Gamma-ray Burst 150821A

(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 21 Aug 15 09:46:49 UT
NOTICE_TYPE:     Swift-BAT GRB Position
TRIGGER_NUM:     652847,   Seg_Num: 0
GRB_RA:          341.906d {+22h 47m 37s} (J2000),
                 342.149d {+22h 48m 36s} (current),
                 341.124d {+22h 44m 30s} (1950)
GRB_DEC:         -57.875d {-57d 52' 30"} (J2000),
                 -57.792d {-57d 47' 32"} (current),
                 -58.139d {-58d 08' 21"} (1950)
GRB_ERROR:       3.00 [arcmin radius, statistical only]
GRB_INTEN:       0 [cnts]    Image_Peak=884 [image_cnts]
TRIGGER_DUR:     152.000 [sec] 
TRIGGER_INDEX:   20000     E_range: 15-50 keV
BKG_INTEN:       0 [cnts]
BKG_TIME:        0.00 SOD {00:00:00.00} UT
BKG_DUR:         0 [sec]
GRB_DATE:        17255 TJD;   233 DOY;   15/08/21
GRB_TIME:        35040.97 SOD {09:44:00.97} UT
GRB_PHI:         147.93 [deg]
GRB_THETA:        53.90 [deg]
SOLN_STATUS:     0x20000013
RATE_SIGNIF:     0.00 [sigma]
IMAGE_SIGNIF:    7.18 [sigma]
MERIT_PARAMS:     +1  +0  +0  +7  +1  -3  +0  +0 +68  +0 
SUN_POSTN:       150.21d {+10h 00m 51s}  +12.15d {+12d 09' 14"}
SUN_DIST:        133.47 [deg]   Sun_angle= 11.2 [hr] (West of Sun)
MOON_POSTN:      220.78d {+14h 43m 08s}  -12.16d {-12d 09' 29"}
MOON_DIST:        95.34 [deg]
MOON_ILLUM:      36 [%]
GAL_COORDS:      329.55,-52.38 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:      315.98,-45.34 [deg] ecliptic lon,lat of the burst (or transient)
COMMENTS:        SWIFT-BAT GRB Coordinates.  
COMMENTS:        This is an image trigger.  (The RATE_SIGNIF & BKG_{INTEN, TIME, DUR} are undefined.)  
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 = 166.82,0.56 [deg].  
COMMENTS:           
COMMENTS:        NOTE: This BAT event is temporally(20.0<100sec) coincident with the FERMI_GBM event (trignum=461843064).

red DSS finding chart ps-file

GCN NOTICE

TITLE:           GCN/FERMI NOTICE
NOTICE_DATE:     Fri 21 Aug 15 09:44:45 UT
NOTICE_TYPE:     Fermi-GBM Flight Position
RECORD_NUM:      48
TRIGGER_NUM:     461843064
GRB_RA:          316.150d {+21h 04m 36s} (J2000),
                 316.464d {+21h 05m 51s} (current),
                 315.138d {+21h 00m 33s} (1950)
GRB_DEC:         -62.250d {-62d 15' 00"} (J2000),
                 -62.187d {-62d 11' 12"} (current),
                 -62.449d {-62d 26' 56"} (1950)
GRB_ERROR:       14.90 [deg radius, statistical plus systematic]
GRB_INTEN:       100 [cnts/sec]
DATA_SIGNIF:     6.20 [sigma]
INTEG_TIME:      2.048 [sec]
GRB_DATE:        17255 TJD;   233 DOY;   15/08/21
GRB_TIME:        35060.33 SOD {09:44:20.33} UT
GRB_PHI:         122.00 [deg]
GRB_THETA:        45.00 [deg]
DATA_TIME_SCALE: 2.0480 [sec]
HARD_RATIO:      0.88
LOC_ALGORITHM:   3 (version number of)
MOST_LIKELY:      97%  GRB
2nd_MOST_LIKELY:   1%  Generic Transient
DETECTORS:       0,0,0, 0,0,0, 0,0,0, 1,0,1, 0,0,
SUN_POSTN:       150.21d {+10h 00m 50s}  +12.15d {+12d 09' 16"}
SUN_DIST:        129.00 [deg]   Sun_angle= -11.1 [hr] (East of Sun)
MOON_POSTN:      220.77d {+14h 43m 04s}  -12.15d {-12d 09' 14"}
MOON_DIST:        81.90 [deg]
MOON_ILLUM:      36 [%]
GAL_COORDS:      333.04,-39.12 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:      297.39,-43.13 [deg] ecliptic lon,lat of the burst (or transient)
LC_URL:          http://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2015/bn150821406/quicklook/glg_lc_medres34_bn150821406.gif
COMMENTS:        Fermi-GBM Flight-calculated Coordinates.  
COMMENTS:        This trigger occurred at longitude,latitude = 124.73,12.68 [deg].  
COMMENTS:        The LC_URL file will not be created until ~15 min after the trigger.

GCN NOTICE

TITLE:           GCN/FERMI NOTICE
NOTICE_DATE:     Fri 21 Aug 15 09:44:54 UT
NOTICE_TYPE:     Fermi-GBM Flight Position
RECORD_NUM:      58
TRIGGER_NUM:     461843064
GRB_RA:          337.633d {+22h 30m 32s} (J2000),
                 337.893d {+22h 31m 34s} (current),
                 336.796d {+22h 27m 11s} (1950)
GRB_DEC:         -61.183d {-61d 10' 59"} (J2000),
                 -61.103d {-61d 06' 09"} (current),
                 -61.440d {-61d 26' 23"} (1950)
GRB_ERROR:       7.43 [deg radius, statistical plus systematic]
GRB_INTEN:       208 [cnts/sec]
DATA_SIGNIF:     20.30 [sigma]
INTEG_TIME:      4.096 [sec]
GRB_DATE:        17255 TJD;   233 DOY;   15/08/21
GRB_TIME:        35060.33 SOD {09:44:20.33} UT
GRB_PHI:         124.00 [deg]
GRB_THETA:        55.00 [deg]
DATA_TIME_SCALE: 4.0960 [sec]
HARD_RATIO:      0.70
LOC_ALGORITHM:   3 (version number of)
MOST_LIKELY:      97%  GRB
2nd_MOST_LIKELY:   2%  Generic Transient
DETECTORS:       0,0,0, 0,0,0, 0,0,0, 1,0,1, 0,0,
SUN_POSTN:       150.21d {+10h 00m 50s}  +12.15d {+12d 09' 16"}
SUN_DIST:        130.73 [deg]   Sun_angle= 11.5 [hr] (West of Sun)
MOON_POSTN:      220.77d {+14h 43m 04s}  -12.15d {-12d 09' 15"}
MOON_DIST:        91.78 [deg]
MOON_ILLUM:      36 [%]
GAL_COORDS:      327.79,-48.59 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:      310.78,-46.96 [deg] ecliptic lon,lat of the burst (or transient)
LC_URL:          http://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2015/bn150821406/quicklook/glg_lc_medres34_bn150821406.gif
COMMENTS:        Fermi-GBM Flight-calculated Coordinates.  
COMMENTS:        This trigger occurred at longitude,latitude = 124.73,12.68 [deg].  
COMMENTS:        The LC_URL file will not be created until ~15 min after the trigger.

GCN NOTICE

TITLE:           GCN/FERMI NOTICE
NOTICE_DATE:     Fri 21 Aug 15 09:45:00 UT
NOTICE_TYPE:     Fermi-GBM Flight Position
RECORD_NUM:      69
TRIGGER_NUM:     461843064
GRB_RA:          337.667d {+22h 30m 40s} (J2000),
                 337.927d {+22h 31m 42s} (current),
                 336.830d {+22h 27m 19s} (1950)
GRB_DEC:         -61.117d {-61d 07' 00"} (J2000),
                 -61.036d {-61d 02' 09"} (current),
                 -61.373d {-61d 22' 23"} (1950)
GRB_ERROR:       6.45 [deg radius, statistical plus systematic]
GRB_INTEN:       320 [cnts/sec]
DATA_SIGNIF:     31.30 [sigma]
INTEG_TIME:      4.096 [sec]
GRB_DATE:        17255 TJD;   233 DOY;   15/08/21
GRB_TIME:        35060.33 SOD {09:44:20.33} UT
GRB_PHI:         124.00 [deg]
GRB_THETA:        55.00 [deg]
DATA_TIME_SCALE: 4.0960 [sec]
HARD_RATIO:      0.72
LOC_ALGORITHM:   3 (version number of)
MOST_LIKELY:      97%  GRB
2nd_MOST_LIKELY:   2%  Generic Transient
DETECTORS:       0,0,0, 0,0,0, 0,0,0, 1,0,1, 0,0,
SUN_POSTN:       150.21d {+10h 00m 50s}  +12.15d {+12d 09' 16"}
SUN_DIST:        130.79 [deg]   Sun_angle= 11.5 [hr] (West of Sun)
MOON_POSTN:      220.77d {+14h 43m 05s}  -12.15d {-12d 09' 16"}
MOON_DIST:        91.83 [deg]
MOON_ILLUM:      36 [%]
GAL_COORDS:      327.85,-48.64 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:      310.85,-46.92 [deg] ecliptic lon,lat of the burst (or transient)
LC_URL:          http://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2015/bn150821406/quicklook/glg_lc_medres34_bn150821406.gif
COMMENTS:        Fermi-GBM Flight-calculated Coordinates.  
COMMENTS:        This trigger occurred at longitude,latitude = 124.73,12.68 [deg].  
COMMENTS:        The LC_URL file will not be created until ~15 min after the trigger.

GCN NOTICE

TITLE:           GCN/FERMI NOTICE
NOTICE_DATE:     Fri 21 Aug 15 09:45:09 UT
NOTICE_TYPE:     Fermi-GBM Flight Position
RECORD_NUM:      73
TRIGGER_NUM:     461843064
GRB_RA:          337.700d {+22h 30m 48s} (J2000),
                 337.960d {+22h 31m 50s} (current),
                 336.864d {+22h 27m 27s} (1950)
GRB_DEC:         -61.050d {-61d 02' 59"} (J2000),
                 -60.969d {-60d 58' 09"} (current),
                 -61.307d {-61d 18' 24"} (1950)
GRB_ERROR:       5.18 [deg radius, statistical plus systematic]
GRB_INTEN:       486 [cnts/sec]
DATA_SIGNIF:     50.70 [sigma]
INTEG_TIME:      4.096 [sec]
GRB_DATE:        17255 TJD;   233 DOY;   15/08/21
GRB_TIME:        35060.33 SOD {09:44:20.33} UT
GRB_PHI:         124.00 [deg]
GRB_THETA:        55.00 [deg]
DATA_TIME_SCALE: 4.0960 [sec]
HARD_RATIO:      0.82
LOC_ALGORITHM:   3 (version number of)
MOST_LIKELY:      97%  GRB
2nd_MOST_LIKELY:   1%  Generic Transient
DETECTORS:       0,0,0, 0,0,0, 0,0,0, 1,0,1, 0,0,
SUN_POSTN:       150.21d {+10h 00m 50s}  +12.15d {+12d 09' 16"}
SUN_DIST:        130.86 [deg]   Sun_angle= 11.5 [hr] (West of Sun)
MOON_POSTN:      220.77d {+14h 43m 05s}  -12.15d {-12d 09' 17"}
MOON_DIST:        91.87 [deg]
MOON_ILLUM:      36 [%]
GAL_COORDS:      327.91,-48.69 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:      310.92,-46.87 [deg] ecliptic lon,lat of the burst (or transient)
LC_URL:          http://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2015/bn150821406/quicklook/glg_lc_medres34_bn150821406.gif
COMMENTS:        Fermi-GBM Flight-calculated Coordinates.  
COMMENTS:        This trigger occurred at longitude,latitude = 124.73,12.68 [deg].  
COMMENTS:        The LC_URL file will not be created until ~15 min after the trigger.

GCN NOTICE

TITLE:           GCN/FERMI NOTICE
NOTICE_DATE:     Fri 21 Aug 15 09:45:15 UT
NOTICE_TYPE:     Fermi-GBM Ground Position
RECORD_NUM:      57
TRIGGER_NUM:     461843064
GRB_RA:          340.180d {+22h 40m 43s} (J2000),
                 340.425d {+22h 41m 42s} (current),
                 339.391d {+22h 37m 34s} (1950)
GRB_DEC:         -56.860d {-56d 51' 35"} (J2000),
                 -56.778d {-56d 46' 40"} (current),
                 -57.121d {-57d 07' 16"} (1950)
GRB_ERROR:       4.88 [deg radius, statistical only]
DATA_SIGNIF:     17.00 [sigma]
DATA_INTERVAL:   4.096 [sec]
GRB_DATE:        17255 TJD;   233 DOY;   15/08/21
GRB_TIME:        35060.33 SOD {09:44:20.33} UT
GRB_PHI:         129.00 [deg]
GRB_THETA:        57.00 [deg]
E_RANGE:         44.032 - 279.965 [keV]
LOC_ALGORITHM:   4153 (Gnd S/W Version number)
SUN_POSTN:       150.21d {+10h 00m 50s}  +12.15d {+12d 09' 16"}
SUN_DIST:        134.69 [deg]   Sun_angle= 11.3 [hr] (West of Sun)
MOON_POSTN:      220.77d {+14h 43m 05s}  -12.16d {-12d 09' 17"}
MOON_DIST:        95.10 [deg]
MOON_ILLUM:      36 [%]
GAL_COORDS:      331.80,-52.31 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:      315.63,-43.99 [deg] ecliptic lon,lat of the burst (or transient)
LC_URL:          http://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2015/bn150821406/quicklook/glg_lc_medres34_bn150821406.gif
COMMENTS:        Fermi-GBM Ground-calculated Coordinates.  
COMMENTS:        In the LAT Field-of-view.  
COMMENTS:        This Notice was ground-generated -- not flight-generated.  
COMMENTS:        The LC_URL file will not be created/available until ~15 min after the trigger.

GCN NOTICE

TITLE:           GCN/FERMI NOTICE
NOTICE_DATE:     Fri 21 Aug 15 09:46:22 UT
NOTICE_TYPE:     Fermi-GBM Ground Position
RECORD_NUM:      2
TRIGGER_NUM:     461843064
GRB_RA:          343.720d {+22h 54m 53s} (J2000),
                 343.957d {+22h 55m 50s} (current),
                 342.959d {+22h 51m 50s} (1950)
GRB_DEC:         -56.420d {-56d 25' 11"} (J2000),
                 -56.336d {-56d 20' 10"} (current),
                 -56.687d {-56d 41' 11"} (1950)
GRB_ERROR:       2.41 [deg radius, statistical only]
DATA_SIGNIF:     35.00 [sigma]
DATA_INTERVAL:   14.336 [sec]
GRB_DATE:        17255 TJD;   233 DOY;   15/08/21
GRB_TIME:        35060.33 SOD {09:44:20.33} UT
GRB_PHI:         129.00 [deg]
GRB_THETA:        59.00 [deg]
E_RANGE:         44.032 - 279.965 [keV]
LOC_ALGORITHM:   41531 (Gnd S/W Version number)
SUN_POSTN:       150.21d {+10h 00m 51s}  +12.15d {+12d 09' 15"}
SUN_DIST:        134.56 [deg]   Sun_angle= 11.1 [hr] (West of Sun)
MOON_POSTN:      220.78d {+14h 43m 07s}  -12.16d {-12d 09' 25"}
MOON_DIST:        96.96 [deg]
MOON_ILLUM:      36 [%]
GAL_COORDS:      330.26,-54.08 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:      318.26,-44.64 [deg] ecliptic lon,lat of the burst (or transient)
LC_URL:          http://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2015/bn150821406/quicklook/glg_lc_medres34_bn150821406.gif
COMMENTS:        Fermi-GBM Ground-calculated Coordinates.  
COMMENTS:        In the LAT Field-of-view.  
COMMENTS:        This is likely a Long GRB.  
COMMENTS:        This Notice was ground-generated -- not flight-generated.  
COMMENTS:        The LC_URL file will not be created/available until ~15 min after the trigger.  
COMMENTS:           
COMMENTS:        NOTE: This GBM event is temporally(3.0<100sec) coincident with the INTEGRAL_SPIACS event (trignum=7216).

GCN NOTICE

TITLE:           GCN/FERMI NOTICE
NOTICE_DATE:     Fri 21 Aug 15 09:46:46 UT
NOTICE_TYPE:     Fermi-GBM Ground Position
RECORD_NUM:      5
TRIGGER_NUM:     461843064
GRB_RA:          343.380d {+22h 53m 31s} (J2000),
                 343.616d {+22h 54m 28s} (current),
                 342.620d {+22h 50m 29s} (1950)
GRB_DEC:         -55.520d {-55d 31' 11"} (J2000),
                 -55.437d {-55d 26' 11"} (current),
                 -55.786d {-55d 47' 09"} (1950)
GRB_ERROR:       1.15 [deg radius, statistical only]
DATA_SIGNIF:     78.00 [sigma]
DATA_INTERVAL:   23.552 [sec]
GRB_DATE:        17255 TJD;   233 DOY;   15/08/21
GRB_TIME:        35060.33 SOD {09:44:20.33} UT
GRB_PHI:         130.00 [deg]
GRB_THETA:        59.00 [deg]
E_RANGE:         44.032 - 279.965 [keV]
LOC_ALGORITHM:   41531 (Gnd S/W Version number)
SUN_POSTN:       150.21d {+10h 00m 51s}  +12.15d {+12d 09' 14"}
SUN_DIST:        135.47 [deg]   Sun_angle= 11.1 [hr] (West of Sun)
MOON_POSTN:      220.78d {+14h 43m 08s}  -12.16d {-12d 09' 28"}
MOON_DIST:        97.31 [deg]
MOON_ILLUM:      36 [%]
GAL_COORDS:      331.63,-54.54 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:      318.71,-43.78 [deg] ecliptic lon,lat of the burst (or transient)
LC_URL:          http://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2015/bn150821406/quicklook/glg_lc_medres34_bn150821406.gif
COMMENTS:        Fermi-GBM Ground-calculated Coordinates.  
COMMENTS:        In the LAT Field-of-view.  
COMMENTS:        This is likely a Long GRB.  
COMMENTS:        This Notice was ground-generated -- not flight-generated.  
COMMENTS:        The LC_URL file will not be created/available until ~15 min after the trigger.  
COMMENTS:           
COMMENTS:        NOTE: This GBM event is temporally(3.0<100sec) coincident with the INTEGRAL_SPIACS event (trignum=7216).

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Fri 21 Aug 15 09:48:44 UT
NOTICE_TYPE:     Swift-XRT Position
TRIGGER_NUM:     652847,   Seg_Num: 0
GRB_RA:          341.9129d {+22h 47m 39.09s} (J2000),
                 342.1560d {+22h 48m 37.43s} (current),
                 341.1310d {+22h 44m 31.44s} (1950)
GRB_DEC:         -57.8941d {-57d 53' 38.7"} (J2000),
                 -57.8113d {-57d 48' 40.6"} (current),
                 -58.1582d {-58d 09' 29.3"} (1950)
GRB_ERROR:       4.9 [arcsec radius, statistical plus systematic, 90% containment]
GRB_INTEN:       3.49e-09 [erg/cm2/sec]
GRB_SIGNIF:      10.34 [sigma]
IMG_START_DATE:  17255 TJD;   233 DOY;   15/08/21
IMG_START_TIME:  35284.23 SOD {09:48:04.23} UT,   243.3 [sec] since BAT Trigger Time
TAM[0-3]:        327.68 237.23 261.63 243.66
AMPLIFIER:       2
WAVEFORM:        134
SUN_POSTN:       150.21d {+10h 00m 51s}  +12.15d {+12d 09' 13"}
SUN_DIST:        133.45 [deg]   Sun_angle= 11.2 [hr] (West of Sun)
MOON_POSTN:      220.80d {+14h 43m 12s}  -12.16d {-12d 09' 42"}
MOON_DIST:        95.32 [deg]
MOON_ILLUM:      36 [%]
GAL_COORDS:      329.52,-52.37 [deg] galactic lon,lat of the burst
ECL_COORDS:      315.97,-45.36 [deg] ecliptic lon,lat of the burst
COMMENTS:        SWIFT-XRT Coordinates.  
COMMENTS:        The XRT position is 1.15 arcmin from the BAT position.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Fri 21 Aug 15 09:48:59 UT
NOTICE_TYPE:     Swift-XRT Processed Image
TRIGGER_NUM:     652847,   Seg_Num: 0
GRB_RA:          341.9129d {+22h 47m 39.0s} (J2000),
                 342.1560d {+22h 48m 37.4s} (current),
                 341.1310d {+22h 44m 31.4s} (1950)
GRB_DEC:         -57.8941d {-57d 53' 38.7"} (J2000),
                 -57.8113d {-57d 48' 40.6"} (current),
                 -58.1582d {-58d 09' 29.3"} (1950)
GRB_ERROR:       4.7 [arcsec, radius, statistical plus systematic]
GRB_INTEN:       107 [cnts]
IMG_START_DATE:  17255 TJD;   233 DOY;   15/08/21
IMG_START_TIME:  35284.23 SOD {09:48:04.23} UT,   243.3 [sec] since BAT Trigger Time
CENTROID_X:      298.31,  raw= 298  [pixels]
CENTROID_Y:      304.39,  raw= 304  [pixels]
ROLL:            164.15 [deg]
GAIN:            1
MODE:            3, Long Image mode
WAVEFORM:        134
EXPO_TIME:       2.50 [sec]
GRB_POS_XRT_Y:   15.54
GRB_POS_XRT_Z:   -16.47
IMAGE_URL:       sw00652847000msxps_rw.img
SUN_POSTN:       150.21d {+10h 00m 51s}  +12.15d {+12d 09' 13"}
SUN_DIST:        133.45 [deg]   Sun_angle= 11.2 [hr] (West of Sun)
MOON_POSTN:      220.80d {+14h 43m 12s}  -12.16d {-12d 09' 44"}
MOON_DIST:        95.32 [deg]
MOON_ILLUM:      36 [%]
GAL_COORDS:      329.52,-52.37 [deg] galactic lon,lat of the burst
ECL_COORDS:      315.97,-45.36 [deg] ecliptic lon,lat of the burst
COMMENTS:        SWIFT-XRT Processed Image.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Fri 21 Aug 15 09:48:54 UT
NOTICE_TYPE:     Swift-XRT Image
TRIGGER_NUM:     652847,   Seg_Num: 0
GRB_RA:          341.9129d {+22h 47m 39.0s} (J2000),
                 342.1560d {+22h 48m 37.4s} (current),
                 341.1310d {+22h 44m 31.4s} (1950)
GRB_DEC:         -57.8941d {-57d 53' 38.7"} (J2000),
                 -57.8113d {-57d 48' 40.6"} (current),
                 -58.1582d {-58d 09' 29.3"} (1950)
GRB_ERROR:       4.7 [arcsec, radius, statistical plus systematic]
GRB_INTEN:       107 [cnts]
IMG_START_DATE:  17255 TJD;   233 DOY;   15/08/21
IMG_START_TIME:  35284.23 SOD {09:48:04.23} UT,   243.3 [sec] since BAT Trigger Time
CENTROID_X:      298.31,  raw= 298  [pixels]
CENTROID_Y:      304.39,  raw= 304  [pixels]
ROLL:            164.15 [deg]
GAIN:            1
MODE:            3, Long Image mode
WAVEFORM:        134
EXPO_TIME:       2.50 [sec]
GRB_POS_XRT_Y:   15.54
GRB_POS_XRT_Z:   -16.47
IMAGE_URL:       sw00652847000msxps_rw.img
SUN_POSTN:       150.21d {+10h 00m 51s}  +12.15d {+12d 09' 13"}
SUN_DIST:        133.45 [deg]   Sun_angle= 11.2 [hr] (West of Sun)
MOON_POSTN:      220.80d {+14h 43m 12s}  -12.16d {-12d 09' 43"}
MOON_DIST:        95.32 [deg]
MOON_ILLUM:      36 [%]
GAL_COORDS:      329.52,-52.37 [deg] galactic lon,lat of the burst
ECL_COORDS:      315.97,-45.36 [deg] ecliptic lon,lat of the burst
COMMENTS:        SWIFT-XRT Image.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Fri 21 Aug 15 09:49:32 UT
NOTICE_TYPE:     Swift-BAT GRB Lightcurve
TRIGGER_NUM:     652847,   Seg_Num: 0
GRB_RA:          341.906d {+22h 47m 37s} (J2000),
                 342.149d {+22h 48m 36s} (current),
                 341.124d {+22h 44m 30s} (1950)
GRB_DEC:         -57.875d {-57d 52' 30"} (J2000),
                 -57.792d {-57d 47' 32"} (current),
                 -58.139d {-58d 08' 21"} (1950)
GRB_DATE:        17255 TJD;   233 DOY;   15/08/21
GRB_TIME:        35040.97 SOD {09:44:00.97} UT
TRIGGER_INDEX:   20000
GRB_PHI:         147.93 [deg]
GRB_THETA:        53.90 [deg]
DELTA_TIME:      0.00 [sec]
TRIGGER_DUR:     152.000 [sec] 
SOLN_STATUS:     0x13
RATE_SIGNIF:     0.00 [sigma]
IMAGE_SIGNIF:    7.18 [sigma]
LC_URL:          sw00652847000msb.lc
SUN_POSTN:       150.21d {+10h 00m 51s}  +12.15d {+12d 09' 12"}
SUN_DIST:        133.46 [deg]   Sun_angle= 11.2 [hr] (West of Sun)
MOON_POSTN:      220.81d {+14h 43m 14s}  -12.16d {-12d 09' 48"}
MOON_DIST:        95.32 [deg]
MOON_ILLUM:      36 [%]
GAL_COORDS:      329.55,-52.38 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:      315.98,-45.34 [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 an image 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 = 166.82,0.56 [deg].

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Fri 21 Aug 15 09:51:16 UT
NOTICE_TYPE:     Swift-UVOT Source List
TRIGGER_NUM:     652847,   Seg_Num: 0
POINT_RA:        341.903d {+22h 47m 37s} (J2000)
POINT_DEC:       -57.891d {-57d 53' 26"} (J2000)
POINT_ROLL:      164.151d
IMG_START_DATE:  17255 TJD;   233 DOY;   15/08/21
IMG_START_TIME:  35292.33 SOD {09:48:12.33} UT,   251.4 [sec] since BAT Trigger Time
FILTER:          10, White
BKG_MEAN:        1.549
N_STARS:         63
X_OFFSET:        360 [pixels]
Y_OFFSET:        552 [pixels]
X_MAX:           1319 [pixels]
Y_MAX:           1511 [pixels]
DET_THRESH:      10
PHOTO_THRESH:    5
SL_URL:          sw00652847000msufc0251.fits
SUN_POSTN:       150.21d {+10h 00m 51s}  +12.15d {+12d 09' 11"}
SUN_DIST:        133.45 [deg]   Sun_angle= 11.2 [hr] (West of Sun)
MOON_POSTN:      220.82d {+14h 43m 17s}  -12.17d {-12d 10' 00"}
MOON_DIST:        95.30 [deg]
MOON_ILLUM:      37 [%]
GAL_COORDS:      329.53,-52.36 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      315.97,-45.35 [deg] ecliptic lon,lat of the pointing direction
COMMENTS:        SWIFT-UVOT Source List.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Fri 21 Aug 15 09:51:37 UT
NOTICE_TYPE:     Swift-UVOT Processed Source List
TRIGGER_NUM:     652847,   Seg_Num: 0
POINT_RA:        341.903d {+22h 47m 37s} (J2000)
POINT_DEC:       -57.891d {-57d 53' 26"} (J2000)
POINT_ROLL:      164.151d
IMG_START_DATE:  17255 TJD;   233 DOY;   15/08/21
IMG_START_TIME:  35292.33 SOD {09:48:12.33} UT,   251.4 [sec] since BAT Trigger Time
FILTER:          10, White
BKG_MEAN:        1.549
N_STARS:         63
X_OFFSET:        360 [pixels]
Y_OFFSET:        552 [pixels]
X_MAX:           1319 [pixels]
Y_MAX:           1511 [pixels]
DET_THRESH:      10
PHOTO_THRESH:    5
SL_URL:          sw00652847000msufc0251.fits
SUN_POSTN:       150.21d {+10h 00m 51s}  +12.15d {+12d 09' 10"}
SUN_DIST:        133.45 [deg]   Sun_angle= 11.2 [hr] (West of Sun)
MOON_POSTN:      220.82d {+14h 43m 18s}  -12.17d {-12d 10' 02"}
MOON_DIST:        95.30 [deg]
MOON_ILLUM:      37 [%]
GAL_COORDS:      329.53,-52.36 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      315.97,-45.35 [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 21 Aug 15 09:53:14 UT
NOTICE_TYPE:     Swift-UVOT Image
TRIGGER_NUM:     652847,   Seg_Num: 0
POINT_RA:        341.903d {+22h 47m 37s} (J2000)
POINT_DEC:       -57.891d {-57d 53' 26"} (J2000)
ROLL:            164.151d
IMG_START_DATE:  17255 TJD;   233 DOY;   15/08/21
IMG_START_TIME:  35292.33 SOD {09:48:12.33} UT,   251.4 [sec] since BAT Trigger Time
FILTER:          10, White
EXPOSURE_ID:     461843307
X_OFFSET:        801 [pixels]
Y_OFFSET:        820 [pixels]
WIDTH:           160 [pixels]
HEIGHT:          160 [pixels]
X_GRB_POS:       961
Y_GRB_POS:       980
BINNING_INDEX:   1
IM_URL:          sw00652847000msuni0267.fits
SUN_POSTN:       150.22d {+10h 00m 52s}  +12.15d {+12d 09' 09"}
SUN_DIST:        133.45 [deg]   Sun_angle= 11.2 [hr] (West of Sun)
MOON_POSTN:      220.84d {+14h 43m 21s}  -12.17d {-12d 10' 14"}
MOON_DIST:        95.29 [deg]
MOON_ILLUM:      37 [%]
GAL_COORDS:      329.53,-52.36 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      315.97,-45.35 [deg] ecliptic lon,lat of the pointing direction
COMMENTS:        SWIFT-UVOT Image.  
COMMENTS:        The GRB Position came from the XRT Position Command.  
COMMENTS:        The image has 2x2 binning (compression).

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Fri 21 Aug 15 09:53:28 UT
NOTICE_TYPE:     Swift-UVOT Processed Image
TRIGGER_NUM:     652847,   Seg_Num: 0
POINT_RA:        341.903d {+22h 47m 37s} (J2000)
POINT_DEC:       -57.891d {-57d 53' 26"} (J2000)
ROLL:            164.151d
IMG_START_DATE:  17255 TJD;   233 DOY;   15/08/21
IMG_START_TIME:  35292.33 SOD {09:48:12.33} UT,   251.4 [sec] since BAT Trigger Time
FILTER:          10, White
EXPOSURE_ID:     461843307
X_OFFSET:        801 [pixels]
Y_OFFSET:        820 [pixels]
WIDTH:           160 [pixels]
HEIGHT:          160 [pixels]
X_GRB_POS:       961
Y_GRB_POS:       980
BINNING_INDEX:   1
IM_URL:          sw00652847000msuni0267.fits
SUN_POSTN:       150.22d {+10h 00m 52s}  +12.15d {+12d 09' 09"}
SUN_DIST:        133.45 [deg]   Sun_angle= 11.2 [hr] (West of Sun)
MOON_POSTN:      220.84d {+14h 43m 21s}  -12.17d {-12d 10' 15"}
MOON_DIST:        95.29 [deg]
MOON_ILLUM:      37 [%]
GAL_COORDS:      329.53,-52.36 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      315.97,-45.35 [deg] ecliptic lon,lat of the pointing direction
COMMENTS:        SWIFT-UVOT Processed Image.  
COMMENTS:        The GRB Position came from the XRT Position Command.  
COMMENTS:        The image has 2x2 binning (compression).  
COMMENTS:        All 4 attachments are included.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Fri 21 Aug 15 09:56:30 UT
NOTICE_TYPE:     Swift-UVOT Position
TRIGGER_NUM:     652847,   Seg_Num: 0
GRB_RA:          341.9132d {+22h 47m 39.16s} (J2000),
                 342.1563d {+22h 48m 37.50s} (current),
                 341.1313d {+22h 44m 31.52s} (1950)
GRB_DEC:         -57.8939d {-57d 53' 38.0"} (J2000),
                 -57.8111d {-57d 48' 39.9"} (current),
                 -58.1580d {-58d 09' 28.6"} (1950)
GRB_ERROR:       0.6 [arcsec radius, statistical only]
GRB_MAG:         16.47 +/- 0.14 [mag]
FILTER:          10, White
IMG_START_DATE:  17255 TJD;   233 DOY;   15/08/21
IMG_START_TIME:  35290.00 SOD {09:48:10.00} UT,   249.0 [sec] since BAT Trigger Time
SUN_POSTN:       150.22d {+10h 00m 52s}  +12.15d {+12d 09' 06"}
SUN_DIST:        133.44 [deg]   Sun_angle= 11.2 [hr] (West of Sun)
MOON_POSTN:      220.86d {+14h 43m 27s}  -12.18d {-12d 10' 37"}
MOON_DIST:        95.28 [deg]
MOON_ILLUM:      37 [%]
GAL_COORDS:      329.52,-52.37 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:      315.97,-45.36 [deg] ecliptic lon,lat of the burst (or transient)
COMMENTS:        SWIFT UVOT Position Notice.  
COMMENTS:        This Notice was ground-generated -- not flight-generated.  
COMMENTS:        The UVOT position is 0.7 arcsec from the XRT position.  
COMMENTS:        Result based on Genie data.  
COMMENTS:        Notice generated automatically.

GCN Circular #18186
E. Troja (NASA/GSFC/UMCP), M. G. Bernardini (INAF-OAB), S. B. Cenko (GSFC), P. D'Avanzo (INAF-OAB), V. D'Elia (ASDC), P. A. Evans (U Leicester), A. Melandri (INAF-OAB) and K. L. Page (U Leicester) report on behalf of the Swift Team:
At 09:44:00 UT, the Swift Burst Alert Telescope (BAT) triggered and located GRB 150821A (trigger=652847). Swift slewed immediately to the burst. The BAT on-board calculated location is RA, Dec 341.906, -57.875 which is
```
   RA(J2000) = 22h 47m 37s
   Dec(J2000) = -57d 52' 30"
```
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 at least 100 sec. The peak count rate was ~2840 counts/sec (15-350 keV), at ~35 sec after the trigger.
The XRT began observing the field at 09:48:04.2 UT, 243.3 seconds after the BAT trigger. XRT found a bright, uncatalogued X-ray source located at RA, Dec 341.9129, -57.8941 which is equivalent to:
```
   RA(J2000)  = +22h 47m 39.10s
   Dec(J2000) = -57d 53' 38.8"
```
with an uncertainty of 4.9 arcseconds (radius, 90% containment). This location is 70 arcseconds from the BAT onboard position, within the BAT error circle. No event data are yet available to determine the column density using X-ray spectroscopy.
UVOT took a finding chart exposure of 150 seconds with the White filter starting 251 seconds after the BAT trigger. There is a candidate afterglow in the rapidly available 2.7'x2.7' sub-image at
```
  RA(J2000)  =	22:47:39.18 = 341.91326
  DEC(J2000) = -57:53:38.1  = -57.89393
```
with a 90%-confidence error radius of about 0.61 arc sec. This position is 0.9 arc sec. from the center of the XRT error circle. The estimated magnitude is 16.48 with a 1-sigma error of about 0.14. No correction has been made for the expected extinction corresponding to E(B-V) of 0.02.
Burst Advocate for this burst is E. Troja (eleonora.troja 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 NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Fri 21 Aug 15 10:01:18 UT
NOTICE_TYPE:     Swift-UVOT Source List
TRIGGER_NUM:     652847,   Seg_Num: 0
POINT_RA:        341.899d {+22h 47m 36s} (J2000)
POINT_DEC:       -57.892d {-57d 53' 29"} (J2000)
POINT_ROLL:      164.155d
IMG_START_DATE:  17255 TJD;   233 DOY;   15/08/21
IMG_START_TIME:  35897.13 SOD {09:58:17.13} UT,   856.2 [sec] since BAT Trigger Time
FILTER:          10, White
BKG_MEAN:        1.662
N_STARS:         190
X_OFFSET:        241 [pixels]
Y_OFFSET:        260 [pixels]
X_MAX:           1680 [pixels]
Y_MAX:           1699 [pixels]
DET_THRESH:      11
PHOTO_THRESH:    5
SL_URL:          sw00652847000msufc0856.fits
SUN_POSTN:       150.22d {+10h 00m 53s}  +12.15d {+12d 09' 02"}
SUN_DIST:        133.45 [deg]   Sun_angle= 11.2 [hr] (West of Sun)
MOON_POSTN:      220.90d {+14h 43m 37s}  -12.19d {-12d 11' 11"}
MOON_DIST:        95.24 [deg]
MOON_ILLUM:      37 [%]
GAL_COORDS:      329.53,-52.36 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      315.97,-45.35 [deg] ecliptic lon,lat of the pointing direction
COMMENTS:        SWIFT-UVOT Source List.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Fri 21 Aug 15 10:01:35 UT
NOTICE_TYPE:     Swift-UVOT Processed Source List
TRIGGER_NUM:     652847,   Seg_Num: 0
POINT_RA:        341.899d {+22h 47m 36s} (J2000)
POINT_DEC:       -57.892d {-57d 53' 29"} (J2000)
POINT_ROLL:      164.155d
IMG_START_DATE:  17255 TJD;   233 DOY;   15/08/21
IMG_START_TIME:  35897.13 SOD {09:58:17.13} UT,   856.2 [sec] since BAT Trigger Time
FILTER:          10, White
BKG_MEAN:        1.662
N_STARS:         190
X_OFFSET:        241 [pixels]
Y_OFFSET:        260 [pixels]
X_MAX:           1680 [pixels]
Y_MAX:           1699 [pixels]
DET_THRESH:      11
PHOTO_THRESH:    5
SL_URL:          sw00652847000msufc0856.fits
SUN_POSTN:       150.22d {+10h 00m 53s}  +12.15d {+12d 09' 02"}
SUN_DIST:        133.45 [deg]   Sun_angle= 11.2 [hr] (West of Sun)
MOON_POSTN:      220.91d {+14h 43m 38s}  -12.19d {-12d 11' 13"}
MOON_DIST:        95.24 [deg]
MOON_ILLUM:      37 [%]
GAL_COORDS:      329.53,-52.36 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      315.97,-45.35 [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 21 Aug 15 10:02:42 UT
NOTICE_TYPE:     Swift-UVOT Image
TRIGGER_NUM:     652847,   Seg_Num: 0
POINT_RA:        341.899d {+22h 47m 36s} (J2000)
POINT_DEC:       -57.892d {-57d 53' 29"} (J2000)
ROLL:            164.155d
IMG_START_DATE:  17255 TJD;   233 DOY;   15/08/21
IMG_START_TIME:  35897.13 SOD {09:58:17.13} UT,   856.2 [sec] since BAT Trigger Time
FILTER:          10, White
EXPOSURE_ID:     461843912
X_OFFSET:        800 [pixels]
Y_OFFSET:        819 [pixels]
WIDTH:           160 [pixels]
HEIGHT:          160 [pixels]
X_GRB_POS:       960
Y_GRB_POS:       979
BINNING_INDEX:   1
IM_URL:          sw00652847000msuni0872.fits
SUN_POSTN:       150.22d {+10h 00m 53s}  +12.15d {+12d 09' 01"}
SUN_DIST:        133.45 [deg]   Sun_angle= 11.2 [hr] (West of Sun)
MOON_POSTN:      220.92d {+14h 43m 40s}  -12.19d {-12d 11' 21"}
MOON_DIST:        95.24 [deg]
MOON_ILLUM:      37 [%]
GAL_COORDS:      329.53,-52.36 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      315.97,-45.35 [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 21 Aug 15 10:02:50 UT
NOTICE_TYPE:     Swift-UVOT Processed Image
TRIGGER_NUM:     652847,   Seg_Num: 0
POINT_RA:        341.899d {+22h 47m 36s} (J2000)
POINT_DEC:       -57.892d {-57d 53' 29"} (J2000)
ROLL:            164.155d
IMG_START_DATE:  17255 TJD;   233 DOY;   15/08/21
IMG_START_TIME:  35897.13 SOD {09:58:17.13} UT,   856.2 [sec] since BAT Trigger Time
FILTER:          10, White
EXPOSURE_ID:     461843912
X_OFFSET:        800 [pixels]
Y_OFFSET:        819 [pixels]
WIDTH:           160 [pixels]
HEIGHT:          160 [pixels]
X_GRB_POS:       960
Y_GRB_POS:       979
BINNING_INDEX:   1
IM_URL:          sw00652847000msuni0872.fits
SUN_POSTN:       150.22d {+10h 00m 53s}  +12.15d {+12d 09' 01"}
SUN_DIST:        133.45 [deg]   Sun_angle= 11.2 [hr] (West of Sun)
MOON_POSTN:      220.92d {+14h 43m 40s}  -12.19d {-12d 11' 22"}
MOON_DIST:        95.24 [deg]
MOON_ILLUM:      37 [%]
GAL_COORDS:      329.53,-52.36 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      315.97,-45.35 [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 #18187
V. D'Elia (ASI/ASDC and INAF-OAR), T. Kruehler (ESO), K. Wiersema (U. Leicester), N. R. Tanvir (U. Leicester), J. Japelj (U. Ljubljana), G. Pugliese (API/UvA), D. Malesani (DARK/NBI), B. Milvang-Jensen (DARK/NBI), J. P. U. Fynbo (DARK/NBI), report on behalf of a larger collaboration:
We observed the optical counterpart of GRB 150821A (Troja et al., GCN 18186) with the ESO VLT equipped with the X-shooter spectrograph. Four spectra with individual exposure time of 600 s were secured covering the wavelength range 3,000-25,000 AA. Observations were carried out in robotic "rapid response mode" (RRM) and spectroscopy began 12.4 min after the BAT trigger (7.7 min after the XRT position, at which point the VLT was triggered). The afterglow is well detected in our acquisition image, with a magnitude of R ~ 16 (11.1 min after the GRB), calibrated to one nearby USNO star.
We detect a number of absorption features at a common redshift of z = 0.755, including Mg II, Mg I, Fe II, Zn II. We also detect fine-structure lines at the same redshift (e.g. FeII* 2396 / 2389, and Ni II** 2166 / 2217 / 2223), confirming that the absorption system is local to the GRB and not intervening.
We thank the kind assistence of the observing staff at Paranal, in particular Claudia Cid and Marcela Espinoza.
GCN Circular #18190
O.J. Roberts (UCD) reports on behalf of the Fermi GBM team:
"At 09:44:20.33 UT on August 21st 2015, the Fermi Gamma-Ray Burst Monitor triggered and located GRB 150821A (trigger 461843064/150821406), which was also detected by Swift (Troja et al. 2015, GCN 18186).
The trigger resulted in an Autonomous Repoint Request (ARR) due to the high peak flux of the GRB. This ARR was accepted and the spacecraft slewed to the GBM in-flight location. Both the GBM in-flight and on-ground locations are consistent with the Swift position.
The angle of the burst direction to the Fermi LAT boresight is 57 degrees.
The GBM light curve consists of a FRED-like burst, with two unresolved peaks and a duration of about 103 s (50-300 keV). The time-averaged spectrum from T0-2.0s to T0+101.4s is well fit by a Band function with Epeak = 322 +/- 18 keV, Alpha =-1.21 +/- 0.01 and Beta = -2.27 +/- 0.10.
The event fluence (10-1000 keV) in this time interval is (6.87 +/- 0.08)E-05 erg/cm^2. The 1.024 s peak photon flux measured starting from T0+17.1s in the 10-1000 keV band is 11.1 +/- 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 #18191
M.R. Goad, J.P. Osborne, A.P. Beardmore and P.A. Evans (U. Leicester) report on behalf of the Swift-XRT team.
Using 910 s of XRT Photon Counting mode data and 2 UVOT images for GRB 150821A, 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 = 341.91332, -57.89384 which is equivalent to:
```
RA (J2000): 22h 47m 39.20s
Dec (J2000): -57d 53' 37.8"
```
with an uncertainty of 1.8 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 #18192
N. P. M. Kuin (UCL-MSSL) and E. Troja (NASA/GSFC/UMCP) report on behalf of the Swift/UVOT team:
The Swift/UVOT began settled observations of the field of GRB 150821A 251 s after the BAT trigger (Troja et al., GCN Circ. 18186). We use the UVOT position as reported there which is consistent with the enhanced XRT position (Goad et al. GCN Circ. 18191).
Preliminary detections and 3-sigma upper limits using the UVOT photometric system (Breeveld et al. 2011, AIP Conf. Proc. 1358, 373) for the early exposures are:
```
Filter         T_start(s)   T_stop(s)      Exp(s)           Mag

white              251          401          147         16.59 +/- 0.03
v                  560          580           20         17.21 +/- 0.18
b                  484          504           19         17.48 +/- 0.12
u                  460          479           19         16.70 +/- 0.11
w1                 435          629           39         17.62 +/- 0.18
m2                 410         7287          372        >19.8
w2                 535         1904          156         19.85 +/- 0.28
```
The magnitudes in the table are not corrected for the Galactic extinction due to the reddening of E(B-V) = 0.02 in the direction of the burst (Schlegel et al. 1998).
GCN Circular #18194
A. Maselli (INAF-IASFPA), A. Melandri (INAF-OAB), P. D'Avanzo (INAF-OAB), B. Sbarufatti (INAF-OAB/PSU), D.N. Burrows (PSU), T.G.R. Roegiers (PSU), J.P. Osborne (U. Leicester), K.L. Page (U. Leicester), C. Pagani (U. Leicester) and E. Troja report on behalf of the Swift-XRT team:
We have analysed 7.7 ks of XRT data for GRB 150821A (Troja et al. GCN Circ. 18186), from 233 s to 40.6 ks after the BAT trigger. The data comprise 1.1 ks in Windowed Timing (WT) mode (the first 8 s were 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. 18191).
The late-time light curve (from T0+5.9 ks) can be modelled with a power-law decay with a decay index of alpha=1.26 (+0.15, -0.13).
A spectrum formed from the WT mode data can be fitted with an absorbed power-law with a photon spectral index of 1.85 (+/-0.03). The best-fitting absorption column is 1.66 (+0.09, -0.08) x 10^22 cm^-2, at a redshift of 0.755, in addition to the Galactic value of 1.8 x 10^20 cm^-2 (Willingale et al. 2013). The PC mode spectrum has a photon index of 2.21 (+/-0.15) and a best-fitting absorption column of 2.2 (+0.4, -0.3) x 10^22 cm^-2. The counts to observed (unabsorbed) 0.3-10 keV flux conversion factor deduced from this spectrum is 3.7 x 10^-11 (7.1 x 10^-11) erg cm^-2 count^-1.
A summary of the PC-mode spectrum is thus:
```
Galactic foreground: 1.8 x 10^20 cm^-2
Intrinsic column:    2.2 (+0.4, -0.3) x 10^22 cm^-2 at z=0.755
Photon index:	     2.21 (+/-0.15)
```
If the light curve continues to decay with a power-law decay index of 1.26, the count rate at T+24 hours will be 8.4 x 10^-3 count s^-1, corresponding to an observed (unabsorbed) 0.3-10 keV flux of 3.1 x 10^-13 (6.0 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/00652847.
This circular is an official product of the Swift-XRT team.
GCN Circular #18195
T. Kruehler (ESO), F. Schrey, W. Bornemann, A. Rau and J. Greiner (all MPE) report on behalf of a larger collaboration:
We observed the field of GRB 150821A (Swift trigger 652847; Troja et al., GCN 18186) simultaneously in g'r'i'z'JHK with GROND (Greiner et al. 2008, PASP 120, 405) mounted at the 2.2 m MPG telescope at ESO La Silla Observatory (Chile).
Observations started at 02:02 UT on 2015-08-22, 16.3 hours after the GRB trigger. For the optical afterglow (Troja et al., GCN 18186, D'Elia et al. GCN 18187, Kuin & Troja, GCN 18192) we derive magnitudes of:
```
g = 23.2 +- 0.1
r = 22.6 +- 0.1
i = 22.3 +- 0.1
z = 22.0 +- 0.2
```
at a midtime of 17.0 hours after the trigger. This photometry is in the AB system and calibrated against GROND zeropoints. Because GROND is presently being recommissioned, our measurements are preliminary.
GCN Circular #18196
M. Stamatikos (OSU), S. D. Barthelmy (GSFC), J. R. Cummings (GSFC/UMBC), N. Gehrels (GSFC), H. A. Krimm (GSFC/USRA), A. Y. Lien (GSFC/UMBC), C. B. Markwardt (GSFC), D. M. Palmer (LANL), T. Sakamoto (AGU), E. Troja (NASA/GSFC/UMCP), T. N. Ukwatta (LANL) (i.e. the Swift-BAT team):
Using the data set from T-239 to T+963 sec from the recent telemetry downlink, we report further analysis of BAT GRB 150821A (trigger #652847) (Troja, et al., GCN Circ. 18186). The BAT ground-calculated position is RA, Dec = 341.913, -57.883 deg which is
```
  RA(J2000)  =  22h 47m 39.0s
  Dec(J2000) = -57d -52' -58.7"
```
with an uncertainty of 1.7 arcmin, (radius, sys+stat, 90% containment). The partial coding was 1.5%.
Due to the low partial coding fraction of this burst, the light curves and burst durations are created using the special DETECTION mask aperture. However, the spectral analysis are done using the default FLUX aperture for more accurate results, and thus the spectral analysis is only available after T0+174.24 s, when the burst came into the BAT calibrated field of view. Note that the interval used for the spectral analysis included < 1% of the total fluence.
The mask-weighted light curve starts at ~T0+20 s and contains several overlapping pulses. The main structure ends at ~T0+70 s, with a long-lasting tail until ~T0+330 s. T90 (15-350 keV) is 172.1 +- 99.0 sec (estimated error including systematics).
The time-averaged spectrum from T+174.2 to T+330.7 sec is best fit by a simple power-law model. The power law index of the time-averaged spectrum is 2.10 +- 0.37. The fluence in the 15-150 keV band is 7.9 +- 1.9 x 10^-7 erg/cm2. The 1-s peak spectral analysis is unavailable because the 1-s peak duration happens before the burst came into the BAT calibrated field of view. 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/652847/BA/
GCN Circular #18197
C. Guidorzi (U. Ferrara), S. Kobayashi (LJMU), A. Gomboc (U. Ljubljana), C. Mundell (U. Bath) on behalf of a larger collaboration report:
The 1-m LCOGT telescopes in Sutherland (South Africa) began observing Swift GRB 150821A (Troja et al. GCN 18186) on August 21, 19:39 UT (~9.9 hours after the burst trigger) with SDSS r and i filters. At the position of the optical afterglow (Troja et al. GCN 18186; D'Elia et al. GCN 18187; Kuin et al. GCN 18192; Kruehler et al. GCN 18195) we do not detect any source down to the following limits:
```
Mid Time      Exposure       Filter       Magnitude
(hrs)           (s)
---------------------------------------------------
10.4           2880          r'           > 20.4
10.6           2880          i'           > 21.0
---------------------------------------------------
```
Calibration is done against R2 and I values of USNOB-1 nearby stars.
GCN Circular #18199
C. Guidorzi (U. Ferrara), S. Kobayashi (LJMU), A. Gomboc (U. Ljubljana), C. Mundell (U. Bath) on behalf of a larger collaboration report:
The 1-m LCOGT telescopes in Siding Springs (Australia) began observing Swift GRB 150821A (Troja et al. GCN 18186) on August 21, 10:22 UT (38 minutes after the burst trigger) with SDSS r and i filters under initially poor sky conditions. We detect the optical afterglow (Troja et al. GCN 18186; D'Elia et al. GCN 18187; Kuin et al. GCN 18192; Kruehler et al. GCN 18195) with the following magnitudes:
```
Mid Time      Exposure       Filter       Magnitude
(min)           (s)
-----------------------------------------------------
135           1680          r'           19.1 +- 0.4
233            480          r'           19.7 +- 0.3
398            720          r'           20.3 +- 0.2
-----------------------------------------------------
```
Calibration is done against R2 and I values of USNOB-1 nearby stars.
GCN Circular #18200
S. Golenetskii, R. Aptekar, D. Frederiks, V. Pal'shin, P. Oleynik, M. Ulanov, D. Svinkin, A. Tsvetkova, A. Lysenko, A. Kozlova, and T. Cline on behalf of the Konus-Wind team, report:
The long-duration GRB 150821A (Swift-BAT trigger #652847: Troja et al., GCN 18186; Stamatikos et al., GCN 18196; Fermi GBM detection: Roberts, GCN 18190) triggered Konus-Wind at T0=35074.166 s UT (09:44:34.166).
The burst light curve shows a single multi-peaked pulse which started at ~T0-1.4 s and had a total duration of ~161.6 s. The emission is seen up to ~10 MeV.
As observed by Konus-Wind, the burst had a fluence of 9.16(-2.22,+2.38)x10^-5 erg/cm2, and a 64-ms peak flux, measured from T0+4.768 s, of 3.68(-1.02,+1.27)x10^-6 erg/cm2/s (both in the 20 keV - 10 MeV energy range).
The time-averaged spectrum of the burst (measured from T0 to T0+164.096 s) is best fit in the 20 keV - 18 MeV range by the GRB (Band) model with the following parameters: the low-energy photon index alpha = -1.47 (-0.09,+0.15), the high energy photon index beta = -2.21 (-7.79,+0.29), the peak energy 350 (-125,+202) keV (chi2 = 129/97 dof)
The spectrum near the maximum count rate (measured from T0+0.256 to T0+8.448 s) is best fit in the 20 keV - 18 MeV range by the GRB (Band) model with the following parameters: the low-energy photon index alpha = -1.07 (-0.10,+0.15), the high energy photon index beta = -3.13 (-6.87,+0.80), the peak energy 327 (-66,+58) keV (chi2 = 91/91 dof)
The Konus-Wind light curve of this GRB is available at http://www.ioffe.ru/LEA/GRBs/GRB150821_T35074/ The background variations in the soft KW band are due to solar activity.
Assuming the redshift z=0.755 (D'Elia et al., GCN 18187) and a standard cosmology model with H_0 = 70 km/s/Mpc, Omega_M = 0.27, and Omega_Lambda = 0.73, we estimate the following rest-frame parameters: the isotropic energy release E_iso is ~1.4x10^53 erg, the peak luminosity L_iso is ~1.0x10^52 erg/s, and the rest-frame peak energy of the time-integrated spectrum, Ep,i, is ~614 keV.
All the quoted errors are at the 90% confidence level. All the quoted values are preliminary.
GCN Circular #18224
Paul Kuin, Massimiliano de Pasquale (UCL/MSSL), Daniele Malesani (DARK/NBI) and Peter Brown (TAMU) report on behalf of the Swift UVOT team:
The light curve from GRB 150821A as observed by Swift/UVOT has been monitored continuously since its discovery, up to about 300 ks in all seven filters, and in u, v and white since.
The GRB brightness decreased as a straight power law with index -1.32 (+0.06/-0.05) until about 10 ks. At 100 ks there was a clear flattening in the light curve, and around 250 ks a slight brightening may have taken place, but the brightness could also be flat within our observational errors. Data taken at 835 ks are consistent with a flat or slightly decreasing brightness.
The summed 5 ks image in the white band from 300 - 800 ks shows a nearby extended object to the north-west with white = 22.01 +/- 0.17 mag, slightly brighter than the GRB at about 10" distance which currently is at white=23.2 +/- 0.7 magnitudes, and is located about 5" from the edge of the nearby object.
At this time it is unclear whether the observed flattening is due to the host galaxy (hosts at this distance have typically a size of 1" only) or are the emergence of a supernova contribution to the afterglow. At the redshift of z = 0.755 (D'Elia et al., GCN Circ. 18187), the observed brightness would imply a SN significantly brighter than those typically associated with GRBs.
Further ground observations are encouraged.

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Jochen Greiner, last update: 01-Sep-2015 [Disclaimer]