Gamma-ray Burst 051021B

(All information courtesy of the instrument teams.)

Previous IAU Circulars

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Results of Observations

GCN/BACODINE POSITION NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Fri 21 Oct 05 23:32:11 UT
NOTICE_TYPE:     Swift-BAT GRB Position
TRIGGER_NUM:     160672,   Seg_Num: 0
GRB_RA:          126.037d {+08h 24m 09s} (J2000),
                 126.085d {+08h 24m 20s} (current),
                 125.626d {+08h 22m 30s} (1950)
GRB_DEC:         -45.519d {-45d 31' 09"} (J2000),
                 -45.538d {-45d 32' 17"} (current),
                 -45.356d {-45d 21' 22"} (1950)
GRB_ERROR:       4.00 [arcmin radius, statistical only]
GRB_INTEN:       4824 [cnts]    Image_Peak=181 [image_cnts]
TRIGGER_DUR:     1.024 [sec] 
TRIGGER_INDEX:   146     E_range: 25-100 keV
BKG_INTEN:       30949 [cnts]
BKG_TIME:        84696.00 SOD {23:31:36.00} UT
BKG_DUR:         8 [sec]
GRB_DATE:        13664 TJD;   294 DOY;   05/10/21
GRB_TIME:        84713.67 SOD {23:31:53.67} UT
GRB_PHI:         -18.68 [deg]
GRB_THETA:        27.32 [deg]
SOLN_STATUS:     0x83
RATE_SIGNIF:     12.80 [sigma]
IMAGE_SIGNIF:    6.77 [sigma]
MERIT_PARAMS:     +1  +0  +0  +0  +2  +2  +0  +1 -25  +1 
SUN_POSTN:       206.64d {+13h 46m 34s}  -11.00d {-11d 00' 01"}
SUN_DIST:         75.58 [deg]
MOON_POSTN:       83.44d {+05h 33m 45s}  +28.28d {+28d 16' 38"}
MOON_DIST:        83.36 [deg]
MOON_ILLUM:      78 [%]
GAL_COORDS:      262.68, -4.58 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:      150.21,-61.64 [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:        Since the IMAGE_SIGNIF is less than 7 sigma, this is a questionable detection.

red DSS finding chart ps-file

GCN/SWIFT NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Fri 21 Oct 05 23:33:21 UT
NOTICE_TYPE:     Swift-XRT Nack-Position
TRIGGER_NUM:     160672,   Seg_Num: 0
POINT_RA:        126.022d {+08h 24m 05s} (J2000)
POINT_DEC:       -45.519d {-45d 31' 08"} (J2000)
GRB_DATE:        13664 TJD;   294 DOY;   05/10/21
GRB_TIME:        84794.04 SOD {23:33:14.04} UT
COUNTS:          53    Min_needed= 20
STD_DEV:         0.00   Max_StdDev_for_Good=28.44 [arcsec]
PH2_ITER:        4    Max_iter_allowed= 4
ERROR_CODE:      2
COMMENTS:        SWIFT-XRT Nack Position.  
COMMENTS:        Algorithm did not converge; too many interations.

GCN/SWIFT NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Fri 21 Oct 05 23:35:35 UT
NOTICE_TYPE:     Swift-BAT GRB Lightcurve
TRIGGER_NUM:     160672,   Seg_Num: 0
GRB_RA:          126.037d {+08h 24m 09s} (J2000),
                 126.085d {+08h 24m 20s} (current),
                 125.626d {+08h 22m 30s} (1950)
GRB_DEC:         -45.519d {-45d 31' 09"} (J2000),
                 -45.538d {-45d 32' 17"} (current),
                 -45.356d {-45d 21' 22"} (1950)
GRB_DATE:        13664 TJD;   294 DOY;   05/10/21
GRB_TIME:        84713.67 SOD {23:31:53.67} UT
TRIGGER_INDEX:   146
GRB_PHI:         -18.68 [deg]
GRB_THETA:        27.32 [deg]
DELTA_TIME:      12.00 [sec]
TRIGGER_DUR:     1.024 [sec] 
LC_URL:          sw00160672000msb.lc
SUN_POSTN:       206.64d {+13h 46m 34s}  -11.00d {-11d 00' 01"}
SUN_DIST:         75.58 [deg]
MOON_POSTN:       83.44d {+05h 33m 45s}  +28.28d {+28d 16' 38"}
MOON_DIST:        83.36 [deg]
MOON_ILLUM:      78 [%]
GAL_COORDS:      262.68, -4.58 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      150.21,-61.64 [deg] ecliptic lon,lat of the pointing direction
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:        Since the IMAGE_SIGNIF is less than 7 sigma, this is a questionable detection.

GCN/SWIFT NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Fri 21 Oct 05 23:37:03 UT
NOTICE_TYPE:     Swift-XRT Lightcurve
TRIGGER_NUM:     160672,   Seg_Num: 0
POINT_RA:        126.021d {+08h 24m 05s} (J2000)
POINT_DEC:       -45.517d {-45d 31' 00"} (J2000)
LC_START_DATE:   13664 TJD;   294 DOY;   05/10/21
LC_START_TIME:   84796.81 SOD {23:33:16.81} UT
LC_STOP_DATE:    13664 TJD;   294 DOY;   05/10/21
LC_STOP_TIME:    85010.10 SOD {23:36:50.10} UT
LC_LIVE_TIME:    209.58 [sec], 98.3%
DELTA_TIME:      86186.71 [sec]
N_BINS:          100
TERM_COND:       0
LC_URL:          sw00160672000msx.lc
SUN_POSTN:       206.64d {+13h 46m 34s}  -11.00d {-11d 00' 02"}
SUN_DIST:         75.59 [deg]
MOON_POSTN:       83.45d {+05h 33m 48s}  +28.28d {+28d 16' 41"}
MOON_DIST:        83.35 [deg]
MOON_ILLUM:      78 [%]
GAL_COORDS:      262.67, -4.59 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      150.18,-61.64 [deg] ecliptic lon,lat of the pointing direction
COMMENTS:        SWIFT-XRT Lightcurve.

GCN/SWIFT NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Fri 21 Oct 05 23:37:53 UT
NOTICE_TYPE:     Swift-UVOT Source List
TRIGGER_NUM:     160672,   Seg_Num: 0
POINT_RA:        126.022d {+08h 24m 05s} (J2000)
POINT_DEC:       -45.519d {-45d 31' 08"} (J2000)
POINT_ROLL:      91.160d
GRB_DATE:        13664 TJD;   294 DOY;   05/10/21
GRB_TIME:        84791.82 SOD {23:33:11.82} UT
FILTER:          3, V
BKG_MEAN:        1.097
N_STARS:         190
X_OFFSET:        476 [pixels]
Y_OFFSET:        555 [pixels]
X_MAX:           1435 [pixels]
Y_MAX:           1514 [pixels]
DET_THRESH:      9
PHOTO_THRESH:    4
SL_URL:          sw00160672000msufc.fits
SUN_POSTN:       206.64d {+13h 46m 34s}  -11.00d {-11d 00' 02"}
SUN_DIST:         75.59 [deg]
MOON_POSTN:       83.45d {+05h 33m 48s}  +28.28d {+28d 16' 41"}
MOON_DIST:        83.35 [deg]
MOON_ILLUM:      78 [%]
GAL_COORDS:      262.67, -4.59 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      150.19,-61.65 [deg] ecliptic lon,lat of the pointing direction
COMMENTS:        SWIFT-UVOT Source List.

GCN/SWIFT NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Fri 21 Oct 05 23:38:39 UT
NOTICE_TYPE:     Swift-UVOT Processed Source List
TRIGGER_NUM:     160672,   Seg_Num: 0
POINT_RA:        126.022d {+08h 24m 05s} (J2000)
POINT_DEC:       -45.519d {-45d 31' 08"} (J2000)
POINT_ROLL:      91.160d
GRB_DATE:        13664 TJD;   294 DOY;   05/10/21
GRB_TIME:        84791.82 SOD {23:33:11.82} UT
FILTER:          3, V
BKG_MEAN:        1.097
N_STARS:         190
X_OFFSET:        476 [pixels]
Y_OFFSET:        555 [pixels]
X_MAX:           1435 [pixels]
Y_MAX:           1514 [pixels]
DET_THRESH:      9
PHOTO_THRESH:    4
SL_URL:          sw00160672000msufc.fits
SUN_POSTN:       206.64d {+13h 46m 34s}  -11.00d {-11d 00' 02"}
SUN_DIST:         75.59 [deg]
MOON_POSTN:       83.45d {+05h 33m 48s}  +28.28d {+28d 16' 41"}
MOON_DIST:        83.35 [deg]
MOON_ILLUM:      78 [%]
GAL_COORDS:      262.67, -4.59 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      150.19,-61.65 [deg] ecliptic lon,lat of the pointing direction
COMMENTS:        SWIFT-UVOT Processed Source List.  
COMMENTS:        All 4 attachments are included.

GCN/SWIFT NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Fri 21 Oct 05 23:39:03 UT
NOTICE_TYPE:     Swift-UVOT Image
TRIGGER_NUM:     160672,   Seg_Num: 0
POINT_RA:        126.022d {+08h 24m 05s} (J2000)
POINT_DEC:       -45.519d {-45d 31' 08"} (J2000)
ROLL:            91.160d
GRB_DATE:        13664 TJD;   294 DOY;   05/10/21
GRB_TIME:        84791.82 SOD {23:33:11.82} UT
FILTER:          3, V
EXPOSURE_ID:     151630391
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:          sw00160672000msuni.fits
SUN_POSTN:       206.64d {+13h 46m 34s}  -11.00d {-11d 00' 02"}
SUN_DIST:         75.59 [deg]
MOON_POSTN:       83.45d {+05h 33m 48s}  +28.28d {+28d 16' 41"}
MOON_DIST:        83.35 [deg]
MOON_ILLUM:      78 [%]
GAL_COORDS:      262.67, -4.59 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      150.19,-61.65 [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/SWIFT NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Fri 21 Oct 05 23:39:24 UT
NOTICE_TYPE:     Swift-UVOT Processed Image
TRIGGER_NUM:     160672,   Seg_Num: 0
POINT_RA:        126.022d {+08h 24m 05s} (J2000)
POINT_DEC:       -45.519d {-45d 31' 08"} (J2000)
ROLL:            91.160d
GRB_DATE:        13664 TJD;   294 DOY;   05/10/21
GRB_TIME:        84791.82 SOD {23:33:11.82} UT
FILTER:          3, V
EXPOSURE_ID:     151630391
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:          sw00160672000msuni.fits
SUN_POSTN:       206.64d {+13h 46m 34s}  -11.00d {-11d 00' 02"}
SUN_DIST:         75.59 [deg]
MOON_POSTN:       83.45d {+05h 33m 48s}  +28.28d {+28d 16' 41"}
MOON_DIST:        83.35 [deg]
MOON_ILLUM:      78 [%]
GAL_COORDS:      262.67, -4.59 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      150.19,-61.65 [deg] ecliptic lon,lat of the pointing direction
COMMENTS:        SWIFT-UVOT Processed Image.  
COMMENTS:        All 4 attachments are included.

GCN notice #4126
A. Retter (PSU), S. Barthelmy (GSFC), D. Burrows (PSU), M. Chester (PSU), N. Gehrels (GSFC), J. Kennea (PSU), F. Marshall (GSFC), D. Palmer (LANL), J. Racusin (PSU) on behalf of the Swift team:
At 23:31:53 UT, Swift-BAT triggered and located GRB 051021B (trigger=160672). The BAT on-board calculated location is RA,Dec 126.037d,-45.519d {8h 24m 09s,-45d 31' 09"} (J2000), with an uncertainty of 3 arcmin (radius, 90% containment, stat+sys). The BAT light curve shows a single FRED-like peak with structure with a total duration of ~25 sec. There is some pre-trigger emission starting at T-8 sec. The peak count rate was ~1800 counts/sec (15-350 keV), at ~2 seconds after the trigger.
The spacecraft slewed immediately and the XRT began observing at 23:33:14 UT (81 sec after the BAT trigger). The on-board centroiding algorithm was not able to determine a position, but the prompt lightcurve and spectrum strongly suggest that a fading source is present in the field of view. Further analysis will require ground-processed data.
UVOT began observing 23:33:11 UT or 78 sec after the BAT trigger with a 200 sec V-band image. It is a crowded field with high, but uncertain extinction. No new sources are seen in either the small image or the list of sources produced in the on-board processing. The limiting magnitude in the small image is about 19th mag. The on-board list of sources covers the entire BAT error region and is typically complete to about 17th mag.
Further analysis will be delayed due the lack of telemetry downlink passes for several hours.
GCN notice #4128
J. Racusin, D. Morris, C. Pagani, D. Burrows, A. Retter (PSU), N. Gehrels (GSFC) on behalf of the Swift XRT team:
The Swift XRT began observing GRB 051021B (trigger #160672, Retter et al., GCN 4126) at 23:33:14 UT, but was unable to obtain an on-board centroid. Analysis of the first 2 orbits of the ground data reveal a previously uncatalogued, fading X-ray source at the following coordinates:
```
RA(J2000) = 08 24 11.8
Dec(J2000) = -45 32 30.8
```
We estimate an uncertainty of 4 arcseconds (90% containment), including corrections for the XRT boresight offset. This position lies 88 arcseconds from the BAT position reported in GCN 4126.
GCN notice #4135
S. Barthelmy (GSFC), L. Barbier (GSFC), P. Boyd (GSFC-UMBC), J. Cummings (GSFC/NRC), 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), W. Voges (MPE) on behalf of the Swift-BAT team:
Using the full data set from the recent telemetry downlink, we report further analysis of Swift-BAT GRB 051021B (trigger #160672) (Retter, et al., GCN 4126). The ground-analysis position is RA,Dec 126.059,-45.537 {8h 24m 14.2s,-45d 32' 13.0"} (J2000) with an uncertainty of 1.3 arcmin (radius, 90%, stat+sys). T90 is 47 +- 3 sec. The partial coding fraction is 88 %. The lightcurve has single FRED peak starting at T-6 sec (FWHM of ~12 sec) with the decay extending out to greater than T+20 sec. There is a second, smaller peak at ~T+20. Fitting a simple power law over the full interval from T-5.5 to T+51.5 sec, the photon index is 1.52 +/- 0.14 with a fluence of 9.1 +/- 0.8 X 10^-7 erg/cm^2. The peak flux in a 1-sec wide window starting at T-2.5 sec is 0.63 +/- 0.13 ph/cm^2/sec. All values are in the 15-150 keV band at the 90% confidence level.
GCN notice #4146
D. L. Kaplan (MIT), H-W. Chen (Chicago), J. S. Bloom (UCB), J. X. Prochaska (UCO LIck) report on behalf of a large collaboration:
"We obtained deep K-band imaging of the field of GRB 051021b (GCN 4135) with PANIC on the Magellan Baade Telescope starting at 08:42:56 October 22, 2005 UTC. We identify 4 sources within the XRT error circle (GCN 4128):
```
   08:24:11.803 -45:32:30.79 J2000
   08:24:11.598 -45:32:31.93 J2000
   08:24:11.622 -45:32:33.70 J2000
   08:24:11.724 -45:32:34.20 J2000
```
The 1 sigma uncertainty relative to 2MASS is 300 mas. As all of these sources are significantly fainter than the 2MASS detection limit we cannot identify an obvious afterglow candidate."
This message may be cited.
GCN Circular #4160
J. Racusin, C. Pagani, D. Morris, A. Retter, D. Burrows (PSU), N. Gehrels (GSFC) on behalf of the Swift XRT team:
We have analyzed the first 13 orbits of data from GRB051021B (Retter et al., GCN 4126). XRT observations began in Window Timing mode 87 seconds after the BAT trigger and continued for 32 seconds before switching to Photon Counting mode.
The XRT light curve shows an initial decline with a decay slope of 1.9+/-0.1 , followed by a break at ~T+2500s to a shallower decay slope of 0.6+/-0.1.
A preliminary spectral fit using an absorbed power-law to the Photon Counting mode data yields a photon index of 1.64+/-0.12 in the 0.85-10 keV band, fixing nH to the Galactic value of 7.7E21 cm-2.
The observed 0.85-10 keV flux for the Photon Counting mode data in the first orbit is 7.3E-12 ergs cm-2 s-1 corresponding to an unabsorbed flux of 9.0E-12 ergs cm-2 s-1.
GCN Circular #4167
P. J. Brown (PSU), A. Retter (PSU), F. Marshall (GSFC), A. Smale (NASA HQ), N. Gehrels (GSFC) on behalf of the Swift/UVOT team report:
Swift-UVOT observed the field of GRB 051021B (BAT Trigger=160672; Retter et al. GCN 4126) starting at 2005-10-21 23:33:11, 78 seconds after the burst.
No source was detected within the XRT error circle (Racusin et al GCN 4128) during the first 200 second image (Tmid=178 seconds after the burst) down to a 3 sigma limiting magnitude of V=19. Using summed images, we also did not detect a source in any of our 6 filters down to the following 3-sigma magnitude upper limits:
```
Filter  T_range(sec)   Exp(sec)  3sigUL
V       78-19380       1779      19.9
B       444-17793      1634      21.1
U       390-13591      961       19.9
W1      336-12417      1199      19.5
M2      282-12005      1199      19.6
W2      553-18702      1940      20.0
White   498-926        100       19.5
```
Where T_range is time post-trigger.
We note that this position is near the galactic plane, so the extinction and background in this line of sight are high.

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Jochen Greiner, last update: 26-Oct-2005 [Disclaimer]