Gamma-ray Burst 130831B

(All information courtesy of the instrument teams.)

Previous IAU Circulars

none

Results of Observations

GCN/BACODINE POSITION NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Sat 31 Aug 13 14:04:25 UT
NOTICE_TYPE:     Swift-BAT GRB Position
TRIGGER_NUM:     568855,   Seg_Num: 0
GRB_RA:          192.446d {+12h 49m 47s} (J2000),
                 192.630d {+12h 50m 31s} (current),
                 191.773d {+12h 47m 05s} (1950)
GRB_DEC:         -29.177d {-29d 10' 35"} (J2000),
                 -29.251d {-29d 15' 02"} (current),
                 -28.904d {-28d 54' 15"} (1950)
GRB_ERROR:       3.00 [arcmin radius, statistical only]
GRB_INTEN:       8668 [cnts]    Image_Peak=194 [image_cnts]
TRIGGER_DUR:     2.048 [sec] 
TRIGGER_INDEX:   264     E_range: 25-100 keV
BKG_INTEN:       90064 [cnts]
BKG_TIME:        49669.02 SOD {13:47:49.02} UT
BKG_DUR:         24 [sec]
GRB_DATE:        16535 TJD;   243 DOY;   13/08/31
GRB_TIME:        49699.67 SOD {13:48:19.67} UT
GRB_PHI:         -144.61 [deg]
GRB_THETA:        49.84 [deg]
SOLN_STATUS:     0x3
RATE_SIGNIF:     10.63 [sigma]
IMAGE_SIGNIF:    7.44 [sigma]
MERIT_PARAMS:     +1  +0  +0  +1  +2  -2  +0  +0 -65  +0 
SUN_POSTN:       159.97d {+10h 39m 52s}   +8.45d {+08d 26' 47"}
SUN_DIST:         49.10 [deg]   Sun_angle= -2.2 [hr] (East of Sun)
MOON_POSTN:      103.76d {+06h 55m 04s}  +18.31d {+18d 18' 31"}
MOON_DIST:        97.88 [deg]
MOON_ILLUM:      21 [%]
GAL_COORDS:      302.50, 33.69 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:      203.26,-21.87 [deg] ecliptic lon,lat of the burst (or transient)
COMMENTS:        SWIFT-BAT GRB Coordinates.  
COMMENTS:        This Notice was delayed by more than 60 sec past the end of the trigger integration interval;  
COMMENTS:        probably due to it occurring during a Malindi downlink session.  
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 = 16.45,13.40 [deg].

red DSS finding chart ps-file

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Sat 31 Aug 13 14:04:55 UT
NOTICE_TYPE:     Swift-XRT Nack-Position
TRIGGER_NUM:     568855,   Seg_Num: 0
POINT_RA:        192.482d {+12h 49m 56s} (J2000)
POINT_DEC:       -29.183d {-29d 10' 56"} (J2000)
IMG_START_DATE:  16535 TJD;   243 DOY;   13/08/31
IMG_START_TIME:  49826.73 SOD {13:50:26.73} UT,   127.1 [sec] since BAT Trigger Time
COUNTS:          3    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:     Sat 31 Aug 13 14:05:39 UT
NOTICE_TYPE:     Swift-BAT GRB Lightcurve
TRIGGER_NUM:     568855,   Seg_Num: 0
GRB_RA:          192.446d {+12h 49m 47s} (J2000),
                 192.630d {+12h 50m 31s} (current),
                 191.773d {+12h 47m 05s} (1950)
GRB_DEC:         -29.177d {-29d 10' 35"} (J2000),
                 -29.251d {-29d 15' 02"} (current),
                 -28.904d {-28d 54' 15"} (1950)
GRB_DATE:        16535 TJD;   243 DOY;   13/08/31
GRB_TIME:        49699.67 SOD {13:48:19.67} UT
TRIGGER_INDEX:   264
GRB_PHI:         -144.61 [deg]
GRB_THETA:        49.84 [deg]
DELTA_TIME:      -24.00 [sec]
TRIGGER_DUR:     2.048 [sec] 
SOLN_STATUS:     0x3
RATE_SIGNIF:     10.63 [sigma]
IMAGE_SIGNIF:    7.44 [sigma]
LC_URL:          sw00568855000msb.lc
SUN_POSTN:       159.97d {+10h 39m 52s}   +8.45d {+08d 26' 45"}
SUN_DIST:         49.10 [deg]   Sun_angle= -2.2 [hr] (East of Sun)
MOON_POSTN:      103.78d {+06h 55m 06s}  +18.31d {+18d 18' 27"}
MOON_DIST:        97.87 [deg]
MOON_ILLUM:      21 [%]
GAL_COORDS:      302.50, 33.69 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:      203.26,-21.87 [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 = 16.45,13.40 [deg].

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Sat 31 Aug 13 14:07:24 UT
NOTICE_TYPE:     Swift-UVOT Source List
TRIGGER_NUM:     568855,   Seg_Num: 0
POINT_RA:        192.482d {+12h 49m 56s} (J2000)
POINT_DEC:       -29.182d {-29d 10' 53"} (J2000)
POINT_ROLL:      315.235d
IMG_START_DATE:  16535 TJD;   243 DOY;   13/08/31
IMG_START_TIME:  49829.19 SOD {13:50:29.19} UT,   129.5 [sec] since BAT Trigger Time
FILTER:          10, White
BKG_MEAN:        6.004
N_STARS:         67
X_OFFSET:        569 [pixels]
Y_OFFSET:        336 [pixels]
X_MAX:           1528 [pixels]
Y_MAX:           1295 [pixels]
DET_THRESH:      21
PHOTO_THRESH:    12
SL_URL:          sw00568855000msufc0129.fits
SUN_POSTN:       159.97d {+10h 39m 53s}   +8.45d {+08d 26' 44"}
SUN_DIST:         49.12 [deg]   Sun_angle= -2.2 [hr] (East of Sun)
MOON_POSTN:      103.79d {+06h 55m 10s}  +18.31d {+18d 18' 20"}
MOON_DIST:        97.89 [deg]
MOON_ILLUM:      21 [%]
GAL_COORDS:      302.54, 33.69 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      203.30,-21.86 [deg] ecliptic lon,lat of the pointing direction
COMMENTS:        SWIFT-UVOT Source List.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Sat 31 Aug 13 14:07:59 UT
NOTICE_TYPE:     Swift-UVOT Processed Source List
TRIGGER_NUM:     568855,   Seg_Num: 0
POINT_RA:        192.482d {+12h 49m 56s} (J2000)
POINT_DEC:       -29.182d {-29d 10' 53"} (J2000)
POINT_ROLL:      315.235d
IMG_START_DATE:  16535 TJD;   243 DOY;   13/08/31
IMG_START_TIME:  49829.19 SOD {13:50:29.19} UT,   129.5 [sec] since BAT Trigger Time
FILTER:          10, White
BKG_MEAN:        6.004
N_STARS:         67
X_OFFSET:        569 [pixels]
Y_OFFSET:        336 [pixels]
X_MAX:           1528 [pixels]
Y_MAX:           1295 [pixels]
DET_THRESH:      21
PHOTO_THRESH:    12
SL_URL:          sw00568855000msufc0129.fits
SUN_POSTN:       159.97d {+10h 39m 53s}   +8.45d {+08d 26' 43"}
SUN_DIST:         49.12 [deg]   Sun_angle= -2.2 [hr] (East of Sun)
MOON_POSTN:      103.80d {+06h 55m 11s}  +18.30d {+18d 18' 17"}
MOON_DIST:        97.88 [deg]
MOON_ILLUM:      21 [%]
GAL_COORDS:      302.54, 33.69 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      203.30,-21.86 [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:     Sat 31 Aug 13 14:09:07 UT
NOTICE_TYPE:     Swift-UVOT Image
TRIGGER_NUM:     568855,   Seg_Num: 0
POINT_RA:        192.482d {+12h 49m 56s} (J2000)
POINT_DEC:       -29.182d {-29d 10' 53"} (J2000)
ROLL:            315.235d
IMG_START_DATE:  16535 TJD;   243 DOY;   13/08/31
IMG_START_TIME:  49829.19 SOD {13:50:29.19} UT,   129.5 [sec] since BAT Trigger Time
FILTER:          10, White
EXPOSURE_ID:     399649840
X_OFFSET:        888 [pixels]
Y_OFFSET:        655 [pixels]
WIDTH:           160 [pixels]
HEIGHT:          160 [pixels]
X_GRB_POS:       1048
Y_GRB_POS:       815
BINNING_INDEX:   1
IM_URL:          sw00568855000msuni0140.fits
SUN_POSTN:       159.97d {+10h 39m 53s}   +8.45d {+08d 26' 42"}
SUN_DIST:         49.12 [deg]   Sun_angle= -2.2 [hr] (East of Sun)
MOON_POSTN:      103.80d {+06h 55m 13s}  +18.30d {+18d 18' 13"}
MOON_DIST:        97.88 [deg]
MOON_ILLUM:      21 [%]
GAL_COORDS:      302.54, 33.69 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      203.30,-21.86 [deg] ecliptic lon,lat of the pointing direction
COMMENTS:        SWIFT-UVOT Image.  
COMMENTS:        The GRB Position came from the Window Position in the Mode Command.  
COMMENTS:        The image has 2x2 binning (compression).

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Sat 31 Aug 13 14:09:23 UT
NOTICE_TYPE:     Swift-XRT Position
TRIGGER_NUM:     568855,   Seg_Num: 0
GRB_RA:          192.4207d {+12h 49m 40.96s} (J2000),
                 192.6050d {+12h 50m 25.20s} (current),
                 191.7478d {+12h 46m 59.47s} (1950)
GRB_DEC:         -29.1838d {-29d 11' 01.6"} (J2000),
                 -29.2581d {-29d 15' 29.0"} (current),
                 -28.9116d {-28d 54' 41.6"} (1950)
GRB_ERROR:       3.6 [arcsec radius, statistical plus systematic, 90% containment]
GRB_INTEN:       1.00e-10 [erg/cm2/sec]
GRB_SIGNIF:      10.00 [sigma]
IMG_START_DATE:  16535 TJD;   243 DOY;   13/08/31
IMG_START_TIME:  49844.00 SOD {13:50:44.00} UT,   144.3 [sec] since BAT Trigger Time
TAM[0-3]:        100.00 100.00 100.00 100.00
AMPLIFIER:       1
WAVEFORM:        31
SUN_POSTN:       159.97d {+10h 39m 53s}   +8.45d {+08d 26' 42"}
SUN_DIST:         49.08 [deg]   Sun_angle= -2.2 [hr] (East of Sun)
MOON_POSTN:      103.81d {+06h 55m 14s}  +18.30d {+18d 18' 12"}
MOON_DIST:        97.82 [deg]
MOON_ILLUM:      21 [%]
GAL_COORDS:      302.47, 33.69 [deg] galactic lon,lat of the burst
ECL_COORDS:      203.25,-21.88 [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 1.1% < P(seren) < 2.8%.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Sat 31 Aug 13 14:09:20 UT
NOTICE_TYPE:     Swift-UVOT Processed Image
TRIGGER_NUM:     568855,   Seg_Num: 0
POINT_RA:        192.482d {+12h 49m 56s} (J2000)
POINT_DEC:       -29.182d {-29d 10' 53"} (J2000)
ROLL:            315.235d
IMG_START_DATE:  16535 TJD;   243 DOY;   13/08/31
IMG_START_TIME:  49829.19 SOD {13:50:29.19} UT,   129.5 [sec] since BAT Trigger Time
FILTER:          10, White
EXPOSURE_ID:     399649840
X_OFFSET:        888 [pixels]
Y_OFFSET:        655 [pixels]
WIDTH:           160 [pixels]
HEIGHT:          160 [pixels]
X_GRB_POS:       1048
Y_GRB_POS:       815
BINNING_INDEX:   1
IM_URL:          sw00568855000msuni0140.fits
SUN_POSTN:       159.97d {+10h 39m 53s}   +8.45d {+08d 26' 42"}
SUN_DIST:         49.12 [deg]   Sun_angle= -2.2 [hr] (East of Sun)
MOON_POSTN:      103.81d {+06h 55m 14s}  +18.30d {+18d 18' 12"}
MOON_DIST:        97.87 [deg]
MOON_ILLUM:      21 [%]
GAL_COORDS:      302.54, 33.69 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      203.30,-21.86 [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 #15141
D. Malesani (DARK/NBI), J. R. Cummings (NASA/UMBC), V. D'Elia (ASDC), D. Grupe (PSU), J. A. Kennea (PSU), H. A. Krimm (CRESST/GSFC/USRA), V. Mangano (PSU), F. E. Marshall (NASA/GSFC), C. J. Mountford (U Leicester), D. M. Palmer (LANL), M. H. Siegel (PSU), T. N. Ukwatta (MSU) and B.-B. Zhang (UAH) report on behalf of the Swift Team:
At 13:48:19 UT, the Swift Burst Alert Telescope (BAT) triggered and located GRB 130831B (trigger=568855). Swift slewed immediately to the burst. The BAT on-board calculated location is RA, Dec 192.446, -29.177 which is
```
   RA(J2000) = 12h 49m 47s
   Dec(J2000) = -29d 10' 35"
```
with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). The BAT light curve showed a multi-peaked structure with a duration of about 30 sec. The peak count rate was ~1500 counts/sec (15-350 keV), at ~1 sec after the trigger.
The XRT began observing the field at 13:50:26.7 UT, 127.0 seconds after the BAT trigger. Using promptly downlinked data we find an uncatalogued X-ray source located at RA, Dec 192.42070, -29.18380 which is equivalent to:
```
   RA(J2000)  = 12h 49m 40.97s
   Dec(J2000) = -29d 11' 01.7"
```
with an uncertainty of 3.6 arcseconds (radius, 90% containment). This location is 83 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.
A power-law fit to a spectrum formed from promptly downlinked event data gives a column density in excess of the Galactic value (6.20 x 10^20 cm^-2, Kalberla et al. 2005), with an excess column of 2.6 (+1.89/-1.67) x 10^21 cm^-2 (90% confidence).
UVOT took a finding chart exposure of 150 seconds with the White filter starting 129 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 100% 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 0.08.
Burst Advocate for this burst is D. Malesani (malesani AT dark-cosmology.dk). 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:     Sat 31 Aug 13 14:13:47 UT
NOTICE_TYPE:     Swift-UVOT Source List
TRIGGER_NUM:     568855,   Seg_Num: 0
POINT_RA:        192.483d {+12h 49m 56s} (J2000)
POINT_DEC:       -29.181d {-29d 10' 51"} (J2000)
POINT_ROLL:      315.231d
IMG_START_DATE:  16535 TJD;   243 DOY;   13/08/31
IMG_START_TIME:  50564.37 SOD {14:02:44.37} UT,   864.7 [sec] since BAT Trigger Time
FILTER:          10, White
BKG_MEAN:        5.056
N_STARS:         152
X_OFFSET:        329 [pixels]
Y_OFFSET:        96 [pixels]
X_MAX:           1768 [pixels]
Y_MAX:           1535 [pixels]
DET_THRESH:      19
PHOTO_THRESH:    11
SL_URL:          sw00568855000msufc0864.fits
SUN_POSTN:       159.97d {+10h 39m 54s}   +8.44d {+08d 26' 38"}
SUN_DIST:         49.12 [deg]   Sun_angle= -2.2 [hr] (East of Sun)
MOON_POSTN:      103.85d {+06h 55m 23s}  +18.30d {+18d 17' 54"}
MOON_DIST:        97.84 [deg]
MOON_ILLUM:      21 [%]
GAL_COORDS:      302.54, 33.69 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      203.30,-21.86 [deg] ecliptic lon,lat of the pointing direction
COMMENTS:        SWIFT-UVOT Source List.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Sat 31 Aug 13 14:14:09 UT
NOTICE_TYPE:     Swift-UVOT Image
TRIGGER_NUM:     568855,   Seg_Num: 0
POINT_RA:        192.483d {+12h 49m 56s} (J2000)
POINT_DEC:       -29.181d {-29d 10' 51"} (J2000)
ROLL:            315.231d
IMG_START_DATE:  16535 TJD;   243 DOY;   13/08/31
IMG_START_TIME:  50564.37 SOD {14:02:44.37} UT,   864.7 [sec] since BAT Trigger Time
FILTER:          10, White
EXPOSURE_ID:     399650575
X_OFFSET:        888 [pixels]
Y_OFFSET:        655 [pixels]
WIDTH:           160 [pixels]
HEIGHT:          160 [pixels]
X_GRB_POS:       1048
Y_GRB_POS:       815
BINNING_INDEX:   1
IM_URL:          sw00568855000msuni0875.fits
SUN_POSTN:       159.97d {+10h 39m 54s}   +8.44d {+08d 26' 38"}
SUN_DIST:         49.12 [deg]   Sun_angle= -2.2 [hr] (East of Sun)
MOON_POSTN:      103.85d {+06h 55m 24s}  +18.30d {+18d 17' 53"}
MOON_DIST:        97.84 [deg]
MOON_ILLUM:      21 [%]
GAL_COORDS:      302.54, 33.69 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      203.30,-21.86 [deg] ecliptic lon,lat of the pointing direction
COMMENTS:        SWIFT-UVOT Image.  
COMMENTS:        The GRB Position came from the Window Position in the Mode Command.  
COMMENTS:        The image has 2x2 binning (compression).

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Sat 31 Aug 13 14:14:14 UT
NOTICE_TYPE:     Swift-UVOT Processed Source List
TRIGGER_NUM:     568855,   Seg_Num: 0
POINT_RA:        192.483d {+12h 49m 56s} (J2000)
POINT_DEC:       -29.181d {-29d 10' 51"} (J2000)
POINT_ROLL:      315.231d
IMG_START_DATE:  16535 TJD;   243 DOY;   13/08/31
IMG_START_TIME:  50564.37 SOD {14:02:44.37} UT,   864.7 [sec] since BAT Trigger Time
FILTER:          10, White
BKG_MEAN:        5.056
N_STARS:         152
X_OFFSET:        329 [pixels]
Y_OFFSET:        96 [pixels]
X_MAX:           1768 [pixels]
Y_MAX:           1535 [pixels]
DET_THRESH:      19
PHOTO_THRESH:    11
SL_URL:          sw00568855000msufc0864.fits
SUN_POSTN:       159.97d {+10h 39m 54s}   +8.44d {+08d 26' 38"}
SUN_DIST:         49.12 [deg]   Sun_angle= -2.2 [hr] (East of Sun)
MOON_POSTN:      103.85d {+06h 55m 24s}  +18.30d {+18d 17' 52"}
MOON_DIST:        97.84 [deg]
MOON_ILLUM:      21 [%]
GAL_COORDS:      302.54, 33.69 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      203.30,-21.86 [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:     Sat 31 Aug 13 14:14:21 UT
NOTICE_TYPE:     Swift-UVOT Processed Image
TRIGGER_NUM:     568855,   Seg_Num: 0
POINT_RA:        192.483d {+12h 49m 56s} (J2000)
POINT_DEC:       -29.181d {-29d 10' 51"} (J2000)
ROLL:            315.231d
IMG_START_DATE:  16535 TJD;   243 DOY;   13/08/31
IMG_START_TIME:  50564.37 SOD {14:02:44.37} UT,   864.7 [sec] since BAT Trigger Time
FILTER:          10, White
EXPOSURE_ID:     399650575
X_OFFSET:        888 [pixels]
Y_OFFSET:        655 [pixels]
WIDTH:           160 [pixels]
HEIGHT:          160 [pixels]
X_GRB_POS:       1048
Y_GRB_POS:       815
BINNING_INDEX:   1
IM_URL:          sw00568855000msuni0875.fits
SUN_POSTN:       159.97d {+10h 39m 54s}   +8.44d {+08d 26' 38"}
SUN_DIST:         49.12 [deg]   Sun_angle= -2.2 [hr] (East of Sun)
MOON_POSTN:      103.85d {+06h 55m 24s}  +18.30d {+18d 17' 52"}
MOON_DIST:        97.84 [deg]
MOON_ILLUM:      21 [%]
GAL_COORDS:      302.54, 33.69 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      203.30,-21.86 [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:        If you have elected to receive attachments:  
COMMENTS:        The uvot_catalog_image.fits.gz file does not exist; skipping the attachment.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Sat 31 Aug 13 14:14:28 UT
NOTICE_TYPE:     Swift-XRT Position UPDATE
TRIGGER_NUM:     568855,   Seg_Num: 0
GRB_RA:          192.4196d {+12h 49m 40.70s} (J2000),
                 192.6039d {+12h 50m 24.93s} (current),
                 191.7467d {+12h 46m 59.21s} (1950)
GRB_DEC:         -29.1835d {-29d 11' 00.5"} (J2000),
                 -29.2578d {-29d 15' 27.9"} (current),
                 -28.9113d {-28d 54' 40.5"} (1950)
GRB_ERROR:       2.1 [arcsec radius, statistical plus systematic, 90% containment]
GRB_INTEN:       1.00e-10 [erg/cm2/sec]
GRB_SIGNIF:      10.00 [sigma]
IMG_START_DATE:  16535 TJD;   243 DOY;   13/08/31
IMG_START_TIME:  49844.00 SOD {13:50:44.00} UT,   144.3 [sec] since BAT Trigger Time
TAM[0-3]:        100.00 100.00 100.00 100.00
AMPLIFIER:       1
WAVEFORM:        31
SUN_POSTN:       159.97d {+10h 39m 54s}   +8.44d {+08d 26' 38"}
SUN_DIST:         49.08 [deg]   Sun_angle= -2.2 [hr] (East of Sun)
MOON_POSTN:      103.85d {+06h 55m 24s}  +18.30d {+18d 17' 51"}
MOON_DIST:        97.78 [deg]
MOON_ILLUM:      21 [%]
GAL_COORDS:      302.47, 33.69 [deg] galactic lon,lat of the burst
ECL_COORDS:      203.25,-21.88 [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 1.1% < P(seren) < 2.8%.

GCN Circular #15149
M.R. Goad, J.P. Osborne, A.P. Beardmore and P.A. Evans (U. Leicester) report on behalf of the Swift-XRT team.
Using 2499 s of XRT Photon Counting mode data and 5 UVOT images for GRB 130831B, 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 = 192.42038, -29.18331 which is equivalent to:
```
RA (J2000): 12h 49m 40.89s
Dec (J2000): -29d 10' 59.9"
```
with an uncertainty of 1.7 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 #15154
M.C. Stroh (PSU), D.N. Burrows (PSU), J.A. Kennea (PSU), A.P. Beardmore (U. Leicester), P.A. Evans (U. Leicester), B.P. Gompertz (U. Leicester), P. D'Avanzo (INAF-OAB), V. D'Elia (ASDC), A. Maselli (INAF-IASFPA) and D. Malesani report on behalf of the Swift-XRT team:
We have analysed 6.8 ks of XRT data for GRB 130831B (Malesani et al. GCN Circ. 15141), from 112 s to 35.4 ks after the BAT trigger. The data comprise 8 s in Windowed Timing (WT) mode (taken while Swift was slewing), with the remainder in Photon Counting (PC) mode. The enhanced XRT position for this burst was given by Goad et al. (GCN. Circ 15149).
The late-time light curve (from T0+5.1 ks) can be modelled with a power-law decay with a decay index of alpha=1.24 (+0.12, -0.11).
A spectrum formed from the PC mode data can be fitted with an absorbed power-law with a photon spectral index of 2.07 (+0.16, -0.15). The best-fitting absorption column is 1.6 (+/-0.4) x 10^21 cm^-2, in excess of the Galactic value of 6.2 x 10^20 cm^-2 (Kalberla et al. 2005). The counts to observed (unabsorbed) 0.3-10 keV flux conversion factor deduced from this spectrum is 3.7 x 10^-11 (5.3 x 10^-11) erg cm^-2 count^-1.
A summary of the PC-mode spectrum is thus:
```
Total column:	     1.6 (+/-0.4) x 10^21 cm^-2
Galactic foreground: 6.2 x 10^20 cm^-2
Excess significance: 4.2 sigma
Photon index:	     2.07 (+0.16, -0.15)
```
If the light curve continues to decay with a power-law decay index of 1.24, the count rate at T+24 hours will be 9.4 x 10^-3 count s^-1, corresponding to an observed (unabsorbed) 0.3-10 keV flux of 3.5 x 10^-13 (5.0 x 10^-13) erg cm^-2 s^-1.
The results of the XRT-team automatic analysis are available at http://www.swift.ac.uk/xrt_products/00568855.
This circular is an official product of the Swift-XRT team.
GCN Circular #15158
V. Sudilovsky, M. Tanga, and J. Greiner (all MPE Garching) report on behalf of the GROND team:
We observed the field of GRB 130831B (Swift trigger 568855; Malesani et al. 2013, GCN #15141) simultaneously in g'r'i'z'JHK with GROND (Greiner et al. 2008, PASP 120, 405) mounted at the 2.2 m MPG/ESO telescope at La Silla Observatory (Chile).
Observations started at 23:22 UT on 31 Aug. 2013, 10 hours after the GRB trigger. They were performed at an average seeing of 2.2" and at an average airmass of 2.2.
Based on five co-added images with individual exposures of 6 min in g'r'i'z' and 4 min exposure in JHK, we do not detect a source within the 3.6 arcsec Swift-XRT error circle reported by Malesani et al. (2013; GCN #15141) down to (all in the AB system)
```
g' > 23.4,
r' > 23.2,
i' > 22.6,
z' > 22.3,
J > 20.8,
H > 20.2, and
K > 19.6
```
The given limits are derived based on calibrating the images against GROND zeropoints and 2MASS field stars and are not corrected for the Galactic foreground extinction corresponding to a reddening of E_(B-V)= 0.08 in the direction of the burst (Schlegel et al. 1998).
GCN Circular #15160
F.E. Marshall (NASA/GSFC) and D. Malesani (DARK/NBI) report on behalf of the Swift/UVOT team:
The Swift/UVOT began settled observations of the field of GRB 130831B 130 s after the BAT trigger (Malesani et al., GCN Circ. 15141). No optical afterglow consistent with the XRT position (Goad et al. GCN Circ. 15149) is detected in the initial UVOT exposures. Preliminary 3-sigma upper limits using the UVOT photometric system (Breeveld et al. 2011, AIP Conf. Proc. 1358, 373) for the first finding chart (FC) exposures and subsequent exposures are:
```
Filter         T_start(s)   T_stop(s)      Exp(s)         Mag

white_FC           130          279          147         >20.3
u_FC               288          537          246         >19.6
white              130         6384          439         >20.9
v                  618         5490          274         >19.7
b                  543         6312          274         >20.5
u                  288         6106          501         >20.3
w1                 667         5901          274         >20.2
m2                 642         5695          255         >20.9
w2                 593         5285          274         >20.7
```
The magnitudes in the table are not corrected for the Galactic extinction due to the reddening of E(B-V) = 0.08 in the direction of the burst (Schlegel et al. 1998).
GCN Circular #15163
W. H. Baumgartner (GSFC/UMBC), S. D. Barthelmy (GSFC), J. R. Cummings (GSFC/UMBC), E. E. Fenimore (LANL), N. Gehrels (GSFC), H. A. Krimm (GSFC/USRA), A. Y. Lien (NASA/GSFC/ORAU), D. Malesani (DARK/NBI), C. B. Markwardt (GSFC), D. M. Palmer (LANL), T. Sakamoto (AGU), 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+902 sec from the recent telemetry downlink, we report further analysis of BAT GRB 130831B (trigger #568855) (Malesani, et al., GCN Circ. 15141). The BAT ground-calculated position is RA, Dec = 192.454, -29.187 deg which is
```
   RA(J2000)  =  12h 49m 48.9s
   Dec(J2000) = -29d 11' 13.5"
```
with an uncertainty of 2.1 arcmin, (radius, sys+stat, 90% containment). The partial coding was 14%.
BAT mask-weighted light curve shows a multi peak episode starting from ~T-12 sec highest peak around T+1 sec and ending at ~T+30 sec. T90 (15-350 keV) is 37.8 +- 10.4 sec (estimated error including systematics).
The time-averaged spectrum from T-13.9 to T+30.6 sec is best fit by a simple power-law model. The power law index of the time-averaged spectrum is 1.88 +- 0.21. The fluence in the 15-150 keV band is 1.4 +- 0.2 x 10^-06 erg/cm2. The 1-sec peak photon flux measured from T-0.05 sec in the 15-150 keV band is 2.4 +- 0.5 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/568855/BA/
GCN Report 477.1
GCN_Report 477.1 has been posted: http://gcn.gsfc.nasa.gov/reports/report_477_1.pdf by D. Malesani at DARK/NBI titled: "Swift Observations of GRB 130831B"

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Jochen Greiner, last update: 26-Dec-2014 [Disclaimer]