Gamma-ray Burst 210818A

(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 18 Aug 21 01:02:22 UT
NOTICE_TYPE:     Swift-BAT GRB Position
TRIGGER_NUM:     1069169,   Seg_Num: 0
GRB_RA:          149.131d {+09h 56m 32s} (J2000),
                 148.180d {+09h 52m 43s} (current),
                 151.055d {+10h 04m 13s} (1950)
GRB_DEC:         -87.031d {-87d 01' 52"} (J2000),
                 -87.134d {-87d 08' 03"} (current),
                 -86.790d {-86d 47' 23"} (1950)
GRB_ERROR:       3.00 [arcmin radius, statistical only]
GRB_INTEN:       1425 [cnts]    Image_Peak=128 [image_cnts]
TRIGGER_DUR:     0.064 [sec] 
TRIGGER_INDEX:   10427     E_range: 50-350 keV
BKG_INTEN:       17319 [cnts]
BKG_TIME:        3716.43 SOD {01:01:56.43} UT
BKG_DUR:         8 [sec]
GRB_DATE:        19444 TJD;   230 DOY;   21/08/18
GRB_TIME:        3727.95 SOD {01:02:07.95} UT
GRB_PHI:           9.38 [deg]
GRB_THETA:        17.60 [deg]
SOLN_STATUS:     0x103
RATE_SIGNIF:     96.47 [sigma]
IMAGE_SIGNIF:    9.11 [sigma]
MERIT_PARAMS:     +1  +0  +0  -4  +3  +0  +0  +0 +17  +0 
SUN_POSTN:       147.60d {+09h 50m 24s}  +13.08d {+13d 04' 33"}
SUN_DIST:        100.21 [deg]   Sun_angle= -0.0 [hr] (East of Sun)
MOON_POSTN:      266.83d {+17h 47m 19s}  -25.18d {-25d 11' 03"}
MOON_DIST:        66.21 [deg]
MOON_ILLUM:      76 [%]
GAL_COORDS:      300.67,-24.97 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:      263.20,-67.94 [deg] ecliptic lon,lat of the burst (or transient)
COMMENTS:        SWIFT-BAT GRB Coordinates.  
COMMENTS:        This is a rate trigger.  
COMMENTS:        A point_source was found.  
COMMENTS:        This does not match any source in the on-board catalog.  
COMMENTS:        This matches a source in the ground catalog: IGRJ10043-8702,   delta=0.100 [deg].  
COMMENTS:        This is not a GRB.  
COMMENTS:        This trigger occurred at longitude,latitude = 156.11,-13.69 [deg].

red DSS finding chart ps-file

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Wed 18 Aug 21 01:02:35 UT
NOTICE_TYPE:     Swift-BAT Transient Position
TRIGGER_NUM:     1069169,   Seg_Num: 0
GRB_RA:          149.131d {+09h 56m 32s} (J2000),
                 148.180d {+09h 52m 43s} (current),
                 151.055d {+10h 04m 13s} (1950)
GRB_DEC:         -87.031d {-87d 01' 52"} (J2000),
                 -87.134d {-87d 08' 03"} (current),
                 -86.790d {-86d 47' 23"} (1950)
GRB_ERROR:       3.00 [arcmin radius, statistical only]
GRB_INTEN:       1425 [cnts]    Image_Peak=128 [image_cnts]
TRIGGER_DUR:     0.064 [sec] 
TRIGGER_INDEX:   10427     E_range: 50-350 keV
BKG_INTEN:       17319 [cnts]
BKG_TIME:        3716.43 SOD {01:01:56.43} UT
BKG_DUR:         8 [sec]
GRB_DATE:        19444 TJD;   230 DOY;   21/08/18
GRB_TIME:        3727.95 SOD {01:02:07.95} UT
GRB_PHI:           9.38 [deg]
GRB_THETA:        17.60 [deg]
SOLN_STATUS:     0x103
RATE_SIGNIF:     96.47 [sigma]
IMAGE_SIGNIF:    9.11 [sigma]
MERIT_PARAMS:     +1  +0  +0  -4  +3  +0  +0  +0 +17  +0 
SUN_POSTN:       147.60d {+09h 50m 24s}  +13.08d {+13d 04' 33"}
SUN_DIST:        100.21 [deg]   Sun_angle= -0.0 [hr] (East of Sun)
MOON_POSTN:      266.83d {+17h 47m 20s}  -25.18d {-25d 11' 04"}
MOON_DIST:        66.21 [deg]
MOON_ILLUM:      76 [%]
GAL_COORDS:      300.67,-24.97 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:      263.20,-67.94 [deg] ecliptic lon,lat of the burst (or transient)
COMMENTS:        SWIFT-BAT Transient 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 matches a source in the ground catalog: IGRJ10043-8702,   delta=0.100 [deg].  
COMMENTS:        This is not a GRB -- it is a hard x-ray transient.  
COMMENTS:        This trigger occurred at longitude,latitude = 156.11,-13.69 [deg].

GCN NOTICE

TITLE:          GCN/INTEGRAL NOTICE
NOTICE_DATE:    Wed 18 Aug 21 01:03:29 UT
NOTICE_TYPE:    INTEGRAL SPI ACS Trigger
TRIGGER_NUM:    9349,   Sub_Num: 0
GRB_INTEN:      12.87 [sigma]
GRB_TIME:       3727.77 SOD {01:02:07.77} UT
GRB_DATE:       19444 TJD;   230 DOY;   21/08/18
COMMENTS:       INTEGRAL SPI_ACS GRB Trigger.  
COMMENTS:       Time_Scale=1.0000 and Time_Error=0.5000.  
COMMENTS:          
COMMENTS:       NOTE: This SPIACS event is temporally(0.0<100sec) coincident with the SWIFT_BAT event (trignum=1069169).  
COMMENTS:          
COMMENTS:       The SPIACS lightcurve can be found at:  
COMMENTS:       ftp://isdcarc.unige.ch/arc/FTP/ibas/spiacs/2021-08/2021-08-18T01-02-07.5996-03251-31632-0.lc

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Wed 18 Aug 21 01:03:32 UT
NOTICE_TYPE:     Swift-XRT Position
TRIGGER_NUM:     1069169,   Seg_Num: 0
GRB_RA:          148.8492d {+09h 55m 23.80s} (J2000),
                 147.8905d {+09h 51m 33.72s} (current),
                 150.7896d {+10h 03m 09.49s} (1950)
GRB_DEC:         -87.0252d {-87d 01' 30.7"} (J2000),
                 -87.1277d {-87d 07' 39.8"} (current),
                 -86.7843d {-86d 47' 03.4"} (1950)
GRB_ERROR:       4.7 [arcsec radius, statistical plus systematic, 90% containment]
GRB_INTEN:       1.40e-08 [erg/cm2/sec]
GRB_SIGNIF:      16.18 [sigma]
IMG_START_DATE:  19444 TJD;   230 DOY;   21/08/18
IMG_START_TIME:  3786.91 SOD {01:03:06.91} UT,   59.0 [sec] since BAT Trigger Time
TAM[0-3]:        327.64 237.19 261.58 243.17
AMPLIFIER:       2
WAVEFORM:        134
SUN_POSTN:       147.60d {+09h 50m 25s}  +13.08d {+13d 04' 32"}
SUN_DIST:        100.20 [deg]   Sun_angle= -0.0 [hr] (East of Sun)
MOON_POSTN:      266.84d {+17h 47m 22s}  -25.19d {-25d 11' 07"}
MOON_DIST:        66.23 [deg]
MOON_ILLUM:      76 [%]
GAL_COORDS:      300.65,-24.97 [deg] galactic lon,lat of the burst
ECL_COORDS:      263.20,-67.96 [deg] ecliptic lon,lat of the burst
COMMENTS:        SWIFT-XRT Coordinates.  
COMMENTS:        This matches a source in the BAT ground catalog: IGRJ10043-8702,   delta=0.115 [deg].  
COMMENTS:        The XRT position is 0.95 arcmin from the BAT position.  
COMMENTS:        The object found at this position is either a very bright burst or a cosmic ray hit.  
COMMENTS:        Examine the XRT Image to differentiate (CRs are much more compact); see examples at:  
COMMENTS:        http://www.swift.psu.edu/xrt/XRT_Postage_Stamp_Image_Photo_Gallery.htm .

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Wed 18 Aug 21 01:03:41 UT
NOTICE_TYPE:     Swift-XRT Image
TRIGGER_NUM:     1069169,   Seg_Num: 0
GRB_RA:          148.8492d {+09h 55m 23.8s} (J2000),
                 147.8905d {+09h 51m 33.7s} (current),
                 150.7896d {+10h 03m 09.4s} (1950)
GRB_DEC:         -87.0252d {-87d 01' 30.7"} (J2000),
                 -87.1277d {-87d 07' 39.8"} (current),
                 -86.7843d {-86d 47' 03.4"} (1950)
GRB_ERROR:       4.7 [arcsec, radius, statistical plus systematic]
GRB_INTEN:       262 [cnts]
IMG_START_DATE:  19444 TJD;   230 DOY;   21/08/18
IMG_START_TIME:  3786.91 SOD {01:03:06.91} UT,   59.0 [sec] since BAT Trigger Time
CENTROID_X:      304.88,  raw= 305  [pixels]
CENTROID_Y:      318.43,  raw= 318  [pixels]
ROLL:            358.53 [deg]
GAIN:            4
MODE:            3, Long Image mode
WAVEFORM:        134
EXPO_TIME:       2.50 [sec]
GRB_POS_XRT_Y:   47.92
GRB_POS_XRT_Z:   -5.93
IMAGE_URL:       sw01069169000msxps_rw.img
SUN_POSTN:       147.60d {+09h 50m 25s}  +13.08d {+13d 04' 32"}
SUN_DIST:        100.20 [deg]   Sun_angle= -0.0 [hr] (East of Sun)
MOON_POSTN:      266.84d {+17h 47m 23s}  -25.19d {-25d 11' 08"}
MOON_DIST:        66.23 [deg]
MOON_ILLUM:      76 [%]
GAL_COORDS:      300.65,-24.97 [deg] galactic lon,lat of the burst
ECL_COORDS:      263.20,-67.96 [deg] ecliptic lon,lat of the burst
COMMENTS:        SWIFT-XRT Image.  
COMMENTS:        The object found at this position is either a very bright burst or a cosmic ray hit.  
COMMENTS:        Examine the XRT Image to differentiate (CRs are much more compact); see examples at:  
COMMENTS:        http://www.swift.psu.edu/xrt/XRT_Postage_Stamp_Image_Photo_Gallery.htm .

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Wed 18 Aug 21 01:03:43 UT
NOTICE_TYPE:     Swift-XRT Processed Image
TRIGGER_NUM:     1069169,   Seg_Num: 0
GRB_RA:          148.8492d {+09h 55m 23.8s} (J2000),
                 147.8905d {+09h 51m 33.7s} (current),
                 150.7896d {+10h 03m 09.4s} (1950)
GRB_DEC:         -87.0252d {-87d 01' 30.7"} (J2000),
                 -87.1277d {-87d 07' 39.8"} (current),
                 -86.7843d {-86d 47' 03.4"} (1950)
GRB_ERROR:       4.7 [arcsec, radius, statistical plus systematic]
GRB_INTEN:       262 [cnts]
IMG_START_DATE:  19444 TJD;   230 DOY;   21/08/18
IMG_START_TIME:  3786.91 SOD {01:03:06.91} UT,   59.0 [sec] since BAT Trigger Time
CENTROID_X:      304.88,  raw= 305  [pixels]
CENTROID_Y:      318.43,  raw= 318  [pixels]
ROLL:            358.53 [deg]
GAIN:            4
MODE:            3, Long Image mode
WAVEFORM:        134
EXPO_TIME:       2.50 [sec]
GRB_POS_XRT_Y:   47.92
GRB_POS_XRT_Z:   -5.93
IMAGE_URL:       sw01069169000msxps_rw.img
SUN_POSTN:       147.60d {+09h 50m 25s}  +13.08d {+13d 04' 32"}
SUN_DIST:        100.20 [deg]   Sun_angle= -0.0 [hr] (East of Sun)
MOON_POSTN:      266.84d {+17h 47m 23s}  -25.19d {-25d 11' 08"}
MOON_DIST:        66.23 [deg]
MOON_ILLUM:      76 [%]
GAL_COORDS:      300.65,-24.97 [deg] galactic lon,lat of the burst
ECL_COORDS:      263.20,-67.96 [deg] ecliptic lon,lat of the burst
COMMENTS:        SWIFT-XRT Processed Image.  
COMMENTS:        The object found at this position is either a very bright burst or a cosmic ray hit.  
COMMENTS:        Examine the XRT Image to differentiate (CRs are much more compact); see examples at:  
COMMENTS:        http://www.swift.psu.edu/xrt/XRT_Postage_Stamp_Image_Photo_Gallery.htm .

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Wed 18 Aug 21 01:06:43 UT
NOTICE_TYPE:     Swift-BAT GRB Lightcurve
TRIGGER_NUM:     1069169,   Seg_Num: 0
GRB_RA:          149.131d {+09h 56m 32s} (J2000),
                 148.180d {+09h 52m 43s} (current),
                 151.055d {+10h 04m 13s} (1950)
GRB_DEC:         -87.031d {-87d 01' 52"} (J2000),
                 -87.134d {-87d 08' 03"} (current),
                 -86.790d {-86d 47' 23"} (1950)
GRB_DATE:        19444 TJD;   230 DOY;   21/08/18
GRB_TIME:        3728.19 SOD {01:02:08.19} UT
TRIGGER_INDEX:   10427
GRB_PHI:           9.38 [deg]
GRB_THETA:        17.60 [deg]
DELTA_TIME:      -55.00 [sec]
TRIGGER_DUR:     0.064 [sec] 
SOLN_STATUS:     0x103
RATE_SIGNIF:     96.47 [sigma]
IMAGE_SIGNIF:    9.11 [sigma]
LC_URL:          sw01069169000msb.lc
SUN_POSTN:       147.60d {+09h 50m 25s}  +13.07d {+13d 04' 30"}
SUN_DIST:        100.21 [deg]   Sun_angle= -0.0 [hr] (East of Sun)
MOON_POSTN:      266.88d {+17h 47m 31s}  -25.19d {-25d 11' 19"}
MOON_DIST:        66.21 [deg]
MOON_ILLUM:      77 [%]
GAL_COORDS:      300.67,-24.97 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:      263.20,-67.94 [deg] ecliptic lon,lat of the burst (or transient)
COMMENTS:        SWIFT-BAT GRB Lightcurve.  
COMMENTS:           
COMMENTS:        The next comments were copied from the BAT_POS Notice:
COMMENTS:        This is a rate trigger.  
COMMENTS:        A point_source was found.  
COMMENTS:        This does not match any source in the on-board catalog.  
COMMENTS:        This matches a source in the ground catalog: IGRJ10043-8702,   delta=0.100 [deg].  
COMMENTS:        This is not a GRB.  
COMMENTS:        This trigger occurred at longitude,latitude = 156.11,-13.69 [deg].

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Wed 18 Aug 21 01:07:53 UT
NOTICE_TYPE:     Swift-UVOT Source List
TRIGGER_NUM:     1069169,   Seg_Num: 0
POINT_RA:        149.120d {+09h 56m 29s} (J2000)
POINT_DEC:       -87.026d {-87d 01' 34"} (J2000)
POINT_ROLL:      358.519d
IMG_START_DATE:  19444 TJD;   230 DOY;   21/08/18
IMG_START_TIME:  3794.36 SOD {01:03:14.36} UT,   66.4 [sec] since BAT Trigger Time
FILTER:          10, White
BKG_MEAN:        6.343
N_STARS:         59
X_OFFSET:        448 [pixels]
Y_OFFSET:        592 [pixels]
X_MAX:           1407 [pixels]
Y_MAX:           1551 [pixels]
DET_THRESH:      22
PHOTO_THRESH:    13
SL_URL:          sw01069169000msufc0066.fits
SUN_POSTN:       147.61d {+09h 50m 25s}  +13.07d {+13d 04' 29"}
SUN_DIST:        100.20 [deg]   Sun_angle= -0.0 [hr] (East of Sun)
MOON_POSTN:      266.89d {+17h 47m 34s}  -25.19d {-25d 11' 24"}
MOON_DIST:        66.21 [deg]
MOON_ILLUM:      77 [%]
GAL_COORDS:      300.66,-24.96 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      263.19,-67.95 [deg] ecliptic lon,lat of the pointing direction
COMMENTS:        SWIFT-UVOT Source List.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Wed 18 Aug 21 01:08:10 UT
NOTICE_TYPE:     Swift-UVOT Processed Source List
TRIGGER_NUM:     1069169,   Seg_Num: 0
POINT_RA:        149.120d {+09h 56m 29s} (J2000)
POINT_DEC:       -87.026d {-87d 01' 34"} (J2000)
POINT_ROLL:      358.519d
IMG_START_DATE:  19444 TJD;   230 DOY;   21/08/18
IMG_START_TIME:  3794.36 SOD {01:03:14.36} UT,   66.4 [sec] since BAT Trigger Time
FILTER:          10, White
BKG_MEAN:        6.343
N_STARS:         59
X_OFFSET:        448 [pixels]
Y_OFFSET:        592 [pixels]
X_MAX:           1407 [pixels]
Y_MAX:           1551 [pixels]
DET_THRESH:      22
PHOTO_THRESH:    13
SL_URL:          sw01069169000msufc0066.fits
SUN_POSTN:       147.61d {+09h 50m 25s}  +13.07d {+13d 04' 29"}
SUN_DIST:        100.20 [deg]   Sun_angle= -0.0 [hr] (East of Sun)
MOON_POSTN:      266.89d {+17h 47m 34s}  -25.19d {-25d 11' 25"}
MOON_DIST:        66.21 [deg]
MOON_ILLUM:      77 [%]
GAL_COORDS:      300.66,-24.96 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      263.19,-67.95 [deg] ecliptic lon,lat of the pointing direction
COMMENTS:        SWIFT-UVOT Processed Source List.  
COMMENTS:        All 4 attachments are included.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Wed 18 Aug 21 01:10:09 UT
NOTICE_TYPE:     Swift-UVOT Image
TRIGGER_NUM:     1069169,   Seg_Num: 0
POINT_RA:        149.120d {+09h 56m 29s} (J2000)
POINT_DEC:       -87.026d {-87d 01' 34"} (J2000)
ROLL:            358.519d
IMG_START_DATE:  19444 TJD;   230 DOY;   21/08/18
IMG_START_TIME:  3794.36 SOD {01:03:14.36} UT,   66.4 [sec] since BAT Trigger Time
FILTER:          10, White
EXPOSURE_ID:     650941421
X_OFFSET:        765 [pixels]
Y_OFFSET:        799 [pixels]
WIDTH:           160 [pixels]
HEIGHT:          160 [pixels]
X_GRB_POS:       925
Y_GRB_POS:       959
BINNING_INDEX:   1
IM_URL:          sw01069169000msuni0094.fits
SUN_POSTN:       147.61d {+09h 50m 26s}  +13.07d {+13d 04' 27"}
SUN_DIST:        100.20 [deg]   Sun_angle= -0.0 [hr] (East of Sun)
MOON_POSTN:      266.91d {+17h 47m 40s}  -25.19d {-25d 11' 32"}
MOON_DIST:        66.21 [deg]
MOON_ILLUM:      77 [%]
GAL_COORDS:      300.66,-24.96 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      263.19,-67.95 [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 18 Aug 21 01:10:22 UT
NOTICE_TYPE:     Swift-UVOT Processed Image
TRIGGER_NUM:     1069169,   Seg_Num: 0
POINT_RA:        149.120d {+09h 56m 29s} (J2000)
POINT_DEC:       -87.026d {-87d 01' 34"} (J2000)
ROLL:            358.519d
IMG_START_DATE:  19444 TJD;   230 DOY;   21/08/18
IMG_START_TIME:  3794.36 SOD {01:03:14.36} UT,   66.4 [sec] since BAT Trigger Time
FILTER:          10, White
EXPOSURE_ID:     650941421
X_OFFSET:        765 [pixels]
Y_OFFSET:        799 [pixels]
WIDTH:           160 [pixels]
HEIGHT:          160 [pixels]
X_GRB_POS:       925
Y_GRB_POS:       959
BINNING_INDEX:   1
IM_URL:          sw01069169000msuni0094.fits
SUN_POSTN:       147.61d {+09h 50m 26s}  +13.07d {+13d 04' 27"}
SUN_DIST:        100.20 [deg]   Sun_angle= -0.0 [hr] (East of Sun)
MOON_POSTN:      266.92d {+17h 47m 40s}  -25.19d {-25d 11' 33"}
MOON_DIST:        66.21 [deg]
MOON_ILLUM:      77 [%]
GAL_COORDS:      300.66,-24.96 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      263.19,-67.95 [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 18 Aug 21 01:16:55 UT
NOTICE_TYPE:     Swift-UVOT Source List
TRIGGER_NUM:     1069169,   Seg_Num: 0
POINT_RA:        149.069d {+09h 56m 16s} (J2000)
POINT_DEC:       -87.026d {-87d 01' 34"} (J2000)
POINT_ROLL:      358.570d
IMG_START_DATE:  19444 TJD;   230 DOY;   21/08/18
IMG_START_TIME:  4006.22 SOD {01:06:46.22} UT,   278.3 [sec] since BAT Trigger Time
FILTER:          7, U
BKG_MEAN:        2.206
N_STARS:         37
X_OFFSET:        445 [pixels]
Y_OFFSET:        479 [pixels]
X_MAX:           1404 [pixels]
Y_MAX:           1438 [pixels]
DET_THRESH:      12
PHOTO_THRESH:    6
SL_URL:          sw01069169000msufc0278.fits
SUN_POSTN:       147.61d {+09h 50m 27s}  +13.07d {+13d 04' 22"}
SUN_DIST:        100.20 [deg]   Sun_angle= -0.0 [hr] (East of Sun)
MOON_POSTN:      266.99d {+17h 47m 57s}  -25.20d {-25d 11' 57"}
MOON_DIST:        66.21 [deg]
MOON_ILLUM:      77 [%]
GAL_COORDS:      300.66,-24.96 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      263.19,-67.95 [deg] ecliptic lon,lat of the pointing direction
COMMENTS:        SWIFT-UVOT Source List.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Wed 18 Aug 21 01:17:09 UT
NOTICE_TYPE:     Swift-UVOT Processed Source List
TRIGGER_NUM:     1069169,   Seg_Num: 0
POINT_RA:        149.069d {+09h 56m 16s} (J2000)
POINT_DEC:       -87.026d {-87d 01' 34"} (J2000)
POINT_ROLL:      358.570d
IMG_START_DATE:  19444 TJD;   230 DOY;   21/08/18
IMG_START_TIME:  4006.22 SOD {01:06:46.22} UT,   278.3 [sec] since BAT Trigger Time
FILTER:          7, U
BKG_MEAN:        2.206
N_STARS:         37
X_OFFSET:        445 [pixels]
Y_OFFSET:        479 [pixels]
X_MAX:           1404 [pixels]
Y_MAX:           1438 [pixels]
DET_THRESH:      12
PHOTO_THRESH:    6
SL_URL:          sw01069169000msufc0278.fits
SUN_POSTN:       147.61d {+09h 50m 27s}  +13.07d {+13d 04' 21"}
SUN_DIST:        100.20 [deg]   Sun_angle= -0.0 [hr] (East of Sun)
MOON_POSTN:      266.99d {+17h 47m 58s}  -25.20d {-25d 11' 58"}
MOON_DIST:        66.21 [deg]
MOON_ILLUM:      77 [%]
GAL_COORDS:      300.66,-24.96 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      263.19,-67.95 [deg] ecliptic lon,lat of the pointing direction
COMMENTS:        SWIFT-UVOT Processed Source List.  
COMMENTS:        All 4 attachments are included.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Wed 18 Aug 21 01:19:10 UT
NOTICE_TYPE:     Swift-UVOT Image
TRIGGER_NUM:     1069169,   Seg_Num: 0
POINT_RA:          0.000d {+00h 00m 00s} (J2000)
POINT_DEC:        +0.000d {+00d 00' 00"} (J2000)
ROLL:            -87.026d
IMG_START_DATE:  19444 TJD;   230 DOY;   21/08/18
IMG_START_TIME:  4415.02 SOD {01:13:35.02} UT,   687.1 [sec] since BAT Trigger Time
FILTER:          0, illegal value
EXPOSURE_ID:     65537
X_OFFSET:        911 [pixels]
Y_OFFSET:        1277 [pixels]
WIDTH:           386 [pixels]
HEIGHT:          1063 [pixels]
X_GRB_POS:       0
Y_GRB_POS:       0
BINNING_INDEX:   0
IM_URL:          sw01069169000msuni0306.fits
SUN_POSTN:       147.61d {+09h 50m 27s}  +13.07d {+13d 04' 20"}
SUN_DIST:        145.04 [deg]   Sun_angle= 9.8 [hr] (West of Sun)
MOON_POSTN:      267.01d {+17h 48m 03s}  -25.20d {-25d 12' 06"}
MOON_DIST:        93.00 [deg]
MOON_ILLUM:      77 [%]
GAL_COORDS:       96.34,-60.19 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:        0.00,  0.00 [deg] ecliptic lon,lat of the pointing direction
COMMENTS:        SWIFT-UVOT Image.  
COMMENTS:        WARNING: This Notice was received with 1 (or more) critical values out of range.  
COMMENTS:        The GRB Position came from the Window Position in the Mode Command.  
COMMENTS:        The image has 1x1 binning (ie no compression).  
COMMENTS:        This notice was forced out after watchdog timer expiring -- most likely due to missing packet(s);  
COMMENTS:        as a consequence some of the fields may be incoorect (eg TRIGGER_NUM,RA,DEC).

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Wed 18 Aug 21 01:19:23 UT
NOTICE_TYPE:     Swift-UVOT Processed Image
TRIGGER_NUM:     1069169,   Seg_Num: 0
POINT_RA:          0.000d {+00h 00m 00s} (J2000)
POINT_DEC:        +0.000d {+00d 00' 00"} (J2000)
ROLL:            -87.026d
IMG_START_DATE:  19444 TJD;   230 DOY;   21/08/18
IMG_START_TIME:  4415.02 SOD {01:13:35.02} UT,   687.1 [sec] since BAT Trigger Time
FILTER:          0, illegal value
EXPOSURE_ID:     65537
X_OFFSET:        911 [pixels]
Y_OFFSET:        1277 [pixels]
WIDTH:           386 [pixels]
HEIGHT:          1063 [pixels]
X_GRB_POS:       0
Y_GRB_POS:       0
BINNING_INDEX:   0
IM_URL:          sw01069169000msuni0306.fits
SUN_POSTN:       147.61d {+09h 50m 27s}  +13.07d {+13d 04' 20"}
SUN_DIST:        145.04 [deg]   Sun_angle= 9.8 [hr] (West of Sun)
MOON_POSTN:      267.02d {+17h 48m 04s}  -25.20d {-25d 12' 06"}
MOON_DIST:        93.00 [deg]
MOON_ILLUM:      77 [%]
GAL_COORDS:       96.34,-60.19 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:        0.00,  0.00 [deg] ecliptic lon,lat of the pointing direction
COMMENTS:        SWIFT-UVOT Processed Image.  
COMMENTS:        WARNING: This Notice was received with 1 (or more) critical values out of range.  
COMMENTS:        The GRB Position came from the Window Position in the Mode Command.  
COMMENTS:        The image has 1x1 binning (ie no compression).  
COMMENTS:        All 4 attachments are included.  
COMMENTS:        This notice was forced out after watchdog timer expiring -- most likely due to missing packet(s);  
COMMENTS:        as a consequence some of the fields may be incoorect (eg TRIGGER_NUM,RA,DEC).

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Wed 18 Aug 21 01:23:26 UT
NOTICE_TYPE:     Swift-UVOT Source List
TRIGGER_NUM:     1069169,   Seg_Num: 0
POINT_RA:        149.062d {+09h 56m 15s} (J2000)
POINT_DEC:       -87.026d {-87d 01' 33"} (J2000)
POINT_ROLL:      358.576d
IMG_START_DATE:  19444 TJD;   230 DOY;   21/08/18
IMG_START_TIME:  4587.83 SOD {01:16:27.83} UT,   859.9 [sec] since BAT Trigger Time
FILTER:          10, White
BKG_MEAN:        4.486
N_STARS:         190
X_OFFSET:        205 [pixels]
Y_OFFSET:        239 [pixels]
X_MAX:           1644 [pixels]
Y_MAX:           1678 [pixels]
DET_THRESH:      18
PHOTO_THRESH:    10
SL_URL:          sw01069169000msufc0859.fits
SUN_POSTN:       147.62d {+09h 50m 28s}  +13.07d {+13d 04' 16"}
SUN_DIST:        100.20 [deg]   Sun_angle= -0.0 [hr] (East of Sun)
MOON_POSTN:      267.06d {+17h 48m 14s}  -25.21d {-25d 12' 21"}
MOON_DIST:        66.21 [deg]
MOON_ILLUM:      77 [%]
GAL_COORDS:      300.66,-24.96 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      263.19,-67.95 [deg] ecliptic lon,lat of the pointing direction
COMMENTS:        SWIFT-UVOT Source List.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Wed 18 Aug 21 01:23:37 UT
NOTICE_TYPE:     Swift-UVOT Processed Source List
TRIGGER_NUM:     1069169,   Seg_Num: 0
POINT_RA:        149.062d {+09h 56m 15s} (J2000)
POINT_DEC:       -87.026d {-87d 01' 33"} (J2000)
POINT_ROLL:      358.576d
IMG_START_DATE:  19444 TJD;   230 DOY;   21/08/18
IMG_START_TIME:  4587.83 SOD {01:16:27.83} UT,   859.9 [sec] since BAT Trigger Time
FILTER:          10, White
BKG_MEAN:        4.486
N_STARS:         190
X_OFFSET:        205 [pixels]
Y_OFFSET:        239 [pixels]
X_MAX:           1644 [pixels]
Y_MAX:           1678 [pixels]
DET_THRESH:      18
PHOTO_THRESH:    10
SL_URL:          sw01069169000msufc0859.fits
SUN_POSTN:       147.62d {+09h 50m 28s}  +13.07d {+13d 04' 16"}
SUN_DIST:        100.20 [deg]   Sun_angle= -0.0 [hr] (East of Sun)
MOON_POSTN:      267.06d {+17h 48m 15s}  -25.21d {-25d 12' 22"}
MOON_DIST:        66.21 [deg]
MOON_ILLUM:      77 [%]
GAL_COORDS:      300.66,-24.96 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      263.19,-67.95 [deg] ecliptic lon,lat of the pointing direction
COMMENTS:        SWIFT-UVOT Processed Source List.  
COMMENTS:        All 4 attachments are included.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Wed 18 Aug 21 01:24:59 UT
NOTICE_TYPE:     Swift-UVOT Image
TRIGGER_NUM:     1069169,   Seg_Num: 0
POINT_RA:        149.062d {+09h 56m 15s} (J2000)
POINT_DEC:       -87.026d {-87d 01' 33"} (J2000)
ROLL:            358.576d
IMG_START_DATE:  19444 TJD;   230 DOY;   21/08/18
IMG_START_TIME:  4587.83 SOD {01:16:27.83} UT,   859.9 [sec] since BAT Trigger Time
FILTER:          10, White
EXPOSURE_ID:     650942215
X_OFFSET:        764 [pixels]
Y_OFFSET:        798 [pixels]
WIDTH:           160 [pixels]
HEIGHT:          160 [pixels]
X_GRB_POS:       924
Y_GRB_POS:       958
BINNING_INDEX:   1
IM_URL:          sw01069169000msuni0887.fits
SUN_POSTN:       147.62d {+09h 50m 28s}  +13.07d {+13d 04' 15"}
SUN_DIST:        100.20 [deg]   Sun_angle= -0.0 [hr] (East of Sun)
MOON_POSTN:      267.08d {+17h 48m 18s}  -25.21d {-25d 12' 27"}
MOON_DIST:        66.21 [deg]
MOON_ILLUM:      77 [%]
GAL_COORDS:      300.66,-24.96 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      263.19,-67.95 [deg] ecliptic lon,lat of the pointing direction
COMMENTS:        SWIFT-UVOT Image.  
COMMENTS:        The GRB Position came from the Window Position in the Mode Command.  
COMMENTS:        The image has 2x2 binning (compression).

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Wed 18 Aug 21 01:25:05 UT
NOTICE_TYPE:     Swift-UVOT Processed Image
TRIGGER_NUM:     1069169,   Seg_Num: 0
POINT_RA:        149.062d {+09h 56m 15s} (J2000)
POINT_DEC:       -87.026d {-87d 01' 33"} (J2000)
ROLL:            358.576d
IMG_START_DATE:  19444 TJD;   230 DOY;   21/08/18
IMG_START_TIME:  4587.83 SOD {01:16:27.83} UT,   859.9 [sec] since BAT Trigger Time
FILTER:          10, White
EXPOSURE_ID:     650942215
X_OFFSET:        764 [pixels]
Y_OFFSET:        798 [pixels]
WIDTH:           160 [pixels]
HEIGHT:          160 [pixels]
X_GRB_POS:       924
Y_GRB_POS:       958
BINNING_INDEX:   1
IM_URL:          sw01069169000msuni0887.fits
SUN_POSTN:       147.62d {+09h 50m 28s}  +13.07d {+13d 04' 15"}
SUN_DIST:        100.20 [deg]   Sun_angle= -0.0 [hr] (East of Sun)
MOON_POSTN:      267.08d {+17h 48m 18s}  -25.21d {-25d 12' 27"}
MOON_DIST:        66.21 [deg]
MOON_ILLUM:      77 [%]
GAL_COORDS:      300.66,-24.96 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      263.19,-67.95 [deg] ecliptic lon,lat of the pointing direction
COMMENTS:        SWIFT-UVOT Processed Image.  
COMMENTS:        The GRB Position came from the Window Position in the Mode Command.  
COMMENTS:        The image has 2x2 binning (compression).  
COMMENTS:        All 4 attachments are included.

GCN Circular #30652
A. P. Beardmore (U Leicester), J. A. Kennea (PSU), A. Y. Lien (GSFC/UMBC), K. L. Page (U Leicester) and D. M. Palmer (LANL) report on behalf of the Neil Gehrels Swift Observatory Team:
At 01:02:08 UT, the Swift Burst Alert Telescope (BAT) triggered and located GRB 210818A (trigger=1069169). Swift slewed immediately to the burst. The BAT on-board calculated location is RA, Dec 149.131, -87.031 which is
```
   RA(J2000) = 09h 56m 32s
   Dec(J2000) = -87d 01' 52"
```
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 60 sec. The peak count rate was ~28000 counts/sec (15-350 keV), at ~1 sec after the trigger.
The XRT began observing the field at 01:03:06.9 UT, 59.0 seconds after the BAT trigger. Using promptly downlinked data we find a bright, uncatalogued X-ray source with an enhanced position: RA, Dec 148.8666, -87.0253 which is equivalent to:
```
   RA(J2000)  = 09h 55m 27.99s
   Dec(J2000) = -87d 01' 31.0"
```
with an uncertainty of 1.9 arcseconds (radius, 90% containment). This location is 53 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 https://www.swift.ac.uk/sper.
A power-law fit to a spectrum formed from promptly downlinked event data gives a column density in excess of the Galactic value (1.74 x 10^21 cm^-2, Willingale et al. 2013), with an excess column of 4.7 (+2.38/-2.11) x 10^21 cm^-2 (90% confidence).
The initial flux in the 2.5 s image was 1.40e-08 erg cm^-2 s^-1 (0.2-10 keV).
UVOT took a finding chart exposure of 150 seconds with the White filter starting 66 seconds after the BAT trigger. There is a candidate afterglow in the rapidly available 2.7'x2.7' sub-image at
```
  RA(J2000)  =	09:55:28.15 = 148.86729
  DEC(J2000) = -87:01:28.8  = -87.02467
```
with a 90%-confidence error radius of about 0.62 arc sec. This position is 1.9 arc sec. from the center of the XRT error circle. The estimated magnitude is 17.93 with a 1-sigma error of about 0.15. No correction has been made for the expected extinction corresponding to E(B-V) of 0.213.
Although this was originally reported in the GCN Notices as a known source we believe that this is a GRB.
Burst Advocate for this burst is A. P. Beardmore (apb AT star.le.ac.uk). 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 NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Wed 18 Aug 21 01:12:23 UT
NOTICE_TYPE:     Swift-UVOT Position
TRIGGER_NUM:     1069169,   Seg_Num: 0
GRB_RA:          148.8672d {+09h 55m 28.12s} (J2000),
                 147.9094d {+09h 51m 38.25s} (current),
                 150.8057d {+10h 03m 13.37s} (1950)
GRB_DEC:         -87.0246d {-87d 01' 28.5"} (J2000),
                 -87.1272d {-87d 07' 37.7"} (current),
                 -86.7837d {-86d 47' 01.1"} (1950)
GRB_ERROR:       0.6 [arcsec radius, statistical only]
GRB_MAG:         17.93 +/- 0.14 [mag]
FILTER:          10, White
IMG_START_DATE:  19444 TJD;   230 DOY;   21/08/18
IMG_START_TIME:  3791.00 SOD {01:03:11.00} UT,   63.1 [sec] since BAT Trigger Time
SUN_POSTN:       147.61d {+09h 50m 26s}  +13.07d {+13d 04' 25"}
SUN_DIST:        100.20 [deg]   Sun_angle= -0.0 [hr] (East of Sun)
MOON_POSTN:      266.94d {+17h 47m 45s}  -25.19d {-25d 11' 40"}
MOON_DIST:        66.22 [deg]
MOON_ILLUM:      77 [%]
GAL_COORDS:      300.65,-24.97 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:      263.20,-67.96 [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 3.6 arcsec from the XRT position.  
COMMENTS:        Result based on Genie data.  
COMMENTS:        Notice generated automatically.

GCN Circular #30653
J.P. Osborne, A.P. Beardmore, P.A. Evans and M.R. Goad (U. Leicester) report on behalf of the Swift-XRT team.
Using 1521 s of XRT Photon Counting mode data and 1 UVOT images for GRB 210818A, 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 = 148.86765, -87.02526 which is equivalent to:
```
RA (J2000): 09h 55m 28.23s
Dec (J2000): -87d 01' 30.9"
```
with an uncertainty of 2.2 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 #30654
A. Ursi (INAF/IAPS), F. Verrecchia (SSDC, and INAF/OAR), C. Casentini (INAF/IAPS), P. Tempesta (TeleSpazio), M. Tavani (INAF/IAPS, and Univ. Roma Tor Vergata), A. Argan, M. Cardillo, Y. Evangelista, G. Piano (INAF/IAPS), F. Lucarelli, C. Pittori, (SSDC, and INAF/OAR), A. Bulgarelli, V. Fioretti, F. Fuschino, N. Parmiggiani (INAF/OAS-Bologna), M. Marisaldi (INAF/OAS-Bologna, and Bergen University), M. Pilia, A. Trois (INAF/OA-Cagliari), I. Donnarumma (ASI), F. Longo (Univ. Trieste and INFN Trieste), A. Giuliani (INAF/IASF-Mi), report on behalf of the AGILE Team:
The AGILE satellite detected the long GRB 210818A at T0 = 2021-08-18 01:02:08.19 s (UTC), reported by Swift (GCNs #30652, #30653).
The burst is clearly visible in the AGILE scientific ratemeters of the SuperAGILE (SA; 20-60 keV), MiniCALorimeter (MCAL; 0.4-100 MeV), and AntiCoincidence (AC; 50-200 keV) detectors. The event lasted about 35 s and it released a total number of 3020 counts in the SA detector (above a background rate of 70 Hz), 48170 counts in the MCAL detector (above a background rate of 1250 Hz), and 130730 counts in the AC detector (above a background rate of 3650 Hz). The AGILE ratemeter light curves can be found at http://www.agilescienceapp.it/notices/GRB210818A_AGILE_RM.png .
The event also triggered a partial high time resolution MCAL data acquisition, from T1 = 2021-08-18 01:02:07.81 s +/- 0.01 (UTC) to T2 =2021-08-18 01:02:21.18 +/- 0.01 s (UTC), and released 21640 counts in the detector, above a background rate of 625 Hz. The MCAL light curve can be found at: http://www.agilescienceapp.it/notices/074408_GRB_556333328.188243.png .
Additional analysis of AGILE data is in progress. Automatic MCAL GRB alert Notices can be found at: https://gcn.gsfc.nasa.gov/agile_mcal.html.
GCN Circular #30655
V. Prasad (IUCAA), P. Sawant (IUCAA), G. Waratkar (IITB), A. Vibhute (IUCAA), V. Bhalerao (IITB), D. Bhattacharya (IUCAA), A. R. Rao (IUCAA/TIFR), and S. Vadawale (PRL) report on behalf of the AstroSat CZTI collaboration:
Analysis of AstroSat CZTI data with the CIFT framework (Sharma et al, 2020, arxiv:2011.07067) showed detection of a bright long GRB 210818A, which was also detected by Swift-BAT (Beardmore et al., GCN #30652), Swift-XRT (Osborne et al., GCN #30653) and AGILE (Ursi et al., GCN #30654).
The source was clearly detected in the 20-200 keV energy range, with the strongest peak at 2021-08-18 01:02:10.5 UT in the single-peak light curve. The measured peak count rate associated with the burst is 1018 (+64, -64) cts/s above the background in the combined data of four quadrants, with a total of 13993 (+552, -512) cts. The local mean background count rate was 526 (+3, -3) cts/s. Using cumulative rates, we measure a T90 of 33 (+4, -3) s.
It was also clearly detected in the CsI anticoincidence (Veto) detector in the 100-500 keV energy range, with the strongest peak at 2021-08-18 01:02:09.9 UT in the single-peak light curve. The measured peak count rate is 3748 (+116, -126) cts/s above the background in the combined Veto data of four quadrants, with a total of 52829 (+844, -1097) cts. The local mean background count rate was 1616 (+5, -5) cts/s. We measure a T90 of 37 (+3, -2) s from the cumulative Veto light curve.
CZTI GRB detections are reported regularly on the payload site at http://astrosat.iucaa.in/czti/?q=grb [1]. CZTI is built by a TIFR-led consortium of institutes across India, including VSSC, ISAC, IUCAA, SAC, and PRL. The Indian Space Research Organisation funded, managed, and facilitated the project.
```
Links:
------
[1] http://astrosat.iucaa.in/czti/?q=grb
```
GCN Circular #30657
D. Frederiks, S. Golenetskii, A.Lysenko, A. Ridnaia, D. Svinkin, A. Tsvetkova, M. Ulanov, and T. Cline, on behalf of the Konus-Wind team, report:
The long GRB 210818A (Swift detection: Beardmore et al., GCN 30652; AGILE detection: Ursi et al., GCN 30654) triggered Konus-Wind (KW) at T0=3729.710 s UT (01:02:09.710).
The burst light curve started at ~T0 with a bright, short (<0.5s), hard-spectrum initial pulse, which was followed, after a ~0.5 s interval, by a similarly bright and hard, multi-peaked emission, which gradually decays until ~T0+90 s. We also note a QPO-like behavior of the light curve in the interval from ~T0+1.6 s to ~T0+3.2 s, with the quasi period of ~0.21 s.
The emission is seen up to ~7 MeV.
The Konus-Wind light curve of this GRB is available at http://www.ioffe.ru/LEA/GRBs/GRB210818_T03729/
As observed by Konus-Wind, the burst had a fluence of (2.67 � 0.12)x10^-4 erg/cm^2 and a 64-ms peak energy flux, measured from T0 + 0.128 s, of (5.12 � 0.54)x10^-5 erg/cm^2/s (both in the 20 keV - 10 MeV energy range).
The time-averaged spectrum of the burst (measured from T0 to T0+80.640 s) is best fit in the 20 keV - 20 MeV range by a power law with exponential cutoff (CPL) model: dN/dE ~ (E^alpha)*exp(-E*(2+alpha)/Ep) with alpha = -0.99(-0.03,+0.03) and Ep = 1107(-71,+78) keV (chi2 = 117/98 dof). Fitting this spectrum by a Band function yields the same alpha and Ep, and an upper limit on the high energy photon index: beta < -3.2 (chi2 = 117/97 dof).
The spectrum near the peak count rate (measured from T0 to T0+0.256 s, that corresponds to the short initial pulse) is best fit in the 20 keV - 20 MeV range by the CPL model with alpha = -0.28(-0.13,+0.14) and Ep = 1247(-133,+47) keV (chi2 = 38/58 dof). Fitting this spectrum by a Band function yields the same alpha and Ep, and an upper limit on the high energy photon index: beta < -3.4 (chi2 = 38/57 dof).
All the quoted errors are estimated at the 90% confidence level. All the presented results are preliminary.
GCN Circular #30659
H. A. Krimm (NSF), S. D. Barthelmy (GSFC), A. P. Beardmore (U Leicester), S. Laha (GSFC/UMBC), A. Y. Lien (U Tampa), 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-240 to T+962 sec from the recent telemetry downlink, we report further analysis of BAT GRB 210818A (trigger #1069169) (Beardmore et al., GCN Circ. 30652). The BAT ground-calculated position is RA, Dec = 148.949, -87.029 deg which is
```
   RA(J2000)  =  09h 55m 47.7s
   Dec(J2000) = -87d 01' 45.3"
```
with an uncertainty of 1.0 arcmin, (radius, sys+stat, 90% containment). The partial coding was 97%.
The mask-weighted light curve shows many overlapping pulses on top of a general FRED-like structure. The burst emission starts at ~T0, peaks at ~T+2 s, and ends at ~T+130 s. T90 (15-350 keV) is 73.56 +- 1.55 sec (estimated error including systematics).
The time-averaged spectrum from T-0.69 to T+128.97 sec is best fit by a simple power-law model. The power law index of the time-averaged spectrum is 1.22 +- 0.03. The fluence in the 15-150 keV band is 2.6 +- 0.03 x 10^-5 erg/cm2. The 1-sec peak photon flux measured from T+1.20 sec in the 15-150 keV band is 11.2 +- 0.4 ph/cm2/sec. All the quoted errors are at the 90% confidence level.
GCN Circular #30660
P.A. Evans (U. Leicester), J.P. Osborne (U. Leicester), E. Ambrosi (INAF-IASFPA) , M. Capalbi (INAF-IASFPA), M. Perri (SSDC & INAF-OAR), J. D. Gropp (PSU), J.A. Kennea (PSU), A. Tohuvavohu (U. Toronto), K.L. Page (U. Leicester) and A.P. Beardmore report on behalf of the Swift-XRT team:
We have analysed 7.1 ks of XRT data for GRB 210818A (Beardmore et al. GCN Circ. 30652), from 65 s to 69.5 ks after the BAT trigger. The data comprise 188 s in Windowed Timing (WT) mode with the remainder in Photon Counting (PC) mode. The enhanced XRT position for this burst was given by Osborne et al. (GCN Circ. 30653).
The light curve can be modelled with a series of power-law decays. The initial decay index is alpha=1.04 (+/-0.20). At T+111 s the decay steepens to an alpha of 6.8 (+0.7, -0.6). The light curve breaks again at T+157 s to a decay with alpha=0.67 (+0.38, -0.29), before a final break at T+479 s s after which the decay index is 1.50 (+/-0.06).
A spectrum formed from the WT mode data can be fitted with an absorbed power-law with a photon spectral index of 0.86 (+/-0.06). The best-fitting absorption column is 2.5 (+0.5, -0.4) x 10^21 cm^-2, in excess of the Galactic value of 1.7 x 10^21 cm^-2 (Willingale et al. 2013). The PC mode spectrum has a photon index of 1.64 (+0.14, -0.11) and a best-fitting absorption column of 1.94 (+0.56, -0.20) x 10^21 cm^-2. The counts to observed (unabsorbed) 0.3-10 keV flux conversion factor deduced from this spectrum is 4.4 x 10^-11 (5.3 x 10^-11) erg cm^-2 count^-1.
A summary of the PC-mode spectrum is thus:
```
Total column:	     1.94 (+0.56, -0.20) x 10^21 cm^-2
Galactic foreground: 1.7 x 10^21 cm^-2
Excess significance: <1.6 sigma
Photon index:	     1.64 (+0.14, -0.11)
```
If the light curve continues to decay with a power-law decay index of 1.50, the count rate at T+24 hours will be 3.1 x 10^-3 count s^-1, corresponding to an observed (unabsorbed) 0.3-10 keV flux of 1.3 x 10^-13 (1.6 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/01069169.
This circular is an official product of the Swift-XRT team.

GCN Circular #30661
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, D. Cheryasov (Lomonosov Moscow State University, SAI, Physics Department),
R. Podesta, C.Lopez, F. Podesta, C.Francile (Observatorio Astronomico Felix Aguilar OAFA),
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-OAFA robotic telescope (Global MASTER-Net: http://observ.pereplet.ru, Lipunov et al., 2010, Advances in Astronomy, vol. 2010, 30L) located in Argentina (OAFA observatory of San Juan National University) was pointed to the Swift GRB 210818A ( A. P. Beardmore et al., GCN 30652) errorbox 22995 sec after notice time and 23077 sec after trigger time at 2021-08-18 07:27:44 UT, with upper limit up to 18.9 mag. The observations began at zenith distance = 62 deg. The sun altitude is -47.3 deg.
The galactic latitude b = -25 deg., longitude l = 301 deg.
Real time updated cover map and OT discovered available here: https://master.sai.msu.ru/site/master2/observ.php?id=1693376
We obtain a following upper limits.

Tmid-T0  |          Site       |Filt.| Expt. | Limit| Comment
_________|_____________________|_____|_______|______|________


   23167 |         MASTER-OAFA |   C |   180 | 13.8 |        
   23347 |         MASTER-OAFA |   C |   540 | 14.9 |  Coadd 
   23379 |         MASTER-OAFA |   C |   180 | 14.9 |        
   23559 |         MASTER-OAFA |   C |   540 | 15.3 |  Coadd 
   23592 |         MASTER-OAFA |   C |   180 | 14.6 |        
   23812 |         MASTER-OAFA |   C |   180 | 14.3 |        
   24026 |         MASTER-OAFA |   C |   180 | 14.8 |        
   24242 |         MASTER-OAFA |   C |   180 | 15.8 |        
   24456 |         MASTER-OAFA |   C |   180 | 15.0 |        
   24636 |         MASTER-OAFA |   C |   540 | 17.0 |  Coadd 
   24668 |         MASTER-OAFA |   C |   180 | 14.9 |        
   24883 |         MASTER-OAFA |   C |   180 | 16.4 |        
   25099 |         MASTER-OAFA |   C |   180 | 17.3 |        
   25279 |         MASTER-OAFA |   C |   540 | 18.0 |  Coadd 
   25329 |         MASTER-OAFA |   C |   180 | 17.4 |        
   25546 |         MASTER-OAFA |   C |   180 | 17.4 |        
   25762 |         MASTER-OAFA |   C |   180 | 16.9 |        
   25942 |         MASTER-OAFA |   C |   540 | 18.0 |  Coadd 
   25975 |         MASTER-OAFA |   C |   180 | 18.0 |        
   26190 |         MASTER-OAFA |   C |   180 | 17.3 |        
   26405 |         MASTER-OAFA |   C |   180 | 17.3 |        
   26585 |         MASTER-OAFA |   C |   540 | 17.6 |  Coadd 
   26621 |         MASTER-OAFA |   C |   180 | 17.7 |        
   26833 |         MASTER-OAFA |   C |   180 | 17.5 |        
   27049 |         MASTER-OAFA |   C |   180 | 17.7 |        
   27229 |         MASTER-OAFA |   C |   540 | 18.3 |  Coadd 
   27264 |         MASTER-OAFA |   C |   180 | 17.5 |        
   27479 |         MASTER-OAFA |   C |   180 | 17.7 |        
   27691 |         MASTER-OAFA |   C |   180 | 17.5 |        
   27871 |         MASTER-OAFA |   C |   540 | 18.5 |  Coadd 
   27906 |         MASTER-OAFA |   C |   180 | 17.6 |        
   28123 |         MASTER-OAFA |   C |   180 | 18.2 |        
   28337 |         MASTER-OAFA |   C |   180 | 17.7 |        
   28517 |         MASTER-OAFA |   C |   540 | 18.1 |  Coadd 
   28551 |         MASTER-OAFA |   C |   180 | 17.3 |        
   28765 |         MASTER-OAFA |   C |   180 | 18.0 |        
   28983 |         MASTER-OAFA |   C |   180 | 18.0 |        
   29199 |         MASTER-OAFA |   C |   180 | 17.9 |        
   29415 |         MASTER-OAFA |   C |   180 | 17.7 |        
   29595 |         MASTER-OAFA |   C |   540 | 18.0 |  Coadd 
   29630 |         MASTER-OAFA |   C |   180 | 17.5 |        
   29810 |         MASTER-OAFA |   C |   540 | 18.6 |  Coadd 
   29842 |         MASTER-OAFA |   C |   180 | 18.2 |        
   30058 |         MASTER-OAFA |   C |   180 | 18.4 |        
   30272 |         MASTER-OAFA |   C |   180 | 18.2 |        
   30488 |         MASTER-OAFA |   C |   180 | 17.8 |        
   30701 |         MASTER-OAFA |   C |   180 | 18.0 |        
   30881 |         MASTER-OAFA |   C |   540 | 18.9 |  Coadd 
   30917 |         MASTER-OAFA |   C |   180 | 18.1 |        
   31130 |         MASTER-OAFA |   C |   180 | 18.3 |        
   31329 |         MASTER-OAFA |   C |   180 | 18.3 |        
   31729 |         MASTER-OAFA |   C |   180 | 18.4 |        
   31909 |         MASTER-OAFA |   C |   540 | 18.5 |  Coadd 
   31928 |         MASTER-OAFA |   C |   180 | 18.4 |        
   32127 |         MASTER-OAFA |   C |   180 | 18.0 |        
   32327 |         MASTER-OAFA |   C |   180 | 17.4 |        
   32507 |         MASTER-OAFA |   C |   540 | 18.0 |  Coadd 
   32527 |         MASTER-OAFA |   C |   180 | 17.3 |        
   32726 |         MASTER-OAFA |   C |   180 | 17.1 |        
   32926 |         MASTER-OAFA |   C |   180 | 17.3 |        
   33106 |         MASTER-OAFA |   C |   540 | 17.9 |  Coadd 
   33125 |         MASTER-OAFA |   C |   180 | 17.5 |        
   33325 |         MASTER-OAFA |   C |   180 | 17.1 |        
   33524 |         MASTER-OAFA |   C |   180 | 16.7 |

Filter C is a clear (unfiltred) band.
The observation and reduction will continue. The message may be cited.

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Jochen Greiner, last update: 19-Aug-2021 [Disclaimer]