Gamma-ray Burst 110921A

(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:     Wed 21 Sep 11 13:52:05 UT
NOTICE_TYPE:     Swift-BAT GRB Position
TRIGGER_NUM:     503652,   Seg_Num: 0
GRB_RA:          294.078d {+19h 36m 19s} (J2000),
                 294.184d {+19h 36m 44s} (current),
                 293.624d {+19h 34m 30s} (1950)
GRB_DEC:         +36.377d {+36d 22' 36"} (J2000),
                 +36.403d {+36d 24' 13"} (current),
                 +36.264d {+36d 15' 51"} (1950)
GRB_ERROR:       3.00 [arcmin radius, statistical only]
GRB_INTEN:       20146 [cnts]    Image_Peak=330 [image_cnts]
TRIGGER_DUR:     4.096 [sec] 
TRIGGER_INDEX:   303     E_range: 25-100 keV
BKG_INTEN:       179946 [cnts]
BKG_TIME:        49824.61 SOD {13:50:24.61} UT
BKG_DUR:         40 [sec]
GRB_DATE:        15825 TJD;   264 DOY;   11/09/21
GRB_TIME:        49880.16 SOD {13:51:20.16} UT
GRB_PHI:          22.87 [deg]
GRB_THETA:        47.39 [deg]
SOLN_STATUS:     0x3
RATE_SIGNIF:     15.03 [sigma]
IMAGE_SIGNIF:    9.66 [sigma]
MERIT_PARAMS:     +1  +0  +0  +2  +2  +0  +0  +1 +34  +0 
SUN_POSTN:       178.38d {+11h 53m 32s}   +0.70d {+00d 42' 05"}
SUN_DIST:        110.06 [deg]   Sun_angle= -7.7 [hr] (East of Sun)
MOON_POSTN:      100.66d {+06h 42m 39s}  +21.08d {+21d 04' 39"}
MOON_DIST:       121.12 [deg]
MOON_ILLUM:      40 [%]
GAL_COORDS:       70.12,  7.53 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:      306.84, 56.78 [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 = 76.68,1.54 [deg].

red DSS finding chart ps-file

GCN NOTICE

TITLE:           GCN/FERMI NOTICE
NOTICE_DATE:     Wed 21 Sep 11 13:51:37 UT
NOTICE_TYPE:     Fermi-GBM Flight Position
RECORD_NUM:      45
TRIGGER_NUM:     338305884
GRB_RA:          296.600d {+19h 46m 24s} (J2000),
                 296.686d {+19h 46m 45s} (current),
                 296.234d {+19h 44m 56s} (1950)
GRB_DEC:         +47.850d {+47d 51' 00"} (J2000),
                 +47.879d {+47d 52' 45"} (current),
                 +47.726d {+47d 43' 34"} (1950)
GRB_ERROR:       18.53 [deg radius, statistical plus systematic]
GRB_INTEN:       70 [cnts/sec]
DATA_SIGNIF:     6.90 [sigma]
INTEG_TIME:      4.096 [sec]
GRB_DATE:        15825 TJD;   264 DOY;   11/09/21
GRB_TIME:        49882.57 SOD {13:51:22.57} UT
GRB_PHI:          97.00 [deg]
GRB_THETA:        70.00 [deg]
DATA_TIME_SCALE: 4.0960 [sec]
HARD_RATIO:      1.04
LOC_ALGORITHM:   3 (version number of)
MOST_LIKELY:      97%  GRB
2nd_MOST_LIKELY:   1%  Generic SGR
DETECTORS:       0,1,0, 0,0,0, 0,0,0, 0,1,0, 0,0,
SUN_POSTN:       178.38d {+11h 53m 31s}   +0.70d {+00d 42' 05"}
SUN_DIST:        107.99 [deg]   Sun_angle= -7.9 [hr] (East of Sun)
MOON_POSTN:      100.66d {+06h 42m 38s}  +21.08d {+21d 04' 41"}
MOON_DIST:       109.56 [deg]
MOON_ILLUM:      40 [%]
GAL_COORDS:       81.27, 11.31 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:      319.61, 66.77 [deg] ecliptic lon,lat of the burst (or transient)
COMMENTS:        Fermi-GBM Flight-calculated Coordinates.  
COMMENTS:        This trigger occurred at longitude,latitude = 165.42,-9.60 [deg].

GCN NOTICE

TITLE:           GCN/FERMI NOTICE
NOTICE_DATE:     Wed 21 Sep 11 13:54:05 UT
NOTICE_TYPE:     Fermi-GBM Ground Position
RECORD_NUM:      56
TRIGGER_NUM:     338305884
GRB_RA:          297.340d {+19h 49m 22s} (J2000),
                 297.439d {+19h 49m 45s} (current),
                 296.918d {+19h 47m 40s} (1950)
GRB_DEC:         +41.540d {+41d 32' 24"} (J2000),
                 +41.570d {+41d 34' 12"} (current),
                 +41.413d {+41d 24' 47"} (1950)
GRB_ERROR:       6.65 [deg radius, statistical only]
DATA_SIGNIF:     9.40 [sigma]
DATA_INTERVAL:   4.096 [sec]
GRB_DATE:        15825 TJD;   264 DOY;   11/09/21
GRB_TIME:        49882.57 SOD {13:51:22.57} UT
GRB_PHI:         103.00 [deg]
GRB_THETA:        73.00 [deg]
E_RANGE:         44.032 - 279.965 [keV]
LOC_ALGORITHM:   4143 (Gnd S/W Version number)
SUN_POSTN:       178.38d {+11h 53m 32s}   +0.70d {+00d 42' 03"}
SUN_DIST:        110.81 [deg]   Sun_angle= -7.9 [hr] (East of Sun)
MOON_POSTN:      100.68d {+06h 42m 43s}  +21.07d {+21d 04' 29"}
MOON_DIST:       115.46 [deg]
MOON_ILLUM:      40 [%]
GAL_COORDS:       75.92,  7.81 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:      314.79, 60.80 [deg] ecliptic lon,lat of the burst (or transient)
COMMENTS:        Fermi-GBM Ground-calculated Coordinates.  
COMMENTS:        This Notice was ground-generated -- not flight-generated.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Wed 21 Sep 11 13:53:34 UT
NOTICE_TYPE:     Swift-XRT Nack-Position
TRIGGER_NUM:     503652,   Seg_Num: 0
POINT_RA:        294.091d {+19h 36m 22s} (J2000)
POINT_DEC:       +36.367d {+36d 22' 02"} (J2000)
IMG_START_DATE:  15825 TJD;   264 DOY;   11/09/21
IMG_START_TIME:  50002.52 SOD {13:53:22.52} UT,   122.4 [sec] since BAT Trigger Time
COUNTS:          4    Min_needed= 20
STD_DEV:         0.00   Max_StdDev_for_Good=28.44 [arcsec]
PH2_ITER:        1    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 Sep 11 13:55:13 UT
NOTICE_TYPE:     Swift-BAT GRB Lightcurve
TRIGGER_NUM:     503652,   Seg_Num: 0
GRB_RA:          294.078d {+19h 36m 19s} (J2000),
                 294.184d {+19h 36m 44s} (current),
                 293.624d {+19h 34m 30s} (1950)
GRB_DEC:         +36.377d {+36d 22' 36"} (J2000),
                 +36.403d {+36d 24' 13"} (current),
                 +36.264d {+36d 15' 51"} (1950)
GRB_DATE:        15825 TJD;   264 DOY;   11/09/21
GRB_TIME:        49880.16 SOD {13:51:20.16} UT
TRIGGER_INDEX:   303
GRB_PHI:          22.87 [deg]
GRB_THETA:        47.39 [deg]
DELTA_TIME:      45.00 [sec]
TRIGGER_DUR:     4.096 [sec] 
SOLN_STATUS:     0x3
RATE_SIGNIF:     15.03 [sigma]
IMAGE_SIGNIF:    9.66 [sigma]
LC_URL:          sw00503652000msb.lc
SUN_POSTN:       178.38d {+11h 53m 32s}   +0.70d {+00d 42' 02"}
SUN_DIST:        110.06 [deg]   Sun_angle= -7.7 [hr] (East of Sun)
MOON_POSTN:      100.69d {+06h 42m 46s}  +21.07d {+21d 04' 23"}
MOON_DIST:       121.13 [deg]
MOON_ILLUM:      40 [%]
GAL_COORDS:       70.12,  7.53 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:      306.84, 56.78 [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 = 76.68,1.54 [deg].

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Wed 21 Sep 11 13:56:26 UT
NOTICE_TYPE:     Swift-UVOT Source List
TRIGGER_NUM:     503652,   Seg_Num: 0
POINT_RA:        294.091d {+19h 36m 22s} (J2000)
POINT_DEC:       +36.367d {+36d 22' 00"} (J2000)
POINT_ROLL:      286.558d
IMG_START_DATE:  15825 TJD;   264 DOY;   11/09/21
IMG_START_TIME:  50006.09 SOD {13:53:26.09} UT,   125.9 [sec] since BAT Trigger Time
FILTER:          10, White
BKG_MEAN:        2.584
N_STARS:         190
X_OFFSET:        587 [pixels]
Y_OFFSET:        564 [pixels]
X_MAX:           1546 [pixels]
Y_MAX:           1523 [pixels]
DET_THRESH:      13
PHOTO_THRESH:    7
SL_URL:          sw00503652000msufc0125.fits
SUN_POSTN:       178.38d {+11h 53m 32s}   +0.70d {+00d 42' 01"}
SUN_DIST:        110.07 [deg]   Sun_angle= -7.7 [hr] (East of Sun)
MOON_POSTN:      100.70d {+06h 42m 49s}  +21.07d {+21d 04' 17"}
MOON_DIST:       121.14 [deg]
MOON_ILLUM:      40 [%]
GAL_COORDS:       70.12,  7.52 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      306.85, 56.76 [deg] ecliptic lon,lat of the pointing direction
COMMENTS:        SWIFT-UVOT Source List.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Wed 21 Sep 11 13:56:55 UT
NOTICE_TYPE:     Swift-UVOT Processed Source List
TRIGGER_NUM:     503652,   Seg_Num: 0
POINT_RA:        294.091d {+19h 36m 22s} (J2000)
POINT_DEC:       +36.367d {+36d 22' 00"} (J2000)
POINT_ROLL:      286.558d
IMG_START_DATE:  15825 TJD;   264 DOY;   11/09/21
IMG_START_TIME:  50006.09 SOD {13:53:26.09} UT,   125.9 [sec] since BAT Trigger Time
FILTER:          10, White
BKG_MEAN:        2.584
N_STARS:         190
X_OFFSET:        587 [pixels]
Y_OFFSET:        564 [pixels]
X_MAX:           1546 [pixels]
Y_MAX:           1523 [pixels]
DET_THRESH:      13
PHOTO_THRESH:    7
SL_URL:          sw00503652000msufc0125.fits
SUN_POSTN:       178.38d {+11h 53m 32s}   +0.70d {+00d 42' 00"}
SUN_DIST:        110.07 [deg]   Sun_angle= -7.7 [hr] (East of Sun)
MOON_POSTN:      100.71d {+06h 42m 50s}  +21.07d {+21d 04' 14"}
MOON_DIST:       121.14 [deg]
MOON_ILLUM:      40 [%]
GAL_COORDS:       70.12,  7.52 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      306.85, 56.76 [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 Sep 11 13:57:54 UT
NOTICE_TYPE:     Swift-UVOT Image
TRIGGER_NUM:     503652,   Seg_Num: 0
POINT_RA:        294.091d {+19h 36m 22s} (J2000)
POINT_DEC:       +36.367d {+36d 22' 00"} (J2000)
ROLL:            286.558d
IMG_START_DATE:  15825 TJD;   264 DOY;   11/09/21
IMG_START_TIME:  50006.09 SOD {13:53:26.09} UT,   125.9 [sec] since BAT Trigger Time
FILTER:          10, White
EXPOSURE_ID:     338306013
X_OFFSET:        906 [pixels]
Y_OFFSET:        883 [pixels]
WIDTH:           160 [pixels]
HEIGHT:          160 [pixels]
X_GRB_POS:       1066
Y_GRB_POS:       1043
BINNING_INDEX:   1
IM_URL:          sw00503652000msuni0133.fits
SUN_POSTN:       178.39d {+11h 53m 32s}   +0.70d {+00d 41' 59"}
SUN_DIST:        110.07 [deg]   Sun_angle= -7.7 [hr] (East of Sun)
MOON_POSTN:      100.72d {+06h 42m 52s}  +21.07d {+21d 04' 09"}
MOON_DIST:       121.14 [deg]
MOON_ILLUM:      40 [%]
GAL_COORDS:       70.12,  7.52 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      306.85, 56.76 [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 Sep 11 13:58:12 UT
NOTICE_TYPE:     Swift-UVOT Processed Image
TRIGGER_NUM:     503652,   Seg_Num: 0
POINT_RA:        294.091d {+19h 36m 22s} (J2000)
POINT_DEC:       +36.367d {+36d 22' 00"} (J2000)
ROLL:            286.558d
IMG_START_DATE:  15825 TJD;   264 DOY;   11/09/21
IMG_START_TIME:  50006.09 SOD {13:53:26.09} UT,   125.9 [sec] since BAT Trigger Time
FILTER:          10, White
EXPOSURE_ID:     338306013
X_OFFSET:        906 [pixels]
Y_OFFSET:        883 [pixels]
WIDTH:           160 [pixels]
HEIGHT:          160 [pixels]
X_GRB_POS:       1066
Y_GRB_POS:       1043
BINNING_INDEX:   1
IM_URL:          sw00503652000msuni0133.fits
SUN_POSTN:       178.39d {+11h 53m 32s}   +0.70d {+00d 41' 59"}
SUN_DIST:        110.07 [deg]   Sun_angle= -7.7 [hr] (East of Sun)
MOON_POSTN:      100.72d {+06h 42m 53s}  +21.07d {+21d 04' 08"}
MOON_DIST:       121.14 [deg]
MOON_ILLUM:      40 [%]
GAL_COORDS:       70.12,  7.52 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      306.85, 56.76 [deg] ecliptic lon,lat of the pointing direction
COMMENTS:        SWIFT-UVOT Processed Image.  
COMMENTS:        The GRB Position came from the Window Position in the Mode Command.  
COMMENTS:        The image has 2x2 binning (compression).  
COMMENTS:        All 4 attachments are included.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Wed 21 Sep 11 13:58:52 UT
NOTICE_TYPE:     Swift-UVOT Position
TRIGGER_NUM:     503652,   Seg_Num: 0
GRB_RA:          294.0635d {+19h 36m 15.23s} (J2000),
                 294.1698d {+19h 36m 40.74s} (current),
                 293.6103d {+19h 34m 26.46s} (1950)
GRB_DEC:         +36.3906d {+36d 23' 26.1"} (J2000),
                 +36.4173d {+36d 25' 02.1"} (current),
                 +36.2781d {+36d 16' 41.1"} (1950)
GRB_ERROR:       0.7 [arcsec radius, statistical only]
GRB_MAG:         19.98 +/- 0.17 [mag]
FILTER:          10, White
IMG_START_DATE:  15825 TJD;   264 DOY;   11/09/21
IMG_START_TIME:  50006.00 SOD {13:53:26.00} UT,   125.8 [sec] since BAT Trigger Time
SUN_POSTN:       178.39d {+11h 53m 33s}   +0.70d {+00d 41' 58"}
SUN_DIST:        110.05 [deg]   Sun_angle= -7.7 [hr] (East of Sun)
MOON_POSTN:      100.73d {+06h 42m 54s}  +21.07d {+21d 04' 04"}
MOON_DIST:       121.13 [deg]
MOON_ILLUM:      40 [%]
GAL_COORDS:       70.13,  7.55 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:      306.82, 56.79 [deg] ecliptic lon,lat of the burst (or transient)
COMMENTS:        SWIFT UVOT Position Notice.  
COMMENTS:        This Notice was ground-generated -- not flight-generated.  
COMMENTS:        Result based on Genie data.  
COMMENTS:        Notice generated automatically.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Wed 21 Sep 11 13:58:13 UT
NOTICE_TYPE:     Swift-XRT Position
TRIGGER_NUM:     503652,   Seg_Num: 0
GRB_RA:          294.0983d {+19h 36m 23.59s} (J2000),
                 294.2047d {+19h 36m 49.12s} (current),
                 293.6446d {+19h 34m 34.70s} (1950)
GRB_DEC:         +36.3288d {+36d 19' 43.6"} (J2000),
                 +36.3555d {+36d 21' 19.7"} (current),
                 +36.2161d {+36d 12' 58.0"} (1950)
GRB_ERROR:       3.8 [arcsec radius, statistical plus systematic, 90% containment]
GRB_INTEN:       1.00e-10 [erg/cm2/sec]
GRB_SIGNIF:      10.00 [sigma]
IMG_START_DATE:  15825 TJD;   264 DOY;   11/09/21
IMG_START_TIME:  50019.00 SOD {13:53:39.00} UT,   138.8 [sec] since BAT Trigger Time
TAM[0-3]:        100.00 100.00 100.00 100.00
AMPLIFIER:       1
WAVEFORM:        31
SUN_POSTN:       178.39d {+11h 53m 32s}   +0.70d {+00d 41' 59"}
SUN_DIST:        110.09 [deg]   Sun_angle= -7.7 [hr] (East of Sun)
MOON_POSTN:      100.72d {+06h 42m 53s}  +21.07d {+21d 04' 08"}
MOON_DIST:       121.18 [deg]
MOON_ILLUM:      40 [%]
GAL_COORDS:       70.09,  7.49 [deg] galactic lon,lat of the burst
ECL_COORDS:      306.84, 56.73 [deg] ecliptic lon,lat of the burst
COMMENTS:        SWIFT-XRT Coordinates.  
COMMENTS:        This Notice was ground-generated -- not flight-generated.  
COMMENTS:        TAM values, flux and significance fields are not valid.  
COMMENTS:        This position was automatically generated on the ground using  
COMMENTS:        Photon Counting data telemetered via TDRSS (SPER data).  
COMMENTS:        See http://www.swift.ac.uk/sper/docs.php for details.  
COMMENTS:        The probability that this is a serendipitous source in the  
COMMENTS:        SPER window is 0.58% < P(seren) < 1.1%.

GCN Circular #12373
W. H. Baumgartner (GSFC/UMBC), A. P. Beardmore (U Leicester), D. N. Burrows (PSU), S. Campana (INAF-OAB), J. R. Cummings (NASA/UMBC), V. D'Elia (ASDC), P. A. Evans (U Leicester), C. Guidorzi (U Ferrara), S. T. Holland (CRESST/USRA/GSFC), E. A. Hoversten (PSU), J. A. Kennea (PSU), H. A. Krimm (CRESST/GSFC/USRA), O. M. Littlejohns (U Leicester), V. Mangano (INAF-IASFPA), F. E. Marshall (NASA/GSFC), A. Melandri (INAF-OAB), P. T. O'Brien (U Leicester), C. Pagani (U Leicester), K. L. Page (U Leicester), J. L. Racusin (NASA/GSFC), T. Sakamoto (NASA/UMBC), B. Sbarufatti (INAF-OAB/IASFPA), M. H. Siegel (PSU), E. Sonbas (GSFC/USRA/Adiyaman Univ.), R. L. C. Starling (U Leicester) and B.-B. Zhang (PSU) report on behalf of the Swift Team:
At 13:51:20 UT, the Swift Burst Alert Telescope (BAT) triggered and located GRB 110921A (trigger=503652). Swift slewed immediately to the burst. The BAT on-board calculated location is RA, Dec 294.078, +36.377 which is
```
   RA(J2000) = 19h 36m 19s
   Dec(J2000) = +36d 22' 36"
```
with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). The BAT light curve showed a ragged, single-peaked structure with a duration of about 10 sec. The peak count rate was ~1000 counts/sec (15-350 keV), at ~4 sec after the trigger.
The XRT began observing the field at 13:53:22.5 UT, 122.4 seconds after the BAT trigger. Using promptly downlinked data we find an uncatalogued X-ray source located at RA, Dec 294.09838, 36.32882 which is equivalent to:
```
   RA(J2000)  = 19h 36m 23.61s
   Dec(J2000) = +36d 19' 43.8"
```
with an uncertainty of 3.8 arcseconds (radius, 90% containment). This location is 182 arcseconds from the BAT onboard position, outside the BAT error circle. This position may be improved as more data are received; the latest position is available at http://www.swift.ac.uk/sper.
A power-law fit to a spectrum formed from promptly downlinked event data gives a column density in excess of the Galactic value (1.43 x 10^21 cm^-2, Kalberla et al. 2005), with an excess column of 3.1 (+2.28/-1.97) x 10^21 cm^-2 (90% confidence).
UVOT took a finding chart exposure of 150 seconds with the White filter starting 125 seconds after the BAT trigger. No credible afterglow candidate has been found in the initial data products. The 2.7'x2.7' sub-image covers none of the XRT error circle. The 8'x8' region for the list of sources generated on-board covers 100% of the XRT error circle. The list of sources is typically complete to about 18 mag. No correction has been made for the expected extinction corresponding to E(B-V) of 0.14.
Burst Advocate for this burst is W. H. Baumgartner (wayne AT milkyway.gsfc.nasa.gov). Please contact the BA by email if you require additional information regarding Swift followup of this burst. In extremely urgent cases, after trying the Burst Advocate, you can contact the Swift PI by phone (see Swift TOO web site for information: http://www.swift.psu.edu/too.html.)

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Wed 21 Sep 11 14:04:16 UT
NOTICE_TYPE:     Swift-UVOT Source List
TRIGGER_NUM:     503652,   Seg_Num: 0
POINT_RA:        294.090d {+19h 36m 22s} (J2000)
POINT_DEC:       +36.365d {+36d 21' 55"} (J2000)
POINT_ROLL:      286.557d
IMG_START_DATE:  15825 TJD;   264 DOY;   11/09/21
IMG_START_TIME:  50164.44 SOD {13:56:04.44} UT,   284.3 [sec] since BAT Trigger Time
FILTER:          7, U
BKG_MEAN:        0.797
N_STARS:         190
X_OFFSET:        347 [pixels]
Y_OFFSET:        324 [pixels]
X_MAX:           1786 [pixels]
Y_MAX:           1763 [pixels]
DET_THRESH:      8
PHOTO_THRESH:    3
SL_URL:          sw00503652000msufc0284.fits
SUN_POSTN:       178.39d {+11h 53m 33s}   +0.70d {+00d 41' 53"}
SUN_DIST:        110.07 [deg]   Sun_angle= -7.7 [hr] (East of Sun)
MOON_POSTN:      100.78d {+06h 43m 06s}  +21.06d {+21d 03' 37"}
MOON_DIST:       121.16 [deg]
MOON_ILLUM:      40 [%]
GAL_COORDS:       70.12,  7.52 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      306.85, 56.76 [deg] ecliptic lon,lat of the pointing direction
COMMENTS:        SWIFT-UVOT Source List.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Wed 21 Sep 11 14:04:44 UT
NOTICE_TYPE:     Swift-UVOT Processed Source List
TRIGGER_NUM:     503652,   Seg_Num: 0
POINT_RA:        294.090d {+19h 36m 22s} (J2000)
POINT_DEC:       +36.365d {+36d 21' 55"} (J2000)
POINT_ROLL:      286.557d
IMG_START_DATE:  15825 TJD;   264 DOY;   11/09/21
IMG_START_TIME:  50164.44 SOD {13:56:04.44} UT,   284.3 [sec] since BAT Trigger Time
FILTER:          7, U
BKG_MEAN:        0.797
N_STARS:         190
X_OFFSET:        347 [pixels]
Y_OFFSET:        324 [pixels]
X_MAX:           1786 [pixels]
Y_MAX:           1763 [pixels]
DET_THRESH:      8
PHOTO_THRESH:    3
SL_URL:          sw00503652000msufc0284.fits
SUN_POSTN:       178.39d {+11h 53m 33s}   +0.70d {+00d 41' 53"}
SUN_DIST:        110.07 [deg]   Sun_angle= -7.7 [hr] (East of Sun)
MOON_POSTN:      100.78d {+06h 43m 08s}  +21.06d {+21d 03' 35"}
MOON_DIST:       121.17 [deg]
MOON_ILLUM:      40 [%]
GAL_COORDS:       70.12,  7.52 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      306.85, 56.76 [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 Sep 11 14:05:05 UT
NOTICE_TYPE:     Swift-XRT Position UPDATE
TRIGGER_NUM:     503652,   Seg_Num: 0
GRB_RA:          294.0978d {+19h 36m 23.47s} (J2000),
                 294.2042d {+19h 36m 49.00s} (current),
                 293.6441d {+19h 34m 34.58s} (1950)
GRB_DEC:         +36.3286d {+36d 19' 42.9"} (J2000),
                 +36.3553d {+36d 21' 19.0"} (current),
                 +36.2159d {+36d 12' 57.3"} (1950)
GRB_ERROR:       2.2 [arcsec radius, statistical plus systematic, 90% containment]
GRB_INTEN:       1.00e-10 [erg/cm2/sec]
GRB_SIGNIF:      10.00 [sigma]
IMG_START_DATE:  15825 TJD;   264 DOY;   11/09/21
IMG_START_TIME:  50019.00 SOD {13:53:39.00} UT,   138.8 [sec] since BAT Trigger Time
TAM[0-3]:        100.00 100.00 100.00 100.00
AMPLIFIER:       1
WAVEFORM:        31
SUN_POSTN:       178.39d {+11h 53m 34s}   +0.70d {+00d 41' 52"}
SUN_DIST:        110.09 [deg]   Sun_angle= -7.7 [hr] (East of Sun)
MOON_POSTN:      100.78d {+06h 43m 08s}  +21.06d {+21d 03' 33"}
MOON_DIST:       121.20 [deg]
MOON_ILLUM:      40 [%]
GAL_COORDS:       70.09,  7.49 [deg] galactic lon,lat of the burst
ECL_COORDS:      306.84, 56.73 [deg] ecliptic lon,lat of the burst
COMMENTS:        SWIFT-XRT Coordinates.  
COMMENTS:        This Notice was ground-generated -- not flight-generated.  
COMMENTS:        This is an Update Notice -- the RA,Dec values herein supersede the previous XRT_POS Notice.  
COMMENTS:        TAM values, flux and significance fields are not valid.  
COMMENTS:        This position was automatically generated on the ground using  
COMMENTS:        Photon Counting data telemetered via TDRSS (SPER data).  
COMMENTS:        See http://www.swift.ac.uk/sper/docs.php for details.  
COMMENTS:        This position was enhanced using UVOT field astrometry.  
COMMENTS:        The probability that this is a serendipitous source in the  
COMMENTS:        SPER window is 0.58% < P(seren) < 1.1%.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Wed 21 Sep 11 14:05:43 UT
NOTICE_TYPE:     Swift-UVOT Image
TRIGGER_NUM:     503652,   Seg_Num: 0
POINT_RA:        294.090d {+19h 36m 22s} (J2000)
POINT_DEC:       +36.365d {+36d 21' 55"} (J2000)
ROLL:            286.557d
IMG_START_DATE:  15825 TJD;   264 DOY;   11/09/21
IMG_START_TIME:  50164.44 SOD {13:56:04.44} UT,   284.3 [sec] since BAT Trigger Time
FILTER:          7, U
EXPOSURE_ID:     338306171
X_OFFSET:        906 [pixels]
Y_OFFSET:        883 [pixels]
WIDTH:           160 [pixels]
HEIGHT:          160 [pixels]
X_GRB_POS:       1066
Y_GRB_POS:       1043
BINNING_INDEX:   1
IM_URL:          sw00503652000msuni0292.fits
SUN_POSTN:       178.39d {+11h 53m 34s}   +0.70d {+00d 41' 52"}
SUN_DIST:        110.07 [deg]   Sun_angle= -7.7 [hr] (East of Sun)
MOON_POSTN:      100.79d {+06h 43m 10s}  +21.06d {+21d 03' 30"}
MOON_DIST:       121.17 [deg]
MOON_ILLUM:      40 [%]
GAL_COORDS:       70.12,  7.52 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      306.85, 56.76 [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 Sep 11 14:05:53 UT
NOTICE_TYPE:     Swift-UVOT Processed Image
TRIGGER_NUM:     503652,   Seg_Num: 0
POINT_RA:        294.090d {+19h 36m 22s} (J2000)
POINT_DEC:       +36.365d {+36d 21' 55"} (J2000)
ROLL:            286.557d
IMG_START_DATE:  15825 TJD;   264 DOY;   11/09/21
IMG_START_TIME:  50164.44 SOD {13:56:04.44} UT,   284.3 [sec] since BAT Trigger Time
FILTER:          7, U
EXPOSURE_ID:     338306171
X_OFFSET:        906 [pixels]
Y_OFFSET:        883 [pixels]
WIDTH:           160 [pixels]
HEIGHT:          160 [pixels]
X_GRB_POS:       1066
Y_GRB_POS:       1043
BINNING_INDEX:   1
IM_URL:          sw00503652000msuni0292.fits
SUN_POSTN:       178.39d {+11h 53m 34s}   +0.70d {+00d 41' 52"}
SUN_DIST:        110.07 [deg]   Sun_angle= -7.7 [hr] (East of Sun)
MOON_POSTN:      100.79d {+06h 43m 10s}  +21.06d {+21d 03' 29"}
MOON_DIST:       121.17 [deg]
MOON_ILLUM:      40 [%]
GAL_COORDS:       70.12,  7.52 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      306.85, 56.76 [deg] ecliptic lon,lat of the pointing direction
COMMENTS:        SWIFT-UVOT Processed Image.  
COMMENTS:        The GRB Position came from the Window Position in the Mode Command.  
COMMENTS:        The image has 2x2 binning (compression).  
COMMENTS:        All 4 attachments are included.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Wed 21 Sep 11 14:11:17 UT
NOTICE_TYPE:     Swift-UVOT Source List
TRIGGER_NUM:     503652,   Seg_Num: 0
POINT_RA:        294.090d {+19h 36m 22s} (J2000)
POINT_DEC:       +36.365d {+36d 21' 54"} (J2000)
POINT_ROLL:      286.557d
IMG_START_DATE:  15825 TJD;   264 DOY;   11/09/21
IMG_START_TIME:  50743.05 SOD {14:05:43.05} UT,   862.9 [sec] since BAT Trigger Time
FILTER:          10, White
BKG_MEAN:        2.502
N_STARS:         190
X_OFFSET:        347 [pixels]
Y_OFFSET:        324 [pixels]
X_MAX:           1786 [pixels]
Y_MAX:           1763 [pixels]
DET_THRESH:      13
PHOTO_THRESH:    7
SL_URL:          sw00503652000msufc0862.fits
SUN_POSTN:       178.39d {+11h 53m 34s}   +0.70d {+00d 41' 46"}
SUN_DIST:        110.07 [deg]   Sun_angle= -7.7 [hr] (East of Sun)
MOON_POSTN:      100.84d {+06h 43m 22s}  +21.05d {+21d 03' 02"}
MOON_DIST:       121.19 [deg]
MOON_ILLUM:      40 [%]
GAL_COORDS:       70.12,  7.52 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      306.85, 56.76 [deg] ecliptic lon,lat of the pointing direction
COMMENTS:        SWIFT-UVOT Source List.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Wed 21 Sep 11 14:11:37 UT
NOTICE_TYPE:     Swift-UVOT Processed Source List
TRIGGER_NUM:     503652,   Seg_Num: 0
POINT_RA:        294.090d {+19h 36m 22s} (J2000)
POINT_DEC:       +36.365d {+36d 21' 54"} (J2000)
POINT_ROLL:      286.557d
IMG_START_DATE:  15825 TJD;   264 DOY;   11/09/21
IMG_START_TIME:  50743.05 SOD {14:05:43.05} UT,   862.9 [sec] since BAT Trigger Time
FILTER:          10, White
BKG_MEAN:        2.502
N_STARS:         190
X_OFFSET:        347 [pixels]
Y_OFFSET:        324 [pixels]
X_MAX:           1786 [pixels]
Y_MAX:           1763 [pixels]
DET_THRESH:      13
PHOTO_THRESH:    7
SL_URL:          sw00503652000msufc0862.fits
SUN_POSTN:       178.39d {+11h 53m 34s}   +0.70d {+00d 41' 46"}
SUN_DIST:        110.07 [deg]   Sun_angle= -7.7 [hr] (East of Sun)
MOON_POSTN:      100.85d {+06h 43m 23s}  +21.05d {+21d 03' 00"}
MOON_DIST:       121.19 [deg]
MOON_ILLUM:      40 [%]
GAL_COORDS:       70.12,  7.52 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      306.85, 56.76 [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 Sep 11 14:13:05 UT
NOTICE_TYPE:     Swift-UVOT Image
TRIGGER_NUM:     503652,   Seg_Num: 0
POINT_RA:        294.090d {+19h 36m 22s} (J2000)
POINT_DEC:       +36.365d {+36d 21' 54"} (J2000)
ROLL:            286.557d
IMG_START_DATE:  15825 TJD;   264 DOY;   11/09/21
IMG_START_TIME:  50743.05 SOD {14:05:43.05} UT,   862.9 [sec] since BAT Trigger Time
FILTER:          10, White
EXPOSURE_ID:     338306750
X_OFFSET:        906 [pixels]
Y_OFFSET:        883 [pixels]
WIDTH:           160 [pixels]
HEIGHT:          160 [pixels]
X_GRB_POS:       1066
Y_GRB_POS:       1043
BINNING_INDEX:   1
IM_URL:          sw00503652000msuni0870.fits
SUN_POSTN:       178.39d {+11h 53m 35s}   +0.70d {+00d 41' 45"}
SUN_DIST:        110.07 [deg]   Sun_angle= -7.7 [hr] (East of Sun)
MOON_POSTN:      100.86d {+06h 43m 27s}  +21.05d {+21d 02' 53"}
MOON_DIST:       121.19 [deg]
MOON_ILLUM:      40 [%]
GAL_COORDS:       70.12,  7.52 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      306.85, 56.76 [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 Sep 11 14:13:16 UT
NOTICE_TYPE:     Swift-UVOT Processed Image
TRIGGER_NUM:     503652,   Seg_Num: 0
POINT_RA:        294.090d {+19h 36m 22s} (J2000)
POINT_DEC:       +36.365d {+36d 21' 54"} (J2000)
ROLL:            286.557d
IMG_START_DATE:  15825 TJD;   264 DOY;   11/09/21
IMG_START_TIME:  50743.05 SOD {14:05:43.05} UT,   862.9 [sec] since BAT Trigger Time
FILTER:          10, White
EXPOSURE_ID:     338306750
X_OFFSET:        906 [pixels]
Y_OFFSET:        883 [pixels]
WIDTH:           160 [pixels]
HEIGHT:          160 [pixels]
X_GRB_POS:       1066
Y_GRB_POS:       1043
BINNING_INDEX:   1
IM_URL:          sw00503652000msuni0870.fits
SUN_POSTN:       178.39d {+11h 53m 35s}   +0.70d {+00d 41' 44"}
SUN_DIST:        110.07 [deg]   Sun_angle= -7.7 [hr] (East of Sun)
MOON_POSTN:      100.86d {+06h 43m 27s}  +21.05d {+21d 02' 52"}
MOON_DIST:       121.19 [deg]
MOON_ILLUM:      40 [%]
GAL_COORDS:       70.12,  7.52 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      306.85, 56.76 [deg] ecliptic lon,lat of the pointing direction
COMMENTS:        SWIFT-UVOT Processed Image.  
COMMENTS:        The GRB Position came from the Window Position in the Mode Command.  
COMMENTS:        The image has 2x2 binning (compression).  
COMMENTS:        All 4 attachments are included.

GCN Circular #12374
V.Yurkov, Yu.Sergienko, E.Sinyakov, D.Varda, I.Kudelina Blagoveschensk Educational State University, Blagoveschensk
K.Ivanov, S.Yazev, N.M.Budnev, E.Konstantinov, V.Lenok, O.Gres, O.Chuvalaev, V.A.Poleshchuk Irkutsk State University
E. Gorbovskoy, V. Lipunov, V.Kornilov, D.Kuvshinov, A.Belinski, N.Tyurina, N.Shatskiy, P.Balanutsa, V.V.Chazov, P.V.Kortunov, A.Kuznetsov, D.Zimnukhov, M. Kornilov, A.Sankovich Sternberg Astronomical Institute, Moscow State University
A. Tlatov, A.V. Parhomenko, D. Dormidontov Kislovodsk Solar Station of the Pulkovo Observatory
V.Krushinski, I.Zalozhnich, T.Kopytova, A. Popov Ural State University, Kourovka
MASTER II robotic telescopes (MASTER-Net: http://observ.pereplet.ru) located in Amur and in Tunka (Siberia) was pointed to the GRB110921A 7 sec after notice time and 53 sec after GRB time at 2011-09-21 13:52:13.432 UT. On our first (10s exposure) set we haven`t found optical transient within SWIFT error-box (ra=19 36 19 dec=+36 22 48 r=0.050000). Observations were made in polarizing bands. The 5-sigma upper limit has been about 17.2 in Amur and 17.5 in Tunka. Observations and data reduction is continued. The message may be cited.
GCN Circular #12377
L.P. Xin, J.Y. Wei, Y. L. Qiu, J. Wang, J.S. Deng, C. Wu, X. H. Han on behalf of EAFON report:
We began to observe GRB 110921A (Baumgartner et al., GCN 12373) with Xinglong TNT telescope at 13:59:40 (UT), about 8 min after the burst. 25 White-band images and a series of R-band data were obtained. A new source was detected in the combined white band image within the errorbox of XRT position. The brightness of this new source is estimated to be about 20.2 mag derived from USNO B1.0 R2mag.
We propose that this source is the candidate of optical counterpart of GRB 110921A. More deep observations are needed to confirm this.
This message may be cited.
For more information about Xinglong GRBs Follow-up observations, please visit the website: http://www.xinglong-naoc.org:8080/grb/index.html
GCN Circular #12378
K. Tokoyoda, M. Hayashi, Y. Yatsu, Y. Aoki, K. Kawakami, S. Song, R. Usui, and N. Kawai (Tokyo Tech) report on behalf of the MITSuME collaboration:
We observed GRB 110921A (W. H. Baumgartner et al, GCN12373) with the optical three color (g, Rc, and Ic) CCD camera attached to the MITSuME 50 cm telescope of Akeno Observatory, Yamanashi, Japan. The follow-up observation was started at 13:53:08, ~108 sec after the BAT trigger.
We did not find optical counterpart in g'-band and R-band within the enhanced XRT error circle (W. H. Baumgartner et al, GCN12373).
While, in I-band, we detected a very faint OT candidate in the error circle only in the earliest data-set (T0+108s ~ T0 + 348s). Further data analysis for the I-band data is now ongoing.
Photometric results are listed below. We used GSC2.3 catalog for flux calibration.
```
T0+[s]      MID-UT     T-EXP[sec]      g'             Rc           Ic
---------------------------------------------------------------------------------
 +108     14:07:40         1530           >20.0       >19.5       ---
---------------------------------------------------------------------------------
T0+ : Elapsed time after the burst [sec]
T-EXP: Total Exposure time [sec]
```
GCN Circular #12379
M.R. Goad, J.P. Osborne, A.P. Beardmore and P.A. Evans (U. Leicester) report on behalf of the Swift-XRT team.
Using 1830 s of XRT Photon Counting mode data and 3 UVOT images for GRB 110921A, we find an astrometrically corrected X-ray position (using the XRT-UVOT alignment and matching UVOT field sources to the USNO-B1 catalogue): RA, Dec = 294.09821, +36.32864 which is equivalent to:
```
RA (J2000): 19h 36m 23.57s
Dec (J2000): +36d 19' 43.1"
```
with an uncertainty of 1.9 arcsec (radius, 90% confidence).
This position may be improved as more data are received. The latest position can be viewed at http://www.swift.ac.uk/xrt_positions. Position enhancement is described by Goad et al. (2007, A&A, 476, 1401) and Evans et al. (2009, MNRAS, 397, 1177).
This circular was automatically generated, and is an official product of the Swift-XRT team.
GCN Circular #12380
A. Pozanenko (IKI), M. Andreev, A. Sergeev (Terskol Branch of Institute of Astronomy), M. Ibrahimov (MAO) on behalf of larger GRB follow up collaboration report:
We observed the field of the Swift GRB 110921A (Baumgartner et al., GCN 12373) with Zeiss-600 telescope of Mt. Terskol observatory and AZT-22 telescope of Maidanak observatory on Sep. 21. Several images were taken in both observatories in R filter. Within the enhanced XRT error box (Goad et al., GCN 12379) we do not detect the candidate of optical counterpart of GRB 110921A (Xin et al., GCN 12377). Preliminary photometry of a combined image (Zeiss-600) and a single image of AZT-22 is based on the nearby USNO B1.0 stars:
```
UT                 Filter,   Exposure, OT,        Upper Limit (3 sigma) 
Telescope
(mid)                           (s)

Sep.21 16:50  R        1800       n/d           21.1 
Zeiss-600
Sep.21 17:48  R         300       n/d           21.2 
AZT-22
```
Since our photometry is somewhat deeper than photometry of the candidate (Xin et al., GCN 12377), we could suggest the candidate is a real afterglow of GRB 110921A.
GCN Circular #12383
S. D. Barthelmy (GSFC), W. H. Baumgartner (GSFC/UMBC), J. R. Cummings (GSFC/UMBC), E. E. Fenimore (LANL), N. Gehrels (GSFC), H. A. Krimm (GSFC/USRA), C. B. Markwardt (GSFC), D. M. Palmer (LANL), T. Sakamoto (GSFC/UMBC), G. Sato (ISAS), M. Stamatikos (OSU), J. Tueller (GSFC), T. N. Ukwatta (MSU) (i.e. the Swift-BAT team):
Using the data set from T-240 to T+962 sec from the recent telemetry downlink, we report further analysis of BAT GRB 110921A (trigger #503652) (Baumgartner, et al., GCN Circ. 12373). The BAT ground-calculated position is RA, Dec = 294.094, 36.355 deg which is
```
    RA(J2000)  =  19h 36m 22.6s
    Dec(J2000) = +36d 21' 19.8"
```
with an uncertainty of 1.7 arcmin, (radius, sys+stat, 90% containment). The partial coding was 15%.
The mask-weighted light curve shows multiple weak peaks. T90 (15-350 keV) was 48.00 +- 22.63 sec (estimated error including systematics).
The time-averaged spectrum from T-31.55 to T+16.45 sec is best fit by a simple power-law model. The power law index of the time-averaged spectrum is 1.57 +- 0.17. The fluence in the 15-150 keV band is 2.4 +- 0.2 x 10^-06 erg/cm2. The 1-sec peak photon flux measured from T+7.95 sec in the 15-150 keV band is 0.2 +- 0.4 ph/cm2/sec. All the quoted errors are at the 90% confidence level.
The results of the batgrbproduct analysis are available at http://gcn.gsfc.nasa.gov/notices_s/503652/BA/
GCN Circular #12384
P.A. Evans (U. Leicester) and W. H. Baumgartner (GSFC/UMBC) report on behalf of the Swift-XRT team:
We have analysed 9.7 ks of XRT data for GRB 110921A (Baumgartner et al. GCN Circ. 12373), from 134 s to 40.9 ks after the BAT trigger. The data comprise 47 s in Windowed Timing (WT) mode with the remainder in Photon Counting (PC) mode. The enhanced XRT position for this burst was given by Goad et al. (GCN. Circ 12379).
The light curve can be modelled with a power-law decay with a decay index of alpha=0.90 (+/-0.05).
A spectrum formed from the PC mode data can be fitted with an absorbed power-law with a photon spectral index of 2.00 (+0.15, -0.14). The best-fitting absorption column is 2.0 (+0.5, -0.4) x 10^21 cm^-2, in excess of the Galactic value of 1.4 x 10^21 cm^-2 (Kalberla et al. 2005). The counts to observed (unabsorbed) 0.3-10 keV flux conversion factor deduced from this spectrum is 3.9 x 10^-11 (5.6 x 10^-11) erg cm^-2 count^-1.
A summary of the PC-mode spectrum is thus:
```
Total column:	     2.0 (+0.5, -0.4) x 10^21 cm^-2
Galactic foreground: 1.4 x 10^21 cm^-2
Excess significance: 7.9 sigma
Photon index:	     2.00 (+0.15, -0.14)
```
The results of the XRT-team automatic analysis are available at http://www.swift.ac.uk/xrt_products/00503652.
This circular is an official product of the Swift-XRT team.
GCN Circular #12385
D. Xu (WIS), L.P. Xin, J.Y. Wei (NAOC) report on behalf of a larger collaboration:
We performed astrometry to the TNT image (Xin et al., GCN 12377), calibrated with the SDSS field of GRB 110921A (Baumgartner et al., GCN 12373). The optical afterglow is localised at
```
RA (J2000): 19h 36m 23.478s
Dec (J2000): +36d 19' 43.38"
```
with an uncertainty of 1.0 arcsec, in the northwestern part of the enhanced XRT error circle (Goad et al., GCN 12379).
The SDSS field reveals a source at coordinates
```
RA (J2000): 19h 36m 23.382s
Dec (J2000): +36d 19' 42.03"
```
with an uncertainty of 1.0 arcsec and at the southwestern edge of the XRT error circle, which is too faint to be present for the TNT image.
NIR follow-up observation is encouraged.
GCN Circular #12386
G. Fitzpatrick (UCD) reports on behalf of the Fermi GBM Team:
"At 13:51:22.57 UT on 21 September 2011, the Fermi Gamma-Ray Burst Monitor triggered and located GRB 110921A (trigger 338305884 / 110921577), which was detected by the Swift/BAT (Baumgartner et al. 2011, GCN 12373). The GBM on-ground location is consistent with the Swift position.
The GBM light curve shows a single bright peak with a duration (T90) of ~37 s (50-300 keV). The time-averaged spectrum from T0-26 s to T0+9 s is best fit by a power law function with an exponential high-energy cutoff. The power law index is -1.39 +/- 0.12 and the cutoff energy, parameterized as Epeak, is 139 +/- 32 keV.
The event fluence (10-1000 keV) in this time interval is (4.2 +/- 0.4)E-06 erg/cm^2. The 1 s peak photon flux measured starting from T0+0.5 s in the 10-1000 keV band is 2.9 +/- 0.3 ph/s/cm^2.
The spectral analysis results presented above are preliminary; final results will be published in the GBM GRB Catalog."
GCN Circular #12387
Paul Vreeswijk (U. Iceland), Daniele Malesani, Antonio de Ugarte Postigo (DARK, NBI), Dong Xu (WIS), P=E1ll Jakobsson, Steve Schulze (U. Iceland) and Nial Tanvir (U. Leicester) report on behalf of a larger collaboration:
Using ALFOSC on the Nordic Optical Telescope (NOT) we have obtained Sloan r'- (3 x 600 s) and z'-band (6 x 300 s) imaging of the field of GRB 110921A (Baumgartner et al., GCN 12373, Barthelmy et al., GCN 12383), starting on 2011 September 21.925 UT (roughly 8.3 hr after the burst). The observations were performed through clouds, but under good seeing conditions (~0.8").
We do not detect the optical afterglow reported by Xin et al. (GCN 12377, see also Xu et al., GCN 12385), or any other object within the enhanced Swift-XRT error circle (Goad et al., GCN 12379), down to limiting magnitudes of about r'=23.3 and z'=21.0 (calibrated against the SDSS catalog).
Just outside the enhanced XRT error circle, at R.A.(J2000) 19:36:23.38, decl.(J2000) 36:19:42.1 (with an uncertainty of 0.23"), we detect an r'=22.4+-0.2 source, also visible - albeit barely - in the combined z'-band imaging. This apparent point source is consistent, both in position and brightness, with the SDSS object noted by Xu et al. (GCN 12385).
We are grateful for the NOT staff, particularly Fatemeh Sadat Kiaeerad and Marjaana Lindborg, for obtaining these observations.
GCN Circular #12389
A. A. Breeveld (MSSL-UCL) and W. H. Baumgartner (GSFC/UMBC) report on=20 behalf of the Swift/UVOT team:
The Swift/UVOT began settled observations of the field of GRB 110921A=20 126 s after the BAT trigger (Baumgartner et al., GCN Circ. 12373).
A source consistent with the optical position (Xin et al., GCN Circ.=20 12377 and Xu et al., GCN Circ. 12385) is detected at 3.5 sigma in the=20 summed white data, but is not seen in any of the other filters, nor in=20 any of the white exposures individually. Preliminary magnitudes and 3-sigma upper limits using the UVOT=20 photometric system (Poole et al. 2008, MNRAS, 383, 627) for the first=20 finding chart (FC) exposure and subsequent exposures are:
```
Filter         T_start(s)   T_stop(s)      Exp(s)         Mag

white_FC           126          276          147         >21.3
u_FC               284          534          246         >20.6
white              126         1704          411          21.4 =C2=B1 0.3
v                  614         5307          308         >20.3
b                  540         1679          117         >20.7
u                  284         1654          343         >20.9
w1                 664         1629          117         >21.1
m2                 639         1604          117         >19.7
w2                 590         1725          132         >20.6
```
The magnitudes in the table are not corrected for the Galactic extinction due to the reddening of E(B-V) =3D 0.14 in the direction of the burst (Schlegel et al. 1998).
GCN Circular #12410
K. Tokoyoda, M. Hayashi, Y. Yatsu, Y. Aoki, K. Kawakami, S. Song, R. Usui, and N. Kawai (Tokyo Tech) =A0report on behalf of the MITSuME collaboration:
As reported in GCN12378 (Tokoyoda et al.), we detected a very faint objec= t within the XRT error circle of GRB 110921A (W. H. Baumgartner et al, GCN1= 2373) with the MITSuME-Akeno 50cm telescope. Here we report the results of aperture photometry.
We started the follow-up observation at 13:53:08 (UT), ~108 sec after the= BAT trigger(W. H. Baumgartner et al, GCN12373). The optical counterpart can = be seen both in R and I band only in the earliest data-set from T0+108s to T0 + 3= 48s.
For zero-point calibration we used GSC2.3 catalog. The g' magnitudes of the reference stars were estimated based on Sesar et al. (2006). For I-band data we could not find any usable catalog data, therefore we performed a field photometry. The Photometric results are summarized below.
```
Filter T0+[s]  MID-UT T-EXP[sec]  Mag  Mag_err  LimitMag
-------------------------------------------------------------------------
----------
g' =A0 =A0 =A0 =A0+108 =A0 =A013:55:31 =A0 =A0 =A0 =A0240 =A0 =A0 =A0 =A0 --- =A0 =A0 =A0--- =A0 =A0 =A0 =A0 =A0 >19.4
Rc =A0 =A0 =A0+108 =A0 =A013:55:31 =A0 =A0 =A0 =A0240 =A0 =A0 =A0 18.8 =A0 =A00.2 =A0 =A0 =A0 =A0 =A0  ---
Ic =A0 =A0 =A0 =A0+108 =A0 =A013:55:13 =A0 =A0 =A0 =A0210 =A0 =A0 =A0 18.8 =A0 =A00.3 =A0 =A0 =A0 =A0 =A0 ---
-----------------------------------------------------------------------------------
```
GCN Circular #12438
A. Volnova (SAI MSU), A. Pozanenko (IKI), E. Klunko (ISTP), V. Rumyantsev (CrAO), N.Pit (CrAO) on behalf of larger GRB follow up collaboration report:
We observed the field of the Swift GRB 110921A (Baumgartner et al., GCN 12373) with AZT-33IK telescope of Sayan observatory (Mondy) on Sep. 21 between (UT) 14:36:31 -- 16:05:00 and AZT-11 telescope of CrAO on Sep. 21 between (UT) 17:38:46 -- 19:00:15. In a combined image of a few first frames taken with AZT-33IK we detected a faint source which coincides with the optical counterpart of GRB 110921A (Xin et al., GCN 12377; Xu et al., GCN 12385). A photometry is based on the star USNO B1.0 1263-0338839 (19 36 21.52 +36 19 56.2) assuming R=16.13
```
T0+,       Filter,  Exposure, OT,  UL(3 sigma), Telescope
(mid, d)             (s)

0.03934 R 850  22.08 +/- 0.18  22.3    AZT-33IK
0.07558 R 1920 n/d                   22.5    AZT-33IK
0.18620 R 4860 n/d                   21.3    AZT-11
```
In a combined image of a total exposure of 3030 s taken with AZT-33IK telescope we clearly detected the SDSS object noted by Xu et al. (GCN 12385) and Vreeswijk et al. (GCN 12387). The photometry of the SDSS object against the above calibration star is R=22.8 +/- 0.3.
GCN Circular #12617
A. Volnova (SAI MSU), M. Ibrahimov (UBAI), A. Pozanenko (IKI) report on behalf of larger GRB follow-up collaboration:
We update results of Maidanak observations preliminary reported in GCN 12380. We observed the field of the Swift GRB 110921A (Baumgartner et al., GCN 12373) with AZT-22 telescope of Maidanak observatory starting Sep. 21 (UT) 17:45:30. Several images in R-filter of 300 s exposure were taken under moderate seeing (FWHM ~ 1.7"). We detect a source in coordinates (J2000) 19 36 23.363 +36 19 43.02 with uncertainty of 0.2" and brightness of R = 22.0 +/- 0.15. This source is rather consistent both in position and brightness, with the SDSS object (Xu et al. GCN 12385; Vreeswijk et al. GCN 12387). So we do not detect afterglow reported by (Xu et al. GCN 12385; Breeveld et al. GCN 12389; Tokoyoda et al. GCN 12410; Volnova et al. GCN 12438).
```
Tstart UT, T0+,       Filter, Exposure, OT, Upper Limit (3 sigma)
                (mid, d)            (s)
17:45:30  0.17895  R       8*300        n/d   22.5
```

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Jochen Greiner, last update: 04-Dec-2011 [Disclaimer]