Gamma-ray Burst 210306A

(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:     Sat 06 Mar 21 03:54:08 UT
NOTICE_TYPE:     Swift-BAT GRB Position
TRIGGER_NUM:     1035994,   Seg_Num: 0
GRB_RA:          129.965d {+08h 39m 52s} (J2000),
                 130.393d {+08h 41m 34s} (current),
                 128.947d {+08h 35m 47s} (1950)
GRB_DEC:         +60.196d {+60d 11' 46"} (J2000),
                 +60.120d {+60d 07' 12"} (current),
                 +60.373d {+60d 22' 23"} (1950)
GRB_ERROR:       3.00 [arcmin radius, statistical only]
GRB_INTEN:       930 [cnts]    Image_Peak=184 [image_cnts]
TRIGGER_DUR:     0.064 [sec] 
TRIGGER_INDEX:   10420     E_range: 25-100 keV
BKG_INTEN:       15858 [cnts]
BKG_TIME:        14021.38 SOD {03:53:41.38} UT
BKG_DUR:         8 [sec]
GRB_DATE:        19279 TJD;    65 DOY;   21/03/06
GRB_TIME:        14037.06 SOD {03:53:57.06} UT
GRB_PHI:         -124.33 [deg]
GRB_THETA:        31.55 [deg]
SOLN_STATUS:     0x20000003
RATE_SIGNIF:     75.37 [sigma]
IMAGE_SIGNIF:    14.16 [sigma]
MERIT_PARAMS:     +1  +0  +0  -4  +2  +3  +0  +0 +47  +0 
SUN_POSTN:       346.93d {+23h 07m 43s}   -5.60d {-05d 35' 56"}
SUN_DIST:        118.88 [deg]   Sun_angle= -9.6 [hr] (East of Sun)
MOON_POSTN:      255.81d {+17h 03m 14s}  -22.87d {-22d 52' 17"}
MOON_DIST:       127.08 [deg]
MOON_ILLUM:      49 [%]
GAL_COORDS:      156.41, 36.67 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:      114.68, 40.14 [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 = 270.40,13.40 [deg].  
COMMENTS:           
COMMENTS:        NOTE: This BAT event is temporally(0.0<100sec) coincident with the FERMI_GBM event (trignum=636695642).

red DSS finding chart ps-file

GCN NOTICE

TITLE:           GCN/FERMI NOTICE
NOTICE_DATE:     Sat 06 Mar 21 03:54:22 UT
NOTICE_TYPE:     Fermi-GBM Flight Position
RECORD_NUM:      47
TRIGGER_NUM:     636695642
GRB_RA:          134.150d {+08h 56m 36s} (J2000),
                 134.610d {+08h 58m 26s} (current),
                 133.055d {+08h 52m 13s} (1950)
GRB_DEC:         +66.000d {+66d 00' 00"} (J2000),
                 +65.918d {+65d 55' 03"} (current),
                 +66.192d {+66d 11' 31"} (1950)
GRB_ERROR:       4.12 [deg radius, statistical plus systematic]
GRB_INTEN:       1185 [cnts/sec]
DATA_SIGNIF:     29.40 [sigma]
INTEG_TIME:      0.256 [sec]
GRB_DATE:        19279 TJD;    65 DOY;   21/03/06
GRB_TIME:        14037.11 SOD {03:53:57.11} UT
GRB_PHI:         255.00 [deg]
GRB_THETA:        20.00 [deg]
DATA_TIME_SCALE: 0.2560 [sec]
HARD_RATIO:      1.12
LOC_ALGORITHM:   3 (version number of)
MOST_LIKELY:      98%  GRB
2nd_MOST_LIKELY:   1%  Generic SGR
DETECTORS:       0,0,0, 0,0,0, 1,1,0, 0,0,0, 0,0,
SUN_POSTN:       346.93d {+23h 07m 43s}   -5.60d {-05d 35' 56"}
SUN_DIST:        115.61 [deg]   Sun_angle= -9.8 [hr] (East of Sun)
MOON_POSTN:      255.81d {+17h 03m 14s}  -22.87d {-22d 52' 19"}
MOON_DIST:       123.34 [deg]
MOON_ILLUM:      49 [%]
GAL_COORDS:      148.80, 37.20 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:      114.17, 46.23 [deg] ecliptic lon,lat of the burst (or transient)
LC_URL:          http://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2021/bn210306162/quicklook/glg_lc_medres34_bn210306162.gif
COMMENTS:        Fermi-GBM Flight-calculated Coordinates.  
COMMENTS:        This trigger occurred at longitude,latitude = 273.30,8.58 [deg].  
COMMENTS:        The LC_URL file will not be created until ~15 min after the trigger.  
COMMENTS:           
COMMENTS:        NOTE: This GBM event is temporally(0.0<100sec) coincident with the SWIFT_BAT event (trignum=1035994).

GCN NOTICE

TITLE:           GCN/FERMI NOTICE
NOTICE_DATE:     Sat 06 Mar 21 03:54:43 UT
NOTICE_TYPE:     Fermi-GBM Ground Position
RECORD_NUM:      59
TRIGGER_NUM:     636695642
GRB_RA:          139.380d {+09h 17m 31s} (J2000),
                 139.825d {+09h 19m 18s} (current),
                 138.320d {+09h 13m 17s} (1950)
GRB_DEC:         +66.280d {+66d 16' 48"} (J2000),
                 +66.190d {+66d 11' 25"} (current),
                 +66.490d {+66d 29' 23"} (1950)
GRB_ERROR:       2.06 [deg radius, statistical only]
DATA_SIGNIF:     35.90 [sigma]
DATA_INTERVAL:   0.256 [sec]
GRB_DATE:        19279 TJD;    65 DOY;   21/03/06
GRB_TIME:        14037.11 SOD {03:53:57.11} UT
GRB_PHI:         253.00 [deg]
GRB_THETA:        22.00 [deg]
E_RANGE:         44.032 - 279.965 [keV]
LOC_ALGORITHM:   4173 (Gnd S/W Version number)
SUN_POSTN:       346.93d {+23h 07m 43s}   -5.60d {-05d 35' 56"}
SUN_DIST:        116.55 [deg]   Sun_angle= -10.2 [hr] (East of Sun)
MOON_POSTN:      255.81d {+17h 03m 15s}  -22.87d {-22d 52' 21"}
MOON_DIST:       121.24 [deg]
MOON_ILLUM:      49 [%]
GAL_COORDS:      147.55, 39.09 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:      116.80, 47.37 [deg] ecliptic lon,lat of the burst (or transient)
LC_URL:          http://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2021/bn210306162/quicklook/glg_lc_medres34_bn210306162.gif
POS_MAP_URL:     http://gcn.gsfc.nasa.gov/notices_f/gbm_gnd_loc_map_636695642.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.  
COMMENTS:           
COMMENTS:        NOTE: This GBM event is temporally(0.0<100sec) coincident with the SWIFT_BAT event (trignum=1035994).

GCN NOTICE

TITLE:           GCN/FERMI NOTICE
NOTICE_DATE:     Sat 06 Mar 21 03:55:27 UT
NOTICE_TYPE:     Fermi-GBM Ground Position
RECORD_NUM:      2
TRIGGER_NUM:     636695642
GRB_RA:          139.650d {+09h 18m 36s} (J2000),
                 140.094d {+09h 20m 23s} (current),
                 138.592d {+09h 14m 22s} (1950)
GRB_DEC:         +66.300d {+66d 17' 60"} (J2000),
                 +66.210d {+66d 12' 35"} (current),
                 +66.511d {+66d 30' 38"} (1950)
GRB_ERROR:       1.61 [deg radius, statistical only]
DATA_SIGNIF:     41.20 [sigma]
DATA_INTERVAL:   6.144 [sec]
GRB_DATE:        19279 TJD;    65 DOY;   21/03/06
GRB_TIME:        14037.11 SOD {03:53:57.11} UT
GRB_PHI:         253.00 [deg]
GRB_THETA:        22.00 [deg]
E_RANGE:         44.032 - 279.965 [keV]
LOC_ALGORITHM:   41731 (Gnd S/W Version number)
SUN_POSTN:       346.93d {+23h 07m 43s}   -5.60d {-05d 35' 55"}
SUN_DIST:        116.58 [deg]   Sun_angle= -10.2 [hr] (East of Sun)
MOON_POSTN:      255.82d {+17h 03m 17s}  -22.87d {-22d 52' 26"}
MOON_DIST:       121.13 [deg]
MOON_ILLUM:      49 [%]
GAL_COORDS:      147.47, 39.18 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:      116.93, 47.44 [deg] ecliptic lon,lat of the burst (or transient)
LC_URL:          http://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2021/bn210306162/quicklook/glg_lc_medres34_bn210306162.gif
POS_MAP_URL:     http://gcn.gsfc.nasa.gov/notices_f/gbm_gnd_loc_map_636695642.fits
COMMENTS:        Fermi-GBM Ground-calculated Coordinates.  
COMMENTS:        In the LAT Field-of-view.  
COMMENTS:        This is likely a Long GRB.  
COMMENTS:        This Notice was ground-generated -- not flight-generated.  
COMMENTS:        The LC_URL file will not be created/available until ~15 min after the trigger.  
COMMENTS:        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(0.0<100sec) coincident with the SWIFT_BAT event (trignum=1035994).

GCN NOTICE

TITLE:           GCN/FERMI NOTICE
NOTICE_DATE:     Sat 06 Mar 21 03:55:40 UT
NOTICE_TYPE:     Fermi-GBM Ground Position
RECORD_NUM:      3
TRIGGER_NUM:     636695642
GRB_RA:          139.180d {+09h 16m 43s} (J2000),
                 139.610d {+09h 18m 26s} (current),
                 138.157d {+09h 12m 38s} (1950)
GRB_DEC:         +64.230d {+64d 13' 48"} (J2000),
                 +64.140d {+64d 08' 26"} (current),
                 +64.439d {+64d 26' 21"} (1950)
GRB_ERROR:       1.00 [deg radius, statistical only]
DATA_SIGNIF:     58.60 [sigma]
DATA_INTERVAL:   9.216 [sec]
GRB_DATE:        19279 TJD;    65 DOY;   21/03/06
GRB_TIME:        14037.11 SOD {03:53:57.11} UT
GRB_PHI:         248.00 [deg]
GRB_THETA:        21.00 [deg]
E_RANGE:         44.032 - 279.965 [keV]
LOC_ALGORITHM:   41731 (Gnd S/W Version number)
SUN_POSTN:       346.93d {+23h 07m 43s}   -5.60d {-05d 35' 55"}
SUN_DIST:        118.26 [deg]   Sun_angle= -10.2 [hr] (East of Sun)
MOON_POSTN:      255.82d {+17h 03m 17s}  -22.87d {-22d 52' 27"}
MOON_DIST:       121.82 [deg]
MOON_ILLUM:      49 [%]
GAL_COORDS:      150.05, 39.78 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:      117.99, 45.49 [deg] ecliptic lon,lat of the burst (or transient)
LC_URL:          http://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2021/bn210306162/quicklook/glg_lc_medres34_bn210306162.gif
POS_MAP_URL:     http://gcn.gsfc.nasa.gov/notices_f/gbm_gnd_loc_map_636695642.fits
COMMENTS:        Fermi-GBM Ground-calculated Coordinates.  
COMMENTS:        In the LAT Field-of-view.  
COMMENTS:        This is likely a Long GRB.  
COMMENTS:        This Notice was ground-generated -- not flight-generated.  
COMMENTS:        The LC_URL file will not be created/available until ~15 min after the trigger.  
COMMENTS:        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(0.0<100sec) coincident with the SWIFT_BAT event (trignum=1035994).

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Sat 06 Mar 21 03:55:47 UT
NOTICE_TYPE:     Swift-XRT Image
TRIGGER_NUM:     1035994,   Seg_Num: 0
GRB_RA:          129.9643d {+08h 39m 51.4s} (J2000),
                 130.3927d {+08h 41m 34.2s} (current),
                 128.9471d {+08h 35m 47.2s} (1950)
GRB_DEC:         +60.2032d {+60d 12' 11.5"} (J2000),
                 +60.1271d {+60d 07' 37.6"} (current),
                 +60.3801d {+60d 22' 48.4"} (1950)
GRB_ERROR:       5.4 [arcsec, radius, statistical plus systematic]
GRB_INTEN:       56 [cnts]
IMG_START_DATE:  19279 TJD;    65 DOY;   21/03/06
IMG_START_TIME:  14112.07 SOD {03:55:12.07} UT,   75.0 [sec] since BAT Trigger Time
CENTROID_X:      267.01,  raw= 267  [pixels]
CENTROID_Y:      298.29,  raw= 298  [pixels]
ROLL:            317.03 [deg]
GAIN:            1
MODE:            3, Long Image mode
WAVEFORM:        134
EXPO_TIME:       2.50 [sec]
GRB_POS_XRT_Y:   0.46
GRB_POS_XRT_Z:   -95.19
IMAGE_URL:       sw01035994000msxps_rw.img
SUN_POSTN:       346.93d {+23h 07m 43s}   -5.60d {-05d 35' 55"}
SUN_DIST:        118.87 [deg]   Sun_angle= -9.6 [hr] (East of Sun)
MOON_POSTN:      255.82d {+17h 03m 18s}  -22.87d {-22d 52' 28"}
MOON_DIST:       127.09 [deg]
MOON_ILLUM:      49 [%]
GAL_COORDS:      156.40, 36.67 [deg] galactic lon,lat of the burst
ECL_COORDS:      114.68, 40.14 [deg] ecliptic lon,lat of the burst
COMMENTS:        SWIFT-XRT Image.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Sat 06 Mar 21 03:55:51 UT
NOTICE_TYPE:     Swift-XRT Processed Image
TRIGGER_NUM:     1035994,   Seg_Num: 0
GRB_RA:          129.9643d {+08h 39m 51.4s} (J2000),
                 130.3927d {+08h 41m 34.2s} (current),
                 128.9471d {+08h 35m 47.2s} (1950)
GRB_DEC:         +60.2032d {+60d 12' 11.5"} (J2000),
                 +60.1271d {+60d 07' 37.6"} (current),
                 +60.3801d {+60d 22' 48.4"} (1950)
GRB_ERROR:       5.4 [arcsec, radius, statistical plus systematic]
GRB_INTEN:       56 [cnts]
IMG_START_DATE:  19279 TJD;    65 DOY;   21/03/06
IMG_START_TIME:  14112.07 SOD {03:55:12.07} UT,   75.0 [sec] since BAT Trigger Time
CENTROID_X:      267.01,  raw= 267  [pixels]
CENTROID_Y:      298.29,  raw= 298  [pixels]
ROLL:            317.03 [deg]
GAIN:            1
MODE:            3, Long Image mode
WAVEFORM:        134
EXPO_TIME:       2.50 [sec]
GRB_POS_XRT_Y:   0.46
GRB_POS_XRT_Z:   -95.19
IMAGE_URL:       sw01035994000msxps_rw.img
SUN_POSTN:       346.93d {+23h 07m 43s}   -5.60d {-05d 35' 55"}
SUN_DIST:        118.87 [deg]   Sun_angle= -9.6 [hr] (East of Sun)
MOON_POSTN:      255.82d {+17h 03m 18s}  -22.87d {-22d 52' 29"}
MOON_DIST:       127.09 [deg]
MOON_ILLUM:      49 [%]
GAL_COORDS:      156.40, 36.67 [deg] galactic lon,lat of the burst
ECL_COORDS:      114.68, 40.14 [deg] ecliptic lon,lat of the burst
COMMENTS:        SWIFT-XRT Processed Image.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Sat 06 Mar 21 03:55:37 UT
NOTICE_TYPE:     Swift-XRT Position
TRIGGER_NUM:     1035994,   Seg_Num: 0
GRB_RA:          129.9643d {+08h 39m 51.43s} (J2000),
                 130.3927d {+08h 41m 34.24s} (current),
                 128.9471d {+08h 35m 47.29s} (1950)
GRB_DEC:         +60.2032d {+60d 12' 11.5"} (J2000),
                 +60.1271d {+60d 07' 37.6"} (current),
                 +60.3801d {+60d 22' 48.4"} (1950)
GRB_ERROR:       5.5 [arcsec radius, statistical plus systematic, 90% containment]
GRB_INTEN:       1.15e-09 [erg/cm2/sec]
GRB_SIGNIF:      7.48 [sigma]
IMG_START_DATE:  19279 TJD;    65 DOY;   21/03/06
IMG_START_TIME:  14112.07 SOD {03:55:12.07} UT,   75.0 [sec] since BAT Trigger Time
TAM[0-3]:        327.66 237.16 261.81 243.68
AMPLIFIER:       2
WAVEFORM:        134
SUN_POSTN:       346.93d {+23h 07m 43s}   -5.60d {-05d 35' 55"}
SUN_DIST:        118.87 [deg]   Sun_angle= -9.6 [hr] (East of Sun)
MOON_POSTN:      255.82d {+17h 03m 17s}  -22.87d {-22d 52' 27"}
MOON_DIST:       127.09 [deg]
MOON_ILLUM:      49 [%]
GAL_COORDS:      156.40, 36.67 [deg] galactic lon,lat of the burst
ECL_COORDS:      114.68, 40.14 [deg] ecliptic lon,lat of the burst
COMMENTS:        SWIFT-XRT Coordinates.  
COMMENTS:        The XRT position is 0.41 arcmin from the BAT position.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Sat 06 Mar 21 03:58:04 UT
NOTICE_TYPE:     Swift-UVOT Source List
TRIGGER_NUM:     1035994,   Seg_Num: 0
POINT_RA:        129.999d {+08h 40m 00s} (J2000)
POINT_DEC:       +60.184d {+60d 11' 01"} (J2000)
POINT_ROLL:      317.028d
IMG_START_DATE:  19279 TJD;    65 DOY;   21/03/06
IMG_START_TIME:  14122.23 SOD {03:55:22.23} UT,   85.2 [sec] since BAT Trigger Time
FILTER:          10, White
BKG_MEAN:        1.627
N_STARS:         19
X_OFFSET:        651 [pixels]
Y_OFFSET:        452 [pixels]
X_MAX:           1610 [pixels]
Y_MAX:           1411 [pixels]
DET_THRESH:      11
PHOTO_THRESH:    5
SL_URL:          sw01035994000msufc0085.fits
SUN_POSTN:       346.93d {+23h 07m 43s}   -5.60d {-05d 35' 53"}
SUN_DIST:        118.90 [deg]   Sun_angle= -9.6 [hr] (East of Sun)
MOON_POSTN:      255.85d {+17h 03m 23s}  -22.88d {-22d 52' 43"}
MOON_DIST:       127.10 [deg]
MOON_ILLUM:      49 [%]
GAL_COORDS:      156.42, 36.69 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      114.71, 40.13 [deg] ecliptic lon,lat of the pointing direction
COMMENTS:        SWIFT-UVOT Source List.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Sat 06 Mar 21 03:58:23 UT
NOTICE_TYPE:     Swift-UVOT Processed Source List
TRIGGER_NUM:     1035994,   Seg_Num: 0
POINT_RA:        129.999d {+08h 40m 00s} (J2000)
POINT_DEC:       +60.184d {+60d 11' 01"} (J2000)
POINT_ROLL:      317.028d
IMG_START_DATE:  19279 TJD;    65 DOY;   21/03/06
IMG_START_TIME:  14122.23 SOD {03:55:22.23} UT,   85.2 [sec] since BAT Trigger Time
FILTER:          10, White
BKG_MEAN:        1.627
N_STARS:         19
X_OFFSET:        651 [pixels]
Y_OFFSET:        452 [pixels]
X_MAX:           1610 [pixels]
Y_MAX:           1411 [pixels]
DET_THRESH:      11
PHOTO_THRESH:    5
SL_URL:          sw01035994000msufc0085.fits
SUN_POSTN:       346.93d {+23h 07m 43s}   -5.60d {-05d 35' 52"}
SUN_DIST:        118.90 [deg]   Sun_angle= -9.6 [hr] (East of Sun)
MOON_POSTN:      255.85d {+17h 03m 24s}  -22.88d {-22d 52' 45"}
MOON_DIST:       127.10 [deg]
MOON_ILLUM:      49 [%]
GAL_COORDS:      156.42, 36.69 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      114.71, 40.13 [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:     Sat 06 Mar 21 04:05:57 UT
NOTICE_TYPE:     Swift-UVOT Image
TRIGGER_NUM:     1035994,   Seg_Num: 0
POINT_RA:        130.004d {+08h 40m 01s} (J2000)
POINT_DEC:       +60.183d {+60d 10' 60"} (J2000)
ROLL:            317.034d
IMG_START_DATE:  19279 TJD;    65 DOY;   21/03/06
IMG_START_TIME:  14334.39 SOD {03:58:54.39} UT,   297.3 [sec] since BAT Trigger Time
FILTER:          7, U
EXPOSURE_ID:     636695961
X_OFFSET:        971 [pixels]
Y_OFFSET:        772 [pixels]
WIDTH:           160 [pixels]
HEIGHT:          160 [pixels]
X_GRB_POS:       1131
Y_GRB_POS:       932
BINNING_INDEX:   1
IM_URL:          sw01035994000msuni0324.fits
SUN_POSTN:       346.93d {+23h 07m 44s}   -5.60d {-05d 35' 45"}
SUN_DIST:        118.90 [deg]   Sun_angle= -9.6 [hr] (East of Sun)
MOON_POSTN:      255.93d {+17h 03m 43s}  -22.89d {-22d 53' 35"}
MOON_DIST:       127.15 [deg]
MOON_ILLUM:      49 [%]
GAL_COORDS:      156.42, 36.69 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      114.71, 40.13 [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:     Sat 06 Mar 21 04:06:08 UT
NOTICE_TYPE:     Swift-UVOT Processed Image
TRIGGER_NUM:     1035994,   Seg_Num: 0
POINT_RA:        130.004d {+08h 40m 01s} (J2000)
POINT_DEC:       +60.183d {+60d 10' 60"} (J2000)
ROLL:            317.034d
IMG_START_DATE:  19279 TJD;    65 DOY;   21/03/06
IMG_START_TIME:  14334.39 SOD {03:58:54.39} UT,   297.3 [sec] since BAT Trigger Time
FILTER:          7, U
EXPOSURE_ID:     636695961
X_OFFSET:        971 [pixels]
Y_OFFSET:        772 [pixels]
WIDTH:           160 [pixels]
HEIGHT:          160 [pixels]
X_GRB_POS:       1131
Y_GRB_POS:       932
BINNING_INDEX:   1
IM_URL:          sw01035994000msuni0324.fits
SUN_POSTN:       346.93d {+23h 07m 44s}   -5.60d {-05d 35' 45"}
SUN_DIST:        118.90 [deg]   Sun_angle= -9.6 [hr] (East of Sun)
MOON_POSTN:      255.93d {+17h 03m 43s}  -22.89d {-22d 53' 36"}
MOON_DIST:       127.15 [deg]
MOON_ILLUM:      49 [%]
GAL_COORDS:      156.42, 36.69 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      114.71, 40.13 [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:     Sat 06 Mar 21 04:04:52 UT
NOTICE_TYPE:     Swift-UVOT Source List
TRIGGER_NUM:     1035994,   Seg_Num: 0
POINT_RA:        130.004d {+08h 40m 01s} (J2000)
POINT_DEC:       +60.183d {+60d 10' 60"} (J2000)
POINT_ROLL:      317.034d
IMG_START_DATE:  19279 TJD;    65 DOY;   21/03/06
IMG_START_TIME:  14334.39 SOD {03:58:54.39} UT,   297.3 [sec] since BAT Trigger Time
FILTER:          7, U
BKG_MEAN:        0.456
N_STARS:         23
X_OFFSET:        651 [pixels]
Y_OFFSET:        452 [pixels]
X_MAX:           1610 [pixels]
Y_MAX:           1411 [pixels]
DET_THRESH:      6
PHOTO_THRESH:    3
SL_URL:          sw01035994000msufc0297.fits
SUN_POSTN:       346.93d {+23h 07m 44s}   -5.60d {-05d 35' 46"}
SUN_DIST:        118.90 [deg]   Sun_angle= -9.6 [hr] (East of Sun)
MOON_POSTN:      255.92d {+17h 03m 40s}  -22.89d {-22d 53' 28"}
MOON_DIST:       127.14 [deg]
MOON_ILLUM:      49 [%]
GAL_COORDS:      156.42, 36.69 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      114.71, 40.13 [deg] ecliptic lon,lat of the pointing direction
COMMENTS:        SWIFT-UVOT Source List.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Sat 06 Mar 21 03:59:20 UT
NOTICE_TYPE:     Swift-UVOT Image
TRIGGER_NUM:     1035994,   Seg_Num: 0
POINT_RA:        129.999d {+08h 40m 00s} (J2000)
POINT_DEC:       +60.184d {+60d 11' 01"} (J2000)
ROLL:            317.028d
IMG_START_DATE:  19279 TJD;    65 DOY;   21/03/06
IMG_START_TIME:  14122.23 SOD {03:55:22.23} UT,   85.2 [sec] since BAT Trigger Time
FILTER:          10, White
EXPOSURE_ID:     636695748
X_OFFSET:        971 [pixels]
Y_OFFSET:        772 [pixels]
WIDTH:           160 [pixels]
HEIGHT:          160 [pixels]
X_GRB_POS:       1131
Y_GRB_POS:       932
BINNING_INDEX:   1
IM_URL:          sw01035994000msuni0112.fits
SUN_POSTN:       346.93d {+23h 07m 43s}   -5.60d {-05d 35' 51"}
SUN_DIST:        118.90 [deg]   Sun_angle= -9.6 [hr] (East of Sun)
MOON_POSTN:      255.86d {+17h 03m 27s}  -22.88d {-22d 52' 51"}
MOON_DIST:       127.11 [deg]
MOON_ILLUM:      49 [%]
GAL_COORDS:      156.42, 36.69 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      114.71, 40.13 [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:     Sat 06 Mar 21 03:59:26 UT
NOTICE_TYPE:     Swift-BAT GRB Lightcurve
TRIGGER_NUM:     1035994,   Seg_Num: 0
GRB_RA:          129.965d {+08h 39m 52s} (J2000),
                 130.393d {+08h 41m 34s} (current),
                 128.947d {+08h 35m 47s} (1950)
GRB_DEC:         +60.196d {+60d 11' 46"} (J2000),
                 +60.120d {+60d 07' 12"} (current),
                 +60.373d {+60d 22' 23"} (1950)
GRB_DATE:        19279 TJD;    65 DOY;   21/03/06
GRB_TIME:        14037.24 SOD {03:53:57.24} UT
TRIGGER_INDEX:   10420
GRB_PHI:         -124.33 [deg]
GRB_THETA:        31.55 [deg]
DELTA_TIME:      14.00 [sec]
TRIGGER_DUR:     0.064 [sec] 
SOLN_STATUS:     0x3
RATE_SIGNIF:     75.37 [sigma]
IMAGE_SIGNIF:    14.16 [sigma]
LC_URL:          sw01035994000msb.lc
SUN_POSTN:       346.93d {+23h 07m 43s}   -5.60d {-05d 35' 51"}
SUN_DIST:        118.88 [deg]   Sun_angle= -9.6 [hr] (East of Sun)
MOON_POSTN:      255.86d {+17h 03m 27s}  -22.88d {-22d 52' 52"}
MOON_DIST:       127.12 [deg]
MOON_ILLUM:      49 [%]
GAL_COORDS:      156.41, 36.67 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:      114.68, 40.14 [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 = 270.40,13.40 [deg].

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Sat 06 Mar 21 03:59:32 UT
NOTICE_TYPE:     Swift-UVOT Processed Image
TRIGGER_NUM:     1035994,   Seg_Num: 0
POINT_RA:        129.999d {+08h 40m 00s} (J2000)
POINT_DEC:       +60.184d {+60d 11' 01"} (J2000)
ROLL:            317.028d
IMG_START_DATE:  19279 TJD;    65 DOY;   21/03/06
IMG_START_TIME:  14122.23 SOD {03:55:22.23} UT,   85.2 [sec] since BAT Trigger Time
FILTER:          10, White
EXPOSURE_ID:     636695748
X_OFFSET:        971 [pixels]
Y_OFFSET:        772 [pixels]
WIDTH:           160 [pixels]
HEIGHT:          160 [pixels]
X_GRB_POS:       1131
Y_GRB_POS:       932
BINNING_INDEX:   1
IM_URL:          sw01035994000msuni0112.fits
SUN_POSTN:       346.93d {+23h 07m 43s}   -5.60d {-05d 35' 51"}
SUN_DIST:        118.90 [deg]   Sun_angle= -9.6 [hr] (East of Sun)
MOON_POSTN:      255.86d {+17h 03m 27s}  -22.88d {-22d 52' 53"}
MOON_DIST:       127.11 [deg]
MOON_ILLUM:      49 [%]
GAL_COORDS:      156.42, 36.69 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      114.71, 40.13 [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 Circular #29597
V. D'Elia (SSDC), E. Ambrosi (INAF-IASFPA), S. D. Barthelmy (GSFC), A. D'Ai (INAF-IASFPA), J. A. Kennea (PSU), N. J. Klingler (PSU), S. Laha (GSFC/UMBC/CRESST), F. E. Marshall (NASA/GSFC), D. M. Palmer (LANL) and A. Tohuvavohu (U Toronto) report on behalf of the Neil Gehrels Swift Observatory Team:
At 03:53:57 UT, the Swift Burst Alert Telescope (BAT) triggered and located GRB 210306A (trigger=1035994). Swift slewed immediately to the burst. The BAT on-board calculated location is RA, Dec 129.965, +60.196 which is
```
   RA(J2000)  =  08h 39m 52s
   Dec(J2000) = +60d 11' 46"
```
with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). The BAT light curve shows multiple peaks in a complex structure with a duration of about 15 sec. The peak count rate was ~20,000 counts/sec (15-350 keV), at ~7 sec after the trigger.
The XRT began observing the field at 03:55:12.07 UT, 74.9 seconds after the BAT trigger. Using promptly downlinked data we find an uncatalogued X-ray source with a position: RA, Dec 129.96204, 60.203271 which is equivalent to:
```
   RA(J2000)  = 08h 39m 50.89s
   Dec(J2000) = +60d 12' 11.7"
```
with an uncertainty of 4.7 arcseconds (radius, 90% containment). This location is 27 arcseconds from the BAT onboard position, within the BAT error circle. This position may be improved as more data are received; the latest position is available at http://www.swift.ac.uk/sper.
UVOT took a finding chart exposure of 150 seconds with the White filter starting 85 seconds after the BAT trigger. There is a candidate afterglow in the rapidly available 2.7'x2.7' sub-image at
```
  RA(J2000)  =	08:39:49.95 = 129.95813
  DEC(J2000) = +60:12:19.4  =  60.20538
```
with a 90%-confidence error radius of about 0.61 arc sec. This position is 13.6 arc sec. from the center of the XRT error circle. The estimated magnitude is 16.22 with a 1-sigma error of about 0.14. No correction has been made for the expected extinction corresponding to E(B-V) of 0.052.
Burst Advocate for this burst is V. D'Elia (delia AT ssdc.asi.it). Please contact the BA by email if you require additional information regarding Swift followup of this burst. In extremely urgent cases, after trying the Burst Advocate, you can contact the Swift PI by phone (see Swift TOO web site for information: http://www.swift.psu.edu/)

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Sat 06 Mar 21 04:05:02 UT
NOTICE_TYPE:     Swift-UVOT Processed Source List
TRIGGER_NUM:     1035994,   Seg_Num: 0
POINT_RA:        130.004d {+08h 40m 01s} (J2000)
POINT_DEC:       +60.183d {+60d 10' 60"} (J2000)
POINT_ROLL:      317.034d
IMG_START_DATE:  19279 TJD;    65 DOY;   21/03/06
IMG_START_TIME:  14334.39 SOD {03:58:54.39} UT,   297.3 [sec] since BAT Trigger Time
FILTER:          7, U
BKG_MEAN:        0.456
N_STARS:         23
X_OFFSET:        651 [pixels]
Y_OFFSET:        452 [pixels]
X_MAX:           1610 [pixels]
Y_MAX:           1411 [pixels]
DET_THRESH:      6
PHOTO_THRESH:    3
SL_URL:          sw01035994000msufc0297.fits
SUN_POSTN:       346.93d {+23h 07m 44s}   -5.60d {-05d 35' 46"}
SUN_DIST:        118.90 [deg]   Sun_angle= -9.6 [hr] (East of Sun)
MOON_POSTN:      255.92d {+17h 03m 41s}  -22.89d {-22d 53' 29"}
MOON_DIST:       127.14 [deg]
MOON_ILLUM:      49 [%]
GAL_COORDS:      156.42, 36.69 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      114.71, 40.13 [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:     Sat 06 Mar 21 04:00:58 UT
NOTICE_TYPE:     Swift-UVOT Position
TRIGGER_NUM:     1035994,   Seg_Num: 0
GRB_RA:          129.9581d {+08h 39m 49.94s} (J2000),
                 130.3865d {+08h 41m 32.76s} (current),
                 128.9408d {+08h 35m 45.78s} (1950)
GRB_DEC:         +60.2053d {+60d 12' 19.0"} (J2000),
                 +60.1292d {+60d 07' 45.2"} (current),
                 +60.3822d {+60d 22' 55.9"} (1950)
GRB_ERROR:       0.6 [arcsec radius, statistical only]
GRB_MAG:         16.21 +/- 0.14 [mag]
FILTER:          10, White
IMG_START_DATE:  19279 TJD;    65 DOY;   21/03/06
IMG_START_TIME:  14119.00 SOD {03:55:19.00} UT,   81.9 [sec] since BAT Trigger Time
SUN_POSTN:       346.93d {+23h 07m 44s}   -5.60d {-05d 35' 50"}
SUN_DIST:        118.87 [deg]   Sun_angle= -9.6 [hr] (East of Sun)
MOON_POSTN:      255.88d {+17h 03m 31s}  -22.88d {-22d 53' 02"}
MOON_DIST:       127.13 [deg]
MOON_ILLUM:      49 [%]
GAL_COORDS:      156.40, 36.67 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:      114.67, 40.14 [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 13.3 arcsec from the XRT position.  
COMMENTS:        Result based on Genie data.  
COMMENTS:        Notice generated automatically.

GCN Circular #29598
Alan M. Watson (UNAM), Nat Butler (ASU), Rosa L. Becerra (UNAM), Simone Dichiara (GSFC/UMD), Alexander Kutyrev (GSFC/UMD), William H. Lee (UNAM), Oc�lotl Lopez (UNAM), Diego Gonzalez (UNAM), Margarita Pereyra (UNAM), Srihari Ravi (ASU), and Eleonora Troja (GSFC/UMD) report:
We observed the field of the Swift/BAT GRB 210306A (D'Elia et al., GCN Circ. 29597) with the DDOTI wide-field imager at the Observatorio Astron�mico Nacional on Sierra San Pedro Martir (http://ddoti.astroscu.unam.mx) starting at 2021-03-06 04:07 UTC (from 14 minutes after the trigger).
We observed a region covering aproximately 7 degrees in RA and 10 degrees in declination (about 70 square degrees) centered on the XRT position in the w filter. We calibrated our images against the APASS catalog.
Compared to the USNO-B1, Pan-STARRS DR1, and APASS DR10 catalogs, we detect a bright source at 08:39:50.04 +60:12:18.9 (J2000) fading from about w = 17. This confirms the afterglow reported in UVOT observations by D'Elia et al. (GCN Circ. 29597)
We thank the staff of the Observatorio Astronomico Nacional in San Pedro Martir.
GCN Circular #29599
```
TITLE:   GCN CIRCULAR
NUMBER:  29599
SUBJECT: GRB 210306A: iTelescope optical afterglow observations
DATE:    21/03/06 05:53:48 GMT
FROM:    Filipp Dmitrievich Romanov at Amateur astronomer  
```
I observed the field of GRB 210306A (D'Elia et al., GCN Circ. 29597) with remote telescope T24 (0.61-m f/6.5 reflector + CCD) of iTelescope.Net in Sierra Remote Observatory (Auberry, California, USA) on 2021-03-06. Two images (exposures 300 seconds, BINx1) were obtained with luminance filter since 04:42:56 UT (2939 seconds after the trigger) and since 04:48:59 UT (3302 seconds after the trigger). I clearly detected the optical afterglow in UVOT position. The following magnitudes were measured from comparison to r magnitudes of nearby stars from Pan-STARRS DR1 catalogue (Chambers et al., 2016): 17.80 (+/- 0.057) and 17.97 (+/- 0.038).
Magnitudes were not corrected for Galactic extinction.
Stacked image available here: https://www.flickr.com/photos/filipp-romanov/51007330278 which is reproduced below:
GCN Circular #29600
R. Strausbaugh (U. of the Virgin Islands), A. Cucchiara (U. of the Virgin Islands/College of Marin) report on behalf of a larger collaboration:
We observed Swift GRB 210306A (D'Elia et al., GCN 29597) with the LCO 1-m Sinistro instrument at the McDonald Observatory, Texas, USA site, on March 6, from 06:49 to 07:06 UT (corresponding to 2.93 to 3.22 hours from the GRB trigger time) with the Bessel R and I filters.
We performed a series of 4x120s exposures in R and I. We clearly detect an optical source in R and I band in stacked images at a location consistent the initial UVOT detection (D'Elia et al., GCN 29597), in agreement with other optical afterglow detections (Watson et al., GCN 29598; Romanov, GCN 29599). Using the USNO-B.1 catalog as reference, we calculate the following magnitudes:
R = 19.00 +/- 0.02
I = 17.70 +/- 0.03
These magnitudes are not corrected for galactic extinction. The fainter R magnitude could indicate a moderately high redshift.
R.S. is funded by NSF AST grant #1831682
GCN Circular #29602
M. Ohno (Hiroshima Univ. & Eotvos Univ.), M. Axelsson (KTH & StockholmUniv.), S. Cutini (INFN Perugia), F. Longo (University & INFN Trieste), and M. Crnogorcevic (Univ. of Maryland & NASA/GSFC) report on behalf of the Fermi-LAT Collaboration:
On March 06, 2021, Fermi-LAT detected high-energy emission from GRB 210306A, which was also detected by Fermi-GBM (trigger 636695642), Swift (D'Elia et al.; GCN 29597), and confirmed the afterglow by ground telescopes (M. Watson et al.; GCN 29598, Dmitrievich Romanov; GCN 29599, Strausbaugh and. Cucchiara; GCN 29600).
The best LAT on-ground location is found to be RA, Dec 130.3, 60.2 (degrees, J2000) with an error radius of 0.38 deg (90% containment, statistical error only). This was 10 deg from the LAT boresight at the time of the GBM trigger:
T0 = 03:53:57.11 UT.
The data from the Fermi-LAT show a significant increase in the event rate after the GBM trigger that is spatially correlated with the GBM emission (5.8 degrees from the GBM location) with high significance. The photon flux above 100 MeV in the time interval 0-3000 s after the GBM trigger is (6.6+/-3.5 e-7) ph/cm2/s.
The estimated photon index above 100 MeV is -2.0(+/-0.4).
The highest-energy photon is a 1.9 GeV event which is observed 790 seconds after the GBM trigger.
The Fermi-LAT point of contact for this burst is Milena Crnogorcevic (mcrnogor@astro.umd.edu).
The Fermi-LAT is a pair conversion telescope designed to cover the energy band from 20 MeV to greater than 300 GeV. It is the product of an international collaboration between NASA and DOE in the U.S. and many scientific institutions across France, Italy, Japan and Sweden.
GCN Circular #29603
Veli-Pekka Hentunen and Markku Nissinen (Taurus Hill Observatory, Varkaus,
Finland) report:
We have detected GRB 210306A optical afterglow using iTelescope T24 (0.61-m f/6.5 + CCD) telescope in Sierra Remote Observatory (Auberry, California, USA). The observations were started at 2021-03-06 05:02:41 (UT).
We used Luminance filter and 300 sec exposures.
The afterglow was detected at the position RA 08 39 50.11 DEC +60 12 18.8.
The following magnitudes were measured from comparison of a nearby star (r = 16.974) from Pan-STARRS DR1 catalogue (Chambers et al., 2016):
Tmid (h:min:sec)+T0 Mag Mag_err
01:11:12 18.08 0.08
01:16:55 17.97 0.06
01:22:47 18.13 0.07
02:06:55 18.41 0.10
02:14:53 18.44 0.09
02:18:53 18.52 0.10
02:24:37 18.63 0.10
03:03:34 18.82 0.11
03:09:13 18.85 0.11
03:20:45 18.87 0.12
03:26:56 18.91 0.12
03:32:55 18.84 0.13
04:33:44 19.33 0.19
04:39:39 19.22 0.18
05:03:57 19.33 0.21
05:27:40 19.61 0.38
Magnitudes were not corrected for galactic extinction.
URL link for the L filter 300s image:
https://www.kassiopeia.net/2021/03/06/grb-210306a-havainto/
GCN Circular #29604
B. Stecklum, S. Klose, A. Nicuesa Guelbenzu, S. Melnikov, and S. Hoegner (all Tautenburg) report:
We observed the field of GRB 210306A (D'Elia et al., GCN 29597) with the Tautenburg 1.34m Schmidt telescope equipped with the TAUKAM 6kx6k CCD camera.
Between 4:29 UT and 4:48 UT the afterglow was fading from R=17.33 +/- 0.02 to 17.53 +/- 0.09 mag (Vega), calibrated against the USNO B1 star at R.A., Decl. (J2000) = 129.924281, +60.163889 (DS9, R2mag = 15.23) close to the afterglow position.
GCN Circular #29605
P. Veres (UAH) reports on behalf of the Fermi GBM Team:
"At 03:53:57.11 UT on 6 March 2021, the Fermi Gamma-Ray Burst Monitor (GBM) triggered and located GRB 210306A (trigger 636695642 / 210306162). which was also detected by the Swift/BAT (D'Elia et al., GCN 29597) and Fermi/LAT (Ohno et al., GCN 29602). The GBM on-ground location is consistent with the Swift position.

The GBM light curve shows multiple overlapping pulses with a duration (T90) of about 9.5 s (50-300 keV). The time-averaged spectrum from T0-0.6 s to T0+11.6 s is best fit by a Band function with Epeak = 59.4 +/- 2.2 keV, alpha = -0.60 +/- 0.08, and beta = -2.53 +/- 0.06.
The event fluence (10-1000 keV) in this time interval is (9.82 +/- 0.20)E-6 erg/cm^2. The 1-sec peak photon flux measured starting from T0+7.6 s in the 10-1000 keV band is 26.6 +/- 0.4 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 #29606
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-Tavrida robotic telescope (Global MASTER-Net: http://observ.pereplet.ru, Lipunov et al., 2010, Advances in Astronomy, vol. 2010, 30L) located in Russia (Lomonosov MSU, SAI Crimea astronomical station) was pointed to the Swift GRB 210306A ( V. D'Elia et al., GCN 29597) errorbox 57322 sec after notice time and 57335 sec after trigger time at 2021-03-06 19:49:32 UT, with upper limit up to 20.0 mag. The observations began at zenith distance = 17 deg. The sun altitude is -42.8 deg.
The galactic latitude b = 37 deg., longitude l = 157 deg.
Real time updated cover map and OT discovered available here: https://master.sai.msu.ru/site/master2/observ.php?id=1562037
We obtain a following upper limits.
```
Tmid-T0  |          Site       |Filt.| Expt. | Limit| Comment
_________|_____________________|_____|_______|______|________

   30222 |             MASTER- |   C |    60 | 18.5 |        
   31162 |             MASTER- |   C |    60 | 18.4 |        
   32113 |             MASTER- |   C |    60 | 18.9 |        
   57426 |      MASTER-Tavrida |   C |   180 | 20.0 |        
```
Filter C is a clear (unfiltred) band.
The observation and reduction will continue. The message may be cited.
GCN Circular #29607
Z.P. Zhu (NAOC, HUST), S.Y. Fu, X. Liu, D. Xu (NAOC), X. Gao (Urumqi No.1 Senior High School), J.Z. Liu (XAO) report:
We observed the field of GRB 210306A (D'Elia et al., GCN 29597) using the NEXT-0.6m optical telescope located at Nanshan, Xinjiang, China. Observations started at 16:11:33 UT on 2021-03-06, i.e., 12.29 hr after the BAT trigger. We obtained 15x200 s frames in the Sloan r-filter.
The previously reported optical afterglow (e.g., D'Elia et al., GCN 29597; Watson et al., GCN 29598; Romanov F., GCN 29599; Strausbaugh et al., GCN 29600; Hentunen et al., GCN 29603; Stecklum et al., GCN 29604) is clearly detected in our stacked image, with r = 21.0 +/- 0.1 mag at 12.76 hr post-burst, calibrated with nearby PS1 stars.
GCN Circular #29608
R. Hosokawa, R. Adachi, K. L. Murata, M. Niwano, F. Ogawa, N. Nakamura, N. Ito, S. Ogata, H. Takamatsu, H. Hara, Y. Yatsu, and N. Kawai (TokyoTech) report on behalf of the MITSuME collaboration:
We observed the field of GRB 210306A (D'Elia et al. GCN #29597, Watson et al. GCN 29598, Romanov GCN #29599, Strausbaugh et al. GCN #29600, Ohno et al. GCN #29602, Hentunen et al. GCN #29603, Stecklum et al. GCN #29604, Veres et al. GCN #29605, Lipunov et al. GCN #29606, Zhu et al. GCN #29607) 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 60 sec exposures started at 2021-03-06 09:12:03 UT (5.3 hours after Swift BAT trigger). We stacked the images with good conditions. We marginally detected the point source at the position consistent with the afterglow detected previously(D'Elia et al. GCN #29597, Watson et al. GCN 29598, Romanov GCN #29599, Strausbaugh et al. GCN #29600, Hentunen et al. GCN #29603, Stecklum et al. GCN #29604, Zhu et al. GCN #29607). We measured the magnitudes as follows.
```
T0+[hour] MID-UT T-EXP[sec] measured magnitudes
------------------------------------------------------------------------------------------------
5.3 11:38:10 8160 g'=20.0+/-0.4, Rc=20.2+/-0.4, Ic=19.0+/-0.3
------------------------------------------------------------------------------------------------
T0+ : Elapsed time after the burst
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 #29616
S. Belkin (IKI), A. Pozanenko (IKI), E. Klunko (ISTP), N. Pankov (HSE) report on behalf of GRB IKI FuN:
We observed the field of GRB 210306A (D'Elia et al., GCN 29597; Ohno et al., GCN 29602) with AZT-33IK telescope of Sayan observatory (Mondy) starting on 2021-03-06 (UT) 14:50:30. The optical afterglow (D'Elia et al., GCN 29597; Watson et al., GCN 29598; Romanov, GCN 29599; Strausbaugh et al., GCN 29600; Hentunen et al., GCN 29603; Stecklum et al., GCN 29604; Lipunov et al. GCN 29606, Zhu et al. GCN 29607; Hosokawa et al., GCN 29608) is clearly detected in a combined image. Preliminary photometry of the object in a combined image is following
```
Date       UT start   t-T0       Filter Exp.    OT    Err.  UL(3sigma)
                       (mid, days)        (s)

2021-03-06 14:50:30   0.47677    R      30*120  20.48 0.05  22.0
```
The photometry is based on the nearby USNO-B1.0 stars
```
USNO-B1.0_id R2
1501-0181731 15.23
1502-0183049 17.69
1501-0181697 17.1
```
GCN Circular #29617
S. Laha (GSFC/UMBC), S. D. Barthelmy (GSFC), J. R. Cummings (CPI), V. D'Elia (SSDC), H. A. Krimm (NSF), A. Y. Lien (GSFC/UMBC), C. B. Markwardt (GSFC), D. M. Palmer (LANL), T. Sakamoto (AGU), M. Stamatikos (OSU), T. N. Ukwatta (LANL) (i.e. the Swift-BAT team):
Using the data set from T-240 to T+600 sec from the recent telemetry downlink, we report further analysis of BAT GRB 210306A (trigger #1035994) (D'Elia, et al., GCN Circ. 29597). The BAT ground-calculated position is RA, Dec = 129.964, 60.203 deg which is
```
    RA(J2000)  =  08h 39m 51.3s
    Dec(J2000) = +60d 12' 11.5"
```
with an uncertainty of 1.0 arcmin, (radius, sys+stat, 90% containment). The partial coding was 53%.
The BAT light curve showed a complex structure with a duration of about ~10 sec. T90 (15-350 keV) is 9.12 +- 0.31 sec (estimated error including systematics).
The time-averaged spectrum from T-0.18 to T+13.16 sec is best fit by a power law with an exponential cutoff. This fit gives a photon index 1.16 +- 0.19, and Epeak of 58.4 +- 3.9 keV (chi squared 59.11 for 56 d.o.f.). For this model the total fluence in the 15-150 keV band is 5.7 +- 0.1 x 10^-6 erg/cm2 and the 1-sec peak flux measured from T+7.50 sec in the 15-150 keV band is 20.9 +- 0.7 ph/cm2/sec. A fit to a simple power law gives a photon index of 1.91 +- 0.04 (chi squared 111.38 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/1035994/BA/
GCN Circular #29618
Dimple (ARIES), A. Ghosh (ARIES), G. Singh (ARIES), R. Gupta (ARIES), A. Kumar (ARIES), K. Misra (ARIES), S.B. Pandey (ARIES) report:
We observed the afterglow of the GRB 210306A (D'Elia et al. GCN #29597, Watson et al. GCN 29598, Romanov GCN #29599, Strausbaugh et al. GCN #29600, Ohno et al. GCN #29602, Hentunen et al. GCN #29603, Stecklum et al. GCN #29604, Veres et al. GCN #29605, Lipunov et al. GCN #29606, Zhu et al. GCN #29607) with 1.3m Devasthal Fast Optical Telescope (DFOT) at Devasthal observatory of Aryabhatta Research Institute of observational sciencES (ARIES), India. We took observations in B,V,R,I bands. We detect the optical afterglow with a magnitude of 20.24 +- 0.13 in R-band at 9.8 hrs after the burst. Further observations are ongoing with 1.3m DFOT.
The magnitude is not corrected for the Galactic extinction in the direction of the burst. The photometric calibration is performed using the standard stars from the USNO-B1.0 catalog.
GCN Circular #29620
S. Belkin (IKI), A. Pozanenko (IKI), E. Klunko (ISTP), N. Pankov (HSE) report on behalf of GRB IKI FuN:
We continue observations (Belkin et al., GCN 29616) the field of GRB 210306A (D'Elia et al., GCN 29597; Ohno et al., GCN 29602) with AZT-33IK telescope of Sayan observatory (Mondy). The optical afterglow (D'Elia et al., GCN 29597; Watson et al., GCN 29598; Romanov, GCN 29599; Strausbaugh et al., GCN 29600; Hentunen et al., GCN 29603; Stecklum et al., GCN 29604; Lipunov et al. GCN 29606, Zhu et al. GCN 29607; Hosokawa et al., GCN 29608; Dimple et al., GCN 29618) is still detected in a combined image. Preliminary photometry of the afterglow in the combined image is following
```
Date       UT start   t-T0       Filter Exp.    OT    Err.  UL(3sigma)
                       (mid, days)        (s)

2021-03-07 13:43:24   1.41281    R      5*120  22.09 0.25  22.1
```
The photometry is based on the nearby USNO-B1.0 stars
```
USNO-B1.0_id R2
1501-0181731 15.23
1502-0183049 17.69
1501-0181697 17.1
```
GCN Circular #29622
V. D'Elia (SSDC & INAF-OAR), A. D'Ai (INAF-IASFPA), D.N. Burrows (PSU), J. D. Gropp (PSU), J.A. Kennea (PSU), J.P. Osborne (U. Leicester), K.L. Page (U. Leicester), A.P. Beardmore (U. Leicester) and A. Melandri (INAF-OAB) report on behalf of the Swift-XRT team:
We have analysed 10 ks of XRT data for GRB 210306A (D'Elia et al. GCN Circ. 29597), from 65 s to 182.6 ks after the BAT trigger. The data comprise 576 s in Windowed Timing (WT) mode (the first 7 s were taken while Swift was slewing) with the remainder in Photon Counting (PC) mode. Using 3375 s of PC mode data and 9 UVOT images, we find an enhanced XRT position (using the XRT-UVOT alignment and matching UVOT field sources to the USNO-B1 catalogue): RA, Dec = 129.95774, +60.20523 which is equivalent to:
RA (J2000): 08h 39m 49.86s Dec(J2000): +60d 12' 18.8"
with an uncertainty of 1.4 arcsec (radius, 90% confidence).
The light curve can be modelled with an initial power-law decay with an index of alpha=0.435 (+/-0.027), followed by a break at T+1548 s to an alpha of 1.58 (+/-0.06).
A spectrum formed from the WT mode data can be fitted with an absorbed power-law with a photon spectral index of 1.89 (+0.05, -0.04). The best-fitting absorption column is 1.53 (+0.15, -0.14) x 10^21 cm^-2, in excess of the Galactic value of 4.2 x 10^20 cm^-2 (Willingale et al. 2013). The PC mode spectrum has a photon index of 1.98 (+0.14, -0.13) and a best-fitting absorption column of 1.7 (+/-0.4) x 10^21 cm^-2. The counts to observed (unabsorbed) 0.3-10 keV flux conversion factor deduced from this spectrum is 3.5 x 10^-11 (4.7 x 10^-11) erg cm^-2 count^-1.
A summary of the PC-mode spectrum is thus:
```
Total column:	     1.7 (+/-0.4) x 10^21 cm^-2
Galactic foreground: 4.2 x 10^20 cm^-2
Excess significance: 5.2 sigma
Photon index:	     1.98 (+0.14, -0.13)
```
The results of the XRT-team automatic analysis are available at http://www.swift.ac.uk/xrt_products/01035994.
This circular is an official product of the Swift-XRT team.
GCN Circular #29635
S. Belkin (IKI), A. Pozanenko (IKI), E. Klunko (ISTP), N. Pankov (HSE) report on behalf of GRB IKI FuN:
We continue observations (Belkin et al., GCNs 29616,29620) the field of GRB 210306A (D'Elia et al., GCN 29597; Ohno et al., GCN 29602) with AZT-33IK telescope of Sayan observatory (Mondy). The optical afterglow (D'Elia et al., GCN 29597; Watson et al., GCN 29598; Romanov, GCN 29599; Strausbaugh et al., GCN 29600; Hentunen et al., GCN 29603; Stecklum et al., GCN 29604; Lipunov et al. GCN 29606, Zhu et al. GCN 29607; Hosokawa et al., GCN 29608; Dimple et al., GCN 29618) is detected in a combined image. Preliminary photometry of the afterglow in the combined image is following
```
Date       UT start   t-T0       Filter Exp.    OT    Err.  UL(3sigma)
                       (mid, days)        (s)

2021-03-08 13:47:43   2.43317    R      30*120  22.68 0.18  22.9
```
The photometry is based on the nearby USNO-B1.0 stars
```
USNO-B1.0_id R2
1501-0181731 15.23
1502-0183049 17.69
1501-0181697 17.11
```
GCN Circular #29636
GRB 210306A: Swift/UVOT Detection
K. K. Simpson (PSU) and V. D'Elia (SSDC) report on behalf of the Swift/UVOT team:
The Swift/UVOT began settled observations of the field of GRB 210306A 85 s after the BAT trigger (D'Elia et al., GCN Circ. 29597). A source consistent with the XRT position (D'Elia et al. GCN Circ. 29597) is detected in the initial UVOT exposures.
The preliminary UVOT position is:
```
    RA  (J2000) =  08:39:49.98 = 129.95824 (deg.)
    Dec (J2000) = +60:12:19.2  =  60.20533 (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               85          235          147         16.23 +/- 0.03
v                  628          648           20         17.42 +/- 0.24
b                  553          573           20         17.32 +/- 0.13
u                  297          547          246         16.86 +/- 0.04
```
The magnitudes in the table are not corrected for the Galactic extinction due to the reddening of E(B-V) = 0.052 in the direction of the burst (Schlegel et al. 1998).
GCN Circular #29638
P.S. Smith, Z. Chen, P. Milne, D. Sand, N. Smith, D. Stark, and G.G. Williams (Steward Observatory, University of Arizona)
Observations of the optical counterpart of GRB 210306A using the B&C Spectrograph and the University of Arizona, Steward Observatory 2.3m Bok Telescope located on Kitt Peak, Arizona began at 07:07:50 on March 6, 2021 UTC and ended at 08:23:13 UT. Three, 1500 s exposures were obtained centered at 3.384, 3.859, and 4.279 hours after the Swift/BAT detection of the burst (D�Elia et al.; GCN Circ. 29597). Comparison with a spectrophotometric standard star observed immediately after the optical afterglow observations suggest that the counterpart was at an approximate V magnitude of 19.18, 19.33, and 19.46 for the three exposures, respectively. All spectra show a featureless blue continuum from 350-760nm. A fit to the least noisy portion (450-750nm) of the scaled median spectrum from the three observations yields a slope of about -1.25 in log(F_lambda) vs. log(wavelength). No corrections for Galactic extinction and reddening have been made.
GCN Circular #29642
A. Ridnaia, S. Golenetskii, D. Frederiks, M. Ulanov, D. Svinkin, A. Tsvetkova, A. Lysenko, and T. Cline on behalf of the Konus-Wind team, report:
The long-duration GRB 210306A (Swift-BAT detection: D'Elia et al., GCN 29597, Laha et al., GCN 29617; Fermi-LAT detection: Ohno et al., GCN 29602; Fermi-GBM observation: Veres, GCN 29605) triggered Konus-Wind at T0=14040.731 s UT (03:54:00.731).
The burst light curve shows a multi-peaked emission complex, which starts at ~T0-0.2 s and has a total duration of ~11 s. The emission is seen up to ~1 MeV.
The Konus-Wind light curve of this GRB is available at http://www.ioffe.ru/LEA/GRBs/GRB210306_T14040/
As observed by Konus-Wind, the burst had a fluence of 7.01(-0.45,+0.48)x10^-6 erg/cm2, and a 64-ms peak flux, measured from T0+7.648 s, of 3.99(-0.60,+0.67)x10^-6 erg/cm2/s (both in the 20 keV - 10 MeV energy range).
The time-averaged spectrum of the burst (measured from T0 to T0+16.640 s) is best fit in the 20 keV - 1 MeV range by a power law with exponential cutoff model: dN/dE ~ (E^alpha)*exp(-E*(2+alpha)/Ep) with alpha = -1.21(-0.20,+0.22) and Ep = 77(-7,+7) keV (chi2 = 48/49 dof). Fitting by a GRB (Band) model yields the same alpha and Ep, and an upper limit on the high energy photon index: beta < -2.6 (chi2 = 46/48 dof).
The spectrum near the peak count rate (measured from T0+0.256 to T0+8.448 s) is best fit in the 20 keV - 1 MeV range by the GRB (Band) model with the following parameters: the low-energy photon index alpha = -1.17(-0.23,+0.30), the high energy photon index beta = -2.97(-1.31,+0.34), the peak energy Ep = 70(-7,+7) keV (chi2 = 56/49 dof).
All the quoted errors are at the 90% confidence level. All the quoted values are preliminary.
GCN Circular #29644
S. Klose, B. Stecklum, A. Nicuesa Guelbenzu, S. Melnikov, and S. Hoegner (all Tautenburg) report:
We continued observations of the field of GRB 210306A (D'Elia et al., GCN 29597) with the Tautenburg 1.34m Schmidt telescope. For the optical afterglow (Simpson & D'Elia, GCN 29636; Belkin et al., GCN 29635, and references therein) we measure:
March 07, 00:21 UT : Rc = 20.47 +/- 0.13 (Vega mag)
March 07, 02:12 UT : Rc = 20.53 +/- 0.14
March 07, 19:34 UT : Rc > 21.2.
Data calibration followed Stecklum et al. (GCN 29604).
GCN Circular #29645
A Rossi (INAF-OAS) report on behalf of the CIBO collaboration:
We observed the field of GRB 210306A (D'Elia et al., GCN 29597) simultaneously in the r' and z' bands with the LBC imager mounted on LBT (Mt Graham, AZ, USA). We obtained 20min of imaging on 2021-03-11, 5.06 days after the burst trigger. Observations were performed under good weather conditions with an average seeing of ~1.2".
We clearly detect the afterglow and we preliminary measure
r=24.2+-0.2 (AB system),
calibrated against SDSS field stars. This is still in agreement with the late decay index alpha~1.1 (after an initial plateau ending at ~2hours after the burst trigger) obtained modelling the photometry available (Strausbaugh et al., GCN29600; Zhu et al., GCN 29607; Hentunen & Nissinen GCN 29603; Hosokawa et al., GCN29608; Dimple et al., GCN 29618; Belkin et al., GCN 29616, GCN 29620, 29635; Klose et al., GCN 29644).
We acknowledge the excellent support from the LBTO and LBT-INAF staff, particularly J. Power, J. Williams F. Cusano, and D. Paris, in obtaining these observations.
GCN Circular #29654
H. Kumar (IITB), A. Dutta (IIA), R. Gupta (ARIES), V. Bhalerao (IITB), G. C. Anupama (IIA), S. Barway (IIA), D.K. Sahu (IIA), A. Kumar (ARIES), Dimple (ARIES), A. Ghosh (ARIES), S. B. Pandey (ARIES), and K. Misra (ARIES) report:
We observed GRB 210306A detected by Swift Burst Alert Telescope (V. D'Elia et. al., GCN 29597) and optical afterglow confirmed by Alan M. Watson et. al., (GCN 29598) with the 2.0m Himalayan Chandra Telescope (HCT) of the Indian Astronomical Observatory. We obtained 6 exposures of 300 sec each in the Bessell R filter. We did not detect the afterglow in our stacked image. The photometric upper limit is:
--------------------------------------------------------
JD (mid) | T_mid-T0(hrs) | Filter | Lim_mag (5-sigma) |
--------------------------------------------------------
2459282.110905 | 58.76 | Bessell R | > 23.22 |
--------------------------------------------------------
The magnitudes are in the AB system of magnitude calibrated against PanSTARRS (Flewelling et al., 2018) using Lupton's transformation equations available at http://classic.sdss.org/dr4/algorithms/sdssUBVRITransform.html#Lupton2005. The magnitudes are not corrected for galactic extinction.
These observations were carried out under the ToO program HCT-2021-C1-P2. We thank the HCT staff for their support during the observations. The Indian Astronomical Observatory is operated by the Indian Institute of Astrophysics, Bengaluru, India.
GCN Circular #29657
H. Kumar(IITB), K. Sharma (IITB), J. Stanzin (IAO), A. Dutta(IIA), V. Bhalerao(IITB), G. C. Anupama(IIA), S. Barway(IIA) report on behalf of the GIT team:
We observed GRB 210306A detected by Swift Burst Alert Telescope (V. D'Elia et. al., GCN 29597) and optical afterglow confirmed by (Alan M. Watson et. al., GCN 29598), with the 0.7m GROWTH-India Telescope (GIT). We obtained multiple exposures in the r' filter. We clearly detected the afterglow in our stacked image at R.A. = 08:39:49.99, DEC. = +60:12:19.09. The photometric results follow as:
--------------------------------------------------------
JD (mid) | T_mid-T0(hrs) | Filter | Magnitude (AB) |
--------------------------------------------------------
2459280.20139 | 12.9 | r' | 20.87 +/0.05 |
--------------------------------------------------------
The magnitude is in agreement with that reported by Z.P. Zhu et al., (GCN 29607), around the same time of our observation. 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 #30080
A Rossi (INAF-OAS) and D. B. Malesani (DTU space) report on behalf of the CIBO collaboration:
We observed the field of GRB 210306A (D'Elia et al., GCN 29597) simultaneously in the r' and z' bands with the LBC imager mounted on LBT (Mt Graham, AZ, USA). We obtained 20min of imaging on 2021-05-10, 65 days after the burst trigger and 60 days after our first observation (Rossi et al., GCN 29645). Observations were performed under good weather conditions with an average seeing of ~1.3".
At the location of the optical afterglow, we detected an object which is likely the GRB host galaxy. We measure the following AB magnitudes:
```
r=24.6+-0.2
z=24.4+-0.4
```
calibrated against SDSS field stars.
We acknowledge the excellent support from the LBTO and LBT-INAF staff, particularly A. Cardwell, S. Allanson, F. Cusano, S. Paiano and D. Paris, in obtaining these observations.

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Jochen Greiner, last update: 26-May-2021 [Disclaimer]