Gamma-ray Burst 210610B

(All information courtesy of the instrument teams.)

Previous IAU Circulars

none

Results of Observations

GCN/BACODINE POSITION NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Thu 10 Jun 21 20:00:47 UT
NOTICE_TYPE:     Swift-BAT GRB Position
TRIGGER_NUM:     1054681,   Seg_Num: 0
GRB_RA:          243.939d {+16h 15m 45s} (J2000),
                 244.186d {+16h 16m 45s} (current),
                 243.363d {+16h 13m 27s} (1950)
GRB_DEC:         +14.391d {+14d 23' 29"} (J2000),
                 +14.339d {+14d 20' 21"} (current),
                 +14.515d {+14d 30' 54"} (1950)
GRB_ERROR:       3.00 [arcmin radius, statistical only]
GRB_INTEN:       4340 [cnts]    Image_Peak=210 [image_cnts]
TRIGGER_DUR:     1.024 [sec] 
TRIGGER_INDEX:   155     E_range: 50-350 keV
BKG_INTEN:       16212 [cnts]
BKG_TIME:        71468.82 SOD {19:51:08.82} UT
BKG_DUR:         8 [sec]
GRB_DATE:        19375 TJD;   161 DOY;   21/06/10
GRB_TIME:        71487.51 SOD {19:51:27.51} UT
GRB_PHI:          43.05 [deg]
GRB_THETA:        38.34 [deg]
SOLN_STATUS:     0x20000003
RATE_SIGNIF:     46.52 [sigma]
IMAGE_SIGNIF:    10.54 [sigma]
MERIT_PARAMS:     +1  +0  +0  +0  +3  +0  +0  +0 +76  +0 
SUN_POSTN:        79.29d {+05h 17m 10s}  +23.07d {+23d 04' 14"}
SUN_DIST:        139.78 [deg]   Sun_angle= -11.0 [hr] (East of Sun)
MOON_POSTN:       83.83d {+05h 35m 20s}  +24.52d {+24d 31' 04"}
MOON_DIST:       136.67 [deg]
MOON_ILLUM:      0 [%]
GAL_COORDS:       28.66, 40.91 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:      238.68, 35.04 [deg] ecliptic lon,lat of the burst (or transient)
COMMENTS:        SWIFT-BAT GRB Coordinates.  
COMMENTS:        This Notice was delayed by more than 60 sec past the end of the trigger integration interval;  
COMMENTS:        probably due to it occurring during a Malindi downlink session.  
COMMENTS:        This is a rate trigger.  
COMMENTS:        A point_source was found.  
COMMENTS:        This does not match any source in the on-board catalog.  
COMMENTS:        This does not match any source in the ground catalog.  
COMMENTS:        This is a GRB.  
COMMENTS:        This trigger occurred at longitude,latitude = 11.24,3.22 [deg].  
COMMENTS:           
COMMENTS:        NOTE: This BAT event is temporally(22.0<100sec) coincident with the FERMI_GBM event (trignum=645047470).

GCN NOTICE

TITLE:           GCN/FERMI NOTICE
NOTICE_DATE:     Thu 10 Jun 21 19:51:29 UT
NOTICE_TYPE:     Fermi-GBM Flight Position
RECORD_NUM:      47
TRIGGER_NUM:     645047470
GRB_RA:          259.083d {+17h 16m 20s} (J2000),
                 259.335d {+17h 17m 20s} (current),
                 258.497d {+17h 13m 59s} (1950)
GRB_DEC:         +11.200d {+11d 11' 60"} (J2000),
                 +11.178d {+11d 10' 40"} (current),
                 +11.254d {+11d 15' 15"} (1950)
GRB_ERROR:       22.85 [deg radius, statistical plus systematic]
GRB_INTEN:       62 [cnts/sec]
DATA_SIGNIF:     5.50 [sigma]
INTEG_TIME:      4.096 [sec]
GRB_DATE:        19375 TJD;   161 DOY;   21/06/10
GRB_TIME:        71465.05 SOD {19:51:05.05} UT
GRB_PHI:         177.00 [deg]
GRB_THETA:        65.00 [deg]
DATA_TIME_SCALE: 4.0960 [sec]
HARD_RATIO:      1.26
LOC_ALGORITHM:   3 (version number of)
MOST_LIKELY:      96%  GRB
2nd_MOST_LIKELY:   2%  SGR_1806n20
DETECTORS:       0,0,0, 0,0,0, 1,0,0, 0,0,1, 0,0,
SUN_POSTN:        79.28d {+05h 17m 08s}  +23.07d {+23d 04' 13"}
SUN_DIST:        145.75 [deg]   Sun_angle= 12.0 [hr] (West of Sun)
MOON_POSTN:       83.75d {+05h 35m 00s}  +24.51d {+24d 30' 26"}
MOON_DIST:       144.06 [deg]
MOON_ILLUM:      0 [%]
GAL_COORDS:       32.46, 26.14 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:      257.03, 34.15 [deg] ecliptic lon,lat of the burst (or transient)
LC_URL:          http://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2021/bn210610827/quicklook/glg_lc_medres34_bn210610827.gif
COMMENTS:        Fermi-GBM Flight-calculated Coordinates.  
COMMENTS:        This trigger occurred at longitude,latitude = 74.68,25.53 [deg].  
COMMENTS:        The LC_URL file will not be created until ~15 min after the trigger.

GCN NOTICE

TITLE:           GCN/FERMI NOTICE
NOTICE_DATE:     Thu 10 Jun 21 19:51:41 UT
NOTICE_TYPE:     Fermi-GBM Flight Position
RECORD_NUM:      66
TRIGGER_NUM:     645047470
GRB_RA:          219.800d {+14h 39m 12s} (J2000),
                 220.380d {+14h 41m 31s} (current),
                 218.471d {+14h 33m 53s} (1950)
GRB_DEC:         -75.800d {-75d 47' 59"} (J2000),
                 -75.891d {-75d 53' 28"} (current),
                 -75.584d {-75d 35' 02"} (1950)
GRB_ERROR:       6.75 [deg radius, statistical plus systematic]
GRB_INTEN:       353 [cnts/sec]
DATA_SIGNIF:     8.20 [sigma]
INTEG_TIME:      2.048 [sec]
GRB_DATE:        19375 TJD;   161 DOY;   21/06/10
GRB_TIME:        71465.05 SOD {19:51:05.05} UT
GRB_PHI:         168.00 [deg]
GRB_THETA:       155.00 [deg]
DATA_TIME_SCALE: 2.0480 [sec]
HARD_RATIO:      0.39
LOC_ALGORITHM:   3 (version number of)
MOST_LIKELY:      96%  GRB
2nd_MOST_LIKELY:   3%  Generic Transient
DETECTORS:       0,0,0, 0,0,0, 1,0,0, 0,0,1, 0,0,
SUN_POSTN:        79.28d {+05h 17m 08s}  +23.07d {+23d 04' 13"}
SUN_DIST:        123.68 [deg]   Sun_angle= -9.4 [hr] (East of Sun)
MOON_POSTN:       83.75d {+05h 35m 00s}  +24.51d {+24d 30' 27"}
MOON_DIST:       124.30 [deg]
MOON_ILLUM:      0 [%]
GAL_COORDS:      309.52,-14.33 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:      250.41,-55.79 [deg] ecliptic lon,lat of the burst (or transient)
LC_URL:          http://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2021/bn210610827/quicklook/glg_lc_medres34_bn210610827.gif
COMMENTS:        Fermi-GBM Flight-calculated Coordinates.  
COMMENTS:        This trigger occurred at longitude,latitude = 74.68,25.53 [deg].  
COMMENTS:        The LC_URL file will not be created until ~15 min after the trigger.

GCN NOTICE

TITLE:           GCN/FERMI NOTICE
NOTICE_DATE:     Thu 10 Jun 21 19:51:50 UT
NOTICE_TYPE:     Fermi-GBM Flight Position
RECORD_NUM:      70
TRIGGER_NUM:     645047470
GRB_RA:          230.517d {+15h 22m 04s} (J2000),
                 230.747d {+15h 22m 59s} (current),
                 229.981d {+15h 19m 55s} (1950)
GRB_DEC:         +25.933d {+25d 55' 60"} (J2000),
                 +25.858d {+25d 51' 27"} (current),
                 +26.111d {+26d 06' 41"} (1950)
GRB_ERROR:       9.67 [deg radius, statistical plus systematic]
GRB_INTEN:       205 [cnts/sec]
DATA_SIGNIF:     17.20 [sigma]
INTEG_TIME:      4.096 [sec]
GRB_DATE:        19375 TJD;   161 DOY;   21/06/10
GRB_TIME:        71465.05 SOD {19:51:05.05} UT
GRB_PHI:         143.00 [deg]
GRB_THETA:        55.00 [deg]
DATA_TIME_SCALE: 4.0960 [sec]
HARD_RATIO:      0.29
LOC_ALGORITHM:   3 (version number of)
MOST_LIKELY:      97%  GRB
2nd_MOST_LIKELY:   1%  Generic Transient
DETECTORS:       0,0,0, 0,0,0, 1,0,0, 0,0,1, 0,0,
SUN_POSTN:        79.28d {+05h 17m 08s}  +23.07d {+23d 04' 13"}
SUN_DIST:        123.81 [deg]   Sun_angle= -10.1 [hr] (East of Sun)
MOON_POSTN:       83.75d {+05h 35m 01s}  +24.51d {+24d 30' 28"}
MOON_DIST:       120.38 [deg]
MOON_ILLUM:      0 [%]
GAL_COORDS:       39.63, 56.41 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:      218.99, 42.64 [deg] ecliptic lon,lat of the burst (or transient)
LC_URL:          http://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2021/bn210610827/quicklook/glg_lc_medres34_bn210610827.gif
COMMENTS:        Fermi-GBM Flight-calculated Coordinates.  
COMMENTS:        This trigger occurred at longitude,latitude = 74.68,25.53 [deg].  
COMMENTS:        The LC_URL file will not be created until ~15 min after the trigger.

GCN NOTICE

TITLE:           GCN/FERMI NOTICE
NOTICE_DATE:     Thu 10 Jun 21 19:51:56 UT
NOTICE_TYPE:     Fermi-GBM Flight Position
RECORD_NUM:      73
TRIGGER_NUM:     645047470
GRB_RA:          230.800d {+15h 23m 12s} (J2000),
                 231.029d {+15h 24m 07s} (current),
                 230.265d {+15h 21m 04s} (1950)
GRB_DEC:         +26.150d {+26d 08' 60"} (J2000),
                 +26.075d {+26d 04' 29"} (current),
                 +26.327d {+26d 19' 37"} (1950)
GRB_ERROR:       5.22 [deg radius, statistical plus systematic]
GRB_INTEN:       747 [cnts/sec]
DATA_SIGNIF:     45.40 [sigma]
INTEG_TIME:      2.048 [sec]
GRB_DATE:        19375 TJD;   161 DOY;   21/06/10
GRB_TIME:        71465.05 SOD {19:51:05.05} UT
GRB_PHI:         143.00 [deg]
GRB_THETA:        55.00 [deg]
DATA_TIME_SCALE: 2.0480 [sec]
HARD_RATIO:      0.39
LOC_ALGORITHM:   3 (version number of)
MOST_LIKELY:      96%  GRB
2nd_MOST_LIKELY:   3%  Generic Transient
DETECTORS:       0,0,0, 0,0,0, 1,0,0, 0,0,1, 0,0,
SUN_POSTN:        79.28d {+05h 17m 08s}  +23.07d {+23d 04' 13"}
SUN_DIST:        123.76 [deg]   Sun_angle= -10.1 [hr] (East of Sun)
MOON_POSTN:       83.75d {+05h 35m 01s}  +24.51d {+24d 30' 28"}
MOON_DIST:       120.35 [deg]
MOON_ILLUM:      0 [%]
GAL_COORDS:       40.10, 56.20 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:      219.21, 42.93 [deg] ecliptic lon,lat of the burst (or transient)
LC_URL:          http://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2021/bn210610827/quicklook/glg_lc_medres34_bn210610827.gif
COMMENTS:        Fermi-GBM Flight-calculated Coordinates.  
COMMENTS:        This trigger occurred at longitude,latitude = 74.68,25.53 [deg].  
COMMENTS:        The LC_URL file will not be created until ~15 min after the trigger.

GCN NOTICE

TITLE:           GCN/FERMI NOTICE
NOTICE_DATE:     Thu 10 Jun 21 19:52:05 UT
NOTICE_TYPE:     Fermi-GBM Flight Position
RECORD_NUM:      93
TRIGGER_NUM:     645047470
GRB_RA:          227.050d {+15h 08m 12s} (J2000),
                 227.270d {+15h 09m 05s} (current),
                 226.538d {+15h 06m 09s} (1950)
GRB_DEC:         +32.267d {+32d 16' 00"} (J2000),
                 +32.186d {+32d 11' 08"} (current),
                 +32.457d {+32d 27' 26"} (1950)
GRB_ERROR:       4.13 [deg radius, statistical plus systematic]
GRB_INTEN:       1179 [cnts/sec]
DATA_SIGNIF:     103.00 [sigma]
INTEG_TIME:      4.096 [sec]
GRB_DATE:        19375 TJD;   161 DOY;   21/06/10
GRB_TIME:        71465.05 SOD {19:51:05.05} UT
GRB_PHI:         137.00 [deg]
GRB_THETA:        50.00 [deg]
DATA_TIME_SCALE: 4.0960 [sec]
HARD_RATIO:      0.36
LOC_ALGORITHM:   3 (version number of)
MOST_LIKELY:      96%  GRB
2nd_MOST_LIKELY:   3%  Generic Transient
DETECTORS:       0,0,0, 0,0,0, 1,0,0, 0,0,1, 0,0,
SUN_POSTN:        79.28d {+05h 17m 08s}  +23.07d {+23d 04' 13"}
SUN_DIST:        116.84 [deg]   Sun_angle= -9.9 [hr] (East of Sun)
MOON_POSTN:       83.76d {+05h 35m 01s}  +24.51d {+24d 30' 29"}
MOON_DIST:       113.46 [deg]
MOON_ILLUM:      0 [%]
GAL_COORDS:       51.13, 59.99 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:      211.68, 47.39 [deg] ecliptic lon,lat of the burst (or transient)
LC_URL:          http://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2021/bn210610827/quicklook/glg_lc_medres34_bn210610827.gif
COMMENTS:        Fermi-GBM Flight-calculated Coordinates.  
COMMENTS:        This trigger occurred at longitude,latitude = 74.68,25.53 [deg].  
COMMENTS:        The LC_URL file will not be created until ~15 min after the trigger.

GCN NOTICE

TITLE:          GCN/INTEGRAL NOTICE
NOTICE_DATE:    Thu 10 Jun 21 19:52:28 UT
NOTICE_TYPE:    INTEGRAL SPI ACS Trigger
TRIGGER_NUM:    9261,   Sub_Num: 0
GRB_INTEN:      9.27 [sigma]
GRB_TIME:       71473.48 SOD {19:51:13.48} UT
GRB_DATE:       19375 TJD;   161 DOY;   21/06/10
COMMENTS:       INTEGRAL SPI_ACS GRB Trigger.  
COMMENTS:       Time_Scale=2.0000 and Time_Error=1.0000.  
COMMENTS:          
COMMENTS:       NOTE: This SPIACS event is temporally(8.0<100sec) coincident with the FERMI_GBM event (trignum=645047470).  
COMMENTS:          
COMMENTS:       The SPIACS lightcurve can be found at:  
COMMENTS:       ftp://isdcarc.unige.ch/arc/FTP/ibas/spiacs/2021-06/2021-06-10T19-51-13.3438-00846-60304-0.lc

GCN NOTICE

TITLE:           GCN/FERMI NOTICE
NOTICE_DATE:     Thu 10 Jun 21 19:51:51 UT
NOTICE_TYPE:     Fermi-GBM Ground Position
RECORD_NUM:      57
TRIGGER_NUM:     645047470
GRB_RA:          244.790d {+16h 19m 10s} (J2000),
                 245.023d {+16h 20m 06s} (current),
                 244.246d {+16h 16m 59s} (1950)
GRB_DEC:         +20.970d {+20d 58' 12"} (J2000),
                 +20.919d {+20d 55' 10"} (current),
                 +21.090d {+21d 05' 23"} (1950)
GRB_ERROR:       8.65 [deg radius, statistical only]
DATA_SIGNIF:     6.50 [sigma]
DATA_INTERVAL:   4.096 [sec]
GRB_DATE:        19375 TJD;   161 DOY;   21/06/10
GRB_TIME:        71465.05 SOD {19:51:05.05} UT
GRB_PHI:         160.00 [deg]
GRB_THETA:        57.00 [deg]
E_RANGE:         44.032 - 279.965 [keV]
LOC_ALGORITHM:   4173 (Gnd S/W Version number)
SUN_POSTN:        79.28d {+05h 17m 08s}  +23.07d {+23d 04' 13"}
SUN_DIST:        133.87 [deg]   Sun_angle= -11.0 [hr] (East of Sun)
MOON_POSTN:       83.75d {+05h 35m 01s}  +24.51d {+24d 30' 28"}
MOON_DIST:       131.06 [deg]
MOON_ILLUM:      0 [%]
GAL_COORDS:       37.29, 42.50 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:      237.85, 41.64 [deg] ecliptic lon,lat of the burst (or transient)
LC_URL:          http://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2021/bn210610827/quicklook/glg_lc_medres34_bn210610827.gif
POS_MAP_URL:     http://gcn.gsfc.nasa.gov/notices_f/gbm_gnd_loc_map_645047470.fits
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.  
COMMENTS:        The POS_MAP_URL file will not be created/available until ~1.5 min after the notice.

GCN NOTICE

TITLE:           GCN/FERMI NOTICE
NOTICE_DATE:     Thu 10 Jun 21 19:52:40 UT
NOTICE_TYPE:     Fermi-GBM Ground Position
RECORD_NUM:      0
TRIGGER_NUM:     645047470
GRB_RA:          246.810d {+16h 27m 14s} (J2000),
                 247.064d {+16h 28m 15s} (current),
                 246.217d {+16h 24m 52s} (1950)
GRB_DEC:         +10.500d {+10d 30' 00"} (J2000),
                 +10.453d {+10d 27' 12"} (current),
                 +10.611d {+10d 36' 39"} (1950)
GRB_ERROR:       6.28 [deg radius, statistical only]
DATA_SIGNIF:     8.50 [sigma]
DATA_INTERVAL:   10.240 [sec]
GRB_DATE:        19375 TJD;   161 DOY;   21/06/10
GRB_TIME:        71465.05 SOD {19:51:05.05} UT
GRB_PHI:         164.00 [deg]
GRB_THETA:        67.00 [deg]
E_RANGE:         44.032 - 279.965 [keV]
LOC_ALGORITHM:   41731 (Gnd S/W Version number)
SUN_POSTN:        79.28d {+05h 17m 08s}  +23.07d {+23d 04' 13"}
SUN_DIST:        144.41 [deg]   Sun_angle= -11.2 [hr] (East of Sun)
MOON_POSTN:       83.76d {+05h 35m 03s}  +24.51d {+24d 30' 31"}
MOON_DIST:       141.43 [deg]
MOON_ILLUM:      0 [%]
GAL_COORDS:       25.64, 36.73 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:      242.90, 31.78 [deg] ecliptic lon,lat of the burst (or transient)
LC_URL:          http://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2021/bn210610827/quicklook/glg_lc_medres34_bn210610827.gif
POS_MAP_URL:     http://gcn.gsfc.nasa.gov/notices_f/gbm_gnd_loc_map_645047470.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(8.0<100sec) coincident with the INTEGRAL_SPIACS event (trignum=9261).

GCN NOTICE

TITLE:           GCN/FERMI NOTICE
NOTICE_DATE:     Thu 10 Jun 21 19:53:24 UT
NOTICE_TYPE:     Fermi-GBM Ground Position
RECORD_NUM:      3
TRIGGER_NUM:     645047470
GRB_RA:          241.540d {+16h 06m 10s} (J2000),
                 241.792d {+16h 07m 10s} (current),
                 240.953d {+16h 03m 49s} (1950)
GRB_DEC:         +12.400d {+12d 24' 00"} (J2000),
                 +12.343d {+12d 20' 36"} (current),
                 +12.534d {+12d 32' 02"} (1950)
GRB_ERROR:       2.79 [deg radius, statistical only]
DATA_SIGNIF:     19.20 [sigma]
DATA_INTERVAL:   20.480 [sec]
GRB_DATE:        19375 TJD;   161 DOY;   21/06/10
GRB_TIME:        71465.05 SOD {19:51:05.05} UT
GRB_PHI:         158.00 [deg]
GRB_THETA:        66.00 [deg]
E_RANGE:         44.032 - 279.965 [keV]
LOC_ALGORITHM:   41731 (Gnd S/W Version number)
SUN_POSTN:        79.29d {+05h 17m 08s}  +23.07d {+23d 04' 13"}
SUN_DIST:        140.66 [deg]   Sun_angle= -10.8 [hr] (East of Sun)
MOON_POSTN:       83.77d {+05h 35m 04s}  +24.51d {+24d 30' 34"}
MOON_DIST:       137.36 [deg]
MOON_ILLUM:      0 [%]
GAL_COORDS:       24.94, 42.21 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:      236.47, 32.59 [deg] ecliptic lon,lat of the burst (or transient)
LC_URL:          http://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2021/bn210610827/quicklook/glg_lc_medres34_bn210610827.gif
POS_MAP_URL:     http://gcn.gsfc.nasa.gov/notices_f/gbm_gnd_loc_map_645047470.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(8.0<100sec) coincident with the INTEGRAL_SPIACS event (trignum=9261).

GCN NOTICE

TITLE:           GCN/FERMI NOTICE
NOTICE_DATE:     Thu 10 Jun 21 19:53:11 UT
NOTICE_TYPE:     Fermi-GBM Ground Position
RECORD_NUM:      2
TRIGGER_NUM:     645047470
GRB_RA:          244.410d {+16h 17m 38s} (J2000),
                 244.660d {+16h 18m 38s} (current),
                 243.827d {+16h 15m 19s} (1950)
GRB_DEC:         +12.930d {+12d 55' 48"} (J2000),
                 +12.879d {+12d 52' 43"} (current),
                 +13.052d {+13d 03' 05"} (1950)
GRB_ERROR:       4.75 [deg radius, statistical only]
DATA_SIGNIF:     15.70 [sigma]
DATA_INTERVAL:   17.408 [sec]
GRB_DATE:        19375 TJD;   161 DOY;   21/06/10
GRB_TIME:        71465.05 SOD {19:51:05.05} UT
GRB_PHI:         161.00 [deg]
GRB_THETA:        65.00 [deg]
E_RANGE:         44.032 - 279.965 [keV]
LOC_ALGORITHM:   41731 (Gnd S/W Version number)
SUN_POSTN:        79.29d {+05h 17m 08s}  +23.07d {+23d 04' 13"}
SUN_DIST:        141.30 [deg]   Sun_angle= -11.0 [hr] (East of Sun)
MOON_POSTN:       83.77d {+05h 35m 04s}  +24.51d {+24d 30' 33"}
MOON_DIST:       138.22 [deg]
MOON_ILLUM:      0 [%]
GAL_COORDS:       27.16, 39.90 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:      239.60, 33.71 [deg] ecliptic lon,lat of the burst (or transient)
LC_URL:          http://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2021/bn210610827/quicklook/glg_lc_medres34_bn210610827.gif
POS_MAP_URL:     http://gcn.gsfc.nasa.gov/notices_f/gbm_gnd_loc_map_645047470.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(8.0<100sec) coincident with the INTEGRAL_SPIACS event (trignum=9261).

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Thu 10 Jun 21 20:01:20 UT
NOTICE_TYPE:     Swift-XRT Position
TRIGGER_NUM:     1054681,   Seg_Num: 0
GRB_RA:          243.9180d {+16h 15m 40.32s} (J2000),
                 244.1652d {+16h 16m 39.65s} (current),
                 243.3418d {+16h 13m 22.03s} (1950)
GRB_DEC:         +14.3977d {+14d 23' 51.7"} (J2000),
                 +14.3455d {+14d 20' 43.6"} (current),
                 +14.5214d {+14d 31' 16.8"} (1950)
GRB_ERROR:       6.7 [arcsec radius, statistical plus systematic, 90% containment]
GRB_INTEN:       1.07e-08 [erg/cm2/sec]
GRB_SIGNIF:      4.58 [sigma]
IMG_START_DATE:  19375 TJD;   161 DOY;   21/06/10
IMG_START_TIME:  71571.42 SOD {19:52:51.42} UT,   83.9 [sec] since BAT Trigger Time
TAM[0-3]:        327.68 237.15 261.74 243.74
AMPLIFIER:       2
WAVEFORM:        134
SUN_POSTN:        79.29d {+05h 17m 10s}  +23.07d {+23d 04' 14"}
SUN_DIST:        139.76 [deg]   Sun_angle= -11.0 [hr] (East of Sun)
MOON_POSTN:       83.84d {+05h 35m 21s}  +24.52d {+24d 31' 06"}
MOON_DIST:       136.65 [deg]
MOON_ILLUM:      0 [%]
GAL_COORDS:       28.66, 40.93 [deg] galactic lon,lat of the burst
ECL_COORDS:      238.66, 35.04 [deg] ecliptic lon,lat of the burst
COMMENTS:        SWIFT-XRT Coordinates.  
COMMENTS:        The XRT position is 1.26 arcmin from the BAT position.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Thu 10 Jun 21 20:01:31 UT
NOTICE_TYPE:     Swift-XRT Image
TRIGGER_NUM:     1054681,   Seg_Num: 0
GRB_RA:          243.9180d {+16h 15m 40.3s} (J2000),
                 244.1652d {+16h 16m 39.6s} (current),
                 243.3418d {+16h 13m 22.0s} (1950)
GRB_DEC:         +14.3977d {+14d 23' 51.7"} (J2000),
                 +14.3455d {+14d 20' 43.6"} (current),
                 +14.5214d {+14d 31' 16.8"} (1950)
GRB_ERROR:       6.5 [arcsec, radius, statistical plus systematic]
GRB_INTEN:       21 [cnts]
IMG_START_DATE:  19375 TJD;   161 DOY;   21/06/10
IMG_START_TIME:  71571.42 SOD {19:52:51.42} UT,   83.9 [sec] since BAT Trigger Time
CENTROID_X:      300.43,  raw= 300  [pixels]
CENTROID_Y:      292.53,  raw= 293  [pixels]
ROLL:            337.94 [deg]
GAIN:            1
MODE:            2, Short Image mode
WAVEFORM:        134
EXPO_TIME:       0.10 [sec]
GRB_POS_XRT_Y:   -13.12
GRB_POS_XRT_Z:   -16.41
IMAGE_URL:       sw01054681000msxps_rw.img
SUN_POSTN:        79.29d {+05h 17m 10s}  +23.07d {+23d 04' 14"}
SUN_DIST:        139.76 [deg]   Sun_angle= -11.0 [hr] (East of Sun)
MOON_POSTN:       83.84d {+05h 35m 22s}  +24.52d {+24d 31' 06"}
MOON_DIST:       136.65 [deg]
MOON_ILLUM:      0 [%]
GAL_COORDS:       28.66, 40.93 [deg] galactic lon,lat of the burst
ECL_COORDS:      238.66, 35.04 [deg] ecliptic lon,lat of the burst
COMMENTS:        SWIFT-XRT Image.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Thu 10 Jun 21 20:01:33 UT
NOTICE_TYPE:     Swift-XRT Processed Image
TRIGGER_NUM:     1054681,   Seg_Num: 0
GRB_RA:          243.9180d {+16h 15m 40.3s} (J2000),
                 244.1652d {+16h 16m 39.6s} (current),
                 243.3418d {+16h 13m 22.0s} (1950)
GRB_DEC:         +14.3977d {+14d 23' 51.7"} (J2000),
                 +14.3455d {+14d 20' 43.6"} (current),
                 +14.5214d {+14d 31' 16.8"} (1950)
GRB_ERROR:       6.5 [arcsec, radius, statistical plus systematic]
GRB_INTEN:       21 [cnts]
IMG_START_DATE:  19375 TJD;   161 DOY;   21/06/10
IMG_START_TIME:  71571.42 SOD {19:52:51.42} UT,   83.9 [sec] since BAT Trigger Time
CENTROID_X:      300.43,  raw= 300  [pixels]
CENTROID_Y:      292.53,  raw= 293  [pixels]
ROLL:            337.94 [deg]
GAIN:            1
MODE:            2, Short Image mode
WAVEFORM:        134
EXPO_TIME:       0.10 [sec]
GRB_POS_XRT_Y:   -13.12
GRB_POS_XRT_Z:   -16.41
IMAGE_URL:       sw01054681000msxps_rw.img
SUN_POSTN:        79.29d {+05h 17m 10s}  +23.07d {+23d 04' 14"}
SUN_DIST:        139.76 [deg]   Sun_angle= -11.0 [hr] (East of Sun)
MOON_POSTN:       83.84d {+05h 35m 22s}  +24.52d {+24d 31' 07"}
MOON_DIST:       136.65 [deg]
MOON_ILLUM:      0 [%]
GAL_COORDS:       28.66, 40.93 [deg] galactic lon,lat of the burst
ECL_COORDS:      238.66, 35.04 [deg] ecliptic lon,lat of the burst
COMMENTS:        SWIFT-XRT Processed Image.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Thu 10 Jun 21 20:01:46 UT
NOTICE_TYPE:     Swift-BAT GRB Lightcurve
TRIGGER_NUM:     1054681,   Seg_Num: 0
GRB_RA:          243.939d {+16h 15m 45s} (J2000),
                 244.186d {+16h 16m 45s} (current),
                 243.363d {+16h 13m 27s} (1950)
GRB_DEC:         +14.391d {+14d 23' 29"} (J2000),
                 +14.339d {+14d 20' 21"} (current),
                 +14.515d {+14d 30' 54"} (1950)
GRB_DATE:        19375 TJD;   161 DOY;   21/06/10
GRB_TIME:        71487.51 SOD {19:51:27.51} UT
TRIGGER_INDEX:   155
GRB_PHI:          43.05 [deg]
GRB_THETA:        38.34 [deg]
DELTA_TIME:      52.00 [sec]
TRIGGER_DUR:     1.024 [sec] 
SOLN_STATUS:     0x3
RATE_SIGNIF:     46.52 [sigma]
IMAGE_SIGNIF:    10.54 [sigma]
LC_URL:          sw01054681000msb.lc
SUN_POSTN:        79.29d {+05h 17m 10s}  +23.07d {+23d 04' 14"}
SUN_DIST:        139.77 [deg]   Sun_angle= -11.0 [hr] (East of Sun)
MOON_POSTN:       83.84d {+05h 35m 22s}  +24.52d {+24d 31' 07"}
MOON_DIST:       136.66 [deg]
MOON_ILLUM:      0 [%]
GAL_COORDS:       28.66, 40.91 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:      238.68, 35.04 [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 = 11.24,3.22 [deg].

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Thu 10 Jun 21 20:03:19 UT
NOTICE_TYPE:     Swift-UVOT Image
TRIGGER_NUM:     1054681,   Seg_Num: 0
POINT_RA:        243.919d {+16h 15m 41s} (J2000)
POINT_DEC:       +14.392d {+14d 23' 30"} (J2000)
ROLL:            337.940d
IMG_START_DATE:  19375 TJD;   161 DOY;   21/06/10
IMG_START_TIME:  71579.43 SOD {19:52:59.43} UT,   91.9 [sec] since BAT Trigger Time
FILTER:          10, White
EXPOSURE_ID:     645047606
X_OFFSET:        838 [pixels]
Y_OFFSET:        882 [pixels]
WIDTH:           160 [pixels]
HEIGHT:          160 [pixels]
X_GRB_POS:       998
Y_GRB_POS:       1042
BINNING_INDEX:   1
IM_URL:          sw01054681000msuni0119.fits
SUN_POSTN:        79.29d {+05h 17m 10s}  +23.07d {+23d 04' 15"}
SUN_DIST:        139.77 [deg]   Sun_angle= -11.0 [hr] (East of Sun)
MOON_POSTN:       83.86d {+05h 35m 26s}  +24.52d {+24d 31' 14"}
MOON_DIST:       136.65 [deg]
MOON_ILLUM:      0 [%]
GAL_COORDS:       28.65, 40.93 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      238.66, 35.04 [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).

red DSS finding chart ps-file

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Thu 10 Jun 21 20:03:34 UT
NOTICE_TYPE:     Swift-UVOT Processed Image
TRIGGER_NUM:     1054681,   Seg_Num: 0
POINT_RA:        243.919d {+16h 15m 41s} (J2000)
POINT_DEC:       +14.392d {+14d 23' 30"} (J2000)
ROLL:            337.940d
IMG_START_DATE:  19375 TJD;   161 DOY;   21/06/10
IMG_START_TIME:  71579.43 SOD {19:52:59.43} UT,   91.9 [sec] since BAT Trigger Time
FILTER:          10, White
EXPOSURE_ID:     645047606
X_OFFSET:        838 [pixels]
Y_OFFSET:        882 [pixels]
WIDTH:           160 [pixels]
HEIGHT:          160 [pixels]
X_GRB_POS:       998
Y_GRB_POS:       1042
BINNING_INDEX:   1
IM_URL:          sw01054681000msuni0119.fits
SUN_POSTN:        79.29d {+05h 17m 10s}  +23.07d {+23d 04' 15"}
SUN_DIST:        139.77 [deg]   Sun_angle= -11.0 [hr] (East of Sun)
MOON_POSTN:       83.86d {+05h 35m 26s}  +24.52d {+24d 31' 15"}
MOON_DIST:       136.65 [deg]
MOON_ILLUM:      0 [%]
GAL_COORDS:       28.65, 40.93 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      238.66, 35.04 [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:     Thu 10 Jun 21 20:05:33 UT
NOTICE_TYPE:     Swift-UVOT Position
TRIGGER_NUM:     1054681,   Seg_Num: 0
GRB_RA:          243.9183d {+16h 15m 40.39s} (J2000),
                 244.1655d {+16h 16m 39.72s} (current),
                 243.3421d {+16h 13m 22.10s} (1950)
GRB_DEC:         +14.3990d {+14d 23' 56.3"} (J2000),
                 +14.3468d {+14d 20' 48.3"} (current),
                 +14.5227d {+14d 31' 21.5"} (1950)
GRB_ERROR:       0.6 [arcsec radius, statistical only]
GRB_MAG:         13.69 +/- 0.14 [mag]
FILTER:          10, White
IMG_START_DATE:  19375 TJD;   161 DOY;   21/06/10
IMG_START_TIME:  71576.00 SOD {19:52:56.00} UT,   88.5 [sec] since BAT Trigger Time
SUN_POSTN:        79.29d {+05h 17m 11s}  +23.07d {+23d 04' 15"}
SUN_DIST:        139.76 [deg]   Sun_angle= -11.0 [hr] (East of Sun)
MOON_POSTN:       83.88d {+05h 35m 31s}  +24.52d {+24d 31' 22"}
MOON_DIST:       136.63 [deg]
MOON_ILLUM:      0 [%]
GAL_COORDS:       28.66, 40.93 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:      238.66, 35.04 [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 4.7 arcsec from the XRT position.  
COMMENTS:        Result based on Genie data.  
COMMENTS:        Notice generated automatically.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Thu 10 Jun 21 20:10:55 UT
NOTICE_TYPE:     Swift-UVOT Processed Source List
TRIGGER_NUM:     1054681,   Seg_Num: 0
POINT_RA:        243.916d {+16h 15m 40s} (J2000)
POINT_DEC:       +14.392d {+14d 23' 32"} (J2000)
POINT_ROLL:      337.939d
IMG_START_DATE:  19375 TJD;   161 DOY;   21/06/10
IMG_START_TIME:  72345.86 SOD {20:05:45.86} UT,   858.4 [sec] since BAT Trigger Time
FILTER:          10, White
BKG_MEAN:        1.626
N_STARS:         111
X_OFFSET:        278 [pixels]
Y_OFFSET:        322 [pixels]
X_MAX:           1717 [pixels]
Y_MAX:           1761 [pixels]
DET_THRESH:      11
PHOTO_THRESH:    5
SL_URL:          sw01054681000msufc0858.fits
SUN_POSTN:        79.30d {+05h 17m 12s}  +23.07d {+23d 04' 16"}
SUN_DIST:        139.76 [deg]   Sun_angle= -11.0 [hr] (East of Sun)
MOON_POSTN:       83.93d {+05h 35m 42s}  +24.53d {+24d 31' 44"}
MOON_DIST:       136.61 [deg]
MOON_ILLUM:      0 [%]
GAL_COORDS:       28.65, 40.93 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      238.66, 35.04 [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:     Thu 10 Jun 21 20:12:51 UT
NOTICE_TYPE:     Swift-UVOT Image
TRIGGER_NUM:     1054681,   Seg_Num: 0
POINT_RA:        243.916d {+16h 15m 40s} (J2000)
POINT_DEC:       +14.392d {+14d 23' 32"} (J2000)
ROLL:            337.939d
IMG_START_DATE:  19375 TJD;   161 DOY;   21/06/10
IMG_START_TIME:  72345.86 SOD {20:05:45.86} UT,   858.4 [sec] since BAT Trigger Time
FILTER:          10, White
EXPOSURE_ID:     645048373
X_OFFSET:        837 [pixels]
Y_OFFSET:        881 [pixels]
WIDTH:           160 [pixels]
HEIGHT:          160 [pixels]
X_GRB_POS:       997
Y_GRB_POS:       1041
BINNING_INDEX:   1
IM_URL:          sw01054681000msuni0886.fits
SUN_POSTN:        79.30d {+05h 17m 12s}  +23.07d {+23d 04' 16"}
SUN_DIST:        139.76 [deg]   Sun_angle= -11.0 [hr] (East of Sun)
MOON_POSTN:       83.94d {+05h 35m 47s}  +24.53d {+24d 31' 51"}
MOON_DIST:       136.60 [deg]
MOON_ILLUM:      0 [%]
GAL_COORDS:       28.65, 40.93 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      238.66, 35.04 [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:     Thu 10 Jun 21 20:13:06 UT
NOTICE_TYPE:     Swift-UVOT Processed Image
TRIGGER_NUM:     1054681,   Seg_Num: 0
POINT_RA:        243.916d {+16h 15m 40s} (J2000)
POINT_DEC:       +14.392d {+14d 23' 32"} (J2000)
ROLL:            337.939d
IMG_START_DATE:  19375 TJD;   161 DOY;   21/06/10
IMG_START_TIME:  72345.86 SOD {20:05:45.86} UT,   858.4 [sec] since BAT Trigger Time
FILTER:          10, White
EXPOSURE_ID:     645048373
X_OFFSET:        837 [pixels]
Y_OFFSET:        881 [pixels]
WIDTH:           160 [pixels]
HEIGHT:          160 [pixels]
X_GRB_POS:       997
Y_GRB_POS:       1041
BINNING_INDEX:   1
IM_URL:          sw01054681000msuni0886.fits
SUN_POSTN:        79.30d {+05h 17m 12s}  +23.07d {+23d 04' 16"}
SUN_DIST:        139.76 [deg]   Sun_angle= -11.0 [hr] (East of Sun)
MOON_POSTN:       83.95d {+05h 35m 47s}  +24.53d {+24d 31' 52"}
MOON_DIST:       136.60 [deg]
MOON_ILLUM:      0 [%]
GAL_COORDS:       28.65, 40.93 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      238.66, 35.04 [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 NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Thu 10 Jun 21 20:06:39 UT
NOTICE_TYPE:     Swift-UVOT Source List
TRIGGER_NUM:     1054681,   Seg_Num: 0
POINT_RA:        243.916d {+16h 15m 40s} (J2000)
POINT_DEC:       +14.392d {+14d 23' 32"} (J2000)
POINT_ROLL:      337.939d
IMG_START_DATE:  19375 TJD;   161 DOY;   21/06/10
IMG_START_TIME:  71791.22 SOD {19:56:31.22} UT,   303.7 [sec] since BAT Trigger Time
FILTER:          7, U
BKG_MEAN:        0.469
N_STARS:         34
X_OFFSET:        518 [pixels]
Y_OFFSET:        562 [pixels]
X_MAX:           1477 [pixels]
Y_MAX:           1521 [pixels]
DET_THRESH:      6
PHOTO_THRESH:    3
SL_URL:          sw01054681000msufc0303.fits
SUN_POSTN:        79.29d {+05h 17m 11s}  +23.07d {+23d 04' 15"}
SUN_DIST:        139.76 [deg]   Sun_angle= -11.0 [hr] (East of Sun)
MOON_POSTN:       83.89d {+05h 35m 33s}  +24.52d {+24d 31' 27"}
MOON_DIST:       136.63 [deg]
MOON_ILLUM:      0 [%]
GAL_COORDS:       28.65, 40.93 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      238.66, 35.04 [deg] ecliptic lon,lat of the pointing direction
COMMENTS:        SWIFT-UVOT Source List.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Thu 10 Jun 21 20:10:41 UT
NOTICE_TYPE:     Swift-UVOT Source List
TRIGGER_NUM:     1054681,   Seg_Num: 0
POINT_RA:        243.916d {+16h 15m 40s} (J2000)
POINT_DEC:       +14.392d {+14d 23' 32"} (J2000)
POINT_ROLL:      337.939d
IMG_START_DATE:  19375 TJD;   161 DOY;   21/06/10
IMG_START_TIME:  72345.86 SOD {20:05:45.86} UT,   858.4 [sec] since BAT Trigger Time
FILTER:          10, White
BKG_MEAN:        1.626
N_STARS:         111
X_OFFSET:        278 [pixels]
Y_OFFSET:        322 [pixels]
X_MAX:           1717 [pixels]
Y_MAX:           1761 [pixels]
DET_THRESH:      11
PHOTO_THRESH:    5
SL_URL:          sw01054681000msufc0858.fits
SUN_POSTN:        79.30d {+05h 17m 11s}  +23.07d {+23d 04' 16"}
SUN_DIST:        139.76 [deg]   Sun_angle= -11.0 [hr] (East of Sun)
MOON_POSTN:       83.92d {+05h 35m 42s}  +24.53d {+24d 31' 43"}
MOON_DIST:       136.61 [deg]
MOON_ILLUM:      0 [%]
GAL_COORDS:       28.65, 40.93 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      238.66, 35.04 [deg] ecliptic lon,lat of the pointing direction
COMMENTS:        SWIFT-UVOT Source List.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Thu 10 Jun 21 20:07:45 UT
NOTICE_TYPE:     Swift-UVOT Image
TRIGGER_NUM:     1054681,   Seg_Num: 0
POINT_RA:        243.916d {+16h 15m 40s} (J2000)
POINT_DEC:       +14.392d {+14d 23' 32"} (J2000)
ROLL:            337.939d
IMG_START_DATE:  19375 TJD;   161 DOY;   21/06/10
IMG_START_TIME:  71791.22 SOD {19:56:31.22} UT,   303.7 [sec] since BAT Trigger Time
FILTER:          7, U
EXPOSURE_ID:     645047818
X_OFFSET:        838 [pixels]
Y_OFFSET:        882 [pixels]
WIDTH:           160 [pixels]
HEIGHT:          160 [pixels]
X_GRB_POS:       998
Y_GRB_POS:       1042
BINNING_INDEX:   1
IM_URL:          sw01054681000msuni0331.fits
SUN_POSTN:        79.30d {+05h 17m 11s}  +23.07d {+23d 04' 15"}
SUN_DIST:        139.76 [deg]   Sun_angle= -11.0 [hr] (East of Sun)
MOON_POSTN:       83.90d {+05h 35m 35s}  +24.53d {+24d 31' 31"}
MOON_DIST:       136.62 [deg]
MOON_ILLUM:      0 [%]
GAL_COORDS:       28.65, 40.93 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      238.66, 35.04 [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:     Thu 10 Jun 21 20:02:03 UT
NOTICE_TYPE:     Swift-UVOT Source List
TRIGGER_NUM:     1054681,   Seg_Num: 0
POINT_RA:        243.919d {+16h 15m 41s} (J2000)
POINT_DEC:       +14.392d {+14d 23' 30"} (J2000)
POINT_ROLL:      337.940d
IMG_START_DATE:  19375 TJD;   161 DOY;   21/06/10
IMG_START_TIME:  71579.43 SOD {19:52:59.43} UT,   91.9 [sec] since BAT Trigger Time
FILTER:          10, White
BKG_MEAN:        1.630
N_STARS:         47
X_OFFSET:        488 [pixels]
Y_OFFSET:        704 [pixels]
X_MAX:           1447 [pixels]
Y_MAX:           1663 [pixels]
DET_THRESH:      11
PHOTO_THRESH:    5
SL_URL:          sw01054681000msufc0091.fits
SUN_POSTN:        79.29d {+05h 17m 10s}  +23.07d {+23d 04' 14"}
SUN_DIST:        139.77 [deg]   Sun_angle= -11.0 [hr] (East of Sun)
MOON_POSTN:       83.85d {+05h 35m 23s}  +24.52d {+24d 31' 09"}
MOON_DIST:       136.65 [deg]
MOON_ILLUM:      0 [%]
GAL_COORDS:       28.65, 40.93 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      238.66, 35.04 [deg] ecliptic lon,lat of the pointing direction
COMMENTS:        SWIFT-UVOT Source List.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Thu 10 Jun 21 20:07:59 UT
NOTICE_TYPE:     Swift-UVOT Processed Image
TRIGGER_NUM:     1054681,   Seg_Num: 0
POINT_RA:        243.916d {+16h 15m 40s} (J2000)
POINT_DEC:       +14.392d {+14d 23' 32"} (J2000)
ROLL:            337.939d
IMG_START_DATE:  19375 TJD;   161 DOY;   21/06/10
IMG_START_TIME:  71791.22 SOD {19:56:31.22} UT,   303.7 [sec] since BAT Trigger Time
FILTER:          7, U
EXPOSURE_ID:     645047818
X_OFFSET:        838 [pixels]
Y_OFFSET:        882 [pixels]
WIDTH:           160 [pixels]
HEIGHT:          160 [pixels]
X_GRB_POS:       998
Y_GRB_POS:       1042
BINNING_INDEX:   1
IM_URL:          sw01054681000msuni0331.fits
SUN_POSTN:        79.30d {+05h 17m 11s}  +23.07d {+23d 04' 15"}
SUN_DIST:        139.76 [deg]   Sun_angle= -11.0 [hr] (East of Sun)
MOON_POSTN:       83.90d {+05h 35m 36s}  +24.53d {+24d 31' 32"}
MOON_DIST:       136.62 [deg]
MOON_ILLUM:      0 [%]
GAL_COORDS:       28.65, 40.93 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      238.66, 35.04 [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:     Thu 10 Jun 21 20:06:53 UT
NOTICE_TYPE:     Swift-UVOT Processed Source List
TRIGGER_NUM:     1054681,   Seg_Num: 0
POINT_RA:        243.916d {+16h 15m 40s} (J2000)
POINT_DEC:       +14.392d {+14d 23' 32"} (J2000)
POINT_ROLL:      337.939d
IMG_START_DATE:  19375 TJD;   161 DOY;   21/06/10
IMG_START_TIME:  71791.22 SOD {19:56:31.22} UT,   303.7 [sec] since BAT Trigger Time
FILTER:          7, U
BKG_MEAN:        0.469
N_STARS:         34
X_OFFSET:        518 [pixels]
Y_OFFSET:        562 [pixels]
X_MAX:           1477 [pixels]
Y_MAX:           1521 [pixels]
DET_THRESH:      6
PHOTO_THRESH:    3
SL_URL:          sw01054681000msufc0303.fits
SUN_POSTN:        79.30d {+05h 17m 11s}  +23.07d {+23d 04' 15"}
SUN_DIST:        139.76 [deg]   Sun_angle= -11.0 [hr] (East of Sun)
MOON_POSTN:       83.89d {+05h 35m 34s}  +24.52d {+24d 31' 28"}
MOON_DIST:       136.63 [deg]
MOON_ILLUM:      0 [%]
GAL_COORDS:       28.65, 40.93 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      238.66, 35.04 [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:     Thu 10 Jun 21 20:02:17 UT
NOTICE_TYPE:     Swift-UVOT Processed Source List
TRIGGER_NUM:     1054681,   Seg_Num: 0
POINT_RA:        243.919d {+16h 15m 41s} (J2000)
POINT_DEC:       +14.392d {+14d 23' 30"} (J2000)
POINT_ROLL:      337.940d
IMG_START_DATE:  19375 TJD;   161 DOY;   21/06/10
IMG_START_TIME:  71579.43 SOD {19:52:59.43} UT,   91.9 [sec] since BAT Trigger Time
FILTER:          10, White
BKG_MEAN:        1.630
N_STARS:         47
X_OFFSET:        488 [pixels]
Y_OFFSET:        704 [pixels]
X_MAX:           1447 [pixels]
Y_MAX:           1663 [pixels]
DET_THRESH:      11
PHOTO_THRESH:    5
SL_URL:          sw01054681000msufc0091.fits
SUN_POSTN:        79.29d {+05h 17m 10s}  +23.07d {+23d 04' 14"}
SUN_DIST:        139.77 [deg]   Sun_angle= -11.0 [hr] (East of Sun)
MOON_POSTN:       83.85d {+05h 35m 24s}  +24.52d {+24d 31' 09"}
MOON_DIST:       136.65 [deg]
MOON_ILLUM:      0 [%]
GAL_COORDS:       28.65, 40.93 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      238.66, 35.04 [deg] ecliptic lon,lat of the pointing direction
COMMENTS:        SWIFT-UVOT Processed Source List.  
COMMENTS:        All 4 attachments are included.

GCN Circular #30170
K. L. Page (U Leicester), J.D. Gropp (PSU), J. A. Kennea (PSU), F. E. Marshall (NASA/GSFC), D. M. Palmer (LANL) and M. H. Siegel (PSU) report on behalf of the Neil Gehrels Swift Observatory Team:
At 19:51:27 UT, the Swift Burst Alert Telescope (BAT) triggered and located GRB 210610B (trigger=1054681). Swift slewed immediately to the burst. The BAT on-board calculated location is RA, Dec 243.939, +14.391 which is
```
   RA(J2000) = 16h 15m 45s
   Dec(J2000) = +14d 23' 29"
```
with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). The BAT light curve showed a comlex structure with a duration of about 100 sec. The peak count rate was ~11000 counts/sec (15-350 keV), at ~8 sec after the trigger.
The XRT began observing the field at 19:52:51.4 UT, 83.9 seconds after the BAT trigger. XRT found a bright, uncatalogued X-ray source located at RA, Dec 243.9180, 14.3977 which is equivalent to:
```
   RA(J2000)  = 16h 15m 40.32s
   Dec(J2000) = +14d 23' 51.7"
```
with an uncertainty of 6.7 arcseconds (radius, 90% containment). This location is 77 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.
The initial flux in the 0.1 s image was 1.07e-08 erg cm^-2 s^-1 (0.2-10 keV).
UVOT took a finding chart exposure of 150 seconds with the White filter starting 91 seconds after the BAT trigger. There is a candidate afterglow in the rapidly available 2.7'x2.7' sub-image at
```
  RA(J2000)  =  16:15:40.41 = 243.91836
  DEC(J2000) = +14:23:56.7  =  14.39909
```
with a 90%-confidence error radius of about 0.61 arc sec. This position is 5.2 arc sec. from the center of the XRT error circle. The estimated magnitude is 13.70 with a 1-sigma error of about 0.14. No correction has been made for the expected extinction corresponding to E(B-V) of 0.044.
Burst Advocate for this burst is K. L. Page (klp5 AT leicester.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 Circular #30171
B. Biltzinger, F. Kunzweiler, F. Berlato, J. Burgess & J. Greiner (all MPE Garching) report:
The public trigdat data of the Fermi Gamma-ray Burst Monitor (GBM) trigger 645047470 at 19:51:05 on 10 June 2021 were automatically fitted for spectrum and sky location with BALROG (Burgess et al. 2018, MNRAS 476, 1427; Berlato et al. 2019, ApJ 873, 60).
The best-fit position (1 sigma statistical errors) is:
```
RA(2000.0) = 244.2+/-0.6 deg
Decl.(2000.0) = 16.5+/-1.2 deg
```
We estimate an additional systematic error of 1 deg.
Further details are available at: https://grb.mpe.mpg.de/grb/GRB210610827/
The Healpix map can be downloaded from: https://grb.mpe.mpg.de/grb/GRB210610827/healpix
The location parameters are available as JSON at: https://grb.mpe.mpg.de/grb/GRB210610827/json
GCN Circular #30173
V. Lipunov, E. Gorbovskoy, V.Kornilov, D.Kuvshinov, N.Tyurina, P.Balanutsa, A.Kuznetsov, D. Vlasenko, F. Balakin Lomonosov Moscow State University, Sternberg Astronomical Institute, Moscow State University
A. Tlatov, V.Senik, A.V. Parhomenko, D. Dormidontov Kislovodsk Solar Station of the Pulkovo Observatory
K. Ivanov, O. Gres, N.M. Budnev, S. Yazev, O. Chuvalaev, V. Poleshchuk Irkutsk State University
V. Yurkov, A. Gabovich, Yu. Sergienko Blagoveschensk Educational State University, Blagoveschensk
R. Podesta, Carlos Lopez and F. Podesta Observatorio Astronomico Felix Aguilar (OAFA)
R. Rebolo, M. Serra, N. Lodieu, G. Israelian, L. Suarez-Andres The Instituto de Astrofisica de Canarias
D. Buckley, S. Potter, A. Kniazev, M. Kotze South African Astronomical Observatory
MASTER-Kislovodsk robotic telescope (Global MASTER-Net: http://observ.pereplet.ru, Lipunov et al., 2010, Advances in Astronomy, vol. 2010, 30L) located in Russia (Lomonosov MSU, Kislovodsk Solar Station of Pulkovo observatory) was pointed to the GRB210610.83 145 sec after trigger time at 2021-06-10 19:53:52 UT. On our 3-th (130s exposure) set , obtained 656 sec after tigger time at 2021-06-10 20:02:24 UT, we found 1 optical transient within Swift error-box (ra=243.938 dec=14.3906 r=0.05) brighter than 17.7.
```
 T-Tmid      Date      Time       Expt.        Ra                Dec           Mag
---------|---------------------|-------|-----------------|-----------------|-------
     721   2021-06-10 20:02:24     130   (16h 15m 40.49s , +14d 23m 56.4s)     15.2
```
The 5-sigma upper limit has been about 17.7mag The message may be cited.
GCN Circular #30174
H. Kumar(IITB), J. Stanzin (IAO), V. Bhalerao(IITB), G. C. Anupama(IIA), S. Barway(IIA) report on behalf of the GIT team:
We observed GRB 210610B detected by Swift-BAT (K. L. Page et al., GCN #30170), with the 0.7m GROWTH-India Telescope (GIT). We obtained a 60-sec exposure in the r' filter. We clearly detected the afterglow in our image at R.A.= 16:15:40.44 and DEC.= +14:23:56.65 with an uncertainty of ~0.67 arcsec. The photometric results follow as:
-------------------------------------------------------------------
JD (start) | T_mid-T0(hrs) | Filter | Magnitude (AB) |
-------------------------------------------------------------------
2459376.3429 | 0.37 | r' | 15.98 +/- 0.1 |
-------------------------------------------------------------------
The magnitudes are calibrated against PanSTARRS (Flewelling et al., 2018) and not corrected for Galactic extinction.
The GROWTH India Telescope (GIT) is a 70-cm telescope with a 0.7-degree field of view, set up by the Indian Institute of Astrophysics and the Indian Institute of Technology Bombay with support from the Indo-US Science and Technology Forum (IUSSTF) and the Science and Engineering Research Board (SERB) of the Department of Science and Technology (DST), Government of India (https://sites.google.com/view/growthindia/). It is located at the Indian Astronomical Observatory (Hanle), operated by the Indian Institute of Astrophysics (IIA).
GCN Circular #30175
V. Rumyantsev (CrAO), A. Pozanenko (IKI), S. Belkin (IKI), N. Pankov (HSE) report on behalf of GRB IKI FuN:
We observed the GRB 210610B (Page et al., GCN 30170) with ZTSh 2.6m telescope of CrAO observatory starting on June., 10 (UT) 20:19:24. We detect the bright optical afterglow (Page et al., GCN 30170). We continue observations and will report photometry after data receiving.

GCN Circular #30176
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-Kislovodsk robotic telescope (Global MASTER-Net: http://observ.pereplet.ru, Lipunov et al., 2010, Advances in Astronomy, vol. 2010, 30L) located in Russia (Lomonosov MSU, Kislovodsk Solar Station of Pulkovo observatory) was pointed to the Swift GRB 210610B ( K. L. Page et al., GCN 30170) errorbox 145 sec after trigger time at 2021-06-10 19:53:52 UT, with upper limit up to 18.9 mag. The observations began at zenith distance = 30 deg. The sun altitude is -21.6 deg.
MASTER-SAAO robotic telescope located in South Africa (South African Astronomical Observatory) was pointed to the Swift GRB 210610B errorbox 0 sec after notice time and 582 sec after trigger time at 2021-06-10 20:01:10 UT, with upper limit up to 19.2 mag. The observations began at zenith distance = 52 deg. The sun altitude is -54.2 deg.
MASTER-Tavrida robotic telescope located in Russia (Lomonosov MSU, SAI Crimea astronomical station) was pointed to the Swift GRB 210610B errorbox 15 sec after notice time and 598 sec after trigger time at 2021-06-10 20:01:25 UT, with upper limit up to 20.3 mag. The observations began at zenith distance = 31 deg. The sun altitude is -19.1 deg.
MASTER-IAC robotic telescope located in Spain (IAC Teide Observatory) was pointed to the Swift GRB 210610B errorbox 3486 sec after notice time and 4069 sec after trigger time at 2021-06-10 20:59:16 UT, with upper limit up to 17.6 mag. Observations started at twilight. The observations began at zenith distance = 44 deg. The sun altitude is -12.3 deg.
The galactic latitude b = 40 deg., longitude l = 29 deg.
Real time updated cover map and OT discovered available here: https://master.sai.msu.ru/site/master2/observ.php?id=1633397
We obtain a following upper limits.

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

     160 |   MASTER-Kislovodsk |   C |    30 | 17.5 |        
     215 |   MASTER-Kislovodsk |   C |    40 | 17.7 |        
     643 |         MASTER-SAAO | P\  |   120 | 18.3 |        
     798 |         MASTER-SAAO | P\  |   430 | 19.0 |  Coadd 
     658 |      MASTER-Tavrida |   C |   120 | 19.1 |        
     838 |      MASTER-Tavrida |   C |   480 | 20.0 |  Coadd 
     658 |      MASTER-Tavrida |   C |   120 | 19.1 |        
     722 |   MASTER-Kislovodsk |   C |   130 | 18.2 |        
     722 |   MASTER-Kislovodsk |  P| |   130 | 18.3 |        
     792 |         MASTER-SAAO | P\  |   140 | 18.4 |        
     813 |      MASTER-Tavrida |   C |   150 | 19.2 |        
     813 |      MASTER-Tavrida |   C |   150 | 19.1 |        
     967 |         MASTER-SAAO | P\  |   170 | 18.5 |        
     997 |      MASTER-Tavrida |   C |   180 | 19.2 |        
     997 |      MASTER-Tavrida |   C |   180 | 19.1 |        
    1161 |         MASTER-SAAO | P\  |   180 | 18.5 |        
    1341 |         MASTER-SAAO | P\  |   540 | 19.1 |  Coadd 
    1197 |      MASTER-Tavrida |   C |   180 | 19.4 |        
    1359 |   MASTER-Kislovodsk |   C |   180 | 13.7 |        
    1359 |   MASTER-Kislovodsk |  P| |   180 | 18.5 |        
    1361 |         MASTER-SAAO | P\  |   180 | 18.6 |        
    1403 |      MASTER-Tavrida |   C |   180 | 19.5 |        
    1403 |      MASTER-Tavrida |   C |   180 | 19.1 |        
    1560 |         MASTER-SAAO | P\  |   180 | 18.5 |        
    1603 |      MASTER-Tavrida |   C |   180 | 19.5 |        
    1603 |      MASTER-Tavrida |   C |   180 | 19.3 |        
    1760 |         MASTER-SAAO | P\  |   180 | 18.6 |        
    1940 |         MASTER-SAAO | P\  |   540 | 19.2 |  Coadd 
    1802 |      MASTER-Tavrida |   C |   180 | 19.4 |        
    1802 |      MASTER-Tavrida |   C |   180 | 19.1 |        
    1959 |         MASTER-SAAO | P\  |   180 | 18.7 |        
    2001 |      MASTER-Tavrida |   C |   180 | 19.5 |        
    2181 |      MASTER-Tavrida |   C |   540 | 20.2 |  Coadd 
    2001 |      MASTER-Tavrida |   C |   180 | 19.1 |        
    2019 |   MASTER-Kislovodsk |   C |   180 | 18.2 |        
    2019 |   MASTER-Kislovodsk |  P| |   180 | 18.9 |        
    2159 |         MASTER-SAAO | P\  |   180 | 18.5 |        
    2201 |      MASTER-Tavrida |   C |   180 | 19.5 |        
    2201 |      MASTER-Tavrida |   C |   180 | 19.3 |        
    2358 |         MASTER-SAAO | P\  |   180 | 18.6 |        
    2401 |      MASTER-Tavrida |   C |   180 | 19.6 |        
    2401 |      MASTER-Tavrida |   C |   180 | 19.4 |        
    2558 |         MASTER-SAAO | P\  |   180 | 16.5 |        
    2600 |      MASTER-Tavrida |   C |   180 | 19.6 |        
    2780 |      MASTER-Tavrida |   C |   540 | 20.3 |  Coadd 
    2600 |      MASTER-Tavrida |   C |   180 | 19.3 |        
    2743 |   MASTER-Kislovodsk |   C |   180 | 13.8 |        
    2743 |   MASTER-Kislovodsk |  P| |   180 | 18.9 |        
    2757 |         MASTER-SAAO | P\  |   180 | 15.7 |        
    2800 |      MASTER-Tavrida |   C |   180 | 19.6 |        
    2800 |      MASTER-Tavrida |   C |   180 | 19.4 |        
    2957 |         MASTER-SAAO | P\  |   180 | 17.3 |        
    2999 |      MASTER-Tavrida |   C |   180 | 19.7 |        
    2999 |      MASTER-Tavrida |   C |   180 | 19.4 |        
    3156 |         MASTER-SAAO | P\  |   180 | 16.6 |        
    3199 |      MASTER-Tavrida |   C |   180 | 18.8 |        
    3379 |      MASTER-Tavrida |   C |   540 | 19.9 |  Coadd 
    3199 |      MASTER-Tavrida |   C |   180 | 18.3 |        
    3356 |         MASTER-SAAO | P\  |   180 | 17.2 |        
    3398 |      MASTER-Tavrida |   C |   180 | 19.6 |        
    3398 |      MASTER-Tavrida |   C |   180 | 18.9 |        
    3418 |   MASTER-Kislovodsk |   C |   180 | 18.3 |        
    3418 |   MASTER-Kislovodsk |  P| |   180 | 18.8 |        
    3555 |         MASTER-SAAO | P\  |   180 | 17.0 |        
    3598 |      MASTER-Tavrida |   C |   180 | 19.6 |        
    3598 |      MASTER-Tavrida |   C |   180 | 19.2 |        
    3755 |         MASTER-SAAO | P\  |   180 | 17.3 |        
    3797 |      MASTER-Tavrida |   C |   180 | 19.5 |        
    3797 |      MASTER-Tavrida |   C |   180 | 19.2 |        
    3954 |         MASTER-SAAO | P\  |   180 | 15.7 |        
    3997 |      MASTER-Tavrida |   C |   180 | 19.8 |        
    3997 |      MASTER-Tavrida |   C |   180 | 19.4 |        
    4154 |         MASTER-SAAO | P\  |   180 | 16.4 |        
    4099 |          MASTER-IAC |   C |    60 | 17.6 |        
    4099 |          MASTER-IAC |   C |    60 | 17.3 |        
    4239 |          MASTER-IAC |   I |   180 | 16.9 |        
    4239 |          MASTER-IAC |   R |   180 | 17.1 |

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

GCN Circular #30177
Y.-D. Hu, T.-R. Sun, E. Fernandez-Garcia, A. J. Castro-Tirado, M.D. Caballero-Garcia, M. A. Castro Tirado (IAA-CSIC), C. Perez del Pulgar, A. Castellon, I. Carrasco (Univ. de Malaga), R. Fernandez-Munoz (IHSM/UMA-CSIC) and M. Jelinek (ASU-CAS), on behalf of a larger collaboration, report:
The 60cm BOOTES-2/TELMA robotic telescope at IHSM La Mayora (UMA-CSIC) in Algarrobo Costa (Malaga, Spain) automatically responded to the Swift trigger of GRB 210610B (Page et al. GCNC 30170). Images were taken starting after the twilight as soon as it was possible. In the first co-added 7 x 10 s exposure image, we detect the reported optical afterglow with r = 17.5+-0.2 at 20:27 UT (~0.6 hr after trigger), also pinpointed by UVOT/Swift (Page et al. GCNC 30170), MASTER (Lipunov et al. GCNC 30173) and GIT (Kumar et al. GCNC 30174). Further observations are ongoing.
We thank the staff at La Mayora for its excellent support.
GCN Circular #30178
V. Rumyantsev (CrAO), A. Pozanenko (IKI), S. Belkin (IKI), N. Pankov (HSE) report on behalf of GRB IKI FuN:
We report photometry of GRB 210610B afterglow (Page et al., GCN 30170; Lipunov et al. GCNs 30173, 30176; Kumar et al. GCN 30174; Rumyantsev et al., GCN 30175; Hu et al., GCN 30177) obtained with ZTSh 2.6m telescope of CrAO observatory.
Preliminary photometry of the optical afterglow in R- filter is following
```
Date       UT start    Filter Exp.   OT    Err.  UL(3sigma)
                               (s)

2021-06-10 20:19:24    R      1*10  16.11  0.02 21.5
2021-06-10 20:59:50    R      1*10  16.99  0.02 21.2
```
The photometry is based on the nearby USNO-A2.0 star
```
USNO-A2.0_id
1043-0282589 16:15:36.30 +14:23:18.2 R=16.88
```
We continue observations in BVRI filters and will report photometry after data receiving.
GCN Circular #30180
S. de Wet (UCT), P.J. Groot (Radboud/UCT/SAAO), A.J. Levan and P.M. Vreeswijk (Radboud) report on behalf of the MeerLICHT consortium:
"Following the detection of GRB210610B by Swift and its optical counterpart (Page et al., GCN 30170), the 0.6m MeerLICHT telescope, located at Sutherland, South Africa began observations of the field at 2021-06-10, 21:00:54 UT (1h9m after burst) with a repeating sequence of optical filters: q,u,q,g,q,r,q,i,q,z, at 60s integration time each. The q-band wavelength limits are 440-720nm.
First detections are:
```
q_AB = 17.25 +/- 0.01 +/- 0.02 at 21:00:54 UT
u_AB = 17.48 +/- 0.05 +/- 0.05 at 21:02:18 UT
g_AB = 17.39 +/- 0.02 +/- 0.03 at 21:05:27 UT
i_AB = 17.12 +/- 0.03 +/- 0.01 at 21:11:25 UT
z_AB = 17.10 +/- 0.07 +/- 0.02 at 21:14:26 UT
r_AB = 17.37 +/- 0.02 +/- 0.02 at 21:23:29 UT
```
where the first uncertainty on the magnitude is the statistical uncertainty and the second is the uncertainty on the photometric calibration. No correction for Galactic extinction has been made.
Inspection of DECaLS/DR3 data (Dey et al., 2019, AJ 157, 168) shows an underlying blue galaxy, centered on RA,Dec (J2000) = 243.91823, +14.39901, with magnitude g=22.97, r=22.87 and z=22.57.
Further monitoring is continuing.
MeerLICHT is built and run by a consortium consisting of Radboud University, University of Cape Town, the South African Astronomical Observatory, the University of Oxford, the University of Manchester and the University of Amsterdam."
GCN Circular #30181
I observed the field of GRB 201223A (Page et al., GCN Circ. 30170) with remote telescope T18 (0.32-m f/8.0 reflector + CCD) of iTelescope.Net in observatory AstroCamp at Nerpio (Spain). Two images (with exposures 300 seconds, BINx1) were obtained with Astrodon luminance filter on 2021-06-10 since 21:40:19 UTC (1 hour 48 minutes 52 seconds after the trigger) and since 21:47:05 UTC (1 hour 55 minutes 38 seconds after the trigger).
I clearly detected the optical afterglow with position: RA 16:15:40.38 Dec +14:23:56.5 (+/- 0.15"). The following magnitudes were measured from comparison to r magnitudes of nearby stars from Pan-STARRS DR1 catalogue (Chambers et al., 2016): 17.33 (+/- 0.033) and 17.281 (+/- 0.029).
Magnitudes were not corrected for Galactic extinction.
Stacked image available here: https://www.flickr.com/photos/filipp-romanov/51238249632
GCN Circular #30182
J. P. U. Fynbo (DAWN/NBI), L. Izzo (DARK/NBI), A. de Ugarte Postigo (HETH/IAA-CSIC), D. B. Malesani (DTU Space), T. Pursimo (NOT), report on behalf of a larger collaboration:
We observed the optical afterglow of GRB 210610B (Page et al., GCN 30170; Kumar et al., GCN 30174; Rumyantsev et al., GCN 30175; Hu et al., GCN 30177; de Wet et al., GCN 30180; Romanov et al., GCN 30181) with the Nordic Optical Telescope (NOT) equipped with the ALFOSC imager.
The optical afterglow is well detected, and we measure for it the following coordinates (J2000, against the Gaia reference system):
```
RA = 16:15:40.38
Dec = +14:23:56.6
```
Our observation was carried out with a clear filter. Calibrating the photometry against the r-band magnitudes of nearby Pan-STARRS point sources, we get an AB magnitude r = 17.3 +- 0.1, at a mean epoch of 1.69 hr after the GRB.
Two spectra by 600 s each were obtained using grism #4, covering the wavelength range 3600-9400 AA. The continuum is detected at high S/N. While there are no strong features, we can identify the Mg II doublet and Mg I at a redshift of z = 1.13. We propose this value as the tentative redshift of GRB 210610B.
GCN Circular #30184
Instead "the field of GRB 201223A" meant "the field of GRB 210610B": this line was copied from my observation of the optical afterglow of GRB 201223A (GCN Circular #29165) with the same telescope.
GCN Circular #30187
A. S. Moskvitin (SAO RAS) on behalf of the GRB follow-up team report.
We observed the field of the GRB 210610B with the SAO RAS 1-m telescope Zeiss-1000 + CCD-photometer in BVRc Johnson-Cousins filters. The observations started on June 10, 20:21:53 UT, since half an hour after the burst detection by the Swift/BAT (Page et al., GCN #30170).
We clearly detected the OT (Page et al., GCN #30170; Kumar et al., GCN #30174; Rumyantsev et al., GCNs #30175, #30178; Hu et al., GCN #30177; de Wet et al., GCN #30180; Romanov, GCN #30181; Fynbo et al., GCN #30182) with the following brightness:
```
UT_mid     T_mid-T0, h  Exp., s   Rc mag (+/- 0.01 mag)
20:22:03   0.510        20        16.15
20:32:40   0.687        60        16.43
20:48:12   0.946        60        16.75
21:19:20   1.448        60        17.13
21:28:10   1.612        60        17.22
21:53:21   2.032        60        17.26
22:13:03   2.360        60        17.19
22:36:03   2.743       180        17.17
23:04:20   3.215       120        17.20
23:52:38   4.020       120        17.19
```
The preliminary photometry is based on the USNO-A2.0 star from GCN #30178 (Rumyantsev et al.). Magnitudes were not corrected for MW extinction.
GCN Circular #30188
S.Y. Fu, Z.P. Zhu, D. Xu, X. Liu (NAOC) report on behalf of a larger collaboration:
We checked the archives of Legacy Survey (LS), PanSTAR, and SDSS for GRB 210610B (Page et al., GCN 30170). From the LS, the GRB optical afterglow (e.g., Page et al., GCN 30170) is positionally located in a bright nucleus, which lies in the south-eastern part of an extended source in the direction of NorthWest-SouthEast.
The source has the multi-band photometric magnitudes g = 22.97, r = 22.87, z = 22.57, and a redshift z_ph = 0.96 +/- 0.44 from LS, and also PSF magnitudes g = 24.32 +/- 0.5 , r = 23.09 +/- 0.12, i = 24.33 +/- 0.47, z = 23.61 +/- 0.69 from PanSTAR. The source is marginally detected by SDSS, and we measure its magnitude r ~22.8. The r-band magnitudes from three surveys are basically consistent with each other, considering difference of photometric methods. The LS's z_ph = 0.96 +/- 0.44 is also consistent with the spectroscopic tentative redshift z=1.13 of the GRB optical afterglow from the NOT (Fynbo et al., GCN 30182).
We thus think the source is likely the host galaxy of the GRB.
GCN Circular #30189
J.P. Osborne, A.P. Beardmore, P.A. Evans and M.R. Goad (U. Leicester) report on behalf of the Swift-XRT team.
Using 516 s of XRT Photon Counting mode data and 1 UVOT images for GRB 210610B, 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 = 243.91883, +14.39881 which is equivalent to:
```
RA (J2000): 16h 15m 40.52s
Dec (J2000): +14d 23' 55.7"
```
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 #30190
Rosa L. Becerra (UNAM), Alan M. Watson (UNAM), Nat Butler (ASU), Alexander Kutyrev (GSFC), William H. Lee (UNAM), Michael G. Richer (UNAM), Ori Fox (STScI), J. Xavier Prochaska (UCSC), Josh Bloom (UCB), Antonino Cucchiara (UVI), Eleonora Troja (GSFC), Owen Littlejohns (ASU), Enrico Ramirez-Ruiz (UCSC), Jes�s Gonz�lez (UNAM), Carlos Rom�n-Z��iga (UNAM), Harvey Moseley (GSFC), John Capone (UMD), V. Zach Golkhou (U. Wash.), and Vicki Toy (UMD) report:
We observed the field of GRB 210610B (K.L. Page, et al., GCN 30170 and J.P. Osborne, et al., GCN 30189) with the Reionization and Transients Infrared Camera (RATIR) on the 1.5m Harold Johnson Telescope at the Observatorio Astron�mico Nacional on Sierra San Pedro M�rtir from 2021/06 11.16 to 2021/06 11.18 UTC (7.91 to 8.38 hours after the BAT trigger), obtaining a total of 0.33 hours exposure in the r and i bands and 0.15 hours exposure in the Z, Y, J, and H bands.
For a source within the Swift-XRT error circle, in comparison with the SDSS DR9 and 2MASS catalogs, we obtain the following detections and upper limits (3-sigma):
```
  r = 18.03 +/- 0.01
  i = 17.86 +/- 0.01
  Z = 17.65 +/- 0.01
  Y = 17.47 +/- 0.02
  J = 17.55 +/- 0.03
  H = 17.43 +/- 0.03
```
These magnitudes are in the AB system and are not corrected for Galactic extinction in the direction of the GRB. Further observations are planned.
We thank the staff of the Observatorio Astron�mico Nacional in San Pedro M�rtir.
GCN Circular #30193
Y-L Mong (1); K. Wiersema (2); R. Starling (3); K. Ackley (1); M. Dyer (4); D. K. Galloway (1); J. Lyman (2); K. Ulaczyk (2); D. Steeghs (2); V. Dhillon (4); P. O'Brien (3); G. Ramsay (5); S. Poshyachinda (6); R. Kotak (7); L. Nuttall (8); D. Pollacco (2); R. Breton (9)
((1) Monash University, (2) Warwick University, (3) University of Leicester, (4) University of Sheffield, (5) Armagh Observatory & Planetarium, (6) National Astronomical Research Institute of Thailand, (7) University of Turku, (8) University of Portsmouth, (9) University of Manchester) report on behalf of the GOTO collaboration:
We carried out observations with the Gravitational-wave Optical Transient Observer (GOTO) on La Palma in response to GRB 210610B (Page et al; GCN 30170). We detect an uncatalogued source consistent with the OT reported by Swift UVOT (Page et al.; GCN 30170) and other facilities.
We made a series of 4x90 s exposures using our wide L-band filter(400-700 nm) beginning around ~4hrs after the trigger, with midtime of the first observation 23:50:18.136 UT on 10 June 2021.
We detect an uncatalogued source located at (J2000):
RA 16:15:40.369Dec +14:23:57.19
confirming the OT (Page et al.; GCN 30170, Kumar et al.; GCN 30174, Rumyantsev et al.; GCN 30175, 30178, Hu et al.; GCN 30177, de Wet et al.; GCN 30180, Romanov; GCN 30181, Fynbo et al.; GCN 30182, Moskvitin et al.; GCN 30187, Osborne Et al.; GCN 30189, Becerra et al.; GCN 30190).
We find an equivalent magnitude of g = (17.86 +/- 0.05) mag based on calibration against PanSTARRS DR1 photometry in ATLAS_REFCAT2 (Tonry et al. 2018).
Observations are continuing.
GOTO is operated at the La Palma observing facilities of the Universityof Warwick on behalf of a consortium including the University ofWarwick, Monash University, Armagh Observatory, the University ofLeicester, the University of Sheffield, the National AstronomicalResearch Institute of Thailand (NARIT), Turku University, Portsmouth University, Manchester University and the Instituto de Astrofisicade Canarias (IAC) (https://goto-observatory.org)
GCN Circular #30194
A. de Ugarte Postigo (HETH/IAA-CSIC, DARK/NBI), C. Thoene, J.F. Agui Fernandez, M. Blazek, D. A. Kann (all HETH/IAA-CSIC), J. P. U. Fynbo (DAWN/NBI), L. Izzo (DARK/NBI), and D. Garcia Alvarez (GTC) report:
We observed the afterglow of GRB 210610B (Page et al., GCN 30170; Kumar et al., GCN 30174; Rumyantsev et al., GCN 30175; Hu et al., GCN 30177; de Wet et al., GCN 30180; Romanov, GCN 30181; Fynbo et al GCN 30182; Moskvitin et al. GCN 30187; Becerra et al. GCN 30190; Mong et al. GCN 30193) with OSIRIS at the 10.4m GTC telescope, located at Roque de los Muchachos Observatory, in La Palma (Spain). Observation consisted of 3 x 900 s exposures with grism R1000B, covering the range between 3700 and 7800 AA. The first spectrum started at 01:36:20 UT (5.75 hr after the burst).
The spectrum shows a very strong continuum with very weak superposed lines. We detect lines corresponding to FeII, MgII and MgI at a common redshift of z = 1.1345, in agreement with the measurement from the NOT (Fynbo et al. GCN 30182). Additionally, the high SNR allows us to detect a weak intervening system through the identification of MgII at a redshift of z = 0.557. Although the redshift 1.1345 is, strictly speaking, a lower limit, the lack of any further features at higher redshift, especially considering the high SNR of the spectrum, allows us to consider this as the redshift of the GRB.
We note that the features detected at the redshift of the GRB are very weak. We can compare their strength to a sample of long GRB afterglow features using the line strength parameter, following the method of de Ugarte Postigo et al. (2012, A&A 548, A11). For this spectrum we measure LSP = -2.1 +/- 0.8, which implies that the lines are weaker than 99.8% of the sample.
GCN Circular #30195
A. Ursi (INAF/IAPS), F. Verrecchia (SSDC, and INAF/OAR), F. Longo (Univ. Trieste and INFN Trieste), M. Tavani (INAF/IAPS, and Univ. Roma Tor Vergata), A. Argan, M. Cardillo, C. Casentini, 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), A. Giuliani (INAF/IASF-Mi), report on behalf of the AGILE Team:
The AGILE satellite detected the long GRB 210610B at T0 = 2021-06-10 19:51:32 s (UTC), reported by Swift (GCNs #30170, #30189).
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 30 s and it released a total number of 2340 counts in the SA detector (above a background rate of 65 Hz), 37190 counts in the MCAL detector (above a background rate of 1280 Hz), and 110300 counts in the AC detector (above a background rate of 3800 Hz). The AGILE ratemeter light curves can be found at http://www.agilescienceapp.it/notices/GRB210610B_AGILE_RM.png .
The event also triggered a partial high time resolution MCAL data acquisition, from T1 = 2021-06-10 19:51:22.88 s +/- 0.01 (UTC) to T2 = 2021-06-10 19:51:40.27 +/- 0.01 s (UTC), and released 11740 counts in the detector, above a background rate of 525 Hz. The MCAL light curve can be found at: http://www.agilescienceapp.it/notices/073428_GRB_MCAL_550439491.834857.png . The time-integrated spectrum between T1 and T2 can be fitted in the energy range 0.4-5 MeV with a power law model with ph.ind. -2.9 -0.33/+0.40. The fit results in a reduced chi-squared of 0.95 (36 d.o.f.) and a fluence of 8.06e-06 ergs/cm^2 (90% confidence level), in the same energy range.
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 #30196
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 210610B (Swift detection: Page et al., GCN 30170; AGILE detection: Ursi et al., GCN 30195) triggered Konus-Wind (KW) at T0=71488.184 s UT (19:51:28.184).
The burst light curve shows a bright, multi-peaked emission pulse which starts at ~T0-27 s, and has a total duration of ~100 s. The emission is seen up to ~10 MeV.
The Konus-Wind light curve of this GRB is available at http://www.ioffe.ru/LEA/GRBs/GRB210610_T71488/
As observed by Konus-Wind, the burst had a fluence of (1.3 � 0.1)x10^-4 erg/cm^2 and a 64-ms peak energy flux, measured from T0 + 10.175 s, of (1.0 � 0.1)x10^-5 erg/cm^2/s (both in the 20 keV - 10 MeV energy range).
The time-integrated spectrum (measured from T0 to T0+80.384 s) is best fit in the 20 keV - 20 MeV range by the GRB (Band) function with the following model parameters: the low-energy photon index alpha = -0.61 (-0.04,+0.04), the high energy photon index beta = -2.77 (-0.37,+0.21), the peak energy Ep = 257 (-14,+15) keV, chi2 = 97/97 dof.
The spectrum near the peak count rate (measured from T0+8.192 to T0+11.775 s) is best fit in the 20 keV - 15 MeV range by the GRB (Band) function with the following model parameters: the low-energy photon index alpha = -0.20 (-0.10,+0.12), the high energy photon index beta = -3.04 (-0.64,+0.34), the peak energy Ep = 333 (-24,+23) keV, chi2 = 60/76 dof.
Assuming the redshift z=1.1345 (de Ugarte Postigo et al., GCN 30194) and a standard cosmology with H_0 = 67.3 km/s/Mpc, Omega_M = 0.315, and Omega_Lambda = 0.685 (Planck Collaboration, 2014), we estimate the isotropic energy release E_iso to ~4.6x10^53 erg, the isotropic luminosity L_iso to ~7.6x10^52 erg/s, and the rest-frame peak energy of the time-integrated spectrum Ep,z to ~550 keV. With these values, GRB 210204A is within 68% prediction bands for both 'Amati' and 'Yonetoku' relations for the sample of >300 long KW GRBs with known redshifts (Tsvetkova et al., 2021, ApJ, 908, 83), see http://www.ioffe.ru/LEA/GRBs/GRB210610_T71488/GRB210610B_rest_frame.pdf
All the quoted errors are estimated at the 90% confidence level. All the presented results are preliminary.
GCN Circular #30198
Alessandro Marchini, Andrea Lorini (University of Siena Observatory, Siena, Italy), Simone Leonini (Montarrenti Observatory, Sovicille (SI), Italy), Giacomo Bonnoli (IAA-CSIC, Granada, Spain) report:
We observed the field of GRB 210610B (Swift trigger 1054681, K.L. Page et al., GCN Circ. 30170) with the 0.3 m telescope at University of Siena Observatory (Siena, Italy, K54). The GRB was extensively observed at all wavelengths, including optical photometry from many observatories (see e.g GCN Circulars 30173, 30174, 30175, 30176, 30177, 30178, 30180, 30181, 30185, 30187, 30188, 30190, 30191, 30193).
Our observations began under good weather conditions at 2021-06-10 20:37:53 UT (~0.75 h after GRB onset) with a series of 300s CCD exposures in the Rc filter, that were later added in groups of four for the photometry and further analysis. The optical afterglow was clearly detected at a sky position in agreement with the UVOT astrometry reported in GCN Circ. 30170. Our data cover continuously almost 6 hours of observations until the field set below the dome horizon.
The preliminary Rc-band photometry was calibrated with stars from the APASS10 catalog (Henden et al., 2019) after conversion between the two photometric systems with the simple formula from Dymock & Miles (2009) for the CMC15 catalog: Rc=r’-0.22. Measurements are not corrected for galactic extinction. Reported uncertainties are statistical only.
The first and last measurements of our series are reported hereafter:
```
2021-06-10 h. 20:50 UT JD 2459376.368287, R = 16.83 ± 0.04
2021-06-11 h. 02:26 UT JD 2459376.601458, R = 17.52 ± 0.16
```
The evolution of the brightness is, within the limits of our precision, compatible with a single decay rate with index alpha=0.25 ± 0.04
Any enquiry on these observations can be addressed either to Alessandro Marchini (marchini@unisi.it) or to Giacomo Bonnoli (bonnoli@iaa.es).
A brief description of our instrumental setup is available at the official webpage of the Astronomical Observatory of the University of Siena: https://www.dsfta.unisi.it/en/research/labs/astronomical-observatory
GCN Circular #30199
C. Malacaria (USRA) and B. Hristov (UAH) report on behalf of the Fermi GBM Team:
At 19:51:05.05 UT on the 10th of June 2021, the Fermi Gamma-Ray Burst Monitor (GBM) triggered and located GRB 210610B (trigger 645047470 / 210610827), which was also detected by Swift (Page et al. 2021, GCN 30170). The GBM on-ground location is consistent with the Swift position.
The angle from the Fermi LAT boresight at the GBM trigger time is 63 degrees.
The GBM light curve shows of 3 major peaks with a duration (T90) of about 55 s (50-300 keV). Spectral evolution is clear throughout the burst, therefore we report the spectrum of the brightest peak. The time-averaged spectrum of the first peak from T0+25.6s to T0+28.7 s is best fit by a power law function with an exponential high-energy cutoff. The power law index is -0.28 +/- 0.03 and the cutoff energy, parameterized as Epeak, is 414.3 +/- 11.7 keV.
The event fluence (10-1000 keV) in this time interval is (1.73 +/- 0.03)E-05 erg/cm^2. The 1-sec peak photon flux measured starting from T0+30.1 s in the 10-1000 keV band is 27.4 +/- 0.3 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 #30201
A. Dutta (IIA), H. Kumar (IITB), D. K. Sahu (IIA), B. Kumar (ARIES), G. C. Anupama (IIA), V. Bhalerao (IITB), S. Barway (IIA) report on behalf of a larger Indian collaboration:
We obtained a spectrum of the GRB 210210B detected by Swift-BAT ( K. L. Page et al., GCN #30170 ), with the HFOSC instrument mounted on the 2-m Himalayan Chandra Telescope (HCT) at the Indian Astronomical Observatory (IAO). We obtained a wavelength coverage of 3800 - 8000 angstrom. We took an 1800 second exposure on 2021 June 10 22:02 (UTC).
The spectrum has a relatively featureless blue continuum with weak absorption features due to Fe II (rest-frame wavelength 2587, 2600 A), Mg II (2799 A), Mg I (2853 A) at a redshift of z=1.13. The redshift is consistent with that reported by Fynbo et al. GCN #30182, Fu et al. GCN #30188 and A. de Ugarte Postigo et al. GCN #30194. The spectrum has not been corrected for reddening.
We thank the staff at IAO and CREST, Hosakote, for helping with the observations. The Indian Astronomical Observatory and CREST are operated by the Indian Institute of Astrophysics, Bengaluru, India.
GCN Circular #30204
WeiKang Zheng and Alexei V. Filippenko (UC Berkeley) report on
behalf of the KAIT GRB team:
The 0.76-m Katzman Automatic Imaging Telescope (KAIT), located at
Lick Observatory, responded to the Swift GRB 210610B (Page et al.,
GCN 30170) starting at ~10.46 hours after the Swift trigger (Page et al.
GCN 30170). A total of 60x60s images were obtained in the clear (roughly R)
filter. The optical afterglow (e.g. Page et al., GCN 30170) was clearly
detected in each single image. We measured its brightness of 18.07 +/- 0.05
mag at 10.46 hours after burst, and decayed to be 18.27 +/- 0.06 mag at
12.20 hours after burst, calibrated to the Pan-STARRS1 catalog.
GCN Circular #30205
P.M. Vreeswijk (Radboud) reports on behalf of E. Broens (Mol, Belgium):
"I observed the field of GRB 210610B (Page et al., GCN 30170; Kumar et al., GCN 30174; Rumyantsev et al., GCN 30175; Hu et al., GCN 30177; de Wet et al., GCN 30180; Romanov et al., GCN 30181, GCN 30182; Fynbo et al, GCN 30182; Moskvitin, GCN 30187) using a 0.28-meter f7 SCT telescope with a Moravian G2-1600 CCD camera and Astrodon Johnson-Cousins BVRcIc filters.
Five 180 s exposures were average combined for each filter. In the B filter the OT was only marginally detected with a SNR ~3. The following magnitudes were measured using eight APASS DR9 stars in the field. The APASS DR9 r’ and i’ magnitudes were transformed to Rc and Ic using the Jester et al. (2009, AJ 130, 873) relations.
```
2021-06-10  23:50:30 UT  Rc  17.20 +/- 0.07
2021-06-11  00:05:37 UT  V   17.74 +/- 0.09
2021-06-11  00:20:20 UT  Ic  16.8  +/- 0.2
2021-06-11  00:36:00 UT  B   18.4  +/- 0.2
2021-06-11  00:51:50 UT  Rc  17.25 +/- 0.08
2021-06-11  01:06:23 UT  V   17.71 +/- 0.09"
```
GCN Circular #30206
D. A. Perley (LJMU), Y. Yao (Caltech), A. Y. Q. Ho (UC Berkeley), M. Bulla (Stockholm/OKC), I. Andreoni (Caltech), M. Coughlin (U. Minnesota), and E. Kool (Stockholm/OKC) report:
The Zwicky Transient Facility (ZTF; ATel #11266) observed the location of GRB 210610B (Page et al., GCN 30170) during the night of 2021-06-11 UT as part of the regular operations of the ZTF high-cadence partnership survey. Four separate observations of the field (ZTF field ID 533) were obtained between 2021-06-11 05:34:44 and 2021-06-11 08:38:29, two each in g-band and r-band.
The associated optical transient (e.g., Page et al., GCN 30170; Kumar et al., GCN 30174) was automatically identified by the ZTF image subtraction pipeline and assigned the identifier ZTF21abfmpwn. The source was independently flagged as a fast transient candidate by both the ZTF fast-transient filter pipeline developed by A. Ho and Y. Yao (Perley et al. 2021, arXiv:2103.01968) and by the ZTFReST pipeline (Andreoni et al. 2021, arXiv:2104.06352), on the basis of its rapid evolution over the course of the night and coincidence with a galaxy in Pan-STARRS and Legacy Survey reference imaging.
We provide the following photometry:
```
MJD           t_GRB(d)     filter   magnitude
59376.2324    0.4050       g        18.49 +/- 0.10
59376.2751    0.4477       r        18.29 +/- 0.07
59376.3206    0.4932       r        18.44 +/- 0.07
59376.3600    0.5326       g        18.81 +/- 0.07
```
Photometry is as provided by the ZTF alert packets and is reference-subtracted. Magnitudes are AB and are not corrected for Galactic extinction.
ZTF is supported by the National Science Foundation under Grant No. AST-2034437 and a collaboration including Caltech, IPAC, the Weizmann Institute for Science, the Oskar Klein Center at Stockholm University, the University of Maryland, Deutsches Elektronen-Synchrotron and Humboldt University, the TANGO Consortium of Taiwan, the University of Wisconsin at Milwaukee, Trinity College Dublin, Lawrence Livermore National Laboratories, and IN2P3, France. Operations are conducted by COO, IPAC, and UW.
GCN Circular #30207
H. A. Krimm (NSF), S. D. Barthelmy (GSFC), J. R. Cummings (CPI), S. Laha (GSFC/UMBC), A. Y. Lien (GSFC/UMBC), C. B. Markwardt (GSFC), K. L. Page (U Leicester), 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 210610B (trigger #1054681) (Page et al., GCN Circ. 30170). The BAT ground-calculated position is RA, Dec = 243.929, 14.398 deg which is
```
   RA(J2000)  =  16h 15m 42.8s
   Dec(J2000) = +14d 23' 54.5"
```
with an uncertainty of 1.0 arcmin, (radius, sys+stat, 90% containment). The partial coding was 24%.
The mask-weighted light curve shows several overlapping pulses that start at ~T-12 and end at ~T+140 s. The main peak occurs at ~T+8 s. T90 (15-350 keV) is 69.38 +- 2.53 sec (estimated error including systematics).
The time-averaged spectrum from T-12.04 to T+142.47 sec is best fit by a power law with an exponential cutoff. This fit gives a photon index 0.98 +- 0.11, and Epeak of 339.3 +- 218.6 keV (chi squared 27.43 for 56 d.o.f.). For this model the total fluence in the 15-150 keV band is 3.6 +- 0.1 x 10^-5 erg/cm2 and the 1-sec peak flux measured from T+7.95 sec in the 15-150 keV band is 13.5 +- 0.7 ph/cm2/sec. A fit to a simple power law gives a photon index of 1.17 +- 0.03 (chi squared 36.54 for 57 d.o.f.). All the quoted errors are at the 90% confidence level.
The results of the batgrbproduct analysis are available at http://gcn.gsfc.nasa.gov/notices_s/1054681/BA/
GCN Circular #30208
J. D. Gropp (PSU), P.A. Evans (U. Leicester), J.P. Osborne (U. Leicester), P. D'Avanzo (INAF-OAB), M.G. Bernardini (INAF-OAB), E. Ambrosi (INAF-IASFPA) , J.A. Kennea (PSU), A. Tohuvavohu (U. Toronto) and K.L. Page report on behalf of the Swift-XRT team:
We have analysed 5.8 ks of XRT data for GRB 210610B (Page et al. GCN Circ. 30170), from 87 s to 81.7 ks after the BAT trigger. The data comprise 1.3 ks 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. 30189).
The light curve can be modelled with a series of power-law decays. The initial decay index is alpha=1.13 (+0.23, -0.34). At T+133 s the decay steepens to an alpha of 1.86 (+0.06, -0.05). The light curve breaks again at T+397 s to a decay with alpha=0.77 (+0.06, -0.05), before a final break at T+1153 s s after which the decay index is 1.105 (+0.023, -0.022).
A spectrum formed from the WT mode data can be fitted with an absorbed power-law with a photon spectral index of 1.847 (+/-0.022). The best-fitting absorption column is 4.4 (+/-2.5) x 10^20 cm^-2, at a redshift of 1.13, in addition to the Galactic value of 3.9 x 10^20 cm^-2 (Willingale et al. 2013). The PC mode spectrum has a photon index of 1.92 (+/-0.12) and a best-fitting absorption column of 1.1 (+1.4, -1.1) x 10^21 cm^-2. The counts to observed (unabsorbed) 0.3-10 keV flux conversion factor deduced from this spectrum is 3.4 x 10^-11 (3.9 x 10^-11) erg cm^-2 count^-1.
A summary of the PC-mode spectrum is thus:
```
Galactic foreground: 3.9 x 10^20 cm^-2
Intrinsic column:    1.1 (+1.4, -1.1) x 10^21 cm^-2 at z=1.13
Photon index:	     1.92 (+/-0.12)
```
The results of the XRT-team automatic analysis are available at http://www.swift.ac.uk/xrt_products/01054681.
This circular is an official product of the Swift-XRT team.
GCN Circular #30212
N. Pankov (IKI, HSE), A. Pozanenko (IKI), V. Rumyantsev (CrAO), S. Belkin (IKI, HSE) report on behalf of IKI GRB FuN:
We observed the GRB 210610A (Page et al., GCN 30170) with ZTSH 2.6m telescope of CrAO observatory starting on June 11 (UT) 19:46:53. The optical afterglow first reported by UVOT (Page et al., GCN 30170) is clearly detected in each of a single image of 120 exposure in R filter. Preliminary photometry of the afterglow in the first image is following
```
Date       UT start   t-T0    Filter Exp.    OT      err
                      (mid, days)       (s)

2021-06-11 19:46:53   0.99683 R      1*120   19.50   0.12
```
The photometry is based on several nearby USNO-B1.0 (R2) stars
```
USNO-B1.0 id
USNO_B10-1043-00282648
USNO_B10-1043-00282621
```
GCN Circular #30213
N. Pankov (IKI, HSE), A. Pozanenko (IKI), V. Rumyantsev (CrAO), S. Belkin (IKI, HSE) report on behalf of IKI GRB FuN:
In the GCN circ. 30212 we we incorrectly reported GRB 210610A instead of GRB 210610B. The circular should be read as follows.
We observed the GRB 210610B (Page et al., GCN 30170) with ZTSH 2.6m telescope of CrAO observatory starting on June 11 (UT) 19:46:53. The optical afterglow first reported by UVOT (Page et al., GCN 30170) is clearly detected in each of a single image of 120 exposure in R filter. Preliminary photometry of the afterglow in the first image is following
```
Date       UT start   t-T0    Filter Exp.    OT      err
                      (mid, days)       (s)

2021-06-11 19:46:53   0.99683 R      1*120   19.50   0.12
```
The photometry is based on nearby USNO-B1.0 (R2) stars
```
USNO-B1.0 id
USNO_B10-1043-00282648
USNO_B10-1043-00282621
```
GCN Circular #30215
N. Pankov (IKI, HSE), A. Pozanenko (IKI), V. Rumyantsev (CrAO), S. Belkin (IKI, HSE) report on behalf of IKI GRB FuN:
We observed the GRB 210610B (Page et al., GCN 30170) with ZTSH 2.6m telescope of CrAO observatory starting on June 10 (UT) 20:19:24 (Rumyantsev et al., GCNs 30175, 30178). The optical afterglow first reported by UVOT (Page et al., GCN 30170) is clearly detected in each of a single image of 10 exposure in each of BVRI filters on June 10. Based on our observations on June 10 (B, R - filters) and June 11 (Pankov et al., GCN 30213) we report the light curve (LC) of the afterglow which can be found in
http://grb.rssi.ru/GRB210610B/GRB210610B_LC.png
Initial phase of the LC from 0.02 days and up to 0.07 days can be approximated by a single power law with index of -0.9, and after that we observe plateau phase at least up to 0.18 days after trigger (see figure above).
GCN Circular #30216
D. A. Perley (LJMU) reports:
The 2m robotic Liverpool Telescope observed the location of the optical afterglow of GRB 210610B (Page et al., GCN 30170) using the IO:O camera on 2021-06-11 UT between 22:45:44 and 22:55:45. Photometry with reference to SDSS secondary standard stars in the field gives the following magnitudes:
```
dt_GRB(d) magnitude
1.12521   u = 20.43 +/- 0.11
1.12103   g = 20.04 +/- 0.05
1.12244   r = 19.81 +/- 0.02
1.12383   i = 19.61 +/- 0.03
1.12694   z = 19.49 +/- 0.06
```
GCN Circular #30217
T. Laskar (University of Bath), K. D. Alexander (Northwestern), C. Kilpatrick (Northwestern), G. Schroeder (Northwestern), W. Fong (Northwestern), E. Berger (Harvard), R. Margutti (Northwestern), C. G. Mundell (University of Bath), and P. Schady (University of Bath) report on behalf of a larger collaboration:
"We observed GRB 210610B (Page et al. GCN 30170) with the Atacama Large Millimeter/Submillimeter Array (ALMA) beginning on 2021 June 11 at 06:21:02 UT (10.5 hr after the burst) at 90.5 GHz. Preliminary analysis reveals a mm source with flux density of ~ 0.9 mJy at position:
```
RA (J2000) = 16:15:40.410 (+/- 0.005)
Dec (J2000) = +014:23:56.70 (+/- 0.01)
```
consistent with the X-ray position (Osborne et al. GCN 30189) and optical position (Page et al., GCN 30170; Kumar et al. GCN 30174). Follow-up observations are planned.
We thank the JAO staff, AoD, P2G, and the entire ALMA team for their help with these observations."
GCN Circular #30218
K. D. Alexander (Northwestern), T. Laskar (University of Bath), C. Kilpatrick (Northwestern), G. Schroeder (Northwestern), W. Fong (Northwestern), E. Berger (Harvard), R. Margutti (Northwestern), C. G. Mundell (University of Bath), and P. Schady (University of Bath) report on behalf of a larger collaboration:
We observed GRB 210610B (Page et al. GCN 30170) at a mean frequency of 14.7 GHz with the Karl G. Jansky Very Large Array (VLA; Program 21A-241) beginning 2021 June 11.22 UT (9.4 hours after the burst). We detect a radio source with a preliminary flux density of ~0.25 mJy at:
```
RA (J2000) = 16:15:40.381
Dec (J2000) = +14:23:56.59
```
with an uncertainty of 0.07 arcsec in each coordinate. This position is fully consistent with the optical afterglow (Page et al. GCN 30170; Kumar et al. GCN 30174) and the refined Swift/XRT afterglow position (Osborne et al. GCN 30189). Additional follow-up observations are planned.
We thank the VLA staff for rapidly approving and executing these observations.
GCN Circular #30220
R. Noto, R. Hosokawa, K. L. Murata, M. Niwano, N. Ito, H. Takamatsu, Y. Imai, S. Sato, M. Takaku, R. Yamaguchi, Y. Yatsu, and N. Kawai (TokyoTech) report on behalf of the MITSuME collaboration:
We observed the field of GRB 210610B (Page et al. GCN #30170, Ursi et al. GCN #30195, Frederiks et al. GCN #30196, Malacaria et al. GCN #30199) with the optical three color (g', Rc, and Ic) CCD cameras attached to the MITSuME 50 cm telescope Akeno. The observation with a series of 60 sec exposures started at 2021-06-11 10:33:20 UT (14.7 hours after Swift BAT trigger). We stacked the images with good conditions. We detected the afterglow reported previously (Page et al. GCN #30170, Kumar et al. GCN #30174, Rumyantsev et al. GCN #30175, Lipunov et al. GCN #30176, Hu et al. GCN #30177, Rumyantsev et al. GCN #30178, Wet et al. GCN #30180, Romanov et al. GCN #30181, Fynbo et al. GCN #30182, Moskvitin et al. GCN #30187, Becerra et al. GCN #30190, Mong et al. GCN #30193, Postigo et al. GCN #30194, Marchini et al. GCN #30198, Dutta et al. GCN #30201, Zheng et al. GCN #30204, Vreeswijk et al. GCN #30205, Perley et al. GCN #30206, Pankov et al. GCN #30212, Pankov et al. GCN #30215, Perley et al. GCN #30216, Laskar et al. GCN #30217, Alexander et al. GCN #30218)
We measured the magnitudes as follows.
```
MID-UT T-EXP[sec] measured magnitudes
------------------------------------------------------------------------------------------------
2021-06-11 12:51:05 9780 g'=19.3+/-0.2, Rc=18.9+/-0.1, Ic=18.8+/-0.1
------------------------------------------------------------------------------------------------
T-EXP: Total Exposure time
```
We used PS1 catalog for flux calibration. The magnitudes are expressed in the AB system. The images were processed in real-time through the MITSuME GPU reduction pipeline (Niwano et al. 2021, PASJ, Vol.73, Issue 1, Pages 4-24; https://github.com/MNiwano/Eclaire).
GCN Circular #30221
S. Anandagoda, K. Pellegrin, and D. Hartmann report:
We observed the field of GRB 210610B detected by Swift BAT (K. L. Page et al., GCN #30170), BALROG (B. Biltzinger et al., GCN #30171), GIT (H. Kumar et al., GCN #30174), V. Rumyantsev et al., V. Lipunov et al., Hu et al., Romanov, Fynbo et al.,Moskvitin et al. and Becerra et al. using the SARA 0.9m optical telescope located at Kitt Peak, AZ, USA, equipped with the Alta-E6-1105 camera.
Observation started at 04:40:42 UTC on 2021-06-12 and ended at 05:43:44 UTC on 2021-06-12. We obtained a series of 150s exposure frames in the Bessell R filter. We detect the optical afterglow of GRB 210610B at the enhanced Swift-XRT position (Osborne et al. GCN 30189).
The estimated magnitude of the GRB afterglow was 20.35 found by stacking 20 images of 150s each in the Bessell R band filter.
```
T_start-T0 (hrs)   T_end-T0 (hrs)     Start Date (UTC) 	  Filter 	Magnitude (mag)
----------------------------------------------------------------------------------------------------------------
32:34		      33:37       	 2021-06-12T04:40:42       R 	   20.35
```
Photometry is done based on the PanSTARRS catalog.
The Southeastern Association for Research in Astronomy (SARA) consortium operates three telescopes: the 0.9-m SARA-KP at Kitt Peak in Arizona, and the 0.6-m SARA-CT at Cerro Tololo in Chile, and the 1.0-m SARA-RM (formerly the JKT) telescope at Roque de los Muchachos Observatory in the Canary Islands. For more information see: Keel et al. (2016): https://iopscience.iop.org/article/10.1088/1538-3873/129/971/015002
---------------------------------------------------------------------------------------
GCN Circular #30226
M. Ibrahimov, M. Nalivkin, I. Nikolenko (all from INASAN, Moscow, Russia) and O. Pons (IGA, Havana, Cuba) report on behalf of a larger team:
Using Zeiss 1m telescope and 4K FLI PL16803 CCD of Simeiz Obserbatory (Collective Using Center of INASAN), we observed the field of GRB 210610B (Page et al., GCN 30170). 15x120sec images were acquired through Bessel R filter on 2021-06-11/00:03:07 UT (midpoint time, 4.18 hours after the trigger) with a total exposure time of 1800 sec.
Optical afterglow (for a list of the most full references see e.g. Hosokawa et al., GCN 30220 and Anandagoda et al., GCN 30221) was clearly seen in all 15 individual R images.
Photometry of the optical afterglow using stacked R-image calibrated against USNO-B1 R1-mag of 2 nearby stars, resulted in: R = 17.61 +/- 0.02 mag.
Research was supported by Project No. RFMEFI61319X0093 (Russian Ministry of Science and High Education, Agreement No. 075-15-2019-1716 by 2019 Nov 20) and Project No. 19-29-11013 (Russian Foundation of Fundamental Investigation, Agreement No. 19-29-11013\20 by 2021 Jan 21).
GCN Circular #30227
WeiKang Zheng and Alexei V. Filippenko (UC Berkeley) report on behalf of the KAIT GRB team:
We continued observing the optical afterglow of GRB 210610B
(e.g. Page et al., GCN 30170; Zheng & Filippenko, GCN 30204) with
the 0.76-m Katzman Automatic Imaging Telescope (KAIT), located at
Lick Observatory. A total of 30x60s images were obtained in the
clear (roughly R) filter. The optical afterglow was detected in the
coadd image with a mag of 20.0 +/- 0.2 at ~1.44 days after burst,
calibrated to the Pan-STARRS1 catalog.
GCN Circular #30228
Filipp D. Romanov (Russia) and David J. Lane (Saint Mary's University, Canada) report:
Filipp Romanov observed optical afterglow of GRB 210610B (Page et al., GCN Circ. 30170) remotely using telescopes: 0.61-m f/6.5 Corrected Dall-Kirkham of Burke-Gaffney Observatory (BGO, Dave Lane is Observatory Director) and 0.355-m f/6.2 Schmidt-Cassegrain of Abbey Ridge Observatory (ARO, it is owned by D. Lane) on 2021-06-11.
Two images (with exposures 240 and 300 seconds) were obtained on BGO with Sloan i' filter; on ARO were obtained two clear (unfiltered) images (with exposures 840 and 900 seconds) and two images (with exposures 900 and 840 seconds) with Cousins R filter.
F. Romanov measured following magnitudes of afterglow from comparison to i' magnitudes of nearby stars from the SDSS Photometric Catalogue DR12 (Alam et al., 2015) for BGO images and from r' magnitudes for ARO unfiltered images; from comparison to R magnitudes of nearby stars from USNO-A2.0 catalogue (Monet et al., 1998) for ARO Rc images:
```
UTC midtime
of exposure    T_mid-T0, h     Magnitude    Mag. error
-------------------------------------------------------
02:07:55       6.27            17.45  i'    0.12
02:09:15       6.30            17.64  r'    0.03
02:14:20       6.38            17.61  i'    0.08
02:27:12       6.60            17.36  Rc    0.05
02:44:54       6.89            17.78  r'    0.08
03:03:24       7.20            17.50  Rc    0.08
-------------------------------------------------------
```
Magnitudes were not corrected for Galactic extinction.
Images available here:
http://www.ap.smu.ca/~bgo/sm/id.php?app=0&id=15162
http://aro.abbeyridgeobservatory.ca/sm/id.php?app=0&id=3325
http://www.ap.smu.ca/~bgo/sm/id.php?app=0&id=15163
http://aro.abbeyridgeobservatory.ca/sm/id.php?app=0&id=3326
http://aro.abbeyridgeobservatory.ca/sm/id.php?app=0&id=3327
http://aro.abbeyridgeobservatory.ca/sm/id.php?app=0&id=3328
GCN Circular #30230
A. S. Moskvitin and O. A. Maslennikova (SAO RAS), report on behalf of the GRB follow-up team.
We observed the field of the GRB 210610B (Page et al., GCN #30170) with the SAO RAS 1-m telescope Zeiss-1000 + CCD-photometer in BVRc Johnson-Cousins filters on June 11 and 12.
The GRB OT is clearly detected in the stacked frames with the following brightness.
```
Date     UT_start  UT_end    Exp., s  T_mid-T0, d  R mag
June 11  18:54:36--20:03:45  4 x 300  0.98453      19.33 +/- 0.01
June 11  23:14:36--23:49:13  5 x 300  1.15309      19.62 +/- 0.02
June 12  21:28:37--22:47:50  6 x 300  2.09498      20.67 +/- 0.06
```
The preliminary photometry is based on the USNO-A2.0 star from GCN #30178 (Rumyantsev et al.) and previous GCN #30187. Magnitudes were not corrected for MW extinction.
GCN Circular #30231
Markku Nissinen (Taurus Hill Observatory, Varkaus, Finland) and Arto Oksanen (Hankasalmi Observatory, Hankasalmi, Finland) report:
We have detected GRB 210610B optical afterglow (Page et al., GCN30170) using iTelescope T18 (0.32-m f/8.0 + CCD in AstroCamp at Nerpio, Spain), iTelescope T21 (0.43-m f/6.8 + f/4.5 focal reducer + CCD in New Mexico Skies at Mayhill, New Mexico, USA) and iTelescope T11 (0.50-m f/6.8 + f/4.5 focal reducer + CCD in New Mexico Skies at Mayhill, New Mexico, USA).
We took total of 24 exposures with clear (CR), V and R filters.
The afterglow was clearly detected with each filter at the position RA 16:15:40.43 DEC +14:23:57.4.
The following magnitudes were measured from comparison of a nearby star (V = 13.97, r'=13.70) from the APASS DR9 catalogue (Henden+, 2016):
```
------------------------------------------------------------------------------
JD            UTC            Mag    Err   Filter AirMass Telescope Exposure(s)
------------------------------------------------------------------------------
2459376.36806 June 10 20:50  16.79  0.05  CR     1.28    T18       7x60
2459376.37868 June 10 21:05  17.15  0.10  V      1.24    T18       10x60
2459376.64285 June 11 03:25  17.76  0.02  CR     1.29    T21       2x300
2459376.65108 June 11 03:37  17.95  0.12  R      1.26    T11       5x300
------------------------------------------------------------------------------
```
We used r' reference magnitude for the clear filter and the R filter measurements.
GCN Circular #30238
P. D'Avanzo, A. Melandri, S. Covino, D. Fugazza, (INAF-OAB) on behalf of the REM team, report:
We observed the field of GRB 210610B (Page et al., GCN Circ. 30170) with the REM 60cm robotic telescope located at the ESO premise of La Silla (Chile). The observations were performed starting on 2021 June 10 at 23:14:12 UT (i.e. 3.38 hours after the burst) and were carried in the g, r, i, z, J, H and K bands.
The optical/NIR afterglow (Page et al., GCN Circ. 30170) is detected with the following magnitudes:
```
g = 17.48 +/-  0.10 
r = 17.02 +/-  0.06
i = 17.30  +/- 0.10
z = 16.13 +/-  0.15 (*)

(AB; calibrated against the Pan-STARRS catalogue)
(*): image affected by fringes

J = 15.94  +/- 0.23 
(Vega; calibrated against the 2MASS catalogue)
```
at a mid time of t-t0 = 4.01 hours.
GCN Circular #30243
N. Pankov (HSE, IKI), A. Pozanenko (IKI), R. Ya. Inasaridze (AbAO), S. Belkin (IKI), V. R. Ayvazian (AbAO), G. V. Kapanadze (AbAO) report on behalf of IKI GRB FuN:
We observed the GRB 210610B (Page et al., GCN 30170) with AS-32 telescope of Abastumani observatory (AbAO) in R-filter on June, 13. The optical afterglow first reported by UVOT (Page et al., GCN 30170) is clearly detected is detected in stacked image. Preliminary photometry of the afterglow is following
```
Date       UT start   t-T0    Filter Exp.    OT     Err.  UL(3sigma)
                       (mid, days)    (s)

2021-06-13 17:06:46   2.88564  R     72*60   21.25  0.14  22.6
```
The photometry is based on calibrations stars reported in (Pankov et al., GCN 30213).
GCN Circular #30245
N. Pankov (IKI, HSE), A. Pozanenko (IKI), V. Rumyantsev (CrAO), S. Belkin (IKI, HSE) report on behalf of IKI GRB FuN:
We observed the GRB 210610B (Page et al., GCN 30170) with ZTSH 2.6m telescope of CrAO observatory on June 10,11 (Rumyantsev et al., GCNs 30175, 30178; Pankov et al., GCN 30213) and June 12 - 14. The optical afterglow first reported by UVOT (Page et al., GCN 30170) is clearly detected in each epochs. Some preliminary photometry is following.
```
Date       UT start   t-T0    Filter Exp.    OT      err   UL(3 sigma)
                      (mid, days)       (s)

2021-06-12 20:54:55   2.0545  R      2*120   20.80   0.10  22.2
2021-06-12 22:41:00   2.1282  R      2*120   20.89   0.10  22.8
2021-06-14 20:40:19   4.0649  R     25*120   21.90   0.11  23.3
```
The photometry is based on calibrations stars reported in (Pankov et al., GCN 30213).
Based on our observations in ZTSh on June 10-14, AbAO (Pankov et al., GCN 30243) and photometry reported in GCNs we report the light curve of the afterglow which can be found in
http://grb.rssi.ru/GRB210610B/GRB210610B_LC.png
After plateau phase lasting up to ~ 0.3 days in R-filter, the LC can be approximated by a single power law with index of -1.6.

GCN Circular #30247
M. H. Siegel (PSU), M. Baer (PSU) and K. L. Page (U. Leicester) report on behalf of the Swift/UVOT team:
The Swift/UVOT began settled observations of the field of GRB 210610B 92 s after the BAT trigger (Page et al., GCN Circ. 30170). A fading source consistent with the XRT position (Osborne et al. GCN Circ. 30189) and the previously reported optical counterpart (Kumar et al., GCN Circ. 30174; Rumyantsev et al. GCN Circ. 30175; Hu et al., GCN Circ. 30177; de Wet et al., GCN Circ. 30180; Romanov, GCN Circ. 30181; Fynbo et al., GCN Circ. 30182; Moskvitin, GCN Circ. 30187; Fu et al., GCN Circ. 30188) is detected in the initial UVOT exposures.
The preliminary UVOT position is:

   RA  (J2000) =  16:15:40.40 = 243.91833 (deg.)
   Dec (J2000) = +14:23:56.9  =  14.39915 (deg.)

with an estimated uncertainty of 0.42 arc sec. (radius, 90% confidence).
Preliminary detections 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 (fc)          92          242          147      13.63+/-1.10
white              584         1355          225      15.24+/-0.02
white           172034       172423          377      20.22+/-0.14
white           286441       292869          328      20.71+/-0.23
white           452008       515231         4066      21.69+/-0.16
v                  634         1405           97      15.63+/-0.05
v                 6631        51903          659      18.26+/-0.09
b                  560         1331           77      15.78+/-0.04
b                81150       133027          865      20.08+/-0.14
u (fc)             304          554          245      13.86+/-0.03
u                  707         1306           58      14.93+/-0.04
u                 4850         5040          186      16.68+/-0.05
u                45786        46567          761      18.06+/-0.05
u               131743       132650          885      20.00+/-0.18
u               365977       418267         3970      21.42+/-0.29
uvw1               683         1282           58      14.51+/-0.06
uvw1              4645         4845          196      16.26+/-0.07
uvw1              7041        45779          989      17.54+/-0.06
uvw1            125974       137480          881      19.53+/-0.20
uvw1            200561       247267         1111      19.95+/-0.24
uvm2              6836         7036          196      16.61+/-0.10
uvw2               783         1034           38      15.05+/-0.09
uvw2             50521        51421          885      18.44+/-0.10

The magnitudes in the table are not corrected for the Galactic extinction due to the reddening of E(B-V) = 0.044 in the direction of the burst (Schlegel et al. 1998).

GCN Circular #30316
```
TITLE:   GCN CIRCULAR
NUMBER:  30316
SUBJECT: GRB 210610B: T-CAT optical observations
DATE:    21/06/25 14:40:15 GMT
FROM:    Denis Marchais at Amateur astronomer  
```
I observed the field of GRB 210610B (Page et al., GCN #30170) with the T-CAT telescope 0.4-meter f/4 Newton with a f/3 reducer, IR-cut filter at 630nm and ZWO ASI533MC camera, located in Cintegabelle, France, on June 11, 12 and 13.
The camera has a Sony sensor with Bayer filters R,G,B, that fairly match the standard Bc, Vc, and r' filters considering the additional IR-cut filter. Each observation results from stacking 120x 32s exposures.
The GRB OT is clearly detected in the stacked frames at the following location, matching other observations (e.g. , Fynho et al. GCN #30182, Osborne et al. GCN #30186) though approaching the detection limit on third observation, June 13th.
```
   RA(J2000)  = 16h 15m 40.39s
   Dec(J2000) = +14d 23' 56.3"
```
The following magnitudes were obtained thanks to PixInsight photometric calibration using nearby APASS DR10 stars.
```
Date        UT start     Filter   Exp. (s)    OT     err
2021-06-11  23:52:21     Bc       120x 32     20.53  +/- 0.05
2021-06-11  23:52:21     Vc       120x 32     20.00  +/- 0.04
2021-06-11  23:52:21     r'       120x 32     19.64  +/- 0.04
2021-06-12  22:48:22     Bc       120x 32     21.79  +/- 0.11
2021-06-12  22:48:22     Vc       120x 32     20.91  +/- 0.07
2021-06-12  22:48:22     r'       120x 32     20.90  +/- 0.10
2021-06-13  22:45:36     Bc       120x 32     21.77  +/- 0.1
2021-06-13  22:45:36     Vc       120x 32     21.42  +/- 0.09
2021-06-13  22:45:36     r'       120x 32     21.76  +/- 0.2
```
I thank A. Taylor, H.-B. Eggenstein and E. Broens (GCN#30205) for sharing information through the KNCatcher citizen-science programme initiated by S. Antier and A. Klotz as part of GRANDMA initiative (GRANDMA Observations of Advanced LIGO's and Advanced Virgo's Third Observational Campaign, Antier et al. https://arxiv.org/abs/2004.04277v2).
GCN Circular #30360
I.A. Smith (Rice U.), D.A. Perley (LJMU), and N.R. Tanvir (U. of Leicester) report:
We observed the Swift UVOT location of GRB 210610B (Page et al., GCN Circ. 30170) using the SCUBA-2 sub-millimeter continuum camera on the James Clerk Maxwell Telescope. Observations totaling 3.1 hours were obtained on UT 2021-06-11, 2021-06-12, and 2021-06-13 in good weather conditions each day. No counterpart was detected in the individual or combined maps. Combining all the data, the RMS background noise was 0.94 mJy/beam at 850 microns and 5.7 mJy/beam at 450 microns; the mid-point of the run was 1.61 days after the burst trigger.
We thank Patrice Smith, Alexis-Ann Acohido, Harriet Parsons, Mark Rawlings, and the JCMT staff for the prompt support of these observations that were taken under project M21AP020.
GCN Circular #30614
V. Kim (FAI, Pulkovo Observatory), A. Pozanenko (IKI), M. Krugov (FAI), N. Pankov (HSE, IKI), S. Belkin (IKI) report on behalf of GRB IKI FuN:
We observed the field of GRB 210610B (Lien et al., GCN 30600) with AZT-20 telescope of Assy-Turgen observatory starting on 2021-08-07 (UT) 20:45:22.
We clearly detect the optical afterglow (Lien et al., GCN 30600; Hu et al., GCN 30602; Lipunov et al., GCN 30607).
Preliminary photometry of the optical afterglow in a stacked image is following
```
Date       UT start  t-T0       Exp.    Filter  OT    Err.  UL(3sigma)
                    (mid, days)  (s)

2021-08-07 20:45:22  0.47601    75*60   r'      21.28  0.05   23.6
```
The photometry is based on nearby PS1 stars.
GCN Circular #30988
N. Pankov (HSE), S. Nazarov (CrAO), A. Pozanenko (IKI), S. Belkin (IKI, HSE) report on behalf of IKI GRB FuN:
We observed the GRB 210610B (Page et al., GCN 30170) with Sintesz-Newton 350mm f/5 telescope of CrAO observatory. Observation started on 2021-06-10 (UT) 22:07:10, and continued on 2021-06-11 (UT) 20:22:38, 2021-06-12 (UT) 20:39:03, and 2021-06-13 (UT) 19:38:28. The series consists of images with an exposure of 300 s in a Clear filter.
The optical afterglow first reported by UVOT team (Page et al., GCN 30170) is clearly detected in each epoch.
Preliminary photometry of the stacked images is following
```
Date       UT start   t-T0    Filter Exp.     OT    err   UL(3)
                      (mid, days)       (s)

2021-06-10 22:07:10   0.10293  Clear 5*300    17.20 0.03  20.5
2021-06-10 n/d        0.12658  Clear 5*300    17.28 0.08  21.1
2021-06-10 n/d        0.14409  Clear 5*300    17.28 0.06  21.1
2021-06-10 n/d        0.16159  Clear 5*300    17.29 0.06  21.1
2021-06-11 20:22:38   1.02165  Clear 8*300    19.58 0.10  21.2
2021-06-11 20:50:32   1.04103  Clear 6*300    19.50 0.09  21.2
2021-06-11 21:33:21   1.07077  Clear 17*300   19.69 0.09  21.5
2021-06-12 20:39:03   2.03479  Clear 14*300   20.57 0.19  21.5
2021-06-13 19:38:28   3.02571  Clear 20*300   21.26 0.17  21.8
```
The photometry is based on nearby USNO-B1.0 (R2) stars USNO_B10-1043-00282648 USNO_B10-1043-00282621

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Jochen Greiner, last update: 25-Oct-2021 [Disclaimer]