Gamma-ray Burst 210610A

(All information courtesy of the instrument teams.)

Previous IAU Circulars

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Results of Observations

GCN/BACODINE POSITION NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Thu 10 Jun 21 15:04:02 UT
NOTICE_TYPE:     Swift-BAT GRB Position
TRIGGER_NUM:     1054627,   Seg_Num: 0
GRB_RA:          204.285d {+13h 37m 08s} (J2000),
                 204.547d {+13h 38m 11s} (current),
                 203.674d {+13h 34m 42s} (1950)
GRB_DEC:         +14.480d {+14d 28' 49"} (J2000),
                 +14.372d {+14d 22' 18"} (current),
                 +14.735d {+14d 44' 05"} (1950)
GRB_ERROR:       3.00 [arcmin radius, statistical only]
GRB_INTEN:       2875 [cnts]    Image_Peak=132 [image_cnts]
TRIGGER_DUR:     1.024 [sec] 
TRIGGER_INDEX:   147     E_range: 25-100 keV
BKG_INTEN:       16961 [cnts]
BKG_TIME:        54204.82 SOD {15:03:24.82} UT
BKG_DUR:         8 [sec]
GRB_DATE:        19375 TJD;   161 DOY;   21/06/10
GRB_TIME:        54223.38 SOD {15:03:43.38} UT
GRB_PHI:          49.36 [deg]
GRB_THETA:        35.78 [deg]
SOLN_STATUS:     0x20000003
RATE_SIGNIF:     18.81 [sigma]
IMAGE_SIGNIF:    7.79 [sigma]
MERIT_PARAMS:     +1  +0  +0  +0  +2  -2  +0  +0 +41  +0 
SUN_POSTN:        79.08d {+05h 16m 19s}  +23.06d {+23d 03' 21"}
SUN_DIST:        114.84 [deg]   Sun_angle= -8.4 [hr] (East of Sun)
MOON_POSTN:       81.14d {+05h 24m 34s}  +24.17d {+24d 09' 57"}
MOON_DIST:       112.64 [deg]
MOON_ILLUM:      0 [%]
GAL_COORDS:      345.31, 73.47 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:      196.77, 22.82 [deg] ecliptic lon,lat of the burst (or transient)
COMMENTS:        SWIFT-BAT GRB Coordinates.  
COMMENTS:        This is a rate trigger.  
COMMENTS:        A point_source was found.  
COMMENTS:        This does not match any source in the on-board catalog.  
COMMENTS:        This does not match any source in the ground catalog.  
COMMENTS:        This is a GRB.  
COMMENTS:        This trigger occurred at longitude,latitude = 102.11,-3.90 [deg].  
COMMENTS:           
COMMENTS:        NOTE: This BAT event is temporally(1.0<100sec) coincident with the FERMI_GBM event (trignum=645030227).

red DSS finding chart ps-file

GCN NOTICE

TITLE:           GCN/FERMI NOTICE
NOTICE_DATE:     Thu 10 Jun 21 15:04:07 UT
NOTICE_TYPE:     Fermi-GBM Flight Position
RECORD_NUM:      50
TRIGGER_NUM:     645030227
GRB_RA:          199.950d {+13h 19m 48s} (J2000),
                 200.212d {+13h 20m 51s} (current),
                 199.339d {+13h 17m 21s} (1950)
GRB_DEC:         +17.467d {+17d 28' 00"} (J2000),
                 +17.355d {+17d 21' 17"} (current),
                 +17.729d {+17d 43' 44"} (1950)
GRB_ERROR:       13.43 [deg radius, statistical plus systematic]
GRB_INTEN:       91 [cnts/sec]
DATA_SIGNIF:     7.80 [sigma]
INTEG_TIME:      4.096 [sec]
GRB_DATE:        19375 TJD;   161 DOY;   21/06/10
GRB_TIME:        54222.75 SOD {15:03:42.75} UT
GRB_PHI:         115.98 [deg]
GRB_THETA:        65.00 [deg]
DATA_TIME_SCALE: 4.0960 [sec]
HARD_RATIO:      1.06
LOC_ALGORITHM:   3 (version number of)
MOST_LIKELY:      98%  GRB
2nd_MOST_LIKELY:   1%  Generic SGR
DETECTORS:       0,0,0, 0,0,0, 0,0,0, 1,1,0, 0,0,
SUN_POSTN:        79.08d {+05h 16m 19s}  +23.06d {+23d 03' 21"}
SUN_DIST:        109.71 [deg]   Sun_angle= -8.1 [hr] (East of Sun)
MOON_POSTN:       81.14d {+05h 24m 34s}  +24.17d {+24d 09' 58"}
MOON_DIST:       107.52 [deg]
MOON_ILLUM:      0 [%]
GAL_COORDS:      338.53, 78.33 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:      191.30, 23.88 [deg] ecliptic lon,lat of the burst (or transient)
LC_URL:          http://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2021/bn210610628/quicklook/glg_lc_medres34_bn210610628.gif
COMMENTS:        Fermi-GBM Flight-calculated Coordinates.  
COMMENTS:        This trigger occurred at longitude,latitude = 138.83,25.42 [deg].  
COMMENTS:        The LC_URL file will not be created until ~15 min after the trigger.  
COMMENTS:           
COMMENTS:        NOTE: This GBM event is temporally(1.0<100sec) coincident with the SWIFT_BAT event (trignum=1054627).

GCN NOTICE

TITLE:           GCN/FERMI NOTICE
NOTICE_DATE:     Thu 10 Jun 21 15:04:30 UT
NOTICE_TYPE:     Fermi-GBM Ground Position
RECORD_NUM:      59
TRIGGER_NUM:     645030227
GRB_RA:          212.880d {+14h 11m 31s} (J2000),
                 213.138d {+14h 12m 33s} (current),
                 212.279d {+14h 09m 07s} (1950)
GRB_DEC:         +14.770d {+14d 46' 12"} (J2000),
                 +14.670d {+14d 40' 12"} (current),
                 +15.005d {+15d 00' 17"} (1950)
GRB_ERROR:       6.37 [deg radius, statistical only]
DATA_SIGNIF:     11.20 [sigma]
DATA_INTERVAL:   2.048 [sec]
GRB_DATE:        19375 TJD;   161 DOY;   21/06/10
GRB_TIME:        54222.75 SOD {15:03:42.75} UT
GRB_PHI:         130.00 [deg]
GRB_THETA:        65.00 [deg]
E_RANGE:         44.032 - 279.965 [keV]
LOC_ALGORITHM:   4173 (Gnd S/W Version number)
SUN_POSTN:        79.08d {+05h 16m 19s}  +23.06d {+23d 03' 21"}
SUN_DIST:        121.32 [deg]   Sun_angle= -8.9 [hr] (East of Sun)
MOON_POSTN:       81.15d {+05h 24m 35s}  +24.17d {+24d 09' 60"}
MOON_DIST:       119.13 [deg]
MOON_ILLUM:      0 [%]
GAL_COORDS:        3.42, 67.64 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:      205.09, 26.28 [deg] ecliptic lon,lat of the burst (or transient)
LC_URL:          http://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2021/bn210610628/quicklook/glg_lc_medres34_bn210610628.gif
POS_MAP_URL:     http://gcn.gsfc.nasa.gov/notices_f/gbm_gnd_loc_map_645030227.fits
COMMENTS:        Fermi-GBM Ground-calculated Coordinates.  
COMMENTS:        This Notice was ground-generated -- not flight-generated.  
COMMENTS:        The LC_URL file will not be created/available until ~15 min after the trigger.  
COMMENTS:        The POS_MAP_URL file will not be created/available until ~1.5 min after the notice.  
COMMENTS:           
COMMENTS:        NOTE: This GBM event is temporally(1.0<100sec) coincident with the SWIFT_BAT event (trignum=1054627).

GCN NOTICE

TITLE:           GCN/FERMI NOTICE
NOTICE_DATE:     Thu 10 Jun 21 16:26:41 UT
NOTICE_TYPE:     Fermi-GBM Final Position
RECORD_NUM:      0
TRIGGER_NUM:     645030227
GRB_RA:          212.240d {+14h 08m 58s} (J2000),
                 212.501d {+14h 10m 00s} (current),
                 211.630d {+14h 06m 31s} (1950)
GRB_DEC:         +11.760d {+11d 45' 36"} (J2000),
                 +11.659d {+11d 39' 33"} (current),
                 +11.996d {+11d 59' 47"} (1950)
GRB_ERROR:       4.94 [deg radius, statistical only]
GRB_DATE:        19375 TJD;   161 DOY;   21/06/10
GRB_TIME:        54222.75 SOD {15:03:42.75} UT
GRB_PHI:         130.00 [deg]
GRB_THETA:        68.00 [deg]
E_RANGE:         50.000 - 300.000 [keV]
LOC_ALGORITHM:   415 (Gnd S/W Version number)
SUN_POSTN:        79.14d {+05h 16m 33s}  +23.06d {+23d 03' 36"}
SUN_DIST:        122.66 [deg]   Sun_angle= -8.9 [hr] (East of Sun)
MOON_POSTN:       81.89d {+05h 27m 34s}  +24.27d {+24d 16' 07"}
MOON_DIST:       119.87 [deg]
MOON_ILLUM:      0 [%]
GAL_COORDS:      356.51, 66.19 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:      205.68, 23.25 [deg] ecliptic lon,lat of the burst (or transient)
LC_URL:          http://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2021/bn210610628/quicklook/glg_lc_medres34_bn210610628.gif
LOC_URL:         http://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2021/bn210610628/quicklook/glg_locplot_all_bn210610628.png
COMMENTS:        Fermi-GBM Final Position.  
COMMENTS:        This Notice was ground-generated -- not flight-generated.  
COMMENTS:        The LC_URL file should be available by the time this FINAL notice is produced.  
COMMENTS:        This notice has human-in-the-loop processing.  
COMMENTS:           
COMMENTS:        NOTE: This GBM event is temporally(1.0<100sec) coincident with the SWIFT_BAT event (trignum=1054627).

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Thu 10 Jun 21 15:05:19 UT
NOTICE_TYPE:     Swift-XRT Nack-Position
TRIGGER_NUM:     1054627,   Seg_Num: 0
POINT_RA:        204.263d {+13h 37m 03s} (J2000)
POINT_DEC:       +14.487d {+14d 29' 15"} (J2000)
IMG_START_DATE:  19375 TJD;   161 DOY;   21/06/10
IMG_START_TIME:  54313.35 SOD {15:05:13.35} UT,   90.0 [sec] since BAT Trigger Time
COUNTS:          45    Min_needed= 20
STD_DEV:         0.00   Max_StdDev_for_Good=28.44 [arcsec]
PH2_ITER:        4    Max_iter_allowed= 4
ERROR_CODE:      2
COMMENTS:        SWIFT-XRT Nack Position.  
COMMENTS:        Algorithm did not converge; too many iterations.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Thu 10 Jun 21 15:21:38 UT
NOTICE_TYPE:     Swift-BAT GRB Lightcurve
TRIGGER_NUM:     1054627,   Seg_Num: 0
GRB_RA:          204.285d {+13h 37m 08s} (J2000),
                 204.547d {+13h 38m 11s} (current),
                 203.674d {+13h 34m 42s} (1950)
GRB_DEC:         +14.480d {+14d 28' 49"} (J2000),
                 +14.372d {+14d 22' 18"} (current),
                 +14.735d {+14d 44' 05"} (1950)
GRB_DATE:        19375 TJD;   161 DOY;   21/06/10
GRB_TIME:        54223.38 SOD {15:03:43.38} UT
TRIGGER_INDEX:   147
GRB_PHI:          49.36 [deg]
GRB_THETA:        35.78 [deg]
DELTA_TIME:      31324.00 [sec]
TRIGGER_DUR:     1.024 [sec] 
SOLN_STATUS:     0x2003
RATE_SIGNIF:     18.81 [sigma]
IMAGE_SIGNIF:    7.79 [sigma]
LC_URL:          sw01054627000msb.lc
SUN_POSTN:        79.09d {+05h 16m 22s}  +23.06d {+23d 03' 24"}
SUN_DIST:        114.82 [deg]   Sun_angle= -8.4 [hr] (East of Sun)
MOON_POSTN:       81.30d {+05h 25m 12s}  +24.19d {+24d 11' 17"}
MOON_DIST:       112.50 [deg]
MOON_ILLUM:      0 [%]
GAL_COORDS:      345.31, 73.47 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:      196.77, 22.82 [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:        There is a bright star (mag=6.30) 8.66 arcmin from this position.  
COMMENTS:        This is a GRB.  
COMMENTS:        This trigger occurred at longitude,latitude = 102.11,-3.90 [deg].  
COMMENTS:        The 3rd packet (of 3) was missing in the lightcurve data stream.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Thu 10 Jun 21 15:22:26 UT
NOTICE_TYPE:     Swift-UVOT Source List
TRIGGER_NUM:     1054627,   Seg_Num: 0
POINT_RA:        204.260d {+13h 37m 02s} (J2000)
POINT_DEC:       +14.487d {+14d 29' 12"} (J2000)
POINT_ROLL:      304.232d
IMG_START_DATE:  19375 TJD;   161 DOY;   21/06/10
IMG_START_TIME:  54317.29 SOD {15:05:17.29} UT,   93.9 [sec] since BAT Trigger Time
FILTER:          10, White
BKG_MEAN:        2.006
N_STARS:         53
X_OFFSET:        353 [pixels]
Y_OFFSET:        690 [pixels]
X_MAX:           1312 [pixels]
Y_MAX:           1649 [pixels]
DET_THRESH:      12
PHOTO_THRESH:    6
SL_URL:          sw01054627000msufc0093.fits
SUN_POSTN:        79.09d {+05h 16m 22s}  +23.06d {+23d 03' 25"}
SUN_DIST:        114.80 [deg]   Sun_angle= -8.4 [hr] (East of Sun)
MOON_POSTN:       81.31d {+05h 25m 14s}  +24.19d {+24d 11' 21"}
MOON_DIST:       112.47 [deg]
MOON_ILLUM:      0 [%]
GAL_COORDS:      345.26, 73.49 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      196.74, 22.82 [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 15:22:47 UT
NOTICE_TYPE:     Swift-UVOT Image
TRIGGER_NUM:     1054627,   Seg_Num: 0
POINT_RA:        204.260d {+13h 37m 02s} (J2000)
POINT_DEC:       +14.487d {+14d 29' 12"} (J2000)
ROLL:            304.232d
IMG_START_DATE:  19375 TJD;   161 DOY;   21/06/10
IMG_START_TIME:  54317.29 SOD {15:05:17.29} UT,   93.9 [sec] since BAT Trigger Time
FILTER:          10, White
EXPOSURE_ID:     645030344
X_OFFSET:        672 [pixels]
Y_OFFSET:        1009 [pixels]
WIDTH:           160 [pixels]
HEIGHT:          160 [pixels]
X_GRB_POS:       832
Y_GRB_POS:       1169
BINNING_INDEX:   1
IM_URL:          sw01054627000msuni0121.fits
SUN_POSTN:        79.09d {+05h 16m 22s}  +23.06d {+23d 03' 25"}
SUN_DIST:        114.80 [deg]   Sun_angle= -8.4 [hr] (East of Sun)
MOON_POSTN:       81.31d {+05h 25m 15s}  +24.19d {+24d 11' 22"}
MOON_DIST:       112.47 [deg]
MOON_ILLUM:      0 [%]
GAL_COORDS:      345.26, 73.49 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      196.74, 22.82 [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 15:23:02 UT
NOTICE_TYPE:     Swift-UVOT Processed Image
TRIGGER_NUM:     1054627,   Seg_Num: 0
POINT_RA:        204.260d {+13h 37m 02s} (J2000)
POINT_DEC:       +14.487d {+14d 29' 12"} (J2000)
ROLL:            304.232d
IMG_START_DATE:  19375 TJD;   161 DOY;   21/06/10
IMG_START_TIME:  54317.29 SOD {15:05:17.29} UT,   93.9 [sec] since BAT Trigger Time
FILTER:          10, White
EXPOSURE_ID:     645030344
X_OFFSET:        672 [pixels]
Y_OFFSET:        1009 [pixels]
WIDTH:           160 [pixels]
HEIGHT:          160 [pixels]
X_GRB_POS:       832
Y_GRB_POS:       1169
BINNING_INDEX:   1
IM_URL:          sw01054627000msuni0121.fits
SUN_POSTN:        79.09d {+05h 16m 22s}  +23.06d {+23d 03' 25"}
SUN_DIST:        114.80 [deg]   Sun_angle= -8.4 [hr] (East of Sun)
MOON_POSTN:       81.31d {+05h 25m 16s}  +24.19d {+24d 11' 24"}
MOON_DIST:       112.47 [deg]
MOON_ILLUM:      0 [%]
GAL_COORDS:      345.26, 73.49 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      196.74, 22.82 [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 15:22:41 UT
NOTICE_TYPE:     Swift-UVOT Processed Source List
TRIGGER_NUM:     1054627,   Seg_Num: 0
POINT_RA:        204.260d {+13h 37m 02s} (J2000)
POINT_DEC:       +14.487d {+14d 29' 12"} (J2000)
POINT_ROLL:      304.232d
IMG_START_DATE:  19375 TJD;   161 DOY;   21/06/10
IMG_START_TIME:  54317.29 SOD {15:05:17.29} UT,   93.9 [sec] since BAT Trigger Time
FILTER:          10, White
BKG_MEAN:        2.006
N_STARS:         53
X_OFFSET:        353 [pixels]
Y_OFFSET:        690 [pixels]
X_MAX:           1312 [pixels]
Y_MAX:           1649 [pixels]
DET_THRESH:      12
PHOTO_THRESH:    6
SL_URL:          sw01054627000msufc0093.fits
SUN_POSTN:        79.09d {+05h 16m 22s}  +23.06d {+23d 03' 25"}
SUN_DIST:        114.80 [deg]   Sun_angle= -8.4 [hr] (East of Sun)
MOON_POSTN:       81.31d {+05h 25m 15s}  +24.19d {+24d 11' 22"}
MOON_DIST:       112.47 [deg]
MOON_ILLUM:      0 [%]
GAL_COORDS:      345.26, 73.49 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      196.74, 22.82 [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 15:24:16 UT
NOTICE_TYPE:     Swift-UVOT Source List
TRIGGER_NUM:     1054627,   Seg_Num: 0
POINT_RA:        204.260d {+13h 37m 02s} (J2000)
POINT_DEC:       +14.487d {+14d 29' 13"} (J2000)
POINT_ROLL:      304.232d
IMG_START_DATE:  19375 TJD;   161 DOY;   21/06/10
IMG_START_TIME:  54529.95 SOD {15:08:49.95} UT,   306.6 [sec] since BAT Trigger Time
FILTER:          7, U
BKG_MEAN:        0.496
N_STARS:         36
X_OFFSET:        113 [pixels]
Y_OFFSET:        450 [pixels]
X_MAX:           1552 [pixels]
Y_MAX:           1889 [pixels]
DET_THRESH:      7
PHOTO_THRESH:    3
SL_URL:          sw01054627000msufc0306.fits
SUN_POSTN:        79.09d {+05h 16m 22s}  +23.06d {+23d 03' 25"}
SUN_DIST:        114.80 [deg]   Sun_angle= -8.4 [hr] (East of Sun)
MOON_POSTN:       81.33d {+05h 25m 18s}  +24.19d {+24d 11' 29"}
MOON_DIST:       112.46 [deg]
MOON_ILLUM:      0 [%]
GAL_COORDS:      345.26, 73.49 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      196.74, 22.82 [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 15:24:40 UT
NOTICE_TYPE:     Swift-UVOT Image
TRIGGER_NUM:     1054627,   Seg_Num: 0
POINT_RA:        204.260d {+13h 37m 02s} (J2000)
POINT_DEC:       +14.487d {+14d 29' 13"} (J2000)
ROLL:            304.232d
IMG_START_DATE:  19375 TJD;   161 DOY;   21/06/10
IMG_START_TIME:  54529.95 SOD {15:08:49.95} UT,   306.6 [sec] since BAT Trigger Time
FILTER:          7, U
EXPOSURE_ID:     645030557
X_OFFSET:        672 [pixels]
Y_OFFSET:        1009 [pixels]
WIDTH:           160 [pixels]
HEIGHT:          160 [pixels]
X_GRB_POS:       832
Y_GRB_POS:       1169
BINNING_INDEX:   1
IM_URL:          sw01054627000msuni0334.fits
SUN_POSTN:        79.09d {+05h 16m 22s}  +23.06d {+23d 03' 25"}
SUN_DIST:        114.80 [deg]   Sun_angle= -8.4 [hr] (East of Sun)
MOON_POSTN:       81.33d {+05h 25m 19s}  +24.19d {+24d 11' 31"}
MOON_DIST:       112.46 [deg]
MOON_ILLUM:      0 [%]
GAL_COORDS:      345.26, 73.49 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      196.74, 22.82 [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 15:24:46 UT
NOTICE_TYPE:     Swift-UVOT Processed Image
TRIGGER_NUM:     1054627,   Seg_Num: 0
POINT_RA:        204.260d {+13h 37m 02s} (J2000)
POINT_DEC:       +14.487d {+14d 29' 13"} (J2000)
ROLL:            304.232d
IMG_START_DATE:  19375 TJD;   161 DOY;   21/06/10
IMG_START_TIME:  54529.95 SOD {15:08:49.95} UT,   306.6 [sec] since BAT Trigger Time
FILTER:          7, U
EXPOSURE_ID:     645030557
X_OFFSET:        672 [pixels]
Y_OFFSET:        1009 [pixels]
WIDTH:           160 [pixels]
HEIGHT:          160 [pixels]
X_GRB_POS:       832
Y_GRB_POS:       1169
BINNING_INDEX:   1
IM_URL:          sw01054627000msuni0334.fits
SUN_POSTN:        79.09d {+05h 16m 22s}  +23.06d {+23d 03' 25"}
SUN_DIST:        114.80 [deg]   Sun_angle= -8.4 [hr] (East of Sun)
MOON_POSTN:       81.33d {+05h 25m 19s}  +24.19d {+24d 11' 31"}
MOON_DIST:       112.46 [deg]
MOON_ILLUM:      0 [%]
GAL_COORDS:      345.26, 73.49 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      196.74, 22.82 [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 15:25:37 UT
NOTICE_TYPE:     Swift-UVOT Source List
TRIGGER_NUM:     1054627,   Seg_Num: 0
POINT_RA:        204.260d {+13h 37m 02s} (J2000)
POINT_DEC:       +14.487d {+14d 29' 13"} (J2000)
POINT_ROLL:      304.232d
IMG_START_DATE:  19375 TJD;   161 DOY;   21/06/10
IMG_START_TIME:  55084.09 SOD {15:18:04.09} UT,   860.7 [sec] since BAT Trigger Time
FILTER:          10, White
BKG_MEAN:        0.419
N_STARS:         37
X_OFFSET:        113 [pixels]
Y_OFFSET:        450 [pixels]
X_MAX:           1552 [pixels]
Y_MAX:           1889 [pixels]
DET_THRESH:      6
PHOTO_THRESH:    2
SL_URL:          sw01054627000msufc0860.fits
SUN_POSTN:        79.09d {+05h 16m 22s}  +23.06d {+23d 03' 25"}
SUN_DIST:        114.80 [deg]   Sun_angle= -8.4 [hr] (East of Sun)
MOON_POSTN:       81.34d {+05h 25m 21s}  +24.19d {+24d 11' 35"}
MOON_DIST:       112.45 [deg]
MOON_ILLUM:      0 [%]
GAL_COORDS:      345.26, 73.49 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      196.74, 22.82 [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 15:24:34 UT
NOTICE_TYPE:     Swift-UVOT Processed Source List
TRIGGER_NUM:     1054627,   Seg_Num: 0
POINT_RA:        204.260d {+13h 37m 02s} (J2000)
POINT_DEC:       +14.487d {+14d 29' 13"} (J2000)
POINT_ROLL:      304.232d
IMG_START_DATE:  19375 TJD;   161 DOY;   21/06/10
IMG_START_TIME:  54529.95 SOD {15:08:49.95} UT,   306.6 [sec] since BAT Trigger Time
FILTER:          7, U
BKG_MEAN:        0.496
N_STARS:         36
X_OFFSET:        113 [pixels]
Y_OFFSET:        450 [pixels]
X_MAX:           1552 [pixels]
Y_MAX:           1889 [pixels]
DET_THRESH:      7
PHOTO_THRESH:    3
SL_URL:          sw01054627000msufc0306.fits
SUN_POSTN:        79.09d {+05h 16m 22s}  +23.06d {+23d 03' 25"}
SUN_DIST:        114.80 [deg]   Sun_angle= -8.4 [hr] (East of Sun)
MOON_POSTN:       81.33d {+05h 25m 19s}  +24.19d {+24d 11' 30"}
MOON_DIST:       112.46 [deg]
MOON_ILLUM:      0 [%]
GAL_COORDS:      345.26, 73.49 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      196.74, 22.82 [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 15:25:52 UT
NOTICE_TYPE:     Swift-UVOT Image
TRIGGER_NUM:     1054627,   Seg_Num: 0
POINT_RA:        204.260d {+13h 37m 02s} (J2000)
POINT_DEC:       +14.487d {+14d 29' 13"} (J2000)
ROLL:            304.232d
IMG_START_DATE:  19375 TJD;   161 DOY;   21/06/10
IMG_START_TIME:  55084.09 SOD {15:18:04.09} UT,   860.7 [sec] since BAT Trigger Time
FILTER:          10, White
EXPOSURE_ID:     645031111
X_OFFSET:        672 [pixels]
Y_OFFSET:        1009 [pixels]
WIDTH:           160 [pixels]
HEIGHT:          160 [pixels]
X_GRB_POS:       832
Y_GRB_POS:       1169
BINNING_INDEX:   1
IM_URL:          sw01054627000msuni0888.fits
SUN_POSTN:        79.09d {+05h 16m 22s}  +23.06d {+23d 03' 25"}
SUN_DIST:        114.80 [deg]   Sun_angle= -8.4 [hr] (East of Sun)
MOON_POSTN:       81.34d {+05h 25m 22s}  +24.19d {+24d 11' 36"}
MOON_DIST:       112.45 [deg]
MOON_ILLUM:      0 [%]
GAL_COORDS:      345.26, 73.49 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      196.74, 22.82 [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 15:25:56 UT
NOTICE_TYPE:     Swift-UVOT Processed Source List
TRIGGER_NUM:     1054627,   Seg_Num: 0
POINT_RA:        204.260d {+13h 37m 02s} (J2000)
POINT_DEC:       +14.487d {+14d 29' 13"} (J2000)
POINT_ROLL:      304.232d
IMG_START_DATE:  19375 TJD;   161 DOY;   21/06/10
IMG_START_TIME:  55084.09 SOD {15:18:04.09} UT,   860.7 [sec] since BAT Trigger Time
FILTER:          10, White
BKG_MEAN:        0.419
N_STARS:         37
X_OFFSET:        113 [pixels]
Y_OFFSET:        450 [pixels]
X_MAX:           1552 [pixels]
Y_MAX:           1889 [pixels]
DET_THRESH:      6
PHOTO_THRESH:    2
SL_URL:          sw01054627000msufc0860.fits
SUN_POSTN:        79.09d {+05h 16m 22s}  +23.06d {+23d 03' 25"}
SUN_DIST:        114.80 [deg]   Sun_angle= -8.4 [hr] (East of Sun)
MOON_POSTN:       81.34d {+05h 25m 22s}  +24.19d {+24d 11' 37"}
MOON_DIST:       112.45 [deg]
MOON_ILLUM:      0 [%]
GAL_COORDS:      345.26, 73.49 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      196.74, 22.82 [deg] ecliptic lon,lat of the pointing direction
COMMENTS:        SWIFT-UVOT Processed Source List.  
COMMENTS:        If you have elected to receive attachments:  
COMMENTS:        The uvot_catalog_srclist.fits.gz file does not exist; skipping the attachment.

GCN Circular #30160
K. L. Page (U Leicester), M. A. Baer (PSU), J.D. Gropp (PSU), N. J. Klingler (PSU), A. Y. Lien (GSFC/UMBC), 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 15:03:43 UT, the Swift Burst Alert Telescope (BAT) triggered and located GRB 210610A (trigger=1054627). Swift slewed immediately to the burst. The BAT on-board calculated location is RA, Dec 204.285, +14.480 which is
```
   RA(J2000) = 13h 37m 08s
   Dec(J2000) = +14d 28' 49"
```
with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). The BAT light curve showed a complex structure with a duration of about 15 sec. The peak count rate was ~2000 counts/sec (15-350 keV), at ~0 sec after the trigger.
The XRT began observing the field at 15:05:13.3 UT, 90.0 seconds after the BAT trigger. Using promptly downlinked data we find an uncatalogued X-ray source with an enhanced position: RA, Dec 204.2823, 14.4652 which is equivalent to:
```
   RA(J2000)  = 13h 37m 07.76s
   Dec(J2000) = +14d 27' 54.7"
```
with an uncertainty of 2.2 arcseconds (radius, 90% containment). This location is 54 arcseconds from the BAT onboard position, within the BAT error circle. This position may be improved as more data are received; the latest position is available at https://www.swift.ac.uk/sper. No spectrum from the promptly downlinked event data is yet available to determine the column density.
UVOT took a finding chart exposure of 150 seconds with the White filter starting 93 seconds after the BAT trigger. There is a candidate afterglow in the rapidly available 2.7'x2.7' sub-image at
```
  RA(J2000)  =	13:37:07.62 = 204.28174
  DEC(J2000) = +14:27:55.0  =  14.46528
```
with a 90%-confidence error radius of about 0.61 arc sec. This position is 2.2 arc sec. from the center of the XRT error circle. The estimated magnitude is 17.12 with a 1-sigma error of about 0.14. No correction has been made for the expected extinction corresponding to E(B-V) of 0.032.
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 NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Thu 10 Jun 21 15:26:05 UT
NOTICE_TYPE:     Swift-UVOT Processed Image
TRIGGER_NUM:     1054627,   Seg_Num: 0
POINT_RA:        204.260d {+13h 37m 02s} (J2000)
POINT_DEC:       +14.487d {+14d 29' 13"} (J2000)
ROLL:            304.232d
IMG_START_DATE:  19375 TJD;   161 DOY;   21/06/10
IMG_START_TIME:  55084.09 SOD {15:18:04.09} UT,   860.7 [sec] since BAT Trigger Time
FILTER:          10, White
EXPOSURE_ID:     645031111
X_OFFSET:        672 [pixels]
Y_OFFSET:        1009 [pixels]
WIDTH:           160 [pixels]
HEIGHT:          160 [pixels]
X_GRB_POS:       832
Y_GRB_POS:       1169
BINNING_INDEX:   1
IM_URL:          sw01054627000msuni0888.fits
SUN_POSTN:        79.09d {+05h 16m 22s}  +23.06d {+23d 03' 25"}
SUN_DIST:        114.80 [deg]   Sun_angle= -8.4 [hr] (East of Sun)
MOON_POSTN:       81.34d {+05h 25m 22s}  +24.19d {+24d 11' 37"}
MOON_DIST:       112.45 [deg]
MOON_ILLUM:      0 [%]
GAL_COORDS:      345.26, 73.49 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      196.74, 22.82 [deg] ecliptic lon,lat of the pointing direction
COMMENTS:        SWIFT-UVOT Processed Image.  
COMMENTS:        The GRB Position came from the Window Position in the Mode Command.  
COMMENTS:        The image has 2x2 binning (compression).  
COMMENTS:        If you have elected to receive attachments:  
COMMENTS:        The uvot_catalog_image.fits.gz file does not exist; skipping the attachment.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Thu 10 Jun 21 15:25:29 UT
NOTICE_TYPE:     Swift-XRT Position
TRIGGER_NUM:     1054627,   Seg_Num: 0
GRB_RA:          204.2822d {+13h 37m 07.72s} (J2000),
                 204.5442d {+13h 38m 10.61s} (current),
                 203.6711d {+13h 34m 41.07s} (1950)
GRB_DEC:         +14.4650d {+14d 27' 53.9"} (J2000),
                 +14.3563d {+14d 21' 22.7"} (current),
                 +14.7194d {+14d 43' 09.7"} (1950)
GRB_ERROR:       2.2 [arcsec radius, statistical plus systematic, 90% containment]
GRB_INTEN:       1.00e-10 [erg/cm2/sec]
GRB_SIGNIF:      10.00 [sigma]
IMG_START_DATE:  19375 TJD;   161 DOY;   21/06/10
IMG_START_TIME:  54320.00 SOD {15:05:20.00} UT,   96.6 [sec] since BAT Trigger Time
TAM[0-3]:        100.00 100.00 100.00 100.00
AMPLIFIER:       1
WAVEFORM:        31
SUN_POSTN:        79.09d {+05h 16m 22s}  +23.06d {+23d 03' 25"}
SUN_DIST:        114.83 [deg]   Sun_angle= -8.4 [hr] (East of Sun)
MOON_POSTN:       81.34d {+05h 25m 21s}  +24.19d {+24d 11' 35"}
MOON_DIST:       112.48 [deg]
MOON_ILLUM:      0 [%]
GAL_COORDS:      345.27, 73.46 [deg] galactic lon,lat of the burst
ECL_COORDS:      196.77, 22.80 [deg] ecliptic lon,lat of the burst
COMMENTS:        SWIFT-XRT Coordinates.  
COMMENTS:        This Notice was ground-generated -- not flight-generated.  
COMMENTS:        TAM values, flux and significance fields are not valid.  
COMMENTS:        This position was automatically generated on the ground using  
COMMENTS:        Photon Counting data telemetered via TDRSS (SPER data).  
COMMENTS:        See http://www.swift.ac.uk/sper/docs.php for details.  
COMMENTS:        This position was enhanced using UVOT field astrometry.  
COMMENTS:        The probability that this is a serendipitous source in the  
COMMENTS:        SPER window is 1.1% < P(seren) < 2.8%.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Thu 10 Jun 21 15:26:06 UT
NOTICE_TYPE:     Swift-UVOT Position
TRIGGER_NUM:     1054627,   Seg_Num: 0
GRB_RA:          204.2817d {+13h 37m 07.60s} (J2000),
                 204.5437d {+13h 38m 10.49s} (current),
                 203.6706d {+13h 34m 40.95s} (1950)
GRB_DEC:         +14.4652d {+14d 27' 54.7"} (J2000),
                 +14.3565d {+14d 21' 23.4"} (current),
                 +14.7196d {+14d 43' 10.4"} (1950)
GRB_ERROR:       0.6 [arcsec radius, statistical only]
GRB_MAG:         17.12 +/- 0.14 [mag]
FILTER:          10, White
IMG_START_DATE:  19375 TJD;   161 DOY;   21/06/10
IMG_START_TIME:  54314.00 SOD {15:05:14.00} UT,   90.6 [sec] since BAT Trigger Time
SUN_POSTN:        79.09d {+05h 16m 22s}  +23.06d {+23d 03' 25"}
SUN_DIST:        114.83 [deg]   Sun_angle= -8.4 [hr] (East of Sun)
MOON_POSTN:       81.34d {+05h 25m 22s}  +24.19d {+24d 11' 37"}
MOON_DIST:       112.47 [deg]
MOON_ILLUM:      0 [%]
GAL_COORDS:      345.27, 73.46 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:      196.77, 22.80 [deg] ecliptic lon,lat of the burst (or transient)
COMMENTS:        SWIFT UVOT Position Notice.  
COMMENTS:        This Notice was ground-generated -- not flight-generated.  
COMMENTS:        Result based on Genie data.  
COMMENTS:        Notice generated automatically.

GCN Circular #30161
R. Hosokawa, K. L. Murata, M. Niwano, N. Ito, H. Takamatsu, Y. Imai, S. Sato, M. Takaku, R. Noto, R. Yamaguchi, Y. Yatsu, and N. Kawai (TokyoTech) report on behalf of the MITSuME collaboration:
We observed the field of GRB 210610A (K. L. Page et al. GCN Circular #30160) with the optical three color (g', Rc, and Ic) CCD cameras attached to the MITSuME 50 cm telescope of Akeno Observatory, Yamanashi, Japan. The observation with a series of 10 sec exposures started at 2021-06-10 15:04:41 UT (58 seconds after Swift BAT trigger). We stacked the images with good conditions. We detected the point source at the position consistent with the afterglow detected previously (K. L. Page et al. GCN Circular #30160) We measured the magnitudes as follows.
```
filter MID-UT T-EXP[sec] measured magnitudes
------------------------------------------------------------------------------------------------
g' 15:08:47 10 16.4+/-0.4
Rc 15:08:29 50 15.3+/-0.1
Ic 15:08:29 50 15.0+/-0.2
------------------------------------------------------------------------------------------------
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 #30162
D. Xu, Z.P. Zhu, S.Y. Fu, X. Liu (NAOC) report on behalf of a larger collaboration:
We observed the field of GRB 210610A (Page et al., GCN 30160) using the 2.16-m optical telescope located at Xinglong, Hebei, China, equipped with the BFOSC camera. Observations started at 15:28:02 UT on 2021-06-10, i.e., 24.25 min after the burst.
An uncatalogued and varying optical transient is detected at coordinates:
```
R.A. (J2000) = 13:37:07.60
Dec. (J2000) = +14:27:55.0
```
with an error radius of ~ 0.3 arsec, positionally being well consistent with the Swift/UVOT detection (Page et al., GCN 30160). The OT is thus the optical afterglow of the GRB, and it has r = 16.97 +/- 0.01 mag at 26.25 min post-burst, calibrated with the nearby PanSTAR field.
Spectroscopy of the afterglow is underway.
GCN Circular #30163
H. Kumar(IITB), V. Bhalerao(IITB), U. Stanzin (IAO), G. C. Anupama(IIA), S. Barway(IIA) report on behalf of the GIT team:
We observed GRB 210610A detected by Swift-BAT ( K. L. Page et al., GCN #30160, optical counterpart reported by R. Hosokawa et al., GCN #30161 and D. Xu et al., GCN #30162), with the 0.7m GROWTH-India Telescope (GIT). We obtained a 300-sec exposure in the r' filter. We clearly detected the afterglow in our image at R.A.= 13:37:07.64 and DEC.= 14:27:55.10. The photometric results follow as:
-------------------------------------------------------------------
JD (start) | T_mid-T0(hrs) | Filter | Magnitude (AB) |
-------------------------------------------------------------------
2459376.178 | 1.22 | r' | 18.79+/- 0.05 |
-------------------------------------------------------------------
The magnitudes are calibrated against PanSTARRS DR1 (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 #30164
Z.P. Zhu, D. Xu, S.Y. Fu, X. Liu (NAOC) report on behalf of a larger collaboration:
Following the photometry of the optical afterglow (Xu et al., GCN 30162) of GRB 210610A (Page et al., GCN 30160), we carried out 2x1800 s spectroscopy of the afterglow using the BFOSC camera. The spectrum covers the wavelength range 4000-9000 AA. The observation mid time is 2021 June 10.667 UT, i.e., 0.955 hr after the burst.
In our spectra, continuum is detected over the whole observed range. A prominent absorption feature is detected around 5519 AA, which we identify as Ly alpha in absorption, and blueward of which is Ly alpha forest. The interpretation is confirmed by the detection of metal absorption lines such as Si II, Si IV, C IV, all at a common redshift z = 3.54, using old calibrations. The redshift measurement may be improved a bit when new calibrations are available.
We thank the excellent support of the Xinglong-2.16m staff, especially Junjun Jia and Jie Zheng.
GCN Circular #30165
M.R. Goad, J.P. Osborne, A.P. Beardmore and P.A. Evans (U. Leicester) report on behalf of the Swift-XRT team.
Using 792 s of XRT Photon Counting mode data and 1 UVOT images for GRB 210610A, 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 = 204.28211, +14.46540 which is equivalent to:
```
RA (J2000): 13h 37m 7.71s
Dec (J2000): +14d 27' 55.4"
```
with an uncertainty of 2.3 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 #30166
V. Lipunov, K.Zhirkov, V.Kornilov, E.Gorbovskoy, I.Gorbunov,P.Balanutsa,V.Vladimirov,A.Kuznetsov, D. Vlasenko, N.Tiurina, D.Zimnukhov, V.Senik, V.Topolev, A.Chasovnikov, D.Cheryasov (Lomonosov MSU,SAI,PhysicsDepartment), D. Buckley (South African Astronomical Observatory), O.A. Gres, N.M. Budnev (Irkutsk State University, API), R. Podesta, C.Lopez, F. Podesta, C.Francile (Observatorio Astronomico FelixAguilar OAFA), R. Rebolo, M. Serra(The Instituto de Astrofisica de Canarias), A. Tlatov, D. Dormidontov (Kislovodsk Solar Station of the Pulkovo Observatory), A. Gabovich, V.Yurkov (Blagoveschensk Educational StateUniversity)
MASTER Global robotic net (MASTER-Net:http://observ.pereplet.ru Lipunov et al.,2010,Advances in Astronomy,2010,30L) started Swift GRB 210610A (Page et al. GCN 30160) error box observation at 2021-06-10 16:23:35UT at MASTER-SAAO.
There is MASTER OT J133707.60+142755.0 with m_OT~20.1m (unfiltered), that was discovered by Swift-UVOT (Page et al. 30160) and confirmed by Hosokawa et al. GCN 30161, Xu et al. GCN 30162, Kumar et al. GCN 30163, and with redshift z=3.54 detected by Zhu et al. GCN 30164.
Observation and reduction will be continued.
GCN Circular #30167
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-SAAO robotic telescope (Global MASTER-Net: http://observ.pereplet.ru, Lipunov et al., 2010, Advances in Astronomy, vol. 2010, 30L) located in South Africa (South African Astronomical Observatory) was pointed to the Swift GRB 210610A ( K. L. Page et al., GCN 30160) errorbox 4610 sec after notice time and 4632 sec after trigger time at 2021-06-10 16:20:55 UT, with upper limit up to 17.1 mag. Observations started at twilight. The observations began at zenith distance = 58 deg. The sun altitude is -8.5 deg.
The galactic latitude b = 73 deg., longitude l = 346 deg.
Real time updated cover map and OT discovered available here: https://master.sai.msu.ru/site/master2/observ.php?id=1633161
We obtain a following upper limits.
```
Tmid-T0  |          Site       |Filt.| Expt. | Limit| Comment
_________|_____________________|_____|_______|______|________

    4662 |         MASTER-SAAO |   C |    60 | 16.8 |        
    4742 |         MASTER-SAAO |   C |    60 | 16.9 |        
    4822 |         MASTER-SAAO |   C |    60 | 17.1 |        
```
Filter C is a clear (unfiltred) band.
The observation and reduction will continue. The message may be cited.
GCN Circular #30168
S. de Wet (UCT), P.M. Vreeswijk (Radboud), P.J. Groot (Radboud/UCT/SAAO), A. Levan (Radboud) report on behalf of the MeerLICHT consortium:
Following the detection of GRB210610A by Swift and its optical counterpart (Page et al., GCN 30160), reported at a redshift of z=3.54 by Zhu et al. (GCN 30163), the 0.6m MeerLICHT telescope, located at Sutherland, South Africa began observations of the field at 2021-06-10, 16:48:47 UT 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 = 19.60 +/- 0.08 +/- 0.02 at 16:48:47 UT
r_AB = 19.09 +/- 0.10 +/- 0.01 at 16:56:12 UT
i_AB = 18.74 +/- 0.12 +/- 0.02 at 16:59:10 UT
z_AB = 18.37 +/- 0.19 +/- 0.02 at 17:02:09 UT, 
```
where the first uncertainty on the magnitude is the statistical uncertainty and the second is the uncertainty on the photometric calibration.
In g-band the afterglow is detected only once, at 17:08:11 UT, at g_AB = 20.18 +/- 0.18 +/- 0.03, close to the limiting magnitude of the frame.
The source is not detected in the u-band, starting at 16:50:11 UT, at a 5-sigma limiting magnitude of u_AB > 18.76.
Further fading of the source is observed during the ongoing sequence.
MeerLICHT is built and run by a consortium consisting of Radboud University, the University of Cape Town, the South African Astronomical Observatory, the University of Oxford, the University of Manchester and the University of Amsterdam.
GCN Circular #30169
Takashi Horiuchi, Hidekazu Hanayama (NAOJ), Katsuhiro L. Murata, Yoichi Yatsu, Nobuyuki Kawai (Tokyo Tech) report on behalf of the MITSuME collaboration:
We observed the field of GRB 210610A (K. L. Page et al. GCN Circular #30160) with the optical three color (g', Rc, and Ic) CCD cameras attached to the 105 cm Murikabushi telescope of Ishigakijima Astronomical Observatory, Okinawa, Japan.
The observation with a series of 60 sec exposures started on 2021-06-10 15:40:04 UT (37 min after Swift BAT trigger). We detected the point source at the position consistent with the afterglow reported by K. L. Page et al. GCN Circular #30160. Here, we removed bad data (images) with wrong sky conditions and obtained the magnitudes as follows:
```
T0+[min] MID-UT T-EXP[sec] measured magnitudes
------------------------------------------------------------------------------------------------
37 2021-06-10T15:57:45  900 (60s � 15)  g'=19.41+/-0.14, Rc=18.19+/-0.04, Ic=17.73+/-0.10
------------------------------------------------------------------------------------------------
T0+ : Elapsed time after the burst
T-EXP: Total Exposure time
```
The SDSS catalog (DR16) is used for flux calibration.
GCN Circular #30185
T.-R. Sun, Y.-D. Hu, A. Sota, A. J. Castro-Tirado, M. D. Caballero-Garcia, M. A. Castro Tirado and E. Fernandez-Garcia (IAA-CSIC), on behalf of a larger collaboration, report:
Following the detection of GRB 210610A by Swift (Page et al. GCNC 30160), images in BVRI bands were obtained at the 1.5m OSN telescope in Granada (Spain) starting after the twilight as soon as it was possible. In the first I-band 90 s exposure image, the optical afterglow with I = 19.85+-0.18 at 21:12 UT (~6.1 hr after trigger) is clearly seen within the enhanced XRT position (Goad et al. GCNC 30165), which also detected by UVOT/Swift (Page et al. GCNC 30160), MITSuME (Hosokawa et al. GCNC 30161 and Horiuchi et al. GCNC 30169), Xinglong (Xu et al. GCNC 30162), MASTER (Lipunov et al. GCNC 30166) and MeerLICHT (de Wet et al. GCNC 30168). Further observations are ongoing.
We thank the staff at OSN for their excellent support.
GCN Circular #30186
S. D. Barthelmy (GSFC), J. R. Cummings (CPI), H. A. Krimm (NSF), 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+963 sec from the recent telemetry downlink, we report further analysis of BAT GRB 210610A (trigger #1054627) (Page et al., GCN Circ. 30160). The BAT ground-calculated position is RA, Dec = 204.284, 14.476 deg which is
```
   RA(J2000)  =  13h 37m 08.2s
   Dec(J2000) = +14d 28' 32.5"
```
with an uncertainty of 1.7 arcmin, (radius, sys+stat, 90% containment). The partial coding was 26%.
The mask-weighted light curve shows a structure with two overlapping pulses that starts at ~T-6 s and ends at ~T+11 s. The two peaks occur at ~T-2 s and ~T0, respectively. T90 (15-350 keV) is 13.62 +- 3.15 sec (estimated error including systematics).
The time-averaged spectrum from T-5.98 to T+11.35 sec is best fit by a simple power-law model. The power law index of the time-averaged spectrum is 1.41 +- 0.19. The fluence in the 15-150 keV band is 1.0 +- 0.1 x 10^-6 erg/cm2. The 1-sec peak photon flux measured from T-0.29 sec in the 15-150 keV band is 2.5 +- 0.4 ph/cm2/sec. All the quoted errors are at the 90% confidence level.
The results of the batgrbproduct analysis are available at http://gcn.gsfc.nasa.gov/notices_s/1054627/BA/
GCN Circular #30191
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 210610A (Page et al., GCN Circ. 30160) 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 11.18 to 2021/06 11.23 UTC (13.00 to 14.06 hours after the BAT trigger), obtaining a total of 0.61 hours exposure in the r and i bands and 0.25 hours exposure in the Z, Y, J, and H bands.
We detect the afterglow with the following magnitudes and 3-sigma upper limit:
```
  r = 21.39 +/- 0.06
  i = 21.35 +/- 0.07
  Z = 20.74 +/- 0.10
  Y = 21.05 +/- 0.22
  J = 20.70 +/- 0.25
  H > 20.12
```
These magnitudes are in the AB system and are not corrected for Galactic extinction in the direction of the GRB.
We thank the staff of the Observatorio Astron�mico Nacional in San Pedro M�rtir.
GCN Circular #30192
D.N. Burrows (PSU), J. D. Gropp (PSU), A.P. Beardmore (U. Leicester), P.A. Evans (U. Leicester), J.P. Osborne (U. Leicester), T. Sbarrato (INAF-OAB), P. D'Avanzo (INAF-OAB), M.G. Bernardini (INAF-OAB), J.A. Kennea (PSU) and K.L. Page report on behalf of the Swift-XRT team:
We have analysed 7.1 ks of XRT data for GRB 210610A (Page et al. GCN Circ. 30160), from 97 s to 45.9 ks after the BAT trigger. The data are entirely in Photon Counting (PC) mode. The enhanced XRT position for this burst was given by Goad et al. (GCN Circ. 30165).
The late-time light curve (from T0+4.1 ks) can be modelled with a power-law decay with a decay index of alpha=1.05 (+/-0.10).
A spectrum formed from the PC mode data can be fitted with an absorbed power-law with a photon spectral index of 1.84 (+0.12, -0.10). The best-fitting absorption column is 2.6 (+9.0, -2.6) x 10^21 cm^-2, at a redshift of 3.54, in addition to the Galactic value of 2.2 x 10^20 cm^-2 (Willingale et al. 2013). The counts to observed (unabsorbed) 0.3-10 keV flux conversion factor deduced from this spectrum is 3.5 x 10^-11 (3.7 x 10^-11) erg cm^-2 count^-1.
A summary of the PC-mode spectrum is thus:
```
Galactic foreground: 2.2 x 10^20 cm^-2
Intrinsic column:    2.6 (+9.0, -2.6) x 10^21 cm^-2 at z=3.54
Photon index:	     1.84 (+0.12, -0.10)
```
If the light curve continues to decay with a power-law decay index of 1.05, the count rate at T+24 hours will be 9.7 x 10^-3 count s^-1, corresponding to an observed (unabsorbed) 0.3-10 keV flux of 3.4 x 10^-13 (3.6 x 10^-13) erg cm^-2 s^-1.
The results of the XRT-team automatic analysis are available at http://www.swift.ac.uk/xrt_products/01054627.
This circular is an official product of the Swift-XRT team.
GCN Circular #30197
D. Frederiks, S. Golenetskii, A.Lysenko, D. Svinkin, A. Ridnaya, A. Tsvetkova, M. Ulanov, and T. Cline, report:
The long GRB 210610A (Swift-BAT detection: Page et al., GCN 30160; Barthelmy et al., GCN 30186), T0 (BAT) = 15:03:43/387, was detected by Konus-Wind (KW) in the waiting mode.
A Bayesian block analysis of the KW waiting mode data in the 20-400 keV band reveals a ~8 sigma count rate increase over background in the interval from ~T0(BAT)-2 s to ~T0(BAT)+4 s. The KW light curve of this burst is available at http://www.ioffe.ru/LEA/GRBs/GRB210610A/
Modeling the KW 3-channel spectrum by a power law with exponential cutoff (CPL) model dN/dE ~ (E^alpha)*exp(-E*(2+alpha)/Ep) yields alpha = -0.17(-0.83,+1.15) and Ep = 148(-63,+87) keV.
In the 10 keV -10 MeV band, the total burst fluence is (1.3 � 0.5)x10^-6 erg/cm^2, and the 2.944 s peak energy flux is (2.7 � 0.8)x10^-7 erg/cm^2.
Assuming the redshift z=3.54 (Zhu et al., GCN 30164) 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 ~3.5x10^52 erg, the isotropic luminosity L_iso to ~3.3x10^52 erg/s, and the rest-frame peak energy of the time-integrated spectrum Ep,z to ~670 keV. With these values, GRB 210610A is within 90% prediction bands for for the 'Amati' relation 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/GRB210610A/GRB210610A_rest_frame.pdf
All the quoted errors are estimated at the 68% confidence level. All the presented results are preliminary.
GCN Circular #30200
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 210210A detected by Swift-BAT ( K. L. Page et al., GCN #30160), with the HFOSC instrument mounted on the 2-m Himalayan Chandra Telescope at the Indian Astronomical Observatory. We obtained a wavelength coverage of 3800 - 8000 angstrom. We took a 2700 second exposure on 2021 June 10 16:48 (UTC).
The spectrum is continuum-dominated with a broad absorption feature at ~5509 A which we interpret as Lyman alpha (rest-frame wavelength 1216 A) at a redshift of z=3.5, consistent with the redshift reported by Zhu et al. (GCN #30164. Other absorption features due to Si II (1307 A), Si IV (1397 A), CIV (1549 A) at the same redshift are also observed. 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 #30203
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 210610A (Page et al.,
GCN 30160) starting at ~14.22 hours after the Swift trigger (Page et al.
GCN 30160). A total of 30x60s images were obtained in the clear (roughly R)
filters. We detect the optical afterglow (e.g. Page et al., GCN 30160)
in the coadd image with a mag of 21.2 +/- 0.2, calibrated to the
Pan-STARRS1 catalog.
GCN Circular #30211
D. A. Kann (HETH/IAA-CSIC), A. de Ugarte Postigo (HETH/IAA-CSIC, DARK/NBI), J. F. Agui Fernandez, C. C. Thoene, M. Blazek (all HETH/IAA-CSIC), A. Fernandez, I. Hermelo, and S. Pedraz (all CAHA) report:
We observed the afterglow (Page et al., GCN #30160; Hosokawa et al., GCNs #30161, #30169; Xu et a., GCN #30162; Kumar et al., GCN #30163; Lipunov et al., GCN #30166; de Wet et al., GCN #30168; Sun et al., GCN #30185; Watson et al., GCN #30191; Zheng et al., GCN #30203) of GRB 210610A, discovered by Swift (Page et al., GCN #30160) and also detected by Konus-Wind (Frederiks et al., GCN #30197) at redshift z=3.54 (Zhu et al., GCN #30164; Dutta et al., GCN #30200). with CAFOS mounted on the 2.2m telescope at Calar Alto, Almeria, Spain. We obtained 5 x 180 s in Sloan i' before switching to observations of GRB 210610B. After these, we obtained 3 x 300 s each in Sloan r' and g'.
The afterglow is detected in individual frames. Stacking the images, we measure, against nearby comparison stars from the SDSS catalog (AB mags, not corrected for Galactic extinction):
```
i' = 20.18 +/- 0.04 mag at 0.23677 d;
r' = 20.87 +/- 0.05 mag at 0.36333 d;
g' = 21.92 +/- 0.08 mag at 0.37687 d.
```
Using our data as well as data given in the GCN Circulars cited above, we find that after 0.03 d, the light curve can be described with a broken power-law fit, with alpha_1 = 0.84, alpha_2 = 1.24, and t_break = 0.16 d. Earlier data is brighter than the back-extrapolation of the fit, indicating a steeper decay must have taken place.
GCN Circular #30214
S. Belkin (IKI, HSE), A. Pozanenko (IKI), V. Rumyantsev (CrAO), N. Pankov (IKI, HSE) report on behalf of IKI GRB FuN:
We observed the GRB 210610A (Page et al., GCN 30160) with ZTSH 2.6m telescope of CrAO observatory on June 10 starting on (UT) 18:29:17, and June 11 starting on (UT) 18:53:09. The optical afterglow first reported by UVOT (Page et al., GCN 30160) is clearly detected in each of a single images in R filter in both epochs. Preliminary photometry of the afterglow in the first image on June 10, and combined image on the June 11 is following
```
Date       UT start   t-T0    Filter Exp.    OT      err   UL(3 sigma)
                      (mid, days)       (s)

2021-06-10 18:29:17   0.14310 R       1*60   19.47   0.12  20.7
2021-06-11 18:53:09   1.16766 R      12*120  22.19   0.17  23.0
```
The photometry is based on nearby SDSS DR12 stars
```
SDSS-DR12_id RA DEC B(Lupton transformation) R(Lupton transformation)
J133717.13+142854.9 204.32139900 +14.48192200 17.8777 17.0295
J133703.62+142832.7 204.26512000 +14.47576300 19.2842 17.7239
J133658.05+142404.4 204.24188500 +14.40123200 20.3290 18.3616
```
The light curve of can be found in http://grb.rssi.ru/GRB210610A/GRB210610A_LC.png
Initial power law index of the light curve in the first epoch is about -0.82, and it is steepening between the two epochs down to -1.03 which is compatible with broken power-law fit reported by D.A. Kann et al. (GCN 30211).
GCN Circular #30229
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 210610A (Page et al., GCN #30160) with the SAO RAS 1-m telescope Zeiss-1000 + CCD-photometer in Rc band on June 11 and 12.
We clearly detected the GRB OT (Page et al., GCN #30160; Hosokawa et al., GCNs #30161, #30169; Xu et al., GCN #30162; Kumar et al., GCN #30163; Zhu et al., GCN # 30164; Lipunov et al., GCN #30166; de Wet et al., GCN #30168; Horiuchi et al., GCN #30169; Sun et al., GCN #30185; Watson et al., GCN #30191; Dutta et al., GCN #30200; Zheng et al., GCN #30203, Kann et al., GCN #30211; Belkin et al., GCN #30214) in the stacked frame obtained on June 11 and marginally detected the object in the stacked frame obtained on June 12.
```
Date      UT_start  UT_end    Exp., s   T_mid-T0, d   R mag
June, 11  20:12:02--21:08:03   8 x 300  1.23356       22.43 +/- 0.14
June, 12  19:46:09--21:08:36  12 x 300  2.22477       23.3  +/- 0.3
```
The preliminary photometry is based on magnitudes of the nearby SDSS stars (transformed with the Lupton 2005 equations). The OT magnitudes were not corrected for MW extinction.
GCN Circular #30232
D. A. Kann (HETH/IAA-CSIC), A. de Ugarte Postigo (HETH/IAA-CSIC, DARK/NBI), J. F. Agui Fernandez, C. C. Thoene, M. Blazek (all HETH/IAA-CSIC), A. Fernandez-Martin (CAHA), and M. Azzaro (IAA-CSIC) report:
We re-observed the afterglow (Page et al., GCN #30160; Hosokawa et al., GCNs #30161, #30169; Xu et a., GCN #30162; Kumar et al., GCN #30163; Lipunov et al., GCN #30166; de Wet et al., GCN #30168; Sun et al., GCN #30185; Watson et al., GCN #30191; Zheng et al., GCN #30203; Kann et al., GCN #30211; Belkin et al., GCN #30214; Moskvitin et al., GCN #30229) of GRB 210610A, discovered by Swift (Page et al., GCN #30160) and also detected by Konus-Wind (Frederiks et al., GCN #30197) at redshift z = 3.54 (Zhu et al., GCN #30164; Dutta et al., GCN #30200). with CAFOS mounted on the 2.2m telescope at Calar Alto, Almeria, Spain. We obtained 6 x 600 s exposure in Sloan r'.
Stacking the images, the afterglow is well-detected, and we measure, against nearby comparison stars from the SDSS catalog (AB mags, not corrected for Galactic extinction):
r' = 22.57 +/- 0.04 mag at 1.27366 d.
This value is in good agreement with the observations of Belkin et al., GCN #30214; Moskvitin et al., GCN #30229, as well as the extrapolation of the decay found by Kann et al., GCN #30211.
GCN Circular #30233
P. Veres (UAH), B. Hristov (UAH) and C. Fletcher (USRA) and C. Meegan (UAH) report on behalf of the Fermi GBM Team:
"At 15:03:42.75 UT on 10th of June 2021, the Fermi Gamma-Ray Burst Monitor (GBM) triggered and located GRB 210610A (trigger 645030227 / 210610628).
The burst was also detected by the Swift/BAT (Page et al., GCN 30160). The GBM on-ground location is consistent with the Swift position.
The angle from the Fermi LAT boresight at the GBM trigger time is 67 degrees.
The GBM light curve consists of two pulses with a duration (T90) of about 8 s (50-300 keV). The time-averaged spectrum from T0-3.1 s to T0+4.6 s is adequately fit by a power law function with an exponential high-energy cutoff. The power law index is -1.11 +/- 0.15 and the cutoff energy, parameterized as Epeak, is 247 +/- 74 keV.
The event fluence (10-1000 keV) in this time interval is (1.78 +/- 0.23)E-6 erg/cm^2. The 1-sec peak photon flux measured starting from T0+0.7 s in the 10-1000 keV band is 3.6 +/- 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 #30246
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 210610A 94 s after the BAT trigger (Page et al., GCN Circ. 30160). A fading source consistent with the XRT position (Goad et al. GCN Circ. 30165) and the previously reported optical counterpart (Hosokawa et al., GCN. Circ. 30161; Xu et al., GCN. Circ. 30162; Kumar et al., GCN Circ. 30163; Lipunov et al., GCN. 30166; de Wet et al. GCN Circ. 30168; Horiuchi et al., GCN Circ. 30169; Youdong et al., GCN Circ. 30185; Watson et al. GCN Circ. 30191) is detected in the initial UVOT exposures. The lack of detection in the NUV filters for this bright counterpart is consistent with the redshift of 3.5 reported by Zhu et al. (GCN Circ. 30164) and Dutta et al. (GCN Circ. 30200).
The preliminary UVOT position is:
```
   RA  (J2000) =  13:37:07.59 = 204.28161 (deg.)
   Dec (J2000) = +14:27:55.0  =  14.46527 (deg.)
```
with an estimated uncertainty of 0.43 arc sec. (radius, 90% confidence).
Preliminary detections and 3-sigma upper limits using the UVOT photometric system (Breeveld et al. 2011, AIP Conf. Proc. 1358, 373) for the early exposures are:
```
Filter         T_start(s)   T_stop(s)      Exp(s)           Mag

white (fc)          94          244          147      17.09+/-0.03
white              587          892           68      17.92+/-0.07
v                  636          829           38      16.74+/-0.14
v                 4299         4498          196            >18.92
b                  562          754           38      17.69+/-0.12
b                16163        17070          885      20.57+/-0.23
b                23125        45112         1552            >21.16
u                  307          557          245            >20.02
uvw1               685         4908          216            >19.37
uvm2              4503         4703          196            >19.16
uvw2              4094         4294          196            >19.10
```
The magnitudes in the table are not corrected for the Galactic extinction due to the reddening of E(B-V) = 0.032 in the direction of the burst (Schlegel et al. 1998).
GCN Circular #30359
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 210610A (Page et al., GCN Circ. 30160) 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 0.91 mJy/beam at 850 microns and 6.2 mJy/beam at 450 microns; the mid-point of the run was 1.73 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 #30775
S. Belkin (IKI), A. Pozanenko (IKI), O. Burhonov (UBAI), R. Ya. Inasaridze (AbAO), N. Pankov (IKI), V. R. Ayvazian (AbAO), D. Datashvili (AbAO), G. V. Kapanadze (AbAO), Sh. Ehgamberdiev (UBAI) report on behalf of IKI-GRB-FuN:
We observed the field of GRB 210610A (Page et al., GCN 30160) with AZT-22 telescope of Maidanak Observatory and AS-32 telescope of Abastumani observatory (AbAO). The optical afterglow (Page et al., GCN 30160; Hosokawa et al., GCN 30161; Xu et a., GCN 30162; Kumar et al., GCN 30163; Lipunov et al., GCN 30166; de Wet et al., GCN 30168; Hosokawa et al., GCN 30169; Sun et al., GCN 30185; Watson et al., GCN 30191; Zheng et al., GCN 30203; Kann et al., GCN 30211; Belkin et al., GCN 30214; Moskvitin et al., GCN 30229; Kann et al., GCN 30232; Siegel et al., GCN 30246) is clearly detected in the stacked images. Preliminary photometry of the afterglow is following.
```
Date UT start t-T0 Filter Exp. OT UL(3sigma) Telescope
                         (mid, days) (s)

2021-06-10 17:57:56 0.14529 R 14*300 19.62 0.03 24.0 AZT-22
2021-06-10 20:24:59 0.23769 R 42*60  20.46 0.25 20.6 AS-32
2021-06-12 16:34:08 2.07494 R 7*300  23.09 0.20 23.5 AZT-22
2021-06-13 16:44:01 3.09049 R 12*300 23.77 0.21 24.4 AZT-22
2021-06-14 17:25:22 4.11920 R 12*300 24.08 0.28 24.4 AZT-22
```
Photometry is based on the SDSS-DR12 nearby stars (Lupton transformations).
```
SDSS-DR12_id RA DEC R(Lupton)
J133717.13+142854.9 204.32139900 +14.48192200 17.0295
J133703.62+142832.7 204.26512000 +14.47576300 17.7239
```
Using our data in the R filter, it was found that the light curve can be described by a broken power-law with power law indices of -0.82 and -1.39. The break time is 0.23+/-0.17 days. These values are consistent with the result reported by Kann et al. (GCN 30211).
The light curve can be found at http://grb.rssi.ru/GRB210610A/GRB210610A_LC.png

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