Gamma-ray Burst 120803B

(All information courtesy of the instrument teams.)

Previous IAU Circulars

none

Results of Observations

GCN/BACODINE POSITION NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Fri 03 Aug 12 11:06:27 UT
NOTICE_TYPE:     Swift-BAT GRB Position
TRIGGER_NUM:     529606,   Seg_Num: 0
GRB_RA:          314.224d {+20h 56m 54s} (J2000),
                 314.318d {+20h 57m 16s} (current),
                 313.851d {+20h 55m 24s} (1950)
GRB_DEC:         +53.282d {+53d 16' 57"} (J2000),
                 +53.331d {+53d 19' 53"} (current),
                 +53.089d {+53d 05' 20"} (1950)
GRB_ERROR:       3.00 [arcmin radius, statistical only]
GRB_INTEN:       4610 [cnts]    Image_Peak=194 [image_cnts]
TRIGGER_DUR:     1.024 [sec] 
TRIGGER_INDEX:   146     E_range: 25-100 keV
BKG_INTEN:       29662 [cnts]
BKG_TIME:        39950.50 SOD {11:05:50.50} UT
BKG_DUR:         8 [sec]
GRB_DATE:        16142 TJD;   216 DOY;   12/08/03
GRB_TIME:        39966.95 SOD {11:06:06.95} UT
GRB_PHI:         141.17 [deg]
GRB_THETA:        28.08 [deg]
SOLN_STATUS:     0x3
RATE_SIGNIF:     12.48 [sigma]
IMAGE_SIGNIF:    8.12 [sigma]
MERIT_PARAMS:     +1  +0  +0  +0  +2  -2  +0  +1 +33  +0 
SUN_POSTN:       133.97d {+08h 55m 53s}  +17.33d {+17d 19' 42"}
SUN_DIST:        109.34 [deg]   Sun_angle= 12.0 [hr] (West of Sun)
MOON_POSTN:      328.75d {+21h 55m 00s}   -7.35d {-07d 20' 57"}
MOON_DIST:        61.90 [deg]
MOON_ILLUM:      98 [%]
GAL_COORDS:       92.10,  5.08 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:      349.91, 64.94 [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 = 276.29,14.05 [deg].

red DSS finding chart ps-file

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Fri 03 Aug 12 11:07:31 UT
NOTICE_TYPE:     Swift-XRT Nack-Position
TRIGGER_NUM:     529606,   Seg_Num: 0
POINT_RA:        314.221d {+20h 56m 53s} (J2000)
POINT_DEC:       +53.297d {+53d 17' 48"} (J2000)
IMG_START_DATE:  16142 TJD;   216 DOY;   12/08/03
IMG_START_TIME:  40042.42 SOD {11:07:22.42} UT,   75.5 [sec] since BAT Trigger Time
COUNTS:          19    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:     Fri 03 Aug 12 11:09:50 UT
NOTICE_TYPE:     Swift-BAT GRB Lightcurve
TRIGGER_NUM:     529606,   Seg_Num: 0
GRB_RA:          314.224d {+20h 56m 54s} (J2000),
                 314.318d {+20h 57m 16s} (current),
                 313.851d {+20h 55m 24s} (1950)
GRB_DEC:         +53.282d {+53d 16' 57"} (J2000),
                 +53.331d {+53d 19' 53"} (current),
                 +53.089d {+53d 05' 20"} (1950)
GRB_DATE:        16142 TJD;   216 DOY;   12/08/03
GRB_TIME:        39966.95 SOD {11:06:06.95} UT
TRIGGER_INDEX:   146
GRB_PHI:         141.17 [deg]
GRB_THETA:        28.08 [deg]
DELTA_TIME:      -43.00 [sec]
TRIGGER_DUR:     1.024 [sec] 
SOLN_STATUS:     0x3
RATE_SIGNIF:     12.48 [sigma]
IMAGE_SIGNIF:    8.12 [sigma]
LC_URL:          sw00529606000msb.lc
SUN_POSTN:       133.97d {+08h 55m 53s}  +17.33d {+17d 19' 39"}
SUN_DIST:        109.34 [deg]   Sun_angle= 12.0 [hr] (West of Sun)
MOON_POSTN:      328.78d {+21h 55m 07s}   -7.34d {-07d 20' 17"}
MOON_DIST:        61.90 [deg]
MOON_ILLUM:      98 [%]
GAL_COORDS:       92.10,  5.08 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:      349.91, 64.94 [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 = 276.29,14.05 [deg].

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Fri 03 Aug 12 11:10:44 UT
NOTICE_TYPE:     Swift-UVOT Source List
TRIGGER_NUM:     529606,   Seg_Num: 0
POINT_RA:        314.220d {+20h 56m 53s} (J2000)
POINT_DEC:       +53.297d {+53d 17' 48"} (J2000)
POINT_ROLL:      0.283d
IMG_START_DATE:  16142 TJD;   216 DOY;   12/08/03
IMG_START_TIME:  40045.92 SOD {11:07:25.92} UT,   79.0 [sec] since BAT Trigger Time
FILTER:          10, White
BKG_MEAN:        2.681
N_STARS:         111
X_OFFSET:        374 [pixels]
Y_OFFSET:        613 [pixels]
X_MAX:           1333 [pixels]
Y_MAX:           1572 [pixels]
DET_THRESH:      14
PHOTO_THRESH:    7
SL_URL:          sw00529606000msufc0078.fits
SUN_POSTN:       133.97d {+08h 55m 53s}  +17.33d {+17d 19' 39"}
SUN_DIST:        109.33 [deg]   Sun_angle= 12.0 [hr] (West of Sun)
MOON_POSTN:      328.79d {+21h 55m 09s}   -7.34d {-07d 20' 07"}
MOON_DIST:        61.91 [deg]
MOON_ILLUM:      98 [%]
GAL_COORDS:       92.11,  5.09 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      349.92, 64.95 [deg] ecliptic lon,lat of the pointing direction
COMMENTS:        SWIFT-UVOT Source List.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Fri 03 Aug 12 11:11:10 UT
NOTICE_TYPE:     Swift-UVOT Processed Source List
TRIGGER_NUM:     529606,   Seg_Num: 0
POINT_RA:        314.220d {+20h 56m 53s} (J2000)
POINT_DEC:       +53.297d {+53d 17' 48"} (J2000)
POINT_ROLL:      0.283d
IMG_START_DATE:  16142 TJD;   216 DOY;   12/08/03
IMG_START_TIME:  40045.92 SOD {11:07:25.92} UT,   79.0 [sec] since BAT Trigger Time
FILTER:          10, White
BKG_MEAN:        2.681
N_STARS:         111
X_OFFSET:        374 [pixels]
Y_OFFSET:        613 [pixels]
X_MAX:           1333 [pixels]
Y_MAX:           1572 [pixels]
DET_THRESH:      14
PHOTO_THRESH:    7
SL_URL:          sw00529606000msufc0078.fits
SUN_POSTN:       133.97d {+08h 55m 54s}  +17.33d {+17d 19' 38"}
SUN_DIST:        109.33 [deg]   Sun_angle= 12.0 [hr] (West of Sun)
MOON_POSTN:      328.79d {+21h 55m 10s}   -7.33d {-07d 20' 02"}
MOON_DIST:        61.91 [deg]
MOON_ILLUM:      98 [%]
GAL_COORDS:       92.11,  5.09 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      349.92, 64.95 [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:     Fri 03 Aug 12 11:12:09 UT
NOTICE_TYPE:     Swift-UVOT Image
TRIGGER_NUM:     529606,   Seg_Num: 0
POINT_RA:        314.220d {+20h 56m 53s} (J2000)
POINT_DEC:       +53.297d {+53d 17' 48"} (J2000)
ROLL:            0.283d
IMG_START_DATE:  16142 TJD;   216 DOY;   12/08/03
IMG_START_TIME:  40045.92 SOD {11:07:25.92} UT,   79.0 [sec] since BAT Trigger Time
FILTER:          10, White
EXPOSURE_ID:     365684855
X_OFFSET:        693 [pixels]
Y_OFFSET:        932 [pixels]
WIDTH:           160 [pixels]
HEIGHT:          160 [pixels]
X_GRB_POS:       853
Y_GRB_POS:       1092
BINNING_INDEX:   1
IM_URL:          sw00529606000msuni0088.fits
SUN_POSTN:       133.97d {+08h 55m 54s}  +17.33d {+17d 19' 38"}
SUN_DIST:        109.33 [deg]   Sun_angle= 12.0 [hr] (West of Sun)
MOON_POSTN:      328.80d {+21h 55m 12s}   -7.33d {-07d 19' 50"}
MOON_DIST:        61.91 [deg]
MOON_ILLUM:      98 [%]
GAL_COORDS:       92.11,  5.09 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      349.92, 64.95 [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:     Fri 03 Aug 12 11:12:38 UT
NOTICE_TYPE:     Swift-XRT Position
TRIGGER_NUM:     529606,   Seg_Num: 0
GRB_RA:          314.2360d {+20h 56m 56.63s} (J2000),
                 314.3299d {+20h 57m 19.17s} (current),
                 313.8630d {+20h 55m 27.12s} (1950)
GRB_DEC:         +53.3038d {+53d 18' 13.6"} (J2000),
                 +53.3527d {+53d 21' 09.8"} (current),
                 +53.1102d {+53d 06' 36.8"} (1950)
GRB_ERROR:       3.7 [arcsec radius, statistical plus systematic, 90% containment]
GRB_INTEN:       1.00e-10 [erg/cm2/sec]
GRB_SIGNIF:      10.00 [sigma]
IMG_START_DATE:  16142 TJD;   216 DOY;   12/08/03
IMG_START_TIME:  40081.00 SOD {11:08:01.00} UT,   114.1 [sec] since BAT Trigger Time
TAM[0-3]:        100.00 100.00 100.00 100.00
AMPLIFIER:       1
WAVEFORM:        31
SUN_POSTN:       133.97d {+08h 55m 54s}  +17.33d {+17d 19' 37"}
SUN_DIST:        109.32 [deg]   Sun_angle= 12.0 [hr] (West of Sun)
MOON_POSTN:      328.81d {+21h 55m 13s}   -7.33d {-07d 19' 45"}
MOON_DIST:        61.91 [deg]
MOON_ILLUM:      98 [%]
GAL_COORDS:       92.12,  5.09 [deg] galactic lon,lat of the burst
ECL_COORDS:      349.95, 64.95 [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 NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Fri 03 Aug 12 11:12:19 UT
NOTICE_TYPE:     Swift-UVOT Processed Image
TRIGGER_NUM:     529606,   Seg_Num: 0
POINT_RA:        314.220d {+20h 56m 53s} (J2000)
POINT_DEC:       +53.297d {+53d 17' 48"} (J2000)
ROLL:            0.283d
IMG_START_DATE:  16142 TJD;   216 DOY;   12/08/03
IMG_START_TIME:  40045.92 SOD {11:07:25.92} UT,   79.0 [sec] since BAT Trigger Time
FILTER:          10, White
EXPOSURE_ID:     365684855
X_OFFSET:        693 [pixels]
Y_OFFSET:        932 [pixels]
WIDTH:           160 [pixels]
HEIGHT:          160 [pixels]
X_GRB_POS:       853
Y_GRB_POS:       1092
BINNING_INDEX:   1
IM_URL:          sw00529606000msuni0088.fits
SUN_POSTN:       133.97d {+08h 55m 54s}  +17.33d {+17d 19' 38"}
SUN_DIST:        109.33 [deg]   Sun_angle= 12.0 [hr] (West of Sun)
MOON_POSTN:      328.80d {+21h 55m 13s}   -7.33d {-07d 19' 48"}
MOON_DIST:        61.91 [deg]
MOON_ILLUM:      98 [%]
GAL_COORDS:       92.11,  5.09 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      349.92, 64.95 [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 #13566
J. L. Racusin (NASA/GSFC), A. P. Beardmore (U Leicester), D. N. Burrows (PSU), P. A. Evans (U Leicester), C. Guidorzi (U Ferrara), J. A. Kennea (PSU), H. A. Krimm (CRESST/GSFC/USRA), O. M. Littlejohns (U Leicester) and K. L. Page (U Leicester) report on behalf of the Swift Team:
At 11:06:06 UT, the Swift Burst Alert Telescope (BAT) triggered and located GRB 120803B (trigger=529606). Swift slewed immediately to the burst. The BAT on-board calculated location is RA, Dec 314.224, +53.282 which is
```
   RA(J2000) = 20h 56m 54s
   Dec(J2000) = +53d 16' 57"
```
with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). The BAT light curve showed a single-peaked structure with a duration of about 30 sec. The peak count rate was ~3000 counts/sec (15-350 keV), at ~0 sec after the trigger.
The XRT began observing the field at 11:07:22.4 UT, 75.5 seconds after the BAT trigger. Using promptly downlinked data we find an uncatalogued X-ray source located at RA, Dec 314.23606, 53.30380 which is equivalent to:
```
   RA(J2000)  = 20h 56m 56.65s
   Dec(J2000) = +53d 18' 13.7"
```
with an uncertainty of 3.7 arcseconds (radius, 90% containment). This location is 82 arcseconds from the BAT onboard position, within 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. We cannot determine whether the source is fading at the present time.
A power-law fit to a spectrum formed from promptly downlinked event data gives a column density consistent with the Galactic value of 5.67 x 10^21 cm^-2 (Kalberla et al. 2005).
UVOT took a finding chart exposure of 149 seconds with the White filter starting 78 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 3.5% of the XRT error circle. The typical 3-sigma upper limit has been about 19.6 mag. 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 1.71.
Burst Advocate for this burst is J. L. Racusin (judith.racusin AT 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 Circular #13567
C. Guidorzi (U. Ferrara), C.G. Mundell, D. Bersier (LJMU), N.R. Tanvir (U. Leicester) report on behalf of a larger collaboration:
The 2-m Faulkes Telescope North automatically began observing GRB 120803B (Racusin et al. GCN Circ. 13566) on August 03 2012, 11:09:06 UT corresponding to 180 seconds post burst trigger with BVRi' filters. Within the XRT error circle, in the i-band filter we found the following uncatalogued possibly fading source,
```
R.A. = 20:56:56.46
Dec = +53:18:14.4   (J2000)
```
with an uncertainty of about 1". The detection is marginal, with an estimated magnitude of 19.5 +/- 0.5 in the i band at a mean time of 13.2 minutes (100 s exposure) calibrated against nearby USNOB-1 stars. The source is no longer visible in the latest frames. In the R band we see nothing down to 21.4 mag at 32.5 minutes post burst. The faintness and colour of the source might partially be explained by the relatively large foreground extinction, E(B-V)=1.7.
GCN Circular #13570
R. Usui, Y.Aoki, S. Kurita, T. Yoshii, M. Hayashi, Y. Saito, Y. Yatsu, and N. Kawai (Tokyo Tech) report on behalf of the MITSuME collaboration:
We observed GRB 120803B ( Racusin et al., GCN Circular #13566) with the optical three color (g, Rc, and Ic) CCD cameras attached to the MITSuME 50 cm telescope of Akeno Observatory, Yamanashi, Japan.
The observation started on 2012-08-03 11:07:28 UT ( ~ 82 sec after the burst). And we did not find any new point source within the XRT error circle in the three bands. The results of photometry (3sigma upper limits) are listed below.
The photon flux were calibrated against GSC2.3 catalog.
```
T0+[sec]      MID-UT     T-EXP[sec]       g'              Rc           Ic
-------------------------------------------------------------------------------------------
       82         11:09:51          240        > 18.0       > 18.0     > 17.3
      376       11:53:57        3600         >19.2
      376       11:53:32        3660                           >18.9
      376       11:53:02        3720
        >18.3
-------------------------------------------------------------------------------------------
T0+ : Elapsed time after the burst [sec]
T-EXP: Total Exposure time [sec]
```
GCN Circular #13571
M.R. Goad, J.P. Osborne, A.P. Beardmore and P.A. Evans (U. Leicester) report on behalf of the Swift-XRT team.
Using 117 s of XRT Photon Counting mode data and 1 UVOT images for GRB 120803B, 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 = 314.23579, +53.30416 which is equivalent to:
```
RA (J2000): 20h 56m 56.59s
Dec (J2000): +53d 18' 15.0"
```
with an uncertainty of 2.0 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 #13572
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), J. L. Racusin (NASA/GSFC), 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-60 to T+243 sec from recent telemetry downlinks, we report further analysis of BAT GRB 120803B (trigger #529606) (Racusin, et al., GCN Circ. 12566). The BAT ground-calculated position is RA, Dec = 314.223, 53.298 deg, which is
```
   RA(J2000)  =  20h 56m 53.6s 
   Dec(J2000) = +53d 17' 54.2" 
```
with an uncertainty of 1.0 arcmin, (radius, sys+stat, 90% containment). The partial coding was 58%.
The mask-weighted light curve shows a FRED-like pulse starting at ~T-5 sec, peaking at ~T+6 sec, and returning to baseline ~T+60 sec (or possibly T+90 sec). T90 (15-350 keV) is 37.5 +- 7.9 sec (estimated error including systematics).
The time-averaged spectrum from T-2.67 to T+49.16 sec is best fit by a power law with an exponential cutoff. This fit gives a photon index 0.84 +- 0.36, and Epeak of 117.8 +- 77.4 keV (chi squared 53.7 for 56 d.o.f.). For this model the total fluence in the 15-150 keV band is 2.5 +- 0.5 x 10^-6 erg/cm2 and the 1-sec peak flux measured from T+4.49 sec in the 15-150 keV band is 1.5 +- 0.2 ph/cm2/sec. A fit to a simple power law gives a photon index of 1.36 +- 0.08 (chi squared 60.5 for 57 d.o.f.). 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/529606/BA/
GCN Circular #13575
D. Kuroda, K. Yanagisawa, Y. Shimizu, H. Toda (OAO, NAOJ), S. Nagayama (NAOJ), M. Yoshida (Hiroshima), K. Ohta (Kyoto) and N. Kawai(Tokyo Tech) report on behalf of the MITSuME collaboration:
We observed the field of GRB 120803B (Racusin et al., GCNC 13566) with the optical three color (g', Rc and Ic) CCD camera attached to the MITSuME 50cm telescope of Okayama Astrophysical Observatory.
The observation started on 2012-08-03 11:46:48 UT (~41 min after the burst) We did not find any new point source within the XRT circle (Goad et al., GCNC 13571) in all the three bands. We also could not detect the previously reported afterglow (Guidorzi et al., GCNC 13567).
Three sigma upper limits of the OT are listed below. We used GSC2.3 catalog for flux calibration.
```
T0+[day]   MID-UT   T-EXP[sec]    g'     Rc     Ic
------------------------------------------------------
0.06994    12:46:50    6360.0   >20.5  >20.2  >18.9
------------------------------------------------------
T0+ : Elapsed time after the burst [day]
T-EXP: Total Exposure time [sec]
```
GCN Circular #13576
R. Usui, Y.Aoki, S. Kurita, T. Yoshii, M. Hayashi, Y. Saito, Y. Yatsu, and N. Kawai (Tokyo Tech) report on behalf of the MITSuME collaboration:
The target name in the subject line of GCN13570 was not correct. The true target is GRB 120803B (NOT GRB 120803A). Please replace "GRB 120803A" with "GRB120803B".
The main text of the circular is correct.
GCN Circular #13583
C. Pagani (U. Leicester) and J. L. Racusin (NASA/GSFC) report on behalf of the Swift-XRT team:
We have analysed 4.4 ks of XRT data for GRB 120803B (Racusin et al. GCN Circ. 13566), from 79 s to 17.5 ks after the BAT trigger. The data comprise 31 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 13571).
The light curve can be modelled with a power-law decay with a decay index of alpha=1.25 (+0.07, -0.06).
A spectrum formed from the PC mode data can be fitted with an absorbed power-law with a photon spectral index of 1.2 (+/-0.4). The best-fitting absorption column is 8.5 (+4.7, -2.8) x 10^21 cm^-2, consistent with the Galactic value of 5.7 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 8.4 x 10^-11 (1.1 x 10^-10) erg cm^-2 count^-1.
A summary of the PC-mode spectrum is thus:
```
Total column:	     8.5 (+4.7, -2.8) x 10^21 cm^-2
Galactic foreground: 5.7 x 10^21 cm^-2
Excess significance: <1.6 sigma
Photon index:	     1.2 (+/-0.4)
```
The results of the XRT-team automatic analysis are available at http://www.swift.ac.uk/xrt_products/00529606.
This circular is an official product of the Swift-XRT team.
GCN Circular #18183
Xianggao Wang (UC Berkeley, GXU, UNLV), WeiKang Zheng, Alexei V. Filippenko (UC Berkeley), and S. Bradley Cenko (GSFC) report on behalf of the KAIT GRB team:
The 0.76-m Katzman Automatic Imaging Telescope (KAIT), located at Lick Observatory, responded to Swift GRBs 120422A (Troja et al., GCN 13243), 120724A (D'Avanzo et al., GCN 13510), 120803B (Racusin et al. GCN 13566), 120911A (Cannizzo et al., GCN 13744), and 120923A (Yershov et al., GCN 13796) at 510 s, 202 s, 196 s, 147 s, and 236 s after the burst, respectively. Observations were performed with an automatic sequence in the clear (roughly R), V, and I filters, and the exposure time was 20 s per image. We do not detect any new sources within the XRT error circles. We estimate the following upper limits (magnitudes) in clear-band images for each GRB calibrated to USNO B1.0:
```
GRB       Start-Time  Coadd-Images  Mid-time   Upper-Limit (3 sigma)
120422A   510 s        20 s x 6           758 s              20.6
120724A   202 s        20 s x 10         647 s              20.7
120803B   196 s        20 s x 10         644 s              21.7
120911A   147 s        20 s x 6          501 s               20.9
120923A   236 s        20 s x 6          563 s               21.0
```

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Jochen Greiner, last update: 20-Aug-2015 [Disclaimer]