basis of a handful
of objects associated with bright, energetic, Type Ic SNe. Here we report Swift
observations of the recent GRB 060218 (at a redshift of $z=0.0331$) and its
connection to SN 2006aj. GRB 060218 is exceptional in several respects. It is
under-luminous in gamma-rays and extremely long. It shows a delayed non-thermal
X-ray emission which fades and conceals a soft, brightening, optically-thick
thermal (about two million degrees) component that expands and shifts into the
optical/UV band as time passes. We interpret these features as arising from the
break out of a shock driven by a mildly relativistic shell into the dense wind
surrounding the progenitor. Swift observations triggered by this GRB allow us
for the first time to catch a SN in the act of exploding, and to directly
observe the shock breakout. The inferred radius of the shock provides strong
evidence that the progenitor was a Wolf-Rayet star.
- astro-ph/0603377 from 15 Mar 2006
Modjaz: Early-Time Photometry and Spectroscopy of the Fast Evolving SN 2006AJ Associated with GRB 060218
We present early photometric and spectroscopic data on the afterglow of GRB
060218 and report the evolution of the underlying supernova 2006aj. Our data
span a time-range of 4 days to 22 days after the GRB and clearly establish that
SN 2006aj is a fast-evolving broad-lined Type Ic SN with an extremely short
rise-time (~ 10 days) and a large optical luminosity (M_V = -18.9 mag). The SN
properties are deduced well since the GRB afterglow does not contribute a
significant amount to the light output. The spectra show broad lines indicative
of large expansion velocities, but are better matched by those of SN 2002ap and
SN 1997ef than those of the proto-typical GRB-related SN 1998bw. We refine the
redshift estimate to z = 0.0335. The host-galaxy is a low-metallicity dwarf
galaxy (with M_V ~ -15.8 mag), similar to host-galaxies of other GRB-associated
SNe.
- GCN Circular #4898
Malcolm Hicken (CFA), Maryam Modjaz (CFA), Peter Challis (CFA), Robert
Kirshner (CFA), Jose Luis Prieto (OSU), Krzystof Stanek (OSU) and Richard
Cool (Arizona) report:
The CFA Supernova Group obtained UBVRr'i' photometry of 9 comparison stars
in the field of GRB060218/SN2006aj on March 4, 2006 UT. Data was taken
using the FLWO 1.2m telescope at Mt. Hopkins, Arizona. We present our
V-band light curve in Modjaz, et. al. (2006), astro-ph/0603377, submitted
to ApJL. A finding chart, coordinates and photometry can be found at the
following website:
http://cfa-www.harvard.edu/oir/Research/supernova/sn2006aj_compstars.html
It should be noted that our V magnitudes are approximately 0.27 mag
fainter than those derived in GCN 4777 by Cool, et. al. at
http://mizar.as.arizona.edu/~grb/public/GRB060218
There is also an offset in the other bands. In investigating this
photometric offset, Richard Cool has discovered calibration offsets
between the two SDSS photometric reductions of this field indicating
possible non-photometric conditions or other calibration problems in the
SDSS photometry. The problem is being investigated to ensure data with
suspicious photometric quality will be flagged as such in future SDSS GRB
releases.
- GCN Circular #4899
A. Pereyra and A. M. Magalh=E3es (IAG, Univ. of S=E3o Paulo) report:
We obtained optical imaging of GRB 060218/SN 2006aj (Cusumano et al., GCN
4775) on
2006/March 3.958 (UT) using the IAG-USP 60cm telescope at the Laborat=F3r
io Nacional de
Astrof=EDsica (LNA), Brazil. The observation was made under poor sky cond
itions and
through high airmass (>2). A 90-second exposure in the I filter yielded I
=3D (17.06 +/-
0.10) mag. The zero point calibration was obtained using comparison stars
in the GRB
field from Hicken et al. (GCN 4898) and Modjaz et al. (astro-ph/0603377).
This message can be cited.
- GCN Circular #4900
D. Sharapov (MAO, and NOT, La Palma), A. Pozanenko (IKI), and M. Ibrahimov
(MAO) on behalf of larger GRB follow up collaboration report:
We have observed GRB060218/SN 2006aj (Cusumano et al. GCN 4775) with
Maidanak 1.5m telescope in BVR on Feb.27, Mar.08, and in BR bands with
NOT/StanCam on Mar.15. The following photometry is based on Modjaz, et. al.
(2006, astro-ph/0603377) calibration and the same reference stars in each
epochs:
Mid time (UT), B, V, R
Feb.27.63 18.08 (.01) 17.40 (.01) 17.21 (.01)
Mar.08.66 18.98 (.02) 17.83 (.02) 17.39 (.01)
Mar.15.86 19.66 (.03) - 17.84 (.02)
Only measurement errors are presented. The photometry is preliminary,
reduction and observations are continuing. Our observations confirm a
maximum of the light curve (Modjaz, et. al. 2006, astro-ph/0603377) between
Feb.27 and Mar.08. It is also evident gradual reddening of the SN.
The message may be cited.
- astro-ph/0603519 from
Fargion: The GRB060218/SN 2006aj, GRB 050724, SGRs blazing and re-brightening by
A list of puzzles are unanswered by Fireball (even milli-steradiant beamed)
explosive GRB and Magnetar spherical one-shoot SGR models. The early GRB 980425
and the last longest GRB060218 are the most emblematic GRBs out of the tune of
any Fireball cone models. Too nearby, too soft, too underluminous and too long
events. The huge flare of SGR 1806-20 and its radio rebrightening disagree with
Magnetar model. Only a persistent, thin (even less than micro steradiant)
precessing and spinning gamma jet evolution explains X-gamma time structure and
afterglow bumps. The late relic neutron star, X-ray pulsar jet, its spinning
and precessing lepton-gamma jet is the candidate blazing sources as anomalous
X-ray Pulsars (AXRPs) and Soft Gamma-Ray Repeaters (SGRs). Precessing jet are
like SS433 spiral jets. At SN power and in-axis they are GRBs. Late
(weeks-months) GRB blazing jets are seldom orphan of their bright SN-OT. The
last GRB060218 occurred within its SN2006aj smoothly and soft (because
off-axis), ruled by outer jet component and slow by large impact angle. We
foresaw OT and radio bumps and re-brightening, in analogy to the third nearest
GRB030329-SN2003 event. Late decayed Jets are XRFs or brief GRBs and mostly in
galaxy or Local Group distances as SGRs and AXRPs. Electron pairs beams are
showering and feeding gamma-X jet by Synchrotron (or Inverse Compton
Scattering) far from the dense SN star (or a Neutron Star magnetic fields):
energetic and penetrating PeVs muon pairs bundle are the progenitors able to
escape the Supernova shells matter and photon opacity decaying far away into
PeV electron pairs (and gamma) and neutrinos. The mysterious GRBs (and SGRs)
are not the most explosive event of the Universe, but just the most beamed
ones.
- astro-ph/0603686 from
Mirabal: GRB 060218/SN 2006aj: A Gamma-Ray Burst and Prompt Supernova at z=0.0335
We report the imaging and spectroscopic localization of GRB 060218 to a
low-metallicity dwarf starburst galaxy at z = 0.03345 +/- 0.00006. In addition
to making it the second nearest gamma-ray burst known, optical spectroscopy
reveals the earliest detection of weak, supernova-like Si II near 5720
Angstroms, starting 1.95 days after the burst trigger. UBVRI photometry
obtained between 1 and 26 days post-burst confirms the early rise of supernova
light, and agrees with an upper limit Delta t < 159 s for the delay between the
gamma-ray burst and the onset of the supernova explosion if the early
appearance of a soft component in the X-ray spectrum is understood as a ``shock
breakout''. Together, these results verify the long-hypothesized origin of soft
gamma-ray bursts in the deaths of massive stars.
- GCN Circular #4929
F. Terra, (Second University of Roma "Tor Vergata"), D. Nanni
(INAF/OAR and Second University of Roma "Tor Vergata"), G. Greco,
C. Bartolini, A. Guarnieri, A. Piccioni (Bologna University), R.
Gualandi, A. De Blasi (INAF Bologna) and G. Pizzichini (INAF/IASF
Bologna) report:
We observed the OT of GRB 060218/SN 2006aj (Cusumano et al. GCN 4775)
in the V and R bands with the 152 cm Loiano telescope equipped with
the BFOSC camera system.
Observations were carried out on 2006 Mar 7 and 11 under poor
observing conditions (seeing=2.7-3.2 arcsec).
Using the comparison stars reported by Hicken et al. (GCN 4898), we
find the following magnitudes, in agreement with those given by other
authors, e.g. Sollerman et al., astro-ph/0603495 and Pian et al.,
astro-ph/0603530:
Mean UT.........filter.....Exptime(s)....... magnitude
Mar 07.7506 ......Rc...........300..........17.31+/-0.06
Mar 07.7633.......Rc......... 1200..........17.36+/-0.03
Mar 07.7779.......V...........1200..........17.76+/-0.04
Mar 11.7865.......V............300..........18.15+/-0.08
Mar 11.7962.......V...........1200..........18.11+/-0.06
Mar 11.8123.......Rc..........1200..........17.63+/-0.04
Mar 11.8302.......Rc..........1200..........17.60+/-0.04
One of our images is posted in our public directory from where it
can be retrieved by sftp using:
hostname: ermione.bo.astro.it
username: publicGRB
password: GRB_bo.
- GCN Circular #4932
E. Semkov (IA, BAS) on behalf of the BAS/CNRS collaboration report:
We observed the afterglow of GRB 060218 (Cusumano et al., GCN 4775;
Marshall et al., GCN 4800) with the 2m RCC telescope at the National
Astronomical Observatory Rozhen (Bulgaria) on Mar. 21 and 26. The
calibration was made using comparison stars from Hicken et al. (GCN 4898)
and Modjaz et al. (astro-ph/0603377). Observations were made under good
atmospheric conditions through a standard Johnson-Cousins set of filters.
The optical counterpart was detected at the following magnitudes:
Date, UT(R), I, R, V
Mar 21 18:45 17.921 (0.062) 18.340 (0.027) 18.589 (0.026)
Mar 26 18:00 18.106 (0.057) 18.429 (0.022) 18.916 (0.024)
This message may be cited.
- astro-ph/0604016 from 10 Apr 2006
Fan: The Interpretation and Implication of the Afterglow of GRB 060218
The nearby GRB 060216/SN 2006aj was an extremely long, weak and very soft
GRB. While it was peculiar in many aspects its late ($>10^4$ sec) X-ray
afterglow showed a canonical power law decay. Assuming that this component
arises due to a relativistic blast wave decelerated by a circumburst matter we
infer that the blast wave's kinetic energy was rather high, $5 \times 10^{50}$
erg, close to what is seen in other GRBs. The lack of a "jet break" implies
that the outflow was wide $\theta_j \sim 1$. The rather weak early optical
emission rules out a dense circumburst wind profile. It also constrains the
initial Lorentz factor to be significantly lower than usual, $\Gamma_{\rm
ini}\sim 15$. The observed afterglow suggests that the medium surrounding a
massive star progenitor (up to distances of $\sim 10^{17}-10^{18}$ cm) is not
the expected dense stellar wind (a similar result was seen in many other bursts
and in particular in GRB 030329). This implies that the progenitor's wind was
weak during the last 100-1000 years before the burst. This interpretation
requires a different source for the thermal emission seen in the early X-ray
and late optical/UV. We expect that this emission arises from the interaction
of the relativistic ejecta with the stellar envelope.
- astro-ph/0604389 from 18 Apr 2006
Soderberg: Relativistic ejecta from XRF 060218 and the complete census of cosmic explosions
Over the last decade, long-duration gamma-ray bursts (GRBs) and X-ray flashes
(XRFs) have been revealed to be a rare variety of Type Ibc supernova (SN).
While all these events result from the death of massive stars, the
electromagnetic luminosities of GRBs and XRFs exceed those of ordinary Type Ibc
SNe by many orders of magnitude. The essential physical process that causes a
dying star to produce a GRB or XRF, and not just an SN, remains the crucial
open question. Here we present radio and X-ray observations of XRF 060218
(associated with SN 2006aj), the second nearest GRB identified to-date, which
allow us to measure its total energy and place it in the larger context of
cosmic explosions. We show that this event is 100 times less energetic but ten
times more common than cosmological GRBs. Moreover, it is distinguished from
ordinary Type Ibc SNe by the presence of 10^48 erg of mildly-relativistic
ejecta, along with a central engine which produces X-rays for weeks after the
explosion. This suggests that the presence of relativistic ejecta is the key
physical distinction between GRBs/XRFs and ordinary SNe, while the nature of
the central engine (black hole or magnetar) may distinguish cosmological GRBs
from the low-luminosity and spherical events like XRF 060218.
- astro-ph/0604510 from 24 Apr 2006
Dai: GRB 060218/SN 2006aj: Prompt Emission from Inverse-Compton Scattering of Shock Breakout Thermal Photons
The gamma-ray burst (GRB) 060218/SN 2006aj is a peculiar event, with the
second lowest redshift, low luminosity, long duration, chromatic lightcurve
features, and in particular, the presence of a thermal component in the X-ray
and UV-optical spectra. Thanks to detailed temporal and spectral coverage of
the {\em Swift} observatory, the abundant data allow the GRB prompt emission to
be modelled in great detail for the first time. The low flux of prompt
UV/optical emission disfavors the conventional internal shock/synchrotron
radiation models, which generally predict strong UV/optical emission. Here we
show that the unusual prompt emission of GRB 060218 can be produced by
inverse-Compton scattering of shock-accelerated relativistic electrons off the
detected thermal photons. A pair of (forward plus reverse) shocks form when a
relativistic outflow interacts with a preexisting slower shell. The observed
gamma-ray emission and X-ray emission arise from the reverse-shocked and
forward-shocked regions, respectively. A fit to the data requires an initially
increasing outflow luminosity, which is consistent with the prediction of the
popular collapsar model.
- astro-ph/0605058 from 2 May 2006
Ferrero: The GRB 060218/SN 2006aj event in the context of other Gamma-Ray Burst Supernovae
We present VLT FORS multi-color photometry of SN 2006aj, the supernova
associated with GRB 060218 at a redshift of $z$=0.033, the second closest
GRB-SN observed to date. We compare the photometric evolution of the supernova
light curves with the corresponding properties of the present world-sample of
more than 10 GRB-SNe that were either detected photometrically or even
spectroscopically. Using host galaxy extinction measurements, we derive
extinction-corrected GRB-SN luminosities and place SN 2006aj in the context of
this GRB-selected supernova sample.
- astro-ph/0605387 from 16 May 2006
Li: Shock Breakout in Type Ibc Supernovae and Application to GRB 060218/SN 2006aj
Recently, a soft black-body component was observed in the early X-ray
afterglow of GRB 060218, which was interpreted as shock breakout from the thick
wind of the progenitor Wolf-Rayet star of the underlying Type Ic SN 2006aj. In
this paper we present a simple model for computing the characteristic
quantities (including energy, temperature, and time-duration) for the transient
event from the shock breakout in Type Ibc supernovae produced by the
core-collapse of Wolf-Rayet stars surrounded by dense winds. In contrast to the
case of a star without a strong wind, the shock breakout occurs in the wind
region rather than inside the star, caused by the large optical depth in the
wind. We find that, for the case of a Wolf-Rayet star with a dense wind, the
total energy of radiation generated by the supernova shock breakout is larger
than that in the case of the same star without a wind by a factor $\ga 10$. The
temperature can be either hotter or cooler, but the time-duration is always
larger caused by the increase in the effective radius of the star due to the
presence of a thick wind. Then, we apply the model to SN 2006aj. We show that,
the energy released by the shock breakout is too small to explain the
black-body component observed in GRB 060218, unless that the progenitor star
has an unrealistically large core radius (the radius at optical depth of 20),
larger than $80 R_\odot$. Despite this disappointing result, our model is
expected to have important applications to the observations on Type Ibc
supernovae in which the detection of shock breakout will provide important
clues to the progenitors of SNe Ibc.
- astro-ph/0605431 from 17 May 2006
Ghisellini: Are GRB 980425 and GRB 031203 real outliers or twins of GRB 060218?
GRB 980425 and GRB 031203 are apparently two outliers with respect to the
correlation between the isotropic equivalent energy E_iso emitted in the prompt
radiation phase and the peak frequency E_peak of the spectrum in a vF(v)
representation (the so-called Amati relation). We discuss if these two bursts
are really different from the others or if their location in the E_iso-E_peak
plane is the result of other effects, such as viewing them off-axis, or through
a scattering screen, or a misinterpretation of their spectral properties. The
latter case seems particularly interesting after GRB 060218, that, unlike GRB
031203 and GRB 980425, had a prompt emission detected both in hard and soft
X-rays which lasted ~2800 seconds. This allowed to determine its E_peak and
total emitted energy. Although it shares with GRB 031203 the total energetics,
it is not an outlier with respect to the Amati correlation. We then investigate
if a hard-to-soft spectral evolution in GRB 031203 and GRB 980425, consistent
with all the observed properties, can give rise to a time integrated spectrum
with an E_peak consistent with the Amati relation.
- astro-ph/0606565 from 22 Jun 2006
Liang: Thermal Emission from a Hot Cocoon Surrounding the Jet of XRF 060218
It is long speculated that long duration gamma-ray bursts (GRBs) originate
from a relativistic jet emerging from a collapsing massive star progenitor.
Although associations of core-collapsing supernovae with long GRB afterglows
have been identified in a number of systems, including the latest X-ray flash
(XRF) 060218/SN 2006aj connection detected by Swift, direct evidence of a
relativistic jet emerging from a collapsing star is still lacking. Here we
report the detection of a thermal emission component (high-T component)
accompanying the prompt X-ray emission of XRF 060218, with temperature
kT_H=1.21+0.22/-0.24 keV and effective blackbody radius R_H~ 5\times 10^{9} cm.
This high-T component co-exists with another low-T thermal component as
reported by Campana et al. 2006 for at least 2700 seconds, but evolves
independently with respect to the low-T component by tracing the lightcurve of
the non-thermal component. We identify this high-T thermal component as the
emission of a hot cocoon surrounding the relativistic jet, as expected from the
theoretical models.
- GCN Circular #5358
E. Semkov (IA, BAS) on behalf of the BAS/CNRS collaboration report:
We observed the afterglow of GRB 060218 (SN 2006aj) six months after the
burst. Observations were made with the 2m RCC telescope at the National
Astronomical Observatory Rozhen (Bulgaria) on July 24 (UT=01h). The
calibration was made using comparison stars from Hicken et al. (GCN
4898) and Modjaz et al. (astro-ph/0603377). Observations were made under
good atmospheric conditions, but through high airmass (>2.5). A standard
Johnson-Cousins set of filters was used.
The optical counterpart was detected at the following magnitudes:
I=19.53 (+/-0.07), R=19.97 (+/-0.09)
This message may be cited.
- GCN Circular #5376
Spectroscopic Detection of the Late Nebular Phase of
SN 2006aj (associated with GRB 060218)
R. J. Foley, J. S. Bloom, D. A. Perley, and N. R. Butler
(UC Berkeley) report:
"We obtained 2x600 sec spectra of GRB 060218 / SN 2006aj
(GCN 4775) on 20060726 UT, 153 rest-frame days past the
GRB trigger, with Keck I (+ LRIS). The spectrum shows
prominent nebular emission lines attributed to [O I]
6300, 6364, Na D, and the Ca II IR triplet. The spectrum
resembles the nebular spectrum of GRB 980425 / SN 1998bw
at a similar epoch. With a redshift of z = 0.033
(Mirabal & Halpern, GCN 4792), this is the most distant
GRB-SN with a observed nebular spectrum.
The [O I] line has a velocity width of 10700 km/s, which
is quantitatively similar to SN 1998bw 157 rest-frame
days past the GRB trigger. The line has one strong peak,
with a slight shoulder, attributed to [O I] 6364. There
is no obvious asymmetry in this spectrum, consistent with
the models of Mazzali et al. (2005, Science, 308, 1284).
Further spectroscopic observations are encouraged.
A comparison of our spectrum of GRB 060218 / SN 2006aj to
a spectrum of GRB 980425 / SN 1998bw can be found at
http://astro.berkeley.edu/~rfoley/foley_etal-grb060218.jpg
- astro-ph/0608555 from 25 Aug 2006
Ghisellini: Puzzled by GRB 060218
We study the optical-UV/X-ray spectral energy distribution of GRB 060218
during the prompt phase and during what seems to be the afterglow phase. The
results are puzzling, since if the opt-UV and the X-ray emission belong to a
single black body, then its luminosity is too large, and it cannot be
interpreted as the signature of the supernova shock breakout. Problems are also
encountered in associating the expected supernova shock breakout emission with
either the opt-UV or the X-ray emission. In the former case we derive too small
ejecta velocities; in the latter case, on the contrary, the required velocity
is too large. We then present what we think is the most conservative
alternative explanation, namely a synchrotron spectrum, self-absorbed in the
opt-UV and extending up to the X-ray band, where we observe the emission of the
most energetic electrons, which are responsible for the exponential roll-over
of the spectrum. The fit to the data is quite satisfactory, and can explain the
entire spectrum except the black body observed in the X-rays, which must be a
separate component. The puzzling feature of this interpretation is that the
same model is required to explain the spectrum also at later times, up to 10^5
s, because the opt-UV emission remains constant in shape and also
(approximately) in normalisation. Therefore, the observed X-ray flux is
produced by self-Compton emission and the prompt emission phase should last for
~10^5 s or more. Finally, we discuss the nature of the black body observed in
X-rays, up to 7000 seconds. We show that it can be photospheric emission from
the cocoon or stellar material, energized by the GRB jet at radii comparable to
the stellar radius (10^{10}-10^{11} cm), not very far from where this material
becomes transparent (e.g. 10^{12} cm).
- astro-ph/0610417 from 13 Oct 2006
Ferrero: Optical observations of GRB 060218/SN 2006aj and its host galaxy
The supernova SN 2006aj associated with GRB 060218 is the second-closest
GRB-SN observed to date ($z$=0.033) and is the clearest example of a SN
associated with a Swift GRB with the earliest optical spectroscopy. Its optical
data showed that this is the fastest evolving and among the least luminous
GRB-SNe (70% as luminous as SN1998bw). However, its expansion velocity and a
comparison with other stripped-envelope SNe suggest that SN2006aj is an
intermediate object between Type Ic GRB-SNe and those not accompained by a GRB.
High-resolution optical spectroscopy together with SDSS pre-burst observations
revealed that the host galaxy of SN2006aj is a low-luminosity, metal-poor
star-forming dwarf galaxy.
- astro-ph/0610867 from 30 Oct 2006
Toma: Low-Luminosity GRB 060218: A Collapsar Jet from a Neutron Star, Leaving a Magnetar as a Remnant?
The gamma-ray burst (GRB) 060218 has ~10^5 times lower luminosity than
typical long GRBs, and is associated with a supernova (SN). The radio afterglow
displays no jet break, so that this burst might arise from a
mildly-relativistic spherical outflow produced by the SN shock sweeping the
stellar surface. Since this model is energetically difficult, we propose that
the radio afterglow is produced by a non-relativistic phase of an initially
collimated outflow (jet). Our jet model is supported by the detection of
optical linear polarization in the SN component. We also show analytically that
the jet can penetrate a progenitor star. Furthermore, we analyzed the
observational data of the prompt emission of this burst and obtained the
implications that it may last longer than 10^6 s, which prefers a neutron star
engine to a black hole engine. The collimation-corrected event rate of such
low-luminosity GRBs is ~10 times higher than that of typical long GRBs, and
they might form a different GRB population: low-luminosity GRBs are produced by
mildly-relativistic jets from neutron stars at the collapses of massive stars,
while typical long GRBs by highly-relativistic jets from black holes. We
suggest that the central engine of GRB 060218 is a pulsar (or a magnetar) with
the initial rotation period P_0 ~10 ms and the magnetic field B ~10^{16} G. A
giant flare from the magnetar might be observed in future.
- astro-ph/0610956 from 31 Oct 2006
Liang: Temporal Profiles and Spectral Lags of XRF 060218
The spectral and temporal properties of the non-thermal emission ofthe nearby
XRF 060218 in 0.3-150 keV band are studied. We show that both the spectral
energy distribution and the light curve properties suggest the same origin of
the non-thermal emission detected by {\em Swift} BAT and XRT. This event has
the longest pulse duration and spectral lag observed to date among the known
GRBs. The pulse structure and its energy dependence are analogous to typical
GRBs. By extrapolating the observed spectral lag to the {\em CGRO/BATSE} bands
we find that the hypothesis that this event complies with the same
luminosity-lag relation with bright GRBs cannot be ruled out at $2\sigma$
significance level. These intriguing facts, along with its compliance with the
Amati-relation, indicate that XRF 060218 shares the similar radiation physics
as typical GRBs.
- astro-ph/0612621 from 21 Dec 2006
Kocevski: Multicolor Infrared Observations of SN 2006aj, the Supernova Associated with XRF 060218 - Paper I
We report simultaneous multicolor near-infrared (NIR) observations of the
supernova associated with x-ray Flash 060218 during the first 16 days after the
high energy event. We find that the light curve rises and peaks relatively fast
compared to other SN Ic, with the characteristic broad NIR peak seen in all
three bands. We find that the rise profile before the peak is largely
independent of NIR wavelength, each band appearing to transition into a plateau
phase around day 10--13. Since the light curve is in the plateau phase when our
observations end at day 16, we can only place limits on the peak absolute
magnitudes, but we estimate that SN 2006aj is one of the lowest NIR luminosity
XRF/GRB associated SNe observed to date. The broad peaks observed in the {\em
JHK$_s$} bands point to a large increase in the NIR contribution of the total
flux output from days 10--16. This evolution can be seen in the broad color and
SED diagrams constructed using {\em UBVRIJHK$_s$} monochromatic flux
measurements for the first 16 days of the event. Ultimately, a 10-day rise time
would make SN 2006aj an extremely fast rise SN Ic event, faster than SN 1998bw
and SN 2003dh, which combined with its underluminous nature, indicates a lower
amount of $^{56}$Ni ejected by the progenitor compared to other XRF/GRB-SNe.
Furthermore, the lack of significant color change during the rise portion of
the burst points to little or no spectral evolution over the first 10 days of
activity in the NIR.
- astro-ph/0701034 from 2 Jan 2007
Wiersema: The nature of the dwarf starforming galaxy associated with GRB 060218 / SN2006aj
We present high resolution VLT UVES and low resolution FORS optical
spectroscopy of supernova 2006aj and its host galaxy, associated with the
nearby (z = 0.03342) gamma-ray burst GRB 060218. This host galaxy is a unique
case, as it is one of the few nearby GRB host galaxies known, and it is only
the second time high resolution spectra have been taken of a nearby GRB host
galaxy (after GRB 980425). The resolution, wavelength range and S/N of the UVES
spectrum combined with low resolution FORS spectra allow a detailed analysis of
the circumburst and host galaxy environments. We analyse the emission and
absorption lines in the spectrum, combining the high resolution UVES spectrum
with low resolution FORS spectra and find the metallicity and chemical
abundances in the host. We probe the geometry of the host by studying the
emission line profiles. Our spectral analysis shows that the star forming
region in the host is metal poor with 12 + log(O/H) = 7.54 (+0.17, -0.10)
(~0.07 Z_sun), placing it among the most metal deficient subset of
emission-line galaxies. It is also the lowest metallicity found so far for a
GRB host from an emission-line analysis. Given the stellar mass of the galaxy
of ~10^7 M_sun and the SFR (H alpha) = 0.065 +/- 0.005 M_sun/yr, the high
specific star formation rate indicates an age for the galaxy of less than ~200
Myr. The brightest emission lines are clearly asymmetric and are well fit by
two Gaussian components separated by ~22$ km/s. We detect two discrete Na I and
Ca II absorption components at the same redshifts as the emission components.
We tentatively interpret the two components as arising from two different
starforming regions in the host, but high resolution imaging is necessary to
confirm this.
- astro-ph/0702004 from 31 Jan 2007
Ghirlanda: GRB 060218 and the outliers with respect to the Ep-Eiso correlation
GRB 031203 and GRB 980425 are the two outliers with respect to the Ep-Eiso
correlation of long GRBs. Recently Swift discovered a nearby extremely long GRB
060218 associated with a SN event. The spectral properties of this bursts are
striking: on the one hand its broad band SED presents both thermal and
non-thermal components which can be interpreted as due to the emission from the
hot cocoon surrounding the GRB jet and as standard synchrotron self absorbed
emission in the GRB prompt phase, respectively; on the other hand it is its
long duration and its hard--to--soft spectral evolution which make this
underluminous burst consistent with the Ep-Eiso correlation of long GRBs. By
comparing the available spectral informations on the two major outliers we
suggests that they might be twins of 060218 and, therefore, only apparent
outliers with respect to the Ep_Eiso correlation. This interpretation also
suggests that it is of primary importance the study the broad band spectra of
GRBs in order to monitor their spectral evolution throughout their complete
duration.
- astro-ph/0702450 from 16 Feb 2007
Waxman: GRB060218: A Relativistic Supernova Shock Breakout
We show that the prompt and afterglow X-ray emission of GRB060218, as well as
its early (t<=1 d) optical-UV emission, can be explained by a model in
which a
radiation- mediated shock propagates through a compact progenitor star into a
dense wind. The prompt thermal X-ray emission is produced in this model as the
mildly relativistic shock, v/c=0.85 carrying few x 10^49 erg, reaches the wind
(Thomson) photosphere, where the post-shock thermal radiation is released and
the shock becomes collisionless. Adopting this interpretation of the thermal
X-ray emission, a subsequent X-ray afterglow is predicted, due to synchrotron
emission and inverse-Compton scattering of SN UV photons by electrons
accelerated in the collisionless shock. Early optical-UV emission is also
predicted, due to the cooling of the outer \delta M ~10^{-3} M_sun envelope of
the star, which was heated to high temperature during shock passage. The
observed X-ray afterglow and the early optical-UV emission are both consistent
with those expected in this model. Detailed analysis of the early optical-UV
emission may provide detailed constraints on the density distribution near the
stellar surface.
- astro-ph/0703107 from 6 March 2007
Maeda: SN 2006aj Associated with XRF 060218 At Late Phases: Nucleosynthesis-Signature of A Neutron Star-Driven Explosion
Optical spectroscopy and photometry of SN 2006aj have been performed with the
Subaru telescope at t > 200 days after GRB060218, the X-ray Flash with which it
was associated. Strong nebular emission-lines with an expansion velocity of v ~
7,300 km/s were detected. The peaked but relatively broad [OI]6300,6363
suggests the existence of ~ 2 Msun of materials in which ~1.3 Msun is oxygen.
The core might be produced by a mildly asymmetric explosion. The spectra are
unique among SNe Ic in (1) the absence of [CaII]7291,7324 emission, and (2) a
strong emission feature at ~ 7400A, which requires ~ 0.05 Msun of
newly-synthesized 58Ni. Such a large amount of stable neutron-rich Ni strongly
indicates the formation of a neutron star. The progenitor and the explosion
energy are constrained to 18 Msun < Mms < 22 Msun and E ~ (1 - 3) 10^{51} erg,
respectively.
- 0706.3209 from 21 Jun 2007
Dainotti: GRB060218 and GRBs associated with Supernovae Ib/c
Abstract: We plan to fit the complete gamma- and X-ray light curves of the long
duration GRB060218, including the prompt emission, in order to clarify the
nature of the progenitors and the astrophysical scenario of the class of GRBs
associated to SNe Ib/c. The initial total energy of the electron-positron
plasma E_{e^\pm}^{tot}=2.32\times 10^{50} erg has a particularly low value
similarly to the other GRBs associated with SNe. For the first time we observe
a baryon loading B=10^{-2} which coincides with the upper limit for the
dynamical stability of the fireshell. The effective CircumBurst Medium (CBM)
density shows a radial dependence n_{cbm} \propto r^{-\alpha} with
1.0<\alpha<1.7 and monotonically decreases from 1 to 10^{-6} particles/cm^3.
Such a behavior is interpreted as due to a fragmentation in the fireshell.
Analogies with the fragmented density and filling factor characterizing Novae
are outlined. The fit presented is particularly significant in view of the
complete data set available for GRB060218 and of the fact that it fulfills the
Amati relation. We fit GRB060218, usually considered as an X-Ray Flash (XRF),
as a "canonical GRB" within our theoretical model. The smallest possible black
hole, formed by the gravitational collapse of a neutron star in a binary
system, is consistent with the especially low energetics of the class of GRBs
associated with SNe Ib/c. We give the first evidence for a fragmentation in the
fireshell. Such a fragmentation is crucial in explaining both the unusually
large T_{90} and the consequently inferred abnormal low value of the CBM
effective density.
- 0707.0689 from 4 Jul 2007
Ghisellini: Did we observe the supernova shock breakout in GRB 060218?
Abstract: If the early optical data of GRB 060218 up to 1e5 s are
interpreted as the
black-body flux associated with the supernova shock breakout, we can derive
lower limits to the bolometric luminosity and energetics of this black-body
component. These limits are more severe for the very early data that imply
energetics of order of 1e51 erg. These values, puzzlingly large, are rather
independent of the assumed time profile of the emitting surface, provided that
the corresponding radius does not increase superluminally. Another concern is
the luminosity of the black-body component observed in the X-rays, that is
large and appears to be produced by an approximately constant temperature and a
surface area increasing only slowly in time. Although it has been suggested
that the long X-ray black-body duration is consistent with the supernova shock
breakout if anisotropy is assumed, the nearly constant emitting surface
requires some fine tuning, allowing and suggesting an alternative
interpretation, i.e. emission from late dissipation of the fireball bulk
kinetic energy. This in turn requires a small value of the bulk Lorentz factor.
- 0709.1855from 12 Sep 2007
Bjornsson: GRB 060218: The nature of the optical-UV component
Abstract: The optical-UV component in GRB 060218 is assumed to be due to optically
thick cyclotron emission. The key aspect of this model is the high temperature
of the absorbing electrons. The heat input derives from nuclei accelerated in
semi-relativistic internal shocks, like in ordinary gamma-ray bursts. Coulomb
collisions transfer part of that energy to electrons. Inverse Compton cooling
on the X-ray photons leads to electron temperatures around 100 keV. Such a high
brightness temperature for the optical-UV emission implies an emitting area
roughly equal to that of the thermal X-ray component. This suggests a model in
which the radio, optical-UV and thermal X-ray emission are closely related:
Although the optical-UV and thermal X-ray emission are two separate spectral
components, it is argued that they both come from the photosphere of a
quasi-spherical, continuous outflow, whose interaction with the circumstellar
medium gives rise to the radio emission. The properties of GRB 060218, as
measured in the co-moving frame, are similar to those of ordinary gamma-ray
burst; i.e., the main difference is the much lower value of the bulk Lorentz
factor in GRB 060218. The cyclotron absorption implies a magnetic field in
rough equipartition with the matter energy density in the outflow. Hence, the
magnetic field could have a dynamically important role, possibly with a
magnetar as the central engine.
- 0712.0567 from 4 Dec 2007
Dainotti: GRB 060218 and the binaries as progenitors of GRB-SN systems
Abstract: (shortened) We study the Gamma-Ray Burst (GRB) 060218: a particularly close
source at z=0.033 with an extremely long duration, namely T_{90} ~ 2000 s,
related to SN 2006aj. [...] I present the fitting time consuming procedure. In
order to show its sensitivity I also present two examples of fits with the same
value of B and different value of E_{e^\pm}^{tot}. We fit the X- and \gamma-ray
observations by Swift of GRB 060218 in the 0.1-150 keV energy band during the
entire time of observations from 0 all the way to 10^6 s within a unified
theoretical model. The free parameters of our theory are only three, namely the
total energy E_{e\pm}^{tot} of the e^\pm plasma, its baryon loading B \equiv
M_Bc^2/E_{e\pm}^{tot}, as well as the CircumBurst Medium (CBM) distribution. We
justify the extremely long duration of this GRB by a total energy
E_{e\pm}^{tot} = 2.32\times 10^{50} erg, a very high value of the baryon
loading B=1.0\times 10^{-2} and the effective CircumBurst Medium (CBM) density
which shows a radial dependence n_{cbm} \propto r^{-\alpha} with 1.0 \leq
\alpha \leq 1.7 and monotonically decreases from 1 to $10^{-6}$
particles/cm$^3$. We recall that this value of the $B$ parameter is the highest
among the sources we have analyzed and it is very close to its absolute upper
limit expected. [...] We also think that the smallest possible black hole,
formed by the gravitational collapse of a neutron star in a binary system, is
consistent with the especially low energetics of the class of GRBs associated
with SNe Ib/c.
- 0801.0397from 2 Jan 2008
Rujula: Interpreting the X-ray Flash XRF 060218 and its associated supernova
Abstract: Forty years after their discovery, and in spite of a very large body of
observations, the operation of the 'engine' responsible for long-duration
Gamma-Ray Bursts (GRBs) and X-ray flashes --as well as the mechanisms
generating their radiation-- are still the subject of debate and study. In this
respect a recent event, XRF 060218, associated with SN 2006aj, is particularly
significant. It has been argued that, for the first time, the break-out of the
shock involved in the supernova explosion has been observed, thanks to the
detection of a thermal component in the event's radiation; that this XRF was
not a GRB seen 'off-axis', but a member of a new class of energetically feeble
GRBs; and that its 'continued engine activity' may have been driven by a
remnant highly-magnetized neutron star, a magnetar. I argue, on grounds based
on observations and on limpid verified hypothesis, that there is a common,
simpler alternative to these views, with no thermal component, no new feeble
GRBs, and no steady engine activity.
- 0805.2657from 17 May 2008
Sonbas: The stellar-wind envelope around the supernova XRF/GRB060218/SN2006aj massive progenitor star
Abstract: In BTA spectra of the supernova SN2006aj, identified with the X-ray flash
(XRF) and gamma-ray burst XRF/GRB060218/SN2006aj, we detected details
interpreted as hydrogen lines, which is a sign of stellar-wind envelope around
a massive progenitor star of the gamma-ray burst. Results of modeling two early
spectra obtained with the BTA in 2.55 and 3.55 days after the explosion of Type
Ic supernova SN2006aj (z=0.0331) are presented. The spectra were modeled in the
Sobolev approximation with the SYNOW code (Branch et al. 2001; Elmhamdi et al.
2006). In the spectra of the optical afterglow of the X-ray flash XRF/GRB060218
we detected spectral features interpreted as (1) the H_alpha PCyg profile for
the velocity 33000 km s$^{-1}$ -- a wide and almost unnoticeable deformation of
continuum in the range of $\simeq5600 - 6600\AA$ for the first epoch (2.55
days) and (2) a part (``remnant'') of the H_alpha PCyg profile in absorption
blueshifted by 24000 km s$^{-1}$ -- a wide spectral feature with a minimum at
$\simeq6100\AA$ (the rest wavelength) for the second epoch (3.55 days). Taking
into consideration early BTA observations and spectra obtained with other
telescopes (ESO Lick, ESO VLT, NOT) before 2006 Feb. 23 UT, it can be said that
we observe evolution of optical spectra of Type Ic core-collapse supernova SN
2006aj during {\it transition} from the short phase related to the shock
breakout to outer layers of the stellar-wind envelope to spectra of the phase
of increasing brightness corresponding to radioactive heating. Signs of
hydrogen in spectra of the gamma-ray burst afterglow were detected for the
first time.
- 1101.4208 from 24 Jan 11
A. Corsi et al.: PTF 10bzf (SN 2010ah): a broad-line Ic supernova discovered by the Palomar Transient Factory
Kasliwal, Y. Green, D. Murray, D. Xu, S. Ben-ami, J. S. Bloom, B. Cenko, N. M. Law, P. Nugent, R. M. Quimby, V. Pal'shin, J. Cummings, V.
Connaughton, K. Yamaoka, A. Rau, W. Boynton, I. Mitrofanov, J. Goldsten
We present the discovery and follow-up observations of a broad-line type-Ic supernova (SN), PTF 10bzf (SN 2010ah), detected by the Palomar
Transient Factory (PTF) on 2010 February 23. The SN distance is \cong 218 Mpc, greater than GRB 980425 / SN 1998bw and GRB 060218 / SN 2006aj,
but smaller than the other SNe firmly associated with gamma-ray bursts (GRBs). We conducted a multi-wavelength follow-up campaign with
Palomar-48 inch, Gemini-N, Keck, Wise, Swift, the Allen Telescope Array, CARMA, WSRT, and EVLA. Here we compare the properties of PTF 10bzf
with those of SN 1998bw and other broad-line SNe. The optical luminosity and spectral properties of PTF 10bzf suggest that this SN is
intermediate, in kinetic energy and amount of 56Ni, between non GRB-associated SNe like 2002ap or 1997ef, and GRB-associated SNe like 1998bw.
No X-ray or radio counterpart to PTF 10bzf was detected. X-ray upper-limits allow us to exclude the presence of an underlying X-ray afterglow
as luminous as that of GRB 980425. Early-time radio upper-limits do not show evidence for mildly-relativistic ejecta. Late-time radio
upper-limits rule out the presence of an underlying off-axis GRB, with energy and wind density similar to the SN-associated GRB 030329 and GRB
031203. Finally, by performing a search for a GRB in the time window and at the position of PTF 10bzf, we find that no GRB in the IPN catalog
could be associated with this SN.
- 1104.3087 from 18 Apr 11
Rhaana L.C. Starling et al.: Discovery of a gamma-ray burst with an associated supernova
We report the discovery of the nearby long, soft GRB 100316D, and the subsequent unveiling of its host galaxy and associated supernova. We
study the extremely unusual prompt emission with time-resolved gamma-ray to X-ray spectroscopy and find that a thermal component in addition to
the synchrotron spectrum is required. The host galaxy is a bright, blue galaxy with a highly disturbed morphology. From optical photometry and
spectroscopy we provide an accurate astrometry and redshift, and derive the key host properties of star formation rate and stellar age. We
compare our findings for this GRB-SN with the well known previous case of GRB 060218. GRB 100316D is an important addition to the current
sparse sample of spectroscopically confirmed GRB-SNe, from which a better understanding of long GRB progenitors and the GRB-SN connection can
be gleaned.
- 1212.5267 from 24 Dec 12
Roman V. Shcherbakov et al.: Prompt Emission from Tidal Disruptions of White Dwarfs by Intermediate Mass Black Holes
We present a qualitative picture of prompt emission from tidal disruptions of white dwarfs (WD) by intermediate mass black holes (IMBH). The
smaller size of an IMBH compared to a supermassive black hole and a smaller tidal radius of a WD disruption lead to a very fast event with high
peak luminosity. Magnetic field is generated in situ following the tidal disruption, which leads to effective accretion. Since large-scale
magnetic field is also produced, geometrically thick super-Eddington inflow leads to a relativistic jet. The dense jet possesses a photosphere,
which emits quasi-thermal radiation in soft X-rays. The source can be classified as a long low-luminosity gamma-ray burst (ll-GRB). Tidal
compression of a WD causes nuclear ignition, which is observable as an accompanying supernova. We suggest that GRB060218 and SN2006aj is such a
pair of ll-GRB and supernova. We argue that in a flux-limited sample the disruptions of WDs by IMBHs are more frequent then the disruptions of
other stars by IMBHs.
- 1511.00336 from 3 Nov 15
C. M. Irwin et al.: Jet or Shock Breakout? The Low-Luminosity GRB 060218
We consider a model for the low-luminosity gamma-ray burst GRB 060218 that plausibly accounts for multiwavelength observations to day 20. The
model components are: (1) a long-lived ($t_j \sim 3000$ s) central engine and accompanying low-luminosity ($L_j \sim 10^{47}$ erg s$^{-1}$),
semirelativistic ($\gamma \sim 10$) jet; (2) a low-mass ($ \sim 10^{-2} M_\odot$) envelope surrounding the progenitor star; and (3) a modest
amount of dust ($A_V \sim 0.1$ mag) in the interstellar environment. Blackbody emission from the transparency radius in a low-power jet outflow
can fit the prompt thermal X-ray emission, and the nonthermal X-rays and gamma-rays may be produced via Compton scattering of thermal photons
from hot leptons in the jet interior or the external shocks. The later mildly relativistic phase of this outflow can produce the radio emission
via synchrotron radiation from the forward shock. Meanwhile, interaction of the associated SN 2006aj with a circumstellar envelope extending to
$\sim10^{13}$ cm can explain the early optical emission. The X-ray afterglow can be interpreted as a light echo of the prompt emission from
dust at $\sim 30$ pc. Our model is a plausible alternative to that of Nakar, who recently proposed shock breakout of a jet smothered by an
extended envelope as the source of prompt emission. Both our results and Nakar's suggest that bursts such as GRB 060218 may originate from
unusual progenitors with extended circumstellar envelopes, and that a jet is necessary to decouple the prompt emission from the supernova.
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