- GCN/BACODINE POSITION NOTICE
TITLE: GCN/SWIFT NOTICE
NOTICE_DATE: Wed 21 Dec 05 01:51:32 UT
NOTICE_TYPE: Swift-BAT GRB Position
TRIGGER_NUM: 173780, Seg_Num: 0
GRB_RA: 328.711d {+21h 54m 51s} (J2000),
328.782d {+21h 55m 08s} (current),
328.114d {+21h 52m 27s} (1950)
GRB_DEC: +16.896d {+16d 53' 45"} (J2000),
+16.924d {+16d 55' 27"} (current),
+16.659d {+16d 39' 31"} (1950)
GRB_ERROR: 3.00 [arcmin radius, statistical only]
GRB_INTEN: 1239 [cnts] Image_Peak=220 [image_cnts]
TRIGGER_DUR: 0.064 [sec]
TRIGGER_INDEX: 10418 E_range: 50-350 keV
BKG_INTEN: 35491 [cnts]
BKG_TIME: 6664.00 SOD {01:51:04.00} UT
BKG_DUR: 8 [sec]
GRB_DATE: 13725 TJD; 355 DOY; 05/12/21
GRB_TIME: 6675.61 SOD {01:51:15.61} UT
GRB_PHI: -178.58 [deg]
GRB_THETA: 36.61 [deg]
SOLN_STATUS: 0x3
RATE_SIGNIF: 56.02 [sigma]
IMAGE_SIGNIF: 16.39 [sigma]
MERIT_PARAMS: +1 +0 +0 -3 +3 +33 +0 +0 -33 +1
SUN_POSTN: 269.23d {+17h 56m 55s} -23.44d {-23d 26' 09"}
SUN_DIST: 70.79 [deg]
MOON_POSTN: 152.90d {+10h 11m 37s} +14.60d {+14d 36' 10"}
MOON_DIST: 148.21 [deg]
MOON_ILLUM: 75 [%]
GAL_COORDS: 73.56,-28.59 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS: 337.40, 27.67 [deg] ecliptic lon,lat of the burst (or transient)
COMMENTS: SWIFT-BAT GRB Coordinates.
COMMENTS: This is a rate trigger.
COMMENTS: A point_source was found.
COMMENTS: This does not match any source in the on-board catalog.
COMMENTS: This does not match any source in the ground catalog.
COMMENTS: This is a GRB.
COMMENTS: This trigger occurred at longitude,latitude = 142.81,-15.76 [deg].
- red DSS finding chart
ps-file
- GCN NOTICE
TITLE: GCN/SWIFT NOTICE
NOTICE_DATE: Wed 21 Dec 05 01:52:51 UT
NOTICE_TYPE: Swift-XRT Nack-Position
TRIGGER_NUM: 173780, Seg_Num: 0
POINT_RA: 328.694d {+21h 54m 46s} (J2000)
POINT_DEC: +16.890d {+16d 53' 22"} (J2000)
IMG_START_DATE: 13725 TJD; 355 DOY; 05/12/21
IMG_START_TIME: 6763.61 SOD {01:52:43.61} UT, 88.0 [sec] since BAT Trigger Time
COUNTS: 11 Min_needed= 20
STD_DEV: 0.00 Max_StdDev_for_Good=28.44 [arcsec]
PH2_ITER: 2 Max_iter_allowed= 4
ERROR_CODE: 1
COMMENTS: SWIFT-XRT Nack Position.
COMMENTS: No source found in the image.
- GCN NOTICE
TITLE: GCN/SWIFT NOTICE
NOTICE_DATE: Wed 21 Dec 05 01:54:45 UT
NOTICE_TYPE: Swift-BAT GRB Lightcurve
TRIGGER_NUM: 173780, Seg_Num: 0
GRB_RA: 328.711d {+21h 54m 51s} (J2000),
328.782d {+21h 55m 08s} (current),
328.114d {+21h 52m 27s} (1950)
GRB_DEC: +16.896d {+16d 53' 45"} (J2000),
+16.924d {+16d 55' 27"} (current),
+16.659d {+16d 39' 31"} (1950)
GRB_DATE: 13725 TJD; 355 DOY; 05/12/21
GRB_TIME: 6675.86 SOD {01:51:15.86} UT
TRIGGER_INDEX: 10418
GRB_PHI: -178.58 [deg]
GRB_THETA: 36.61 [deg]
DELTA_TIME: 65479.00 [sec]
TRIGGER_DUR: 0.064 [sec]
LC_URL: sw00173780000msb.lc
SUN_POSTN: 269.23d {+17h 56m 55s} -23.44d {-23d 26' 09"}
SUN_DIST: 70.79 [deg]
MOON_POSTN: 152.93d {+10h 11m 43s} +14.59d {+14d 35' 31"}
MOON_DIST: 148.22 [deg]
MOON_ILLUM: 75 [%]
GAL_COORDS: 73.56,-28.59 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS: 337.40, 27.67 [deg] ecliptic lon,lat of the burst (or transient)
COMMENTS: SWIFT-BAT GRB Lightcurve.
COMMENTS:
COMMENTS: The next comments were copied from the BAT_POS Notice:
COMMENTS: This is a rate trigger.
COMMENTS: A point_source was found.
COMMENTS: This does not match any source in the on-board catalog.
COMMENTS: This does not match any source in the ground catalog.
COMMENTS: This is a GRB.
COMMENTS: This trigger occurred at longitude,latitude = 142.81,-15.76 [deg].
- GCN NOTICE
TITLE: GCN/SWIFT NOTICE
NOTICE_DATE: Wed 21 Dec 05 01:55:01 UT
NOTICE_TYPE: Swift-XRT Lightcurve
TRIGGER_NUM: 173780, Seg_Num: 0
POINT_RA: 328.692d {+21h 54m 46s} (J2000)
POINT_DEC: +16.891d {+16d 53' 27"} (J2000)
LC_START_DATE: 13725 TJD; 355 DOY; 05/12/21
LC_START_TIME: 6766.28 SOD {01:52:46.28} UT, 90.7 [sec] since BAT Trigger Time
LC_STOP_DATE: 13725 TJD; 355 DOY; 05/12/21
LC_STOP_TIME: 6889.03 SOD {01:54:49.03} UT
LC_LIVE_TIME: 111.67 [sec], 91.0%
DELTA_TIME: 86277.25 [sec]
N_BINS: 100
TERM_COND: 0
LC_URL: sw00173780000msx.lc
SUN_POSTN: 269.23d {+17h 56m 55s} -23.44d {-23d 26' 09"}
SUN_DIST: 70.77 [deg]
MOON_POSTN: 152.93d {+10h 11m 43s} +14.59d {+14d 35' 28"}
MOON_DIST: 148.22 [deg]
MOON_ILLUM: 75 [%]
GAL_COORDS: 73.54,-28.58 [deg] galactic lon,lat of the pointing direction
ECL_COORDS: 337.38, 27.67 [deg] ecliptic lon,lat of the pointing direction
COMMENTS: SWIFT-XRT Lightcurve.
- GCN NOTICE
TITLE: GCN/SWIFT NOTICE
NOTICE_DATE: Wed 21 Dec 05 02:01:52 UT
NOTICE_TYPE: Swift-UVOT Source List
TRIGGER_NUM: 173780, Seg_Num: 0
POINT_RA: 328.694d {+21h 54m 46s} (J2000)
POINT_DEC: +16.889d {+16d 53' 21"} (J2000)
POINT_ROLL: 236.866d
IMG_START_DATE: 13725 TJD; 355 DOY; 05/12/21
IMG_START_TIME: 6761.70 SOD {01:52:41.70} UT, 86.1 [sec] since BAT Trigger Time
FILTER: 3, V
BKG_MEAN: 2.519
N_STARS: 56
X_OFFSET: 476 [pixels]
Y_OFFSET: 555 [pixels]
X_MAX: 1435 [pixels]
Y_MAX: 1514 [pixels]
DET_THRESH: 13
PHOTO_THRESH: 7
SL_URL: sw00173780000msufc0086.fits
SUN_POSTN: 269.24d {+17h 56m 57s} -23.44d {-23d 26' 10"}
SUN_DIST: 70.77 [deg]
MOON_POSTN: 152.98d {+10h 11m 56s} +14.57d {+14d 34' 04"}
MOON_DIST: 148.24 [deg]
MOON_ILLUM: 75 [%]
GAL_COORDS: 73.54,-28.58 [deg] galactic lon,lat of the pointing direction
ECL_COORDS: 337.38, 27.67 [deg] ecliptic lon,lat of the pointing direction
COMMENTS: SWIFT-UVOT Source List.
- GCN NOTICE
TITLE: GCN/SWIFT NOTICE
NOTICE_DATE: Wed 21 Dec 05 02:02:29 UT
NOTICE_TYPE: Swift-UVOT Processed Source List
TRIGGER_NUM: 173780, Seg_Num: 0
POINT_RA: 328.694d {+21h 54m 46s} (J2000)
POINT_DEC: +16.889d {+16d 53' 21"} (J2000)
POINT_ROLL: 236.866d
IMG_START_DATE: 13725 TJD; 355 DOY; 05/12/21
IMG_START_TIME: 6761.70 SOD {01:52:41.70} UT, 86.1 [sec] since BAT Trigger Time
FILTER: 3, V
BKG_MEAN: 2.519
N_STARS: 56
X_OFFSET: 476 [pixels]
Y_OFFSET: 555 [pixels]
X_MAX: 1435 [pixels]
Y_MAX: 1514 [pixels]
DET_THRESH: 13
PHOTO_THRESH: 7
SL_URL: sw00173780000msufc0086.fits
SUN_POSTN: 269.24d {+17h 56m 57s} -23.44d {-23d 26' 10"}
SUN_DIST: 70.77 [deg]
MOON_POSTN: 152.99d {+10h 11m 57s} +14.57d {+14d 33' 56"}
MOON_DIST: 148.24 [deg]
MOON_ILLUM: 75 [%]
GAL_COORDS: 73.54,-28.58 [deg] galactic lon,lat of the pointing direction
ECL_COORDS: 337.38, 27.67 [deg] ecliptic lon,lat of the pointing direction
COMMENTS: SWIFT-UVOT Processed Source List.
COMMENTS: All 4 attachments are included.
- GCN NOTICE
TITLE: GCN/SWIFT NOTICE
NOTICE_DATE: Wed 21 Dec 05 02:03:19 UT
NOTICE_TYPE: Swift-UVOT Image
TRIGGER_NUM: 173780, Seg_Num: 0
POINT_RA: 328.694d {+21h 54m 46s} (J2000)
POINT_DEC: +16.889d {+16d 53' 21"} (J2000)
ROLL: 236.866d
IMG_START_DATE: 13725 TJD; 355 DOY; 05/12/21
IMG_START_TIME: 6761.70 SOD {01:52:41.70} UT, 86.1 [sec] since BAT Trigger Time
FILTER: 3, V
EXPOSURE_ID: 156822761
X_OFFSET: 795 [pixels]
Y_OFFSET: 874 [pixels]
WIDTH: 160 [pixels]
HEIGHT: 160 [pixels]
X_GRB_POS: 955
Y_GRB_POS: 1034
BINNING_INDEX: 1
IM_URL: sw00173780000msuni0086.fits
SUN_POSTN: 269.24d {+17h 56m 57s} -23.44d {-23d 26' 10"}
SUN_DIST: 70.77 [deg]
MOON_POSTN: 152.99d {+10h 11m 59s} +14.56d {+14d 33' 46"}
MOON_DIST: 148.24 [deg]
MOON_ILLUM: 75 [%]
GAL_COORDS: 73.54,-28.58 [deg] galactic lon,lat of the pointing direction
ECL_COORDS: 337.38, 27.67 [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: Wed 21 Dec 05 02:03:35 UT
NOTICE_TYPE: Swift-UVOT Processed Image
TRIGGER_NUM: 173780, Seg_Num: 0
POINT_RA: 328.694d {+21h 54m 46s} (J2000)
POINT_DEC: +16.889d {+16d 53' 21"} (J2000)
ROLL: 236.866d
IMG_START_DATE: 13725 TJD; 355 DOY; 05/12/21
IMG_START_TIME: 6761.70 SOD {01:52:41.70} UT, 86.1 [sec] since BAT Trigger Time
FILTER: 3, V
EXPOSURE_ID: 156822761
X_OFFSET: 795 [pixels]
Y_OFFSET: 874 [pixels]
WIDTH: 160 [pixels]
HEIGHT: 160 [pixels]
X_GRB_POS: 955
Y_GRB_POS: 1034
BINNING_INDEX: 1
IM_URL: sw00173780000msuni0086.fits
SUN_POSTN: 269.24d {+17h 56m 57s} -23.44d {-23d 26' 10"}
SUN_DIST: 70.77 [deg]
MOON_POSTN: 153.00d {+10h 11m 59s} +14.56d {+14d 33' 42"}
MOON_DIST: 148.24 [deg]
MOON_ILLUM: 75 [%]
GAL_COORDS: 73.54,-28.58 [deg] galactic lon,lat of the pointing direction
ECL_COORDS: 337.38, 27.67 [deg] ecliptic lon,lat of the pointing direction
COMMENTS: SWIFT-UVOT Processed Image.
COMMENTS: If you have elected to receive attachments:
COMMENTS: The uvot_catalog_image.fits.gz file does not exist; skipping the attachment.
- GCN Circular #4363
A. Parsons (GSFC), S. Barthelmy (GSFC), D. Burrows (PSU), M. Capalbi (ASDC),
J. Cummings (GSFC/NRC), N. Gehrels (GSFC), C. Gronwall (PSU),
H. Krimm (GSFC/USRA), C. Markwardt (GSFC/UMD), F. Marshall (GSFC),
K. Page (U Leicester), D. Palmer (LANL),
on behalf of the Swift team:
At 01:51:16 UT, Swift-BAT triggered and located GRB 051221 (trigger=173780).
The spacecraft slewed immediately. The BAT on-board calculated location
is RA,Dec 328.711d,+16.896d {21h 54m 51s,+16d 53' 45"} with an uncertainty
of 3 arcmin (radius, 90% containment, stat+sys). The BAT light curve shows
a single bright short peak at T0 with a duration less than 128 msec
followed by a 2nd smaller and much softer peak at T+1 sec with an exponential
decay lasting ~3 sec. The peak count rate was ~70,000 counts/sec (15-350 keV),
at ~0 seconds after the trigger.
The XRT began observing the target at 01:52:44 UT, 88 sec after the burst.
There was no source bright enough for an on-board centroid determination,
but the TDRSS spectrum and lightcurve suggest the presence of an X-ray source
in the field of view. Further analysis will require the full data dump
through the Malindi ground station.
UVOT took a finding chart exposure of 199.9 seconds with the V filter
starting 86.1 seconds after the BAT trigger. No afterglow candidate has
been found in the initial data products. The 2.7'x2.7' sub-image covers
25% of the BAT error circle. The typical 3-sigma upper limit is about 18.7 mag.
The 8'x8' region for the list of sources generated on-board covers 100%
of the BAT error circle. The list of sources is typically complete
to about 18.0 mag. No correction has been made for the expected
visual extinction of about 0.23 magnitudes.
- GCN Circular #4364
J. S. Bloom (UC Berkeley), on behalf of a larger collaboration, reports:
"We began observations of the bright short burst GRB 051221 (Parsons
GCN #4363) with the PAIRITEL 1.3m at 2005-12-21 02:54:02 UTC, about
30 minute after the GCN circular and 1hr3min after the GRB. In a
stack of the first 313sec, we detect no new sources to at least the
2MASS limit in JHKs bands. A visual comparison with the DSS-2 (F-
plate) shows that most of the sources fainter than 2MASS in the
PAIRITEL mosaics have optical counterparts. Some of the faintest IR
sources do not have detected counterparts but this is likely due to
the redness/faintness of the sources. In particular, we point out
objects at J2000:
A: 21:54:57.84 +16:53:07.5 (inside the error circle)
B: 21:55:00.89 +16:56:50.2 (red, outside the error circle)
C: 21:55:01.58 +16:57:07.1 (red, outside the error circle, extended)
Further analysis is ongoing but we suggest that these sources be
monitored for variability, especially object A."
A RGB (=KsHJ) finding chart may be found at:
http://astro.berkeley.edu/~jbloom/grb051221.ps
This message may be cited.
- GCN Circular #4365
J. Cummings (GSFC/NRC), L. Barbier (GSFC), S. Barthelmy (GSFC),
J. Cannizzo (GSFC-UMBC), 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), M. Tashiro (Saitama U.), J. Tueller (GSFC)
on behalf of the Swift-BAT team:
Using the data from the recent telemetry downlink, we report
further analysis of Swift-BAT GRB 051221 (trigger #173780)
(Parsons, et al., GCN 4363). We have received data covering T-60
to T+120 seconds. The ground-analysis position is
RA,Dec 328.711,+16.892 {21h 54m 50.7s,16d 53' 31.9"} (J2000)
with an uncertainty of 0.8 arcmin (radius, 90%, stat+sys).
T90 is 1.4 +- 0.2 sec. The partial coding fraction is 63%.
The lightcurve has an initial hard spike at T+0.3 sec (FWHM of ~0.25 sec)
followed by 3 softer peaks at T+0.4, T+0.8, and T+1.2 sec.
Fitting a simple power law over the time-averaged interval (T+0.2 to T+2.4 sec),
gives a hard spectrum with a photon index of 1.39 +/- 0.06 and a fluence
of 1.16 +/- 0.04 X 10^-6 erg/cm^2. The peak flux in a 1-sec wide window
starting at T+0.2 sec is 12.1 +/- 0.4 ph/cm^2/sec. All values are
in the 15-150 keV band at the 90% confidence level.
- GCN Circular #4366
D. N. Burrows (PSU), M. Capalbi (ASDC), and D. Grupe (PSU) report on behalf
of the Swift XRT team:
The Swift XRT began observing GRB 051221 (Parsons et al., GCN 4363) at
01:52:44 UT (88 s after the burst). We find a bright, rapidly fading
source located at:
RA(J2000) = 21:54:48.71
Dec(J2000) = +16:53:28.2
The estimated uncertainty is 3.5 arcseconds (90% containment radius),
including corrections for the XRT boresight.
- GCN Circular #4367
J. S. Bloom (UC Berkeley) reports:
Following the discovery of the XRT position of GRB 051221 (Burrows
GCN 4366), we inspected our PAIRITEL mosaics (GCN 4365) and found a
faint, red source to the south of the XRT position by 3.2 arcsec with
the coordinates:
21:54:48.65, +16:53:25.1
Photometry and improved astrometry are still in progress.
A finding chart will be posted to
http://astro.berkeley.edu/~jbloom/grb051221-xrt.ps
- GCN Circular #4368
J. S. Bloom (UC Berkeley) reports:
We have reduced the second epoch of our PAIRITEL imaging (beginning
2005-12-21 03:02:32 UTC; total integration = 690 sec) and detect the
source mentioned in GCN 4367 in a stacked mosaic. The source appears
to be best detected in the full stack J-band image at a revised
position of J2000:
21:54:48.662 +16:53:26.97
The uncertainty relative to the USNOB1.0 is 180 mas in each
coordinate (the previous two circulars were based upon an astrometric
match using far fewer 2MASS sources in the field). This position is
1.41 arcsec from the Burrows et al. XRT position (GCN 4366). Because
the source is observed near the detection level, we cannot confirm
fading behavior at this time. Still, given the proximity to the XRT
location, we advance that this source is the IR counterpart to GRB
051221 (GCN 4363). If so, this would be the first infrared
counterpart detected for a short-hard GRB.
This message may be cited.
- GCN Circular #4369
E. Berger (Carnegie Observatories) reports:
"We observed the BAT error circle of the short GRB 051221 (GCN 4365) with
GMOS on the Gemnini-north telescope starting on 2005 Dec. 21.194 UT (2.8
hours after the burst). A total of 40 min were obtained in the r-band
under excellent seeing conditions (0.45"). Within the XRT error circle
(GCN 4366) we detect a single source at a position coincident with the
source reported in GCN 4367:
RA = 21:54:48.64
DEC= +16:53:27.44
Further analysis is in progress."
- GCN Circular #4370
J. S. Bloom reports:
Correction. GCN 4368 incorrectly stated that our discovery of the
long-wavelength counterpart to 051221 was the first IR counterpart
for a short-hard GRB: the Magellan/PANIC detection of 050724 (Berger
et al. Nature, 438, 988-990, 2005) was the first. I apologize for
this referencing oversight and thank E. Berger for pointing out this
error.
- GCN Circular #4371
E. Berger (Carnegie Observatories) reports:
"Further analysis of the Gemini GMOS data reveals that the object located
within the XRT error circle (GCNs 4367-9) has not changed in brightness
between 227 and 271 min after the burst to a limit of about 0.05 mag in
comparison to several nearby stars. We note that a typical decay rate of
t^-1 would result in a change of about 0.2 mag. The lack of variability
suggests that this is either the host galaxy or an unrelated object, or
that the decay rate is unusually shallow, |alpha|<0.25."
- GCN Circular #4372
E. Berger (Carnegie Observatories) reports:
"Further examination of the Gemini data reveals a clustering of faint
galaxies extending about 1.5' eastward from the position of the X-ray
afterglow (GCN 4366) and the optical/near-IR source possibly associated
with the burst (GCNs 4367-9):
http://www.ociw.edu/~eberger/grb051221-gemini.tif
Additional multi-band photometry and an analysis of spatial clustering are
required in order to verify whether this is a true galaxy cluster and
whether the optical/near-IR source is related to this possible structure.
This analysis is in progress."
- GCN Circular #4373
A. A. Breeveld (UCL-MSSL), F. Marshall (GSFC), A. Parsons (GSFC), P.
Mezsaros (PSU), M. Chester (PSU) on behalf of the Swift/UVOT team
The Swift/UVOT began the settling exposure of the field of GRB 051221 at
01:52:29 on 2005-12-21, 73s after the BAT trigger (Parsons et al. GCN
4363). The 86s delay reported in GCN 4363 did not include the settling
exposure. No source was detected at the XRT position (Burrows et al. GCN
4366) nor the candidate IR position (Bloom, GCN 4368) down to the
following 5-sigma upper limits. No correction has been made for the
expected visual extinction of about 0.23 magnitudes.
Filter T_range(s) Summed exposure times 5sigUL(mag)
V 73 - 12530 1109 19.2
B 453 - 19212 2098 20.8
U 399 - 18305 2098 20.2
W1 345 - 14127 1080 20.3
M2 290 - 13437 1298 20.7
W2 562 - 8341 1119 20.7
white 507 - 934 99.5 19.2
- GCN Circular #4374
M. Capalbi, M. Perri (ASDC), D.N. Burrows, D. Grupe (PSU), P. Boyd
(GSFC-UMBC), W. Voges (MPE) report on behalf of the Swift XRT team:
We have analyzed the first six orbits of the Swift XRT data of GRB
051221 (Parsons et al., GCN 4363).
Data in Windowed Timing (WT) mode started at 01:52:48 UT, 92 seconds
after the BAT trigger, then the XRT switched to Photon Counting mode.
The light curve shows an initial fading behavior up to 2.5 ks with a
decay index of -1.3 =B1 0.7. At later times, an indication of a
re-brightening is present.
A preliminary spectral fit (simple absorbed power-law) to the WT data in
the 0.5-10. 0 keV band yields a photon index of 2.0+/-0.4 and a column
density value consistent with the Galactic one (6.7E20 cm-2; Dickey &
Lockman 1990).
Extrapolating the initial decay, the unabsorbed 0.5-10.0 keV flux at 24
hours after the burst is estimated to be ~5E-14 erg cm^-2 s^-1.
- GCN Circular #4375
A. M. Soderberg (Caltech) and E. Berger (Carnegie Observatories) report:
"Digital image subtraction performed on the individual 240-s r-band frames
obtained with Gemini/GMOS (GCN 4369) reveal a fading source coincident
with the position of the bright NIR (GCN 4367) and optical (GCN 4369)
object located within the XRT error circle (GCN 4366). The fading source
is offset from the center of the bright object, which we identify as the
host galaxy, by about 0.2" to the west. Given the offset and fading
behavior we conclude that this object is the afterglow of GRB 051221.
Detailed photometry is in progress."
- GCN Circular #4377
GRB 051211A: Evidence This Is a Short Burst from Analysis of Spectral Lag
J. Norris, G. Ricker, J-L. Atteia, N. Kawai, D. Lamb, and S. Woosley, on
behalf of the HETE Science Team;
M. Arimoto, T. Donaghy, E. Fenimore, M. Galassi, C. Graziani,
N. Ishikawa, A. Kobayashi, J. Kotoku, M. Maetou, M. Matsuoka,
Y. Nakagawa, T. Sakamoto, R. Sato, T. Shimokawabe, Y. Shirasaki,
S. Sugita, M. Suzuki, T. Tamagawa, K. Tanaka, and A. Yoshida, on behalf
of the HETE WXM Team;
N. Butler, G. Crew, J. Doty, G. Prigozhin, R. Vanderspek,
J. Villasenor, J. G. Jernigan, A. Levine, G. Azzibrouck, J. Braga,
R. Manchanda, G. Pizzichini, and S. Gunasekera, on behalf of the HETE
Operations and HETE Optical-SXC Teams;
M. Boer, J-F Olive, J-P Dezalay, and K. Hurley, on behalf of the HETE
FREGATE Team;
report:
We have performed an analysis of the spectral lag for GRB 051211A,
using FREGATE data in the 30-85 keV and 85-400 keV energy bands. We
obtain a spectral lag of 0.000 +/- 0.024 seconds. This result provides
strong additional evidence that GRB 051211A is a short burst [Norris,
J. P., Scargle, J. D., and Bonnell, J. T. 2001, in Gamma-Ray Bursts in
the Afterglow Era, ed. E. Costa, F. Frontera, and J. Hjorth (Berlin:
Springer), p. 40; and Norris, J. P., and Bonnell, J. T. 2005, ApJ,
submitted (see, e.g., Figure 3)].
- GCN Circular #4380
J. Wren, W.T. Vestrand, R. White, P. Wozniak, and S. Evans report
on behalf of the RAPTOR team at Los Alamos National Laboratory:
Starting at 02:57:05 UT (1.1 hours after the burst), the RAPTOR-S
telescope began a manually initiated response to the short burst
identified by Swift (Parsons et al. 4363). Within the XRT error circle
(Burrows et al. 4366) at a position consistent with the location of the
candidate J-band infrared (Bloom, GCN 4368) and R-band optical (Berger,
GCN 4369) counterparts, a stack of 20 30-second unfiltered RAPTOR images
yields a marginal detection of a source. Using the USNO-B1 catalog for
calibration and ignoring any extinction along the line of sight, our
derived 5-sigma upper limit on the brightness of an optical counterpart
at that epoch (1.3 hours after the trigger) is R=20.2+/-0.2 magnitude.
- GCN Circular #4383
E. Berger (Carnegie Observatories), A. M. Soderberg (Caltech), B. P.
Schmidt (ANU), and P. A. Price (IfA) report:
"We obtained a second epoch of r-band imaging with GMOS on Gemini-north
starting on 2005 Dec. 22.195 UT (26.8 hr after the burst and 24 hr after
the previous set of observations). A total of 960 sec were obtained in
excellent seeing conditions. We find that the optical afterglow candidate
(GCN 4375; see also GCNs 4367 & 4369) has faded by about 1.1 mag between
the two epochs, confirming our earlier claim."
- GCN Circular #4384
E. Berger (Carnegie Observatories) and A. M. Soderberg (Caltech) report:
"We obtained 2x1200 sec spectra of the afterglow + host galaxy of the
short GRB 051221 (GCN 4383) with Gemini/GMOS. We detect several strong
emission lines at the position of the afterglow+host which we identify as
[OIII]4959,5006, H-beta, and [OII]3727 at a redshift of z=0.5465. Weak
absorption at the CaII H&K and G-band wavelengths at the same redshift may
also be present, but at a low significance.
The detection of strong emission lines indicates that the host galaxy is
under-going active star formation, and is possibly similar to that of GRB
050709 (Fox et al. 2005).
At the redshift of 0.5465, the isotropic-equivalent gamma-ray energy
release of the burst is 9e50 erg, the highest measured to date."
- GCN Circular #4385
A.J. van der Horst (University of Amsterdam) reports on behalf of a larger
collaboration:
"We observed the position of the GRB 051221A afterglow at 4.9 GHz with the
Westerbork Synthesis Radio Telescope at December 21 13.90 UT to 18.63 UT,
i.e. 12.05 - 16.78 hours after the burst (GCN 4363).
We do not detect a radio source within the SWIFT/XRT error circle (GCN
4366), in particular at the position of optical (GCN 4369) and infrared
(GCN 4368) counterparts. The formal flux measurement for a point source at
the position of the optical counterpart is 17 +/- 35 microJy."
This message may be cited.
- GCN Circular #4388
J. Norris (GSFC), T. Sakamoto (GSFC/NRC), D. Band (GSFC/UMBC), S. Barthelmy (GSFC)
on behalf of the Swift-BAT team:
The time profile of GRB 051221A binned to 1 ms resolution reveals
that the initial pulse structure (GCN 4363 & 4365) comprises 3 separate pulses
of FWHM ~10-15 ms with peak intensities of ~175,000 counts per sec.
We note for comparison that GRB 050525A, the brightest long burst
so far detected by BAT (in one year) had a peak count rate
of 101,000 cts/sec (corrected to match the same partial-coding as 051221A
of 63%). The GRB 051221A time profile is available at:
http://swift.gsfc.nasa.gov/docs/swift/results/releases/images/GRB051221A/
No extended emission is evident in this burst in the interval 30-120 sec
after the initial pulse structure. The 3 sigma upper limit is 1.16 counts/cm2.
The ratio of (extended emission, 15-50 keV) / (initial pulse complex 15-150 keV)
is < 0.1 (3 sigma). The same ratio for GRB 050724 is 1.9.
The spectral lag is negligible, 0.0+-0.4 ms (0.8+-0.5 ms), between the
15-25 and 50-100 keV (25-50 and 100-350 keV) energy bands -- typical
of spectral lags in short bursts (Norris & Bonnell, submitted to ApJ).
We estimate roughly that the peak flux of GRB 051221A lies in the upper 3%
of short bursts detectable by the BAT.
- GCN Circular #4389
GRB 051221A: Chandra Afterglow Position
D. Grupe (PSU), D. N. Burrows (PSU), and S. Patel (NASA/MSFC) report on
behalf of a larger collaboration:
We executed a Chandra ToO observation of GRB 051221A beginning at 2005-12-22
13:55:20 UT (130 ks after the burst) and lasting for 30.2 ks. A fading
X-ray source was found within the XRT error circle (Burrows et al., GCN
4366) at
RA(J2000) = 21:54:48.626
Dec(J2000) = +16:53:27.16
Chandra positions have typical uncertainties of 0.5 arcseconds
(radius). This
position is 0.55 arcseconds from the optical counterpart identified by
Bloom et al. (GCN 4368)
and 0.34 arcseconds from the position reported by Berger (GCN 4369)
- GCN Circular #4390
P. Roming (PSU), A. A. Breeveld (UCL-MSSL), F. Marshall, A. Parsons, R.
Fink (GSFC), & M. Ajello (MPE) on behalf of the Swift/UVOT team:
We have created a summed image from 2.78 ksec of exposure on GRB051221A
(Parsons et al., GCN 4363) through the "UVW1" filter of the Swift UVOT.
From the summed image we detect a source at 4.8-sigma confidence with a
position coincident with the one reported by Bloom (GCN 4367) and Berger
(GCN 4369). The magnitude of the source is 20.2+/-0.2 as determined by the
Swift analysis tool, uvotsource.
Examination of individual frames suggests that the source is not
distinguishable above background in the individual short (50-s and 100-s)
exposures and is only visible at the 3-sigma level in one of the early ~600
second exposures of the sequence.
- GCN Circular #4392
M. Boettcher and M. Joshi (Ohio University) report:
Starting on 21 Dec., UT 04:02, we observed the optical
afterglow of GRB 051221A (Parsons et al. GCN 4363) with
the MDM 1.3 m telescope in three 600 s exposures (beginning
2.1, 2.4, and 2.6 hr after the trigger). We detect a faint
source consistent with the locations of the IR (Bloom,
GCN 4367 and 4368), optical (Berger, GCN 4369, 4371;
Berger and Soderberg, GCN 4375; Berger et al. GCN 4383),
and X-ray (Burrows et al., GCN 4366; Grupe et al. GCN 4389)
afterglows. Photometry, calibrated on the R-band magnitudes
of 6 comparison stars in our field of view as given by
Aladin, from the UCD data base (UCD: PHOT_PHG_R), yields
the following magnitude estimates (t = time after GRB trigger):
t | R
-------------------
2.1 hr | 19.88 +/- 0.40
2.4 hr | 19.93 +/- 0.39
2.6 hr | 19.98 +/- 0.34
Consequently, there is no evidence for variability between
the three frames. Seeing was rather poor (~ 2 arc sec.), so
the optical afterglow is not resolved from the host galaxy
(Soderberg and Berger, GCN 4375). Given the RAPTOR upper
limit on the fading counterpart of R > 20.2 at 1.3 hr
after the trigger (Wren et al., GCN 4380), our measurement
might in fact be dominated by the host galaxy contribution.
This message may be cited.
- GCN Circular #4393
Y.Endo, M.Tashiro, K.Abe, S. Hong, K.Onda (Saitama U.),
K.Yamaoka, S.Sugita (Aoyama Gakuin U.), M.Ohno,
T.Takahashi, Y.Fukazawa (Hiroshima U.), Y.Terada (RIKEN),
K.Nakazawa, G.Sato, T.Takahashi (ISAS/JAXA), R.Miyawaki,
M.Kokubun, K.Makishima (Univ. of Tokyo) and the HXD-II team
The bright and short burst, GRB 051221A (Parsons et al., GCN4363),
triggered by Swift/BAT was also detected with the Suzaku Wideband
All-sky Monitor (WAM) which covers an energy band of 50 keV - 5 MeV
at 01:51:16 (UT).
The observed light curve exhibits two intense short spikes
with a total duration (T90) of 0.22 sec.
The fluence in 100 - 2000 keV was (2.4 +/- 0.4)X10^-6 erg/cm2.
The 1-sec peak flux was 4.7 +/- 0.8 photons/cm2/s in the
same energy range.
Preliminary result shows that the time-averaged spectrum
is well fitted by a single power law with a photon index
of 1.95 +/- 0.18.
All the quoted errors are at statistical 90% confidence level.
The WAM onboard calibration is still under way, and
systematic errors, such as the flux calibration uncertainties of
about 20%, are not included in the errors.
The WAM light curve of this event is available at
http://www.astro.isas.ac.jp/suzaku/research/HXD-WAM/WAM-GRB/grb/grb_table.html
Further detailed analyses are in progress.
- GCN Circular #4394
S. Golenetskii, R.Aptekar, E. Mazets, V. Pal'shin, D. Frederiks, and
T. Cline on behalf of the Konus-Wind team report:
The GRB 051221A (Swift-BAT trigger #173780;
Parsons et al., GCN 4363; Cummings et al., GCN 4365;
Norris et al., GCN 4388)
triggered Konus-Wind at T0=6672.976 s UT (01:51:12.976).
The Konus-Wind light curve consists of a soft weak precursor
and the main episode with five ~15-ms peaks.
The first peak at T0-16 ms to T0+10 is
substantially softer than the others
(there is no emission in the 380-1160 keV energy range).
After T0+0.250 sec a weak soft emission is marginally seen only
in the G1 (18-70 keV) range up to ~1 sec .
As observed by Konus-Wind the burst had
a fluence of 3.2(-1.7, +0.1)x10^-6 erg/cm2 and
peak flux on 4-ms time scale 4.6(-2.5, +0.2)x10^-5 erg/cm2/sec
(both in the 20 keV - 2 MeV energy range).
The time-integrated spectrum of the GRB (from T0 to T0+0.256 sec)
is well fitted (in the 20 keV - 2 MeV range)
by a power law with exponential cutoff model:
dN/dE ~ E^(-alpha) * exp(-E/E0)
with alpha = 1.08(-0.14, +0.13)
and E0 = 436(-116, +165) keV (chi2 = 65/69dof).
The peak energy Ep = 402(-72, +93) keV.
The fitting by a single power law gives an unacceptable
result: chi2 = 152/70dof (null hypothesis probability = 5.423E-08).
All the quoted errors are at the 90% confidence level.
Assuming z = 0.5465 (Berger and Soderberg, GCN 4384)
and a standard cosmology model with H_0 = 70 km/s/Mpc,
Omega_M = 0.3, Omega_\Lambda = 0.7,
the isotropic energy release is E_iso ~2.5x10^51 erg,
the maximum luminosity is (L_iso)_max ~5.5x10^52 erg/sec.
The Konus-Wind light curve of this GRB can be seen
at http://www.ioffe.rssi.ru/LEA/GRBs/GRB051221_T06672/
- GCN Circular #4416
Dale A. Frail (NRAO) reports on behalf of a larger collaboration:
"We observed the position of the GRB 051221A afterglow at 8.5 GHz with
the Very Large Array on 2005 December 21.99 UT, December 23.02 UT,
December 24.83 UT, and December 27.96 UT (GCN 4366; GCN 4367; GCN
4369). On the first epoch (2005 December 21.99 UT) we detect weak
radio emission coincident with the X-ray and optical afterglow, with a
peak flux density of 88 +/- 26 uJy. The source is not detected on any
subsequent epochs with rms noise levels of 24 to 32 uJy.
No 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."
- astro-ph/0601455 from 20 Jan 2006
Soderberg: The Afterglow and Host Galaxy of the Energetic Short-Hard Gamma-Ray
Burst 051221
We present detailed optical, X-ray and radio observations of the bright
afterglow of the short GRB051221 and an optical spectrum from which we measure
the redshift of the burst, z=0.5459. The isotropic-equivalent prompt energy
release was about 2.4 x 10^51 erg, and using the standard afterglow synchrotron
model we find that the blastwave kinetic energy is similar, E_{KE,iso}~1.4 x
10^51 erg. The lack of an observed jet break to t~13 days indicates that the
opening angle is > 13 deg and the total beaming-corrected energy is > 1 x 10^50
erg, at least an order of magnitude larger than for previous short GRBs. We
further show that the burst experienced an episode of energy injection by a
factor of 3.4 between t=1.4 and 3.4 hours, which was accompanied by reverse
shock emission in the radio band. This result provides continued evidence that
the central engines of short GRBs may be active significantly longer than the
duration of the burst and/or produce a wide range of Lorentz factors. Finally,
we show that the host galaxy is actively forming stars at a rate of about 1.5
M_solar/yr, but at the same time exhibits evidence for an appreciable
population of old stars (~1 Gyr) and near solar metallicity. These properties
are intermediate between those of long GRB hosts and those of previous short
bursts suggesting that the progenitor lifetimes may have a large spread. The
lack of bright supernova emission and the low circumburst density (n~0.001
cm^-3), however, continue to support the idea that short bursts are not related
to the death of massive stars and are instead consistent with a compact object
merger. If the energy release of this burst is in fact few x 10^51 erg then
this suggests that the neutrino annihilation mechanism may not be sufficient
and MHD processes may be required to power the burst.
- GCN Circular #4613
D. Sharapov (MAO, and NOT La Palma), M. Ibrahimov (MAO), A. Pozanenko
(IKI), V. Rumyantsev (CrAO) on behalf of larger GRB follow up collaboration
report:
We observed error box of GRB051221 (Parsons et al., GCN 4363, Cummings et
al., GCN 4365) with 1.5m telescope of Maidanak Astronomical Observatory on
Dec. 22 between (UT) 14:51 and 15:26. The source detected in J (Bloom, GCN
4367, 4368) and r (Berger et al., GCN 4369) is also detected in our stacked
R-image in the position (J2000) RA = 21 54 48.67, Dec = +16 53 27.53 with
an uncertainty in both coordinates of 0.3 arcsec. A photometry of the source
is following:
Obs. time, Exposure, R (mag), Mag.(UL), Seeing
(UT) (s)
Dec.22 14:51-15:26 1800 21.76+/-0.13 22.4 1.3"
(Astrometry and photometry reduction is based on USNO-B1.0). Using host
galaxy brightness obtained in astro-ph/0601455 (Soderberg et al.) we
estimate brightness of optical transient of short GRB050121 at 1.55 days
after the burst as R=23.00 +/- 0.35.
Combined images can be found at
http://grb.rssi.ru/GRB051221/grb051221_051222_R_AZT22.gif
The message may be cited.
- astro-ph/0601556 from 24 Jan 2006
Martinez: GRB 051221A and Tests of Lorentz Symmetry
Various approaches to quantum gravity suggest the possibility of violation of
Lorentz symmetry at very high energies. In these cases we expect a modification
at low energies of the dispersion relation of photons that contains extra
powers of the momentum suppressed by a high energy scale. These terms break
boost invariance and can be tested even at relatively low energies. We use the
light curves of the very bright short Gamma-Ray Burst GRB 051221A and compare
the arrival times of photons at different energies with the expected time delay
due to a modified dispersion relation. As no time delay was observed, we set a
lower bound of 0.0066 E_{pl} \sim 0.66 10^{17} GeV on the scale of Lorentz
invariance violation.
- astro-ph/0604320 from 13 Apr 2006
Burrows: Jet Breaks in Short Gamma-Ray Bursts. II: The Collimated Afterglow of GRB 051221A
We report the first clear detection of a jet break in a short Gamma-Ray Burst
(GRB) afterglow, using Chandra and Swift XRT observations of the X-ray
afterglow of GRB 051221A. The combined X-ray light curve, which has three
breaks, is similar to those commonly observed in Swift observations of long
GRBs. A flat segment of the light curve at ~0.1 days after the burst represents
the first clear case of strong energy injection in the external shock of a
short GRB afterglow. The last break occurs at ~4 days post-burst and breaks to
a power-law decay index of ~2. We interpret this as a jet break, with important
implications for models of short GRBs, since it requires collimation of the
afterglow into a jet with an initial opening angle ~4-8 degrees and implies a
total jet kinetic energy of E_jet ~(1-5) x 10^{49} erg. Combined with the lack
of a jet break in GRB 050724, this suggests a wide range in jet collimation in
short GRBs, with at least some having collimation similar to that found in long
GRBs, though with significantly lower jet energies.
- astro-ph/0605445 from 18 May 2006
Fan: The X-ray afterglow flat segment in short GRB 051221A: Energy injection from a millisecond magnetar?
In GRB 051221A, an X-ray afterglow flat segment lasting $\sim 10^4$ seconds
represents the first clear case of strong energy injection in the external
shock of a short GRB afterglow. In this work, we show that a millisecond pulsar
with dipole magnetic field $\sim 10^{14}$ Gauss could well account for that
energy injection. The good quality X-ray flat segment thus suggests that the
central engine of this short burst may be a millisecond magnetar.
- 1104.5552 from 2 May 11
D.M. Coward et al.: Toward an optimal search strategy of optical and gravitational wave emissions from binary neutron star coalescence
Observations of an optical source coincident with gravitational wave emission detected from a binary neutron star coalescence will improve the
confidence of detection, provide host galaxy localisation, and test models for the progenitors of short gamma ray bursts. We employ optical
observations of three short gamma ray bursts, 050724, 050709, 051221, to estimate the detection rate of a coordinated optical and gravitational
wave search of neutron star mergers. Model R-band optical afterglow light curves of these bursts that include a jet-break are extrapolated for
these sources at the sensitivity horizon of an Advanced LIGO/Virgo network. Using optical sensitivity limits of three telescopes, namely TAROT
(m=18), Zadko (m=21) and an (8-10) meter class telescope (m=26), we approximate detection rates and cadence times for imaging. We find a median
coincident detection rate of 4 yr^{-1} for the three bursts. GRB 050724 like bursts, with wide opening jet angles, offer the most optimistic
rate of 13 coincident detections yr^{-1}, and would be detectable by Zadko up to five days after the trigger. Late time imaging to m=26 could
detect off-axis afterglows for GRB 051221 like bursts several months after the trigger. For a broad distribution of beaming angles, the optimal
strategy for identifying the optical emissions triggered by gravitational wave detectors is rapid response searches with robotic telescopes
followed by deeper imaging at later times if an afterglow is not detected within several days of the trigger.
Previous IAU Circulars 
