Gamma-ray Burst 190821A

(All information courtesy of the instrument teams.)

Previous IAU Circulars

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Results of Observations

GCN/BACODINE POSITION NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Wed 21 Aug 19 17:10:31 UT
NOTICE_TYPE:     Swift-BAT GRB Position
TRIGGER_NUM:     921722,   Seg_Num: 0
GRB_RA:          250.077d {+16h 40m 18s} (J2000),
                 250.398d {+16h 41m 36s} (current),
                 249.260d {+16h 37m 03s} (1950)
GRB_DEC:         -34.022d {-34d 01' 16"} (J2000),
                 -34.058d {-34d 03' 29"} (current),
                 -33.925d {-33d 55' 28"} (1950)
GRB_ERROR:       3.00 [arcmin radius, statistical only]
GRB_INTEN:       3828 [cnts]    Image_Peak=191 [image_cnts]
TRIGGER_DUR:     1.408 [sec] 
TRIGGER_INDEX:   472     E_range: 25-100 keV
BKG_INTEN:       34066 [cnts]
BKG_TIME:        61776.55 SOD {17:09:36.55} UT
BKG_DUR:         16 [sec]
GRB_DATE:        18716 TJD;   233 DOY;   19/08/21
GRB_TIME:        61803.87 SOD {17:10:03.87} UT
GRB_PHI:         -122.75 [deg]
GRB_THETA:        22.26 [deg]
SOLN_STATUS:     0x3
RATE_SIGNIF:     11.26 [sigma]
IMAGE_SIGNIF:    8.80 [sigma]
MERIT_PARAMS:     +1  +0  +0  +0  +2  -1  +0  +1 +24  +0 
SUN_POSTN:       150.53d {+10h 02m 06s}  +12.04d {+12d 02' 25"}
SUN_DIST:        104.82 [deg]   Sun_angle= -6.7 [hr] (East of Sun)
MOON_POSTN:       35.66d {+02h 22m 38s}   +9.04d {+09d 02' 23"}
MOON_DIST:       139.49 [deg]
MOON_ILLUM:      69 [%]
GAL_COORDS:      347.70,  8.30 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:      253.23,-11.73 [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 = 80.29,-8.08 [deg].

red DSS finding chart ps-file

GCN NOTICE

TITLE:           GCN/FERMI NOTICE
NOTICE_DATE:     Wed 21 Aug 19 17:11:13 UT
NOTICE_TYPE:     Fermi-GBM Ground Position
RECORD_NUM:      57
TRIGGER_NUM:     588100239
GRB_RA:          248.570d {+16h 34m 17s} (J2000),
                 248.896d {+16h 35m 35s} (current),
                 247.742d {+16h 30m 58s} (1950)
GRB_DEC:         -35.990d {-35d 59' 23"} (J2000),
                 -36.030d {-36d 01' 46"} (current),
                 -35.886d {-35d 53' 10"} (1950)
GRB_ERROR:       11.80 [deg radius, statistical only]
DATA_SIGNIF:     5.10 [sigma]
DATA_INTERVAL:   4.096 [sec]
GRB_DATE:        18716 TJD;   233 DOY;   19/08/21
GRB_TIME:        61834.08 SOD {17:10:34.08} UT
GRB_PHI:         248.00 [deg]
GRB_THETA:        83.00 [deg]
E_RANGE:         44.032 - 279.965 [keV]
LOC_ALGORITHM:   4153 (Gnd S/W Version number)
SUN_POSTN:       150.53d {+10h 02m 06s}  +12.04d {+12d 02' 24"}
SUN_DIST:        103.76 [deg]   Sun_angle= -6.6 [hr] (East of Sun)
MOON_POSTN:       35.67d {+02h 22m 40s}   +9.04d {+09d 02' 31"}
MOON_DIST:       139.51 [deg]
MOON_ILLUM:      69 [%]
GAL_COORDS:      345.38,  7.92 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:      252.27,-13.86 [deg] ecliptic lon,lat of the burst (or transient)
LC_URL:          http://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2019/bn190821716/quicklook/glg_lc_medres34_bn190821716.gif
POS_MAP_URL:     http://gcn.gsfc.nasa.gov/notices_f/gbm_gnd_loc_map_588100239.fits
COMMENTS:        Fermi-GBM Ground-calculated Coordinates.  
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:        The POS_MAP_URL file will not be created/available until ~1.5 min after the notice.  
COMMENTS:           
COMMENTS:        NOTE: This GBM event is temporally(31.0<100sec) coincident with the SWIFT_BAT event (trignum=921722).

GCN NOTICE

TITLE:           GCN/FERMI NOTICE
NOTICE_DATE:     Wed 21 Aug 19 17:11:01 UT
NOTICE_TYPE:     Fermi-GBM Flight Position
RECORD_NUM:      44
TRIGGER_NUM:     588100239
GRB_RA:          245.233d {+16h 20m 56s} (J2000),
                 245.543d {+16h 22m 10s} (current),
                 244.446d {+16h 17m 47s} (1950)
GRB_DEC:         -30.350d {-30d 21' 00"} (J2000),
                 -30.396d {-30d 23' 43"} (current),
                 -30.232d {-30d 13' 53"} (1950)
GRB_ERROR:       30.70 [deg radius, statistical plus systematic]
GRB_INTEN:       53 [cnts/sec]
DATA_SIGNIF:     4.80 [sigma]
INTEG_TIME:      4.096 [sec]
GRB_DATE:        18716 TJD;   233 DOY;   19/08/21
GRB_TIME:        61834.08 SOD {17:10:34.08} UT
GRB_PHI:         254.00 [deg]
GRB_THETA:        85.00 [deg]
DATA_TIME_SCALE: 4.0960 [sec]
HARD_RATIO:      1.52
LOC_ALGORITHM:   3 (version number of)
MOST_LIKELY:      66%  GRB
2nd_MOST_LIKELY:  16%  SGR_1806n20
DETECTORS:       0,0,0, 0,0,0, 0,1,1, 0,0,0, 0,0,
SUN_POSTN:       150.53d {+10h 02m 06s}  +12.04d {+12d 02' 24"}
SUN_DIST:        100.33 [deg]   Sun_angle= -6.3 [hr] (East of Sun)
MOON_POSTN:       35.66d {+02h 22m 39s}   +9.04d {+09d 02' 29"}
MOON_DIST:       144.90 [deg]
MOON_ILLUM:      69 [%]
GAL_COORDS:      347.66, 13.80 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:      248.55, -8.74 [deg] ecliptic lon,lat of the burst (or transient)
LC_URL:          http://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2019/bn190821716/quicklook/glg_lc_medres34_bn190821716.gif
COMMENTS:        Fermi-GBM Flight-calculated Coordinates.  
COMMENTS:        This trigger occurred at longitude,latitude = 291.63,4.35 [deg].  
COMMENTS:        The LC_URL file will not be created until ~15 min after the trigger.  
COMMENTS:           
COMMENTS:        NOTE: This GBM event is temporally(31.0<100sec) coincident with the SWIFT_BAT event (trignum=921722).

GCN NOTICE

TITLE:           GCN/FERMI NOTICE
NOTICE_DATE:     Wed 21 Aug 19 17:12:20 UT
NOTICE_TYPE:     Fermi-GBM Ground Position
RECORD_NUM:      0
TRIGGER_NUM:     588100239
GRB_RA:          253.990d {+16h 55m 58s} (J2000),
                 254.326d {+16h 57m 18s} (current),
                 253.136d {+16h 52m 33s} (1950)
GRB_DEC:         -38.620d {-38d 37' 11"} (J2000),
                 -38.650d {-38d 38' 58"} (current),
                 -38.541d {-38d 32' 27"} (1950)
GRB_ERROR:       7.21 [deg radius, statistical only]
DATA_SIGNIF:     9.60 [sigma]
DATA_INTERVAL:   5.120 [sec]
GRB_DATE:        18716 TJD;   233 DOY;   19/08/21
GRB_TIME:        61834.08 SOD {17:10:34.08} UT
GRB_PHI:         243.00 [deg]
GRB_THETA:        84.00 [deg]
E_RANGE:         44.032 - 279.965 [keV]
LOC_ALGORITHM:   41531 (Gnd S/W Version number)
SUN_POSTN:       150.53d {+10h 02m 07s}  +12.04d {+12d 02' 23"}
SUN_DIST:        108.21 [deg]   Sun_angle= -6.9 [hr] (East of Sun)
MOON_POSTN:       35.67d {+02h 22m 42s}   +9.05d {+09d 02' 43"}
MOON_DIST:       134.47 [deg]
MOON_ILLUM:      69 [%]
GAL_COORDS:      346.18,  2.93 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:      257.05,-15.90 [deg] ecliptic lon,lat of the burst (or transient)
LC_URL:          http://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2019/bn190821716/quicklook/glg_lc_medres34_bn190821716.gif
POS_MAP_URL:     http://gcn.gsfc.nasa.gov/notices_f/gbm_gnd_loc_map_588100239.fits
COMMENTS:        Fermi-GBM Ground-calculated Coordinates.  
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:        The POS_MAP_URL file will not be created/available until ~1.5 min after the notice.  
COMMENTS:           
COMMENTS:        NOTE: This GBM event is temporally(31.0<100sec) coincident with the SWIFT_BAT event (trignum=921722).

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Wed 21 Aug 19 17:12:06 UT
NOTICE_TYPE:     Swift-XRT Processed Image
TRIGGER_NUM:     921722,   Seg_Num: 0
GRB_RA:          250.0555d {+16h 40m 13.3s} (J2000),
                 250.3766d {+16h 41m 30.3s} (current),
                 249.2392d {+16h 36m 57.4s} (1950)
GRB_DEC:         -34.0073d {-34d 00' 26.2"} (J2000),
                 -34.0443d {-34d 02' 39.4"} (current),
                 -33.9105d {-33d 54' 37.6"} (1950)
GRB_ERROR:       4.7 [arcsec, radius, statistical plus systematic]
GRB_INTEN:       118 [cnts]
IMG_START_DATE:  18716 TJD;   233 DOY;   19/08/21
IMG_START_TIME:  61881.84 SOD {17:11:21.84} UT,   78.0 [sec] since BAT Trigger Time
CENTROID_X:      245.00,  raw= 245  [pixels]
CENTROID_Y:      290.47,  raw= 290  [pixels]
ROLL:            274.86 [deg]
GAIN:            1
MODE:            3, Long Image mode
WAVEFORM:        134
EXPO_TIME:       2.50 [sec]
GRB_POS_XRT_Y:   -17.98
GRB_POS_XRT_Z:   -147.09
IMAGE_URL:       sw00921722000msxps_rw.img
SUN_POSTN:       150.53d {+10h 02m 06s}  +12.04d {+12d 02' 23"}
SUN_DIST:        104.80 [deg]   Sun_angle= -6.7 [hr] (East of Sun)
MOON_POSTN:       35.67d {+02h 22m 42s}   +9.04d {+09d 02' 40"}
MOON_DIST:       139.53 [deg]
MOON_ILLUM:      69 [%]
GAL_COORDS:      347.70,  8.32 [deg] galactic lon,lat of the burst
ECL_COORDS:      253.21,-11.72 [deg] ecliptic lon,lat of the burst
COMMENTS:        SWIFT-XRT Processed Image.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Wed 21 Aug 19 17:11:48 UT
NOTICE_TYPE:     Swift-XRT Position
TRIGGER_NUM:     921722,   Seg_Num: 0
GRB_RA:          250.0555d {+16h 40m 13.31s} (J2000),
                 250.3766d {+16h 41m 30.37s} (current),
                 249.2392d {+16h 36m 57.40s} (1950)
GRB_DEC:         -34.0073d {-34d 00' 26.2"} (J2000),
                 -34.0443d {-34d 02' 39.4"} (current),
                 -33.9105d {-33d 54' 37.6"} (1950)
GRB_ERROR:       5.0 [arcsec radius, statistical plus systematic, 90% containment]
GRB_INTEN:       2.95e-09 [erg/cm2/sec]
GRB_SIGNIF:      10.86 [sigma]
IMG_START_DATE:  18716 TJD;   233 DOY;   19/08/21
IMG_START_TIME:  61881.84 SOD {17:11:21.84} UT,   78.0 [sec] since BAT Trigger Time
TAM[0-3]:        327.66 237.18 261.65 243.61
AMPLIFIER:       2
WAVEFORM:        134
SUN_POSTN:       150.53d {+10h 02m 06s}  +12.04d {+12d 02' 24"}
SUN_DIST:        104.80 [deg]   Sun_angle= -6.7 [hr] (East of Sun)
MOON_POSTN:       35.67d {+02h 22m 41s}   +9.04d {+09d 02' 37"}
MOON_DIST:       139.53 [deg]
MOON_ILLUM:      69 [%]
GAL_COORDS:      347.70,  8.32 [deg] galactic lon,lat of the burst
ECL_COORDS:      253.21,-11.72 [deg] ecliptic lon,lat of the burst
COMMENTS:        SWIFT-XRT Coordinates.  
COMMENTS:        The XRT position is 1.36 arcmin from the BAT position.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Wed 21 Aug 19 17:14:01 UT
NOTICE_TYPE:     Swift-BAT GRB Lightcurve
TRIGGER_NUM:     921722,   Seg_Num: 0
GRB_RA:          250.077d {+16h 40m 18s} (J2000),
                 250.398d {+16h 41m 36s} (current),
                 249.260d {+16h 37m 03s} (1950)
GRB_DEC:         -34.022d {-34d 01' 16"} (J2000),
                 -34.058d {-34d 03' 29"} (current),
                 -33.925d {-33d 55' 28"} (1950)
GRB_DATE:        18716 TJD;   233 DOY;   19/08/21
GRB_TIME:        61803.87 SOD {17:10:03.87} UT
TRIGGER_INDEX:   472
GRB_PHI:         -122.75 [deg]
GRB_THETA:        22.26 [deg]
DELTA_TIME:      -11.00 [sec]
TRIGGER_DUR:     1.408 [sec] 
SOLN_STATUS:     0x3
RATE_SIGNIF:     11.26 [sigma]
IMAGE_SIGNIF:    8.80 [sigma]
LC_URL:          sw00921722000msb.lc
SUN_POSTN:       150.53d {+10h 02m 07s}  +12.04d {+12d 02' 22"}
SUN_DIST:        104.81 [deg]   Sun_angle= -6.7 [hr] (East of Sun)
MOON_POSTN:       35.69d {+02h 22m 45s}   +9.05d {+09d 03' 01"}
MOON_DIST:       139.52 [deg]
MOON_ILLUM:      69 [%]
GAL_COORDS:      347.70,  8.30 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:      253.23,-11.73 [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 = 80.29,-8.08 [deg].

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Wed 21 Aug 19 17:12:04 UT
NOTICE_TYPE:     Swift-XRT Image
TRIGGER_NUM:     921722,   Seg_Num: 0
GRB_RA:          250.0555d {+16h 40m 13.3s} (J2000),
                 250.3766d {+16h 41m 30.3s} (current),
                 249.2392d {+16h 36m 57.4s} (1950)
GRB_DEC:         -34.0073d {-34d 00' 26.2"} (J2000),
                 -34.0443d {-34d 02' 39.4"} (current),
                 -33.9105d {-33d 54' 37.6"} (1950)
GRB_ERROR:       4.7 [arcsec, radius, statistical plus systematic]
GRB_INTEN:       118 [cnts]
IMG_START_DATE:  18716 TJD;   233 DOY;   19/08/21
IMG_START_TIME:  61881.84 SOD {17:11:21.84} UT,   78.0 [sec] since BAT Trigger Time
CENTROID_X:      245.00,  raw= 245  [pixels]
CENTROID_Y:      290.47,  raw= 290  [pixels]
ROLL:            274.86 [deg]
GAIN:            1
MODE:            3, Long Image mode
WAVEFORM:        134
EXPO_TIME:       2.50 [sec]
GRB_POS_XRT_Y:   -17.98
GRB_POS_XRT_Z:   -147.09
IMAGE_URL:       sw00921722000msxps_rw.img
SUN_POSTN:       150.53d {+10h 02m 06s}  +12.04d {+12d 02' 23"}
SUN_DIST:        104.80 [deg]   Sun_angle= -6.7 [hr] (East of Sun)
MOON_POSTN:       35.67d {+02h 22m 41s}   +9.04d {+09d 02' 40"}
MOON_DIST:       139.53 [deg]
MOON_ILLUM:      69 [%]
GAL_COORDS:      347.70,  8.32 [deg] galactic lon,lat of the burst
ECL_COORDS:      253.21,-11.72 [deg] ecliptic lon,lat of the burst
COMMENTS:        SWIFT-XRT Image.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Wed 21 Aug 19 17:17:25 UT
NOTICE_TYPE:     Swift-UVOT Image
TRIGGER_NUM:     921722,   Seg_Num: 0
POINT_RA:        250.104d {+16h 40m 25s} (J2000)
POINT_DEC:       -34.016d {-34d 00' 58"} (J2000)
ROLL:            274.857d
IMG_START_DATE:  18716 TJD;   233 DOY;   19/08/21
IMG_START_TIME:  61892.17 SOD {17:11:32.17} UT,   88.3 [sec] since BAT Trigger Time
FILTER:          10, White
EXPOSURE_ID:     588100315
X_OFFSET:        1081 [pixels]
Y_OFFSET:        750 [pixels]
WIDTH:           160 [pixels]
HEIGHT:          160 [pixels]
X_GRB_POS:       1241
Y_GRB_POS:       910
BINNING_INDEX:   1
IM_URL:          sw00921722000msuni0112.fits
SUN_POSTN:       150.53d {+10h 02m 07s}  +12.04d {+12d 02' 19"}
SUN_DIST:        104.83 [deg]   Sun_angle= -6.7 [hr] (East of Sun)
MOON_POSTN:       35.72d {+02h 22m 52s}   +9.06d {+09d 03' 38"}
MOON_DIST:       139.53 [deg]
MOON_ILLUM:      69 [%]
GAL_COORDS:      347.71,  8.28 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      253.26,-11.73 [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:     Wed 21 Aug 19 17:15:17 UT
NOTICE_TYPE:     Swift-UVOT Source List
TRIGGER_NUM:     921722,   Seg_Num: 0
POINT_RA:        250.104d {+16h 40m 25s} (J2000)
POINT_DEC:       -34.016d {-34d 00' 58"} (J2000)
POINT_ROLL:      274.857d
IMG_START_DATE:  18716 TJD;   233 DOY;   19/08/21
IMG_START_TIME:  61892.17 SOD {17:11:32.17} UT,   88.3 [sec] since BAT Trigger Time
FILTER:          10, White
BKG_MEAN:        4.325
N_STARS:         190
X_OFFSET:        761 [pixels]
Y_OFFSET:        430 [pixels]
X_MAX:           1720 [pixels]
Y_MAX:           1389 [pixels]
DET_THRESH:      17
PHOTO_THRESH:    10
SL_URL:          sw00921722000msufc0088.fits
SUN_POSTN:       150.53d {+10h 02m 07s}  +12.04d {+12d 02' 21"}
SUN_DIST:        104.84 [deg]   Sun_angle= -6.7 [hr] (East of Sun)
MOON_POSTN:       35.70d {+02h 22m 48s}   +9.05d {+09d 03' 15"}
MOON_DIST:       139.52 [deg]
MOON_ILLUM:      69 [%]
GAL_COORDS:      347.71,  8.28 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      253.26,-11.73 [deg] ecliptic lon,lat of the pointing direction
COMMENTS:        SWIFT-UVOT Source List.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Wed 21 Aug 19 17:17:43 UT
NOTICE_TYPE:     Swift-UVOT Processed Image
TRIGGER_NUM:     921722,   Seg_Num: 0
POINT_RA:        250.104d {+16h 40m 25s} (J2000)
POINT_DEC:       -34.016d {-34d 00' 58"} (J2000)
ROLL:            274.857d
IMG_START_DATE:  18716 TJD;   233 DOY;   19/08/21
IMG_START_TIME:  61892.17 SOD {17:11:32.17} UT,   88.3 [sec] since BAT Trigger Time
FILTER:          10, White
EXPOSURE_ID:     588100315
X_OFFSET:        1081 [pixels]
Y_OFFSET:        750 [pixels]
WIDTH:           160 [pixels]
HEIGHT:          160 [pixels]
X_GRB_POS:       1241
Y_GRB_POS:       910
BINNING_INDEX:   1
IM_URL:          sw00921722000msuni0112.fits
SUN_POSTN:       150.53d {+10h 02m 07s}  +12.04d {+12d 02' 19"}
SUN_DIST:        104.83 [deg]   Sun_angle= -6.7 [hr] (East of Sun)
MOON_POSTN:       35.72d {+02h 22m 52s}   +9.06d {+09d 03' 41"}
MOON_DIST:       139.53 [deg]
MOON_ILLUM:      69 [%]
GAL_COORDS:      347.71,  8.28 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      253.26,-11.73 [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:     Wed 21 Aug 19 17:22:32 UT
NOTICE_TYPE:     Swift-UVOT Source List
TRIGGER_NUM:     921722,   Seg_Num: 0
POINT_RA:        250.107d {+16h 40m 26s} (J2000)
POINT_DEC:       -34.015d {-34d 00' 52"} (J2000)
POINT_ROLL:      274.856d
IMG_START_DATE:  18716 TJD;   233 DOY;   19/08/21
IMG_START_TIME:  62105.79 SOD {17:15:05.79} UT,   301.9 [sec] since BAT Trigger Time
FILTER:          7, U
BKG_MEAN:        0.675
N_STARS:         91
X_OFFSET:        761 [pixels]
Y_OFFSET:        430 [pixels]
X_MAX:           1720 [pixels]
Y_MAX:           1389 [pixels]
DET_THRESH:      7
PHOTO_THRESH:    3
SL_URL:          sw00921722000msufc0301.fits
SUN_POSTN:       150.53d {+10h 02m 08s}  +12.04d {+12d 02' 15"}
SUN_DIST:        104.83 [deg]   Sun_angle= -6.7 [hr] (East of Sun)
MOON_POSTN:       35.76d {+02h 23m 02s}   +9.08d {+09d 04' 33"}
MOON_DIST:       139.57 [deg]
MOON_ILLUM:      69 [%]
GAL_COORDS:      347.72,  8.28 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      253.26,-11.72 [deg] ecliptic lon,lat of the pointing direction
COMMENTS:        SWIFT-UVOT Source List.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Wed 21 Aug 19 17:22:49 UT
NOTICE_TYPE:     Swift-UVOT Processed Source List
TRIGGER_NUM:     921722,   Seg_Num: 0
POINT_RA:        250.107d {+16h 40m 26s} (J2000)
POINT_DEC:       -34.015d {-34d 00' 52"} (J2000)
POINT_ROLL:      274.856d
IMG_START_DATE:  18716 TJD;   233 DOY;   19/08/21
IMG_START_TIME:  62105.79 SOD {17:15:05.79} UT,   301.9 [sec] since BAT Trigger Time
FILTER:          7, U
BKG_MEAN:        0.675
N_STARS:         91
X_OFFSET:        761 [pixels]
Y_OFFSET:        430 [pixels]
X_MAX:           1720 [pixels]
Y_MAX:           1389 [pixels]
DET_THRESH:      7
PHOTO_THRESH:    3
SL_URL:          sw00921722000msufc0301.fits
SUN_POSTN:       150.53d {+10h 02m 08s}  +12.04d {+12d 02' 14"}
SUN_DIST:        104.83 [deg]   Sun_angle= -6.7 [hr] (East of Sun)
MOON_POSTN:       35.76d {+02h 23m 02s}   +9.08d {+09d 04' 36"}
MOON_DIST:       139.57 [deg]
MOON_ILLUM:      69 [%]
GAL_COORDS:      347.72,  8.28 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      253.26,-11.72 [deg] ecliptic lon,lat of the pointing direction
COMMENTS:        SWIFT-UVOT Processed Source List.  
COMMENTS:        All 4 attachments are included.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Wed 21 Aug 19 17:24:15 UT
NOTICE_TYPE:     Swift-UVOT Processed Image
TRIGGER_NUM:     921722,   Seg_Num: 0
POINT_RA:        250.107d {+16h 40m 26s} (J2000)
POINT_DEC:       -34.015d {-34d 00' 52"} (J2000)
ROLL:            274.856d
IMG_START_DATE:  18716 TJD;   233 DOY;   19/08/21
IMG_START_TIME:  62105.79 SOD {17:15:05.79} UT,   301.9 [sec] since BAT Trigger Time
FILTER:          7, U
EXPOSURE_ID:     588100529
X_OFFSET:        1081 [pixels]
Y_OFFSET:        750 [pixels]
WIDTH:           160 [pixels]
HEIGHT:          160 [pixels]
X_GRB_POS:       1241
Y_GRB_POS:       910
BINNING_INDEX:   1
IM_URL:          sw00921722000msuni0325.fits
SUN_POSTN:       150.53d {+10h 02m 08s}  +12.04d {+12d 02' 13"}
SUN_DIST:        104.83 [deg]   Sun_angle= -6.7 [hr] (East of Sun)
MOON_POSTN:       35.77d {+02h 23m 05s}   +9.08d {+09d 04' 51"}
MOON_DIST:       139.58 [deg]
MOON_ILLUM:      69 [%]
GAL_COORDS:      347.72,  8.28 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      253.26,-11.72 [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:     Wed 21 Aug 19 17:24:00 UT
NOTICE_TYPE:     Swift-UVOT Image
TRIGGER_NUM:     921722,   Seg_Num: 0
POINT_RA:        250.107d {+16h 40m 26s} (J2000)
POINT_DEC:       -34.015d {-34d 00' 52"} (J2000)
ROLL:            274.856d
IMG_START_DATE:  18716 TJD;   233 DOY;   19/08/21
IMG_START_TIME:  62105.79 SOD {17:15:05.79} UT,   301.9 [sec] since BAT Trigger Time
FILTER:          7, U
EXPOSURE_ID:     588100529
X_OFFSET:        1081 [pixels]
Y_OFFSET:        750 [pixels]
WIDTH:           160 [pixels]
HEIGHT:          160 [pixels]
X_GRB_POS:       1241
Y_GRB_POS:       910
BINNING_INDEX:   1
IM_URL:          sw00921722000msuni0325.fits
SUN_POSTN:       150.53d {+10h 02m 08s}  +12.04d {+12d 02' 13"}
SUN_DIST:        104.83 [deg]   Sun_angle= -6.7 [hr] (East of Sun)
MOON_POSTN:       35.77d {+02h 23m 04s}   +9.08d {+09d 04' 48"}
MOON_DIST:       139.58 [deg]
MOON_ILLUM:      69 [%]
GAL_COORDS:      347.72,  8.28 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      253.26,-11.72 [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 Circular #25427
A. D'Ai (INAF-IASFPA), E. Ambrosi (INAF-IASFPA), V. D'Elia (SSDC), J.D. Gropp (PSU), J. A. Kennea (PSU), N. J. Klingler (PSU), H. A. Krimm (NSF), S. J. LaPorte (PSU), A. Y. Lien (GSFC/UMBC), F. E. Marshall (NASA/GSFC), M. J. Moss (GWU), K. L. Page (U Leicester), D. M. Palmer (LANL), B. Sbarufatti (PSU), K. K. Simpson (PSU) and A. Tohuvavohu (PSU) report on behalf of the Neil Gehrels Swift Observatory Team:
At 17:10:03 UT, the Swift Burst Alert Telescope (BAT) triggered and located GRB 190821A (trigger=921722). Swift slewed immediately to the burst. The BAT on-board calculated location is RA, Dec 250.077, -34.022 which is
```
   RA(J2000) = 16h 40m 18s
   Dec(J2000) = -34d 01' 16"
```
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 100 sec. The peak count rate was ~2200 counts/sec (15-350 keV), at ~30 sec after the trigger.
The XRT began observing the field at 17:11:21.8 UT, 78.0 seconds after the BAT trigger. Using promptly downlinked data we find a bright, uncatalogued X-ray source located at RA, Dec 250.05464, -34.00719 which is equivalent to:
```
   RA(J2000)  = 16h 40m 13.11s
   Dec(J2000) = -34d 00' 25.9"
```
with an uncertainty of 3.6 arcseconds (radius, 90% containment). This location is 85 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 (3.35 x 10^21 cm^-2, Willingale et al. 2013), with an excess column of 3.2 (+2.68/-2.37) x 10^21 cm^-2 (90% confidence).
The initial flux in the 2.5 s image was 2.95e-09 erg cm^-2 s^-1 (0.2-10 keV).
UVOT took a finding chart exposure of 150 seconds with the White filter starting 88 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. Because of the density of catalogued stars, further analysis is required to report an upper limit for any afterglow in the sub-image. The 8'x8' region for the list of sources generated on-board covers 100% of the XRT error circle. Because of the density of catalogued stars, further analysis is required to report an upper limit for any afterglow in the region. No correction has been made for the expected extinction corresponding to E(B-V) of 0.54.
Burst Advocate for this burst is A. D'Ai (antonino.dai AT inaf.it). 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/)
GCN Circular #25428
V. Lipunov, E. Gorbovskoy, V.Kornilov, N.Tyurina, P.Balanutsa, A.Kuznetsov, F.Balakin, V.Vladimirov, D. Vlasenko, I.Gorbunov, D.Zimnukhov, V.Senik, T.Pogrosheva, D.Kuvshinov (Lomonosov Moscow State University, SAI, Physics Department),
R. Podesta, C.Lopez, F. Podesta, C.Francile (Observatorio Astronomico Felix Aguilar OAFA),
H.Levato (Instituto de Ciencias Astronomicas, de la Tierra y del Espacio ICATE),
R. Rebolo, M. Serra (The Instituto de Astrofisica de Canarias),
D. Buckley (South African Astronomical Observatory),
O.A. Gres, N.M. Budnev, O.Ershova (Irkutsk State University, API),
A. Tlatov, D. Dormidontov (Kislovodsk Solar Station of the Pulkovo Observatory),
V. Yurkov, A. Gabovich, Yu. Sergienko (Blagoveschensk Educational State University)
MASTER-SAAO robotic telescope (Global MASTER-Net: http://observ.pereplet.ru, Lipunov et al., 2010, Advances in Astronomy, vol. 2010, 30L) located in South Africa (South African Astronomical Observatory) started inspect of the Fermi GRB190821.72 (trigger No 588100239, 16h 55m 57.60s , -38d 37m 12.00s, R=7.21) errorbox 10 sec after trigger time at 2019-08-21 17:10:44 UT, with upper limit up to 17.3 mag. Observations started at twilight. The observations began at zenit distance = 3 deg. The sun altitude is -12.4 deg.
The galactic latitude b = -60 deg., longitude l = 98 deg.
Real time updated cover map and OT discovered available here: https://master.sai.msu.ru/site/master2/observ.php?id=1111565
We obtain a following upper limits.
```
Tmid-T0  |      Date Time      |          Site       |             Coord (J2000)          |Filt.| Expt. | Limit| Comment
_________|_____________________|_____________________|____________________________________|_____|_______|_______|________

      15 | 2019-08-21 17:10:44 |         MASTER-SAAO | ( 16h 41m 19.25s , -33d 57m 12.76s) |  P\ |    10 | 16.3 |        
      42 | 2019-08-21 17:11:10 |         MASTER-SAAO | ( 16h 40m 18.01s , -33d 57m 11.66s) |  P\ |    10 | 16.4 |        
      67 | 2019-08-21 17:11:10 |         MASTER-SAAO | ( 16h 40m 18.01s , -33d 57m 11.62s) |  P\ |    60 | 17.3 |  Coadd 
      73 | 2019-08-21 17:11:36 |         MASTER-SAAO | ( 16h 40m 18.03s , -33d 57m 11.45s) |  P\ |    20 | 16.9 |        
```
The observation and reduction will continue. The message may be cited.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Wed 21 Aug 19 17:33:44 UT
NOTICE_TYPE:     Swift-XRT Position UPDATE
TRIGGER_NUM:     921722,   Seg_Num: 0
GRB_RA:          250.0546d {+16h 40m 13.10s} (J2000),
                 250.3757d {+16h 41m 30.15s} (current),
                 249.2383d {+16h 36m 57.19s} (1950)
GRB_DEC:         -34.0071d {-34d 00' 25.5"} (J2000),
                 -34.0441d {-34d 02' 38.7"} (current),
                 -33.9103d {-33d 54' 36.9"} (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:  18716 TJD;   233 DOY;   19/08/21
IMG_START_TIME:  61922.00 SOD {17:12:02.00} UT,   118.1 [sec] since BAT Trigger Time
TAM[0-3]:        100.00 100.00 100.00 100.00
AMPLIFIER:       1
WAVEFORM:        31
SUN_POSTN:       150.54d {+10h 02m 10s}  +12.03d {+12d 02' 05"}
SUN_DIST:        104.78 [deg]   Sun_angle= -6.7 [hr] (East of Sun)
MOON_POSTN:       35.85d {+02h 23m 23s}   +9.11d {+09d 06' 33"}
MOON_DIST:       139.70 [deg]
MOON_ILLUM:      69 [%]
GAL_COORDS:      347.69,  8.32 [deg] galactic lon,lat of the burst
ECL_COORDS:      253.21,-11.72 [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:        The probability that this is a serendipitous source in the  
COMMENTS:        SPER window is 0.58% < P(seren) < 1.1%.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Wed 21 Aug 19 17:15:37 UT
NOTICE_TYPE:     Swift-UVOT Processed Source List
TRIGGER_NUM:     921722,   Seg_Num: 0
POINT_RA:        250.104d {+16h 40m 25s} (J2000)
POINT_DEC:       -34.016d {-34d 00' 58"} (J2000)
POINT_ROLL:      274.857d
IMG_START_DATE:  18716 TJD;   233 DOY;   19/08/21
IMG_START_TIME:  61892.17 SOD {17:11:32.17} UT,   88.3 [sec] since BAT Trigger Time
FILTER:          10, White
BKG_MEAN:        4.325
N_STARS:         190
X_OFFSET:        761 [pixels]
Y_OFFSET:        430 [pixels]
X_MAX:           1720 [pixels]
Y_MAX:           1389 [pixels]
DET_THRESH:      17
PHOTO_THRESH:    10
SL_URL:          sw00921722000msufc0088.fits
SUN_POSTN:       150.53d {+10h 02m 07s}  +12.04d {+12d 02' 20"}
SUN_DIST:        104.84 [deg]   Sun_angle= -6.7 [hr] (East of Sun)
MOON_POSTN:       35.70d {+02h 22m 48s}   +9.06d {+09d 03' 18"}
MOON_DIST:       139.52 [deg]
MOON_ILLUM:      69 [%]
GAL_COORDS:      347.71,  8.28 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      253.26,-11.73 [deg] ecliptic lon,lat of the pointing direction
COMMENTS:        SWIFT-UVOT Processed Source List.  
COMMENTS:        All 4 attachments are included.

GCN Circular #25431
Klotz A., Noysena.K., Atteia J.L. (CNRS-OMP-IRAP), Boer, M., Eymar, L. (CNRS-ARTEMIS), Gendre B. (UWA - Univ. Western Australia) Peyrot, A., Teng J.P., Thierry P. (Les Makes observatory) report:
We imaged the field of GRB 190821A detected by SWIFT (trigger 921722) with the T60 tele-operated telescope (D=60cm) located at Les Makes Observatory, Reunion Island, France.
The observations started 790s after the GRB trigger. On the first image of 120s (Clear filter) we detect the optical afterglow compatible with the position of XRT (Lien et al. GCNC 25427).
```
start� end��� R
(sec) (sec)
790�� 910�� 18.4 +/- 0.2
```
Further images are comming.
Magnitudes were estimated with the nearby NOMAD1 stars and are not corrected for galactic dust extinction.
GCN Circular #25433
V. Lipunov, F.Balakin, E. Gorbovskoy, V. Kornilov, N.Tyurina, P.Balanutsa,A.Kuznetsov, F.Balakin, V. Vladimirov, D. Vlasenko, I. Gorbunov,D.Zimnukhov, V.Senik, A.Chasovnikov, A.Pozdnyakov, A.Chasovnikov, V.Topolev, D.Kuvshinov(Lomonosov Moscow State University, SAI, Physics Department), R. Rebolo, M. Serra (The Instituto de Astrofisica de Canarias IAC), R. Podesta, C.Lopez, F. Podesta, C.Francile (Observatorio Astronomico Felix Aguilar OAFA), H. Levato (Instituto de Ciencias Astronomicas, de la Tierra y del Espacio ICATE), D. Buckley (South African Astronomical Observatory SAAO), O. Gress, N.M. Budnev, O.Ershova (Irkutsk State University, API), A. Tlatov, D. Dormidontov (Kislovodsk Solar Station of the Pulkovo Observatory), V. Yurkov, A. Gabovich, Yu. Sergienko (Blagoveschensk Educational State University)
There is known star at Swift XRT position (GCN 25427, GCN 25431). Its brightnes not changes during 1 hour, after 41 sec after trigger in MASTER images (GCN 25429). This message may be cited.
GCN Circular #25435
B. Mailyan, S. Lesage and C. Meegan (all UAH) report on behalf of the Fermi GBM Team:
"At 17:10:34.08 UT on 21 August 2019, the Fermi Gamma-Ray Burst Monitor triggered and located GRB 190821A (trigger 588100239/ 190821716), which was also detected by the Swift/BAT (D'Ai et al. 2019, GCN 25427). The GBM on-ground location is consistent with the Swift position.
The angle from the Fermi LAT boresight at the GBM trigger time is 85 degrees.
The GBM lightcurve shows an initial bright pulse followed by longer duration emission containing multiple peaks. with a duration (T90) of about 60 s (50-300 keV). The time-averaged spectrum from T0-4 s to T0+34 s is best fit by a power law function with an exponential high-energy cutoff. The power law index is -1.7 +/- 0.15 and the cutoff energy, parameterized as Epeak, is 29 +/- 6 keV.
The event fluence (10-1000 keV) in this time interval is (2.54 +/- 0.17)E-06 erg/cm^2. The 1-sec peak photon flux measured starting from T-0.128 s in the 10-1000 keV band is 4.9 +/- 0.25 ph/s/cm^2.
The spectral analysis results presented above are preliminary; final results will be published in the GBM GRB Catalog: https://heasarc.gsfc.nasa.gov/W3Browse/fermi/fermigbrst.html
For Fermi GBM data and info, please visit the official Fermi GBM Support Page: https://fermi.gsfc.nasa.gov/ssc/data/access/gbm/"
GCN Circular #25436
M.R. Goad, J.P. Osborne, A.P. Beardmore and P.A. Evans (U. Leicester) report on behalf of the Swift-XRT team.
Using 1074 s of XRT Photon Counting mode data and 3 UVOT images for GRB 190821A, 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 = 250.05481, -34.00711 which is equivalent to:
```
RA (J2000): 16h 40m 13.15s
Dec (J2000): -34d 00' 25.6"
```
with an uncertainty of 1.6 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 #25444
J. D. Gropp (PSU), A. Tohuvavohu (PSU), J.A. Kennea (PSU), J.P. Osborne (U. Leicester), K.L. Page (U. Leicester), A.P. Beardmore (U. Leicester), A. Melandri (INAF-OAB), P. D'Avanzo (INAF-OAB), M.G. Bernardini (INAF-OAB) and A. D'Ai report on behalf of the Swift-XRT team:
We have analysed 6.7 ks of XRT data for GRB 190821A (D'Ai et al. GCN Circ. 25427), from 84 s to 33.9 ks after the BAT trigger. The data comprise 290 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. 25436).
The light curve can be modelled with a series of power-law decays. The initial decay index is alpha=7.82 (+0.18, -0.87). At T+140 s the decay flattens to an alpha of -0.4 (+/-0.5) before breaking again at T+1047 s to a final decay with index alpha=1.06 (+0.17, -0.16).
A spectrum formed from the PC mode data can be fitted with an absorbed power-law with a photon spectral index of 1.75 (+0.18, -0.11). The best-fitting absorption column is consistent with the Galactic value of 3.3 x 10^21 cm^-2 (Willingale et al. 2013). The counts to observed (unabsorbed) 0.3-10 keV flux conversion factor deduced from this spectrum is 4.4 x 10^-11 (5.9 x 10^-11) erg cm^-2 count^-1.
A summary of the PC-mode spectrum is thus:
```
Total column:	     3.3 (+/-1.0) x 10^21 cm^-2
Galactic foreground: 3.3 x 10^21 cm^-2
Excess significance: <1.6 sigma
Photon index:	     1.75 (+0.18, -0.11)
```
If the light curve continues to decay with a power-law decay index of 1.06, the count rate at T+24 hours will be 0.015 count s^-1, corresponding to an observed (unabsorbed) 0.3-10 keV flux of 6.8 x 10^-13 (9.0 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/00921722.
This circular is an official product of the Swift-XRT team.
GCN Circular #25448
F.Balakin, V. Lipunov, E. Gorbovskoy, V. Kornilov, N.Tyurina, P.Balanutsa,A.Kuznetsov, F.Balakin, V. Vladimirov, D. Vlasenko, I. Gorbunov,D.Zimnukhov, V.Senik, A.Chasovnikov, A.Pozdnyakov, A.Chasovnikov, V.Topolev, D.Kuvshinov(Lomonosov Moscow State University, SAI, Physics Department), R. Rebolo, M. Serra (The Instituto de Astrofisica de Canarias IAC), R. Podesta, C.Lopez, F. Podesta, C.Francile (Observatorio Astronomico Felix Aguilar OAFA), H. Levato (Instituto de Ciencias Astronomicas, de la Tierra y del Espacio ICATE), D. Buckley (South African Astronomical Observatory SAAO), O. Gress, N.M. Budnev, O.Ershova (Irkutsk State University, API), A. Tlatov, D. Dormidontov (Kislovodsk Solar Station of the Pulkovo Observatory), V. Yurkov, A. Gabovich, Yu. Sergienko (Blagoveschensk Educational State University)
MASTER-SAAO very wide field cameras (d=82 mm, FOV = 2x384 sq. degree) syncronously observed GRB190821A (D'Ai et al. GCN 25427) position before, during and after trigger time. We do not see OT at Swift XRT (Gropp et al. GCN 25444) position up to 12 mag. The synchronous observation movie is avalable here:
http://master.sai.msu.ru/static/MASTER_SAAO_GRB190822A.gif
MASTER-SAAO robotic telescope (Global MASTER-Net: http://observ.pereplet.ru, Lipunov et al., 2010, Advances in Astronomy, vol. 2010, 30L) located in South Africa (South African Astronomical Observatory) was pointed to the Swift GRB190821A errorbox 8 sec after notice time and 41 sec after trigger time at 2019-08-21 17:10:44 UT, with upper limit up to 18.4 mag (Lipunov et al. GCN 25429; GCN 25433). Observations started at twilight. We alse do not see OT at Swift XRT. The observations began at zenit distance = 3 deg. The sun altitude is -12.4 deg.
Real time updated cover map and OT discovered available here: https://master.sai.msu.ru/site/master2/observ.php?id=1111516
This message may be cited.
GCN Circular #25450
GRB 190821A: Swift/UVOT Upper Limits
K. K. Simpson (PSU) and A. D'Ai (INAF-IASFPA) report on behalf of the Swift/UVOT team:
The Swift/UVOT began settled observations of the field of GRB 190821A 89 s after the BAT trigger (D'Ai et al., GCN Circ. 25427). No optical afterglow consistent with the XRT position (Goad et al. GCN Circ. 25436) 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) exposure and subsequent exposures are:
```
Filter         T_start(s)   T_stop(s)      Exp(s)         Mag

white_FC            89          239          147         >19.1
white               89         5595          344         >19.5
v                 5806         6006          197         >18.3
b                 5191         5390          197         >19.9
u                  303        11409          336         >19.6
w1                9373         9551          175         >18.9
m2                6011         6164          151         >19.7
w2                5602         5801          197         >20.2
```
The magnitudes in the table are not corrected for the Galactic extinction due to the reddening of E(B-V) = 0.53 in the direction of the burst (Schlegel et al. 1998).
GCN Circular #25464
S. D. Barthelmy (GSFC), J. R. Cummings (CPI), A. D'Ai (INAF-IASFPA), H. A. Krimm (NSF), A. Y. Lien (GSFC/UMBC), C. B. Markwardt (GSFC), D. M. Palmer (LANL), T. Sakamoto (AGU), M. Stamatikos (OSU), 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 190821A (trigger #921722) (D'Ai et al., GCN Circ. 25427). The BAT ground-calculated position is RA, Dec = 250.070, -34.027 deg which is
```
   RA(J2000)  =  16h 40m 16.9s
   Dec(J2000) = -34d 01' 35.5"
```
with an uncertainty of 1.3 arcmin, (radius, sys+stat, 90% containment). The partial coding was 83%.
The mask-weighted light curve shows a multi-peaked structure that starts at ~T-3 s and ends at ~T+60 s. The highest peak occurs at ~T+30 s. T90 (15-350 keV) is 57.1 +- 2.6 sec (estimated error including systematics).
The time-averaged spectrum from T-3.3 to T+59.5 sec is best fit by a simple power-law model. The power law index of the time-averaged spectrum is 2.03 +- 0.10. The fluence in the 15-150 keV band is 2.4 +- 0.1 x 10^-6 erg/cm2. The 1-sec peak photon flux measured from T+29.98 sec in the 15-150 keV band is 2.8 +- 0.3 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/921722/BA/

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Jochen Greiner, last update: 24-Aug-2019 [Disclaimer]