Gamma-ray Burst 210724A

(All information courtesy of the instrument teams.)

Previous IAU Circulars

• none

• GCN/BACODINE POSITION NOTICE
  

  TITLE:           GCN/SWIFT NOTICE
  NOTICE_DATE:     Sat 24 Jul 21 20:23:03 UT
  NOTICE_TYPE:     Swift-BAT GRB Position
  TRIGGER_NUM:     1061482,   Seg_Num: 0
  GRB_RA:          227.407d {+15h 09m 38s} (J2000),
                   227.693d {+15h 10m 46s} (current),
                   226.745d {+15h 06m 59s} (1950)
  GRB_DEC:          -6.274d {-06d 16' 27"} (J2000),
                    -6.356d {-06d 21' 19"} (current),
                    -6.085d {-06d 05' 05"} (1950)
  GRB_ERROR:       3.00 [arcmin radius, statistical only]
  GRB_INTEN:       11424 [cnts]    Image_Peak=232 [image_cnts]
  TRIGGER_DUR:     4.096 [sec] 
  TRIGGER_INDEX:   292     E_range: 15-50 keV
  BKG_INTEN:       101664 [cnts]
  BKG_TIME:        72788.57 SOD {20:13:08.57} UT
  BKG_DUR:         40 [sec]
  GRB_DATE:        19419 TJD;   205 DOY;   21/07/24
  GRB_TIME:        72849.24 SOD {20:14:09.24} UT
  GRB_PHI:          -5.85 [deg]
  GRB_THETA:        46.90 [deg]
  SOLN_STATUS:     0x3
  RATE_SIGNIF:     9.00 [sigma]
  IMAGE_SIGNIF:    7.21 [sigma]
  MERIT_PARAMS:     +1  +0  +0  +2  +1  -3  +0  +0 +24  +0 
  SUN_POSTN:       124.41d {+08h 17m 39s}  +19.68d {+19d 40' 40"}
  SUN_DIST:        104.61 [deg]   Sun_angle= -6.9 [hr] (East of Sun)
  MOON_POSTN:      315.76d {+21h 03m 04s}  -21.56d {-21d 33' 29"}
  MOON_DIST:        85.88 [deg]
  MOON_ILLUM:      99 [%]
  GAL_COORDS:      353.08, 42.75 [deg] galactic lon,lat of the burst (or transient)
  ECL_COORDS:      226.74, 11.00 [deg] ecliptic lon,lat of the burst (or transient)
  COMMENTS:        SWIFT-BAT GRB Coordinates.  
  COMMENTS:        This Notice was delayed by more than 60 sec past the end of the trigger integration interval;  
  COMMENTS:        probably due to it occurring during a Malindi downlink session.  
  COMMENTS:        This is a rate trigger.  
  COMMENTS:        A point_source was found.  
  COMMENTS:        This does not match any source in the on-board catalog.  
  COMMENTS:        This does not match any source in the ground catalog.  
  COMMENTS:        This is a GRB.  
  COMMENTS:        This trigger occurred at longitude,latitude = 11.40,4.11 [deg].  
  

• red DSS finding chart ps-file
  
  
• GCN NOTICE
  

  TITLE:           GCN/SWIFT NOTICE
  NOTICE_DATE:     Sat 24 Jul 21 20:24:41 UT
  NOTICE_TYPE:     Swift-UVOT Source List
  TRIGGER_NUM:     1061482,   Seg_Num: 0
  POINT_RA:        227.415d {+15h 09m 40s} (J2000)
  POINT_DEC:        -6.299d {-06d 17' 54"} (J2000)
  POINT_ROLL:      288.737d
  IMG_START_DATE:  19419 TJD;   205 DOY;   21/07/24
  IMG_START_TIME:  72973.93 SOD {20:16:13.93} UT,   124.7 [sec] since BAT Trigger Time
  FILTER:          10, White
  BKG_MEAN:        2.641
  N_STARS:         72
  X_OFFSET:        655 [pixels]
  Y_OFFSET:        643 [pixels]
  X_MAX:           1614 [pixels]
  Y_MAX:           1602 [pixels]
  DET_THRESH:      13
  PHOTO_THRESH:    7
  SL_URL:          sw01061482000msufc0124.fits
  SUN_POSTN:       124.42d {+08h 17m 40s}  +19.68d {+19d 40' 39"}
  SUN_DIST:        104.62 [deg]   Sun_angle= -6.9 [hr] (East of Sun)
  MOON_POSTN:      315.78d {+21h 03m 08s}  -21.55d {-21d 33' 14"}
  MOON_DIST:        85.88 [deg]
  MOON_ILLUM:      99 [%]
  GAL_COORDS:      353.06, 42.73 [deg] galactic lon,lat of the pointing direction
  ECL_COORDS:      226.75, 10.98 [deg] ecliptic lon,lat of the pointing direction
  COMMENTS:        SWIFT-UVOT Source List.  
  

• GCN NOTICE
  

  TITLE:           GCN/SWIFT NOTICE
  NOTICE_DATE:     Sat 24 Jul 21 20:24:56 UT
  NOTICE_TYPE:     Swift-UVOT Processed Source List
  TRIGGER_NUM:     1061482,   Seg_Num: 0
  POINT_RA:        227.415d {+15h 09m 40s} (J2000)
  POINT_DEC:        -6.299d {-06d 17' 54"} (J2000)
  POINT_ROLL:      288.737d
  IMG_START_DATE:  19419 TJD;   205 DOY;   21/07/24
  IMG_START_TIME:  72973.93 SOD {20:16:13.93} UT,   124.7 [sec] since BAT Trigger Time
  FILTER:          10, White
  BKG_MEAN:        2.641
  N_STARS:         72
  X_OFFSET:        655 [pixels]
  Y_OFFSET:        643 [pixels]
  X_MAX:           1614 [pixels]
  Y_MAX:           1602 [pixels]
  DET_THRESH:      13
  PHOTO_THRESH:    7
  SL_URL:          sw01061482000msufc0124.fits
  SUN_POSTN:       124.42d {+08h 17m 40s}  +19.68d {+19d 40' 39"}
  SUN_DIST:        104.62 [deg]   Sun_angle= -6.9 [hr] (East of Sun)
  MOON_POSTN:      315.78d {+21h 03m 08s}  -21.55d {-21d 33' 12"}
  MOON_DIST:        85.89 [deg]
  MOON_ILLUM:      99 [%]
  GAL_COORDS:      353.06, 42.73 [deg] galactic lon,lat of the pointing direction
  ECL_COORDS:      226.75, 10.98 [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 24 Jul 21 20:26:03 UT
  NOTICE_TYPE:     Swift-UVOT Image
  TRIGGER_NUM:     1061482,   Seg_Num: 0
  POINT_RA:        227.415d {+15h 09m 40s} (J2000)
  POINT_DEC:        -6.299d {-06d 17' 54"} (J2000)
  ROLL:            288.737d
  IMG_START_DATE:  19419 TJD;   205 DOY;   21/07/24
  IMG_START_TIME:  72973.93 SOD {20:16:13.93} UT,   124.7 [sec] since BAT Trigger Time
  FILTER:          10, White
  EXPOSURE_ID:     648850601
  X_OFFSET:        974 [pixels]
  Y_OFFSET:        962 [pixels]
  WIDTH:           160 [pixels]
  HEIGHT:          160 [pixels]
  X_GRB_POS:       1134
  Y_GRB_POS:       1122
  BINNING_INDEX:   1
  IM_URL:          sw01061482000msuni0152.fits
  SUN_POSTN:       124.42d {+08h 17m 40s}  +19.68d {+19d 40' 38"}
  SUN_DIST:        104.62 [deg]   Sun_angle= -6.9 [hr] (East of Sun)
  MOON_POSTN:      315.80d {+21h 03m 11s}  -21.55d {-21d 33' 02"}
  MOON_DIST:        85.90 [deg]
  MOON_ILLUM:      99 [%]
  GAL_COORDS:      353.06, 42.73 [deg] galactic lon,lat of the pointing direction
  ECL_COORDS:      226.75, 10.98 [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:     Sat 24 Jul 21 20:26:12 UT
  NOTICE_TYPE:     Swift-UVOT Processed Image
  TRIGGER_NUM:     1061482,   Seg_Num: 0
  POINT_RA:        227.415d {+15h 09m 40s} (J2000)
  POINT_DEC:        -6.299d {-06d 17' 54"} (J2000)
  ROLL:            288.737d
  IMG_START_DATE:  19419 TJD;   205 DOY;   21/07/24
  IMG_START_TIME:  72973.93 SOD {20:16:13.93} UT,   124.7 [sec] since BAT Trigger Time
  FILTER:          10, White
  EXPOSURE_ID:     648850601
  X_OFFSET:        974 [pixels]
  Y_OFFSET:        962 [pixels]
  WIDTH:           160 [pixels]
  HEIGHT:          160 [pixels]
  X_GRB_POS:       1134
  Y_GRB_POS:       1122
  BINNING_INDEX:   1
  IM_URL:          sw01061482000msuni0152.fits
  SUN_POSTN:       124.42d {+08h 17m 40s}  +19.68d {+19d 40' 38"}
  SUN_DIST:        104.62 [deg]   Sun_angle= -6.9 [hr] (East of Sun)
  MOON_POSTN:      315.80d {+21h 03m 11s}  -21.55d {-21d 33' 01"}
  MOON_DIST:        85.90 [deg]
  MOON_ILLUM:      99 [%]
  GAL_COORDS:      353.06, 42.73 [deg] galactic lon,lat of the pointing direction
  ECL_COORDS:      226.75, 10.98 [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:     Sat 24 Jul 21 20:26:44 UT
  NOTICE_TYPE:     Swift-XRT Position
  TRIGGER_NUM:     1061482,   Seg_Num: 0
  GRB_RA:          227.4151d {+15h 09m 39.62s} (J2000),
                   227.7012d {+15h 10m 48.28s} (current),
                   226.7524d {+15h 07m 00.58s} (1950)
  GRB_DEC:          -6.2919d {-06d 17' 30.8"} (J2000),
                    -6.3729d {-06d 22' 22.4"} (current),
                    -6.1023d {-06d 06' 08.3"} (1950)
  GRB_ERROR:       7.9 [arcsec radius, statistical plus systematic, 90% containment]
  GRB_INTEN:       1.00e-10 [erg/cm2/sec]
  GRB_SIGNIF:      10.00 [sigma]
  IMG_START_DATE:  19419 TJD;   205 DOY;   21/07/24
  IMG_START_TIME:  73029.00 SOD {20:17:09.00} UT,   179.8 [sec] since BAT Trigger Time
  TAM[0-3]:        100.00 100.00 100.00 100.00
  AMPLIFIER:       1
  WAVEFORM:        31
  SUN_POSTN:       124.42d {+08h 17m 40s}  +19.68d {+19d 40' 38"}
  SUN_DIST:        104.62 [deg]   Sun_angle= -6.9 [hr] (East of Sun)
  MOON_POSTN:      315.80d {+21h 03m 13s}  -21.55d {-21d 32' 56"}
  MOON_DIST:        85.91 [deg]
  MOON_ILLUM:      99 [%]
  GAL_COORDS:      353.07, 42.73 [deg] galactic lon,lat of the burst
  ECL_COORDS:      226.75, 10.99 [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:        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:     Sat 24 Jul 21 20:29:52 UT
  NOTICE_TYPE:     Swift-UVOT Source List
  TRIGGER_NUM:     1061482,   Seg_Num: 0
  POINT_RA:        227.415d {+15h 09m 40s} (J2000)
  POINT_DEC:        -6.301d {-06d 18' 02"} (J2000)
  POINT_ROLL:      288.734d
  IMG_START_DATE:  19419 TJD;   205 DOY;   21/07/24
  IMG_START_TIME:  73131.97 SOD {20:18:51.97} UT,   282.7 [sec] since BAT Trigger Time
  FILTER:          7, U
  BKG_MEAN:        0.655
  N_STARS:         53
  X_OFFSET:        415 [pixels]
  Y_OFFSET:        403 [pixels]
  X_MAX:           1854 [pixels]
  Y_MAX:           1842 [pixels]
  DET_THRESH:      7
  PHOTO_THRESH:    3
  SL_URL:          sw01061482000msufc0282.fits
  SUN_POSTN:       124.42d {+08h 17m 40s}  +19.68d {+19d 40' 36"}
  SUN_DIST:        104.62 [deg]   Sun_angle= -6.9 [hr] (East of Sun)
  MOON_POSTN:      315.83d {+21h 03m 20s}  -21.54d {-21d 32' 29"}
  MOON_DIST:        85.93 [deg]
  MOON_ILLUM:      99 [%]
  GAL_COORDS:      353.06, 42.73 [deg] galactic lon,lat of the pointing direction
  ECL_COORDS:      226.75, 10.98 [deg] ecliptic lon,lat of the pointing direction
  COMMENTS:        SWIFT-UVOT Source List.  
  

• GCN NOTICE
  

  TITLE:           GCN/SWIFT NOTICE
  NOTICE_DATE:     Sat 24 Jul 21 20:30:58 UT
  NOTICE_TYPE:     Swift-UVOT Image
  TRIGGER_NUM:     1061482,   Seg_Num: 0
  POINT_RA:        227.415d {+15h 09m 40s} (J2000)
  POINT_DEC:        -6.301d {-06d 18' 02"} (J2000)
  ROLL:            288.734d
  IMG_START_DATE:  19419 TJD;   205 DOY;   21/07/24
  IMG_START_TIME:  73131.97 SOD {20:18:51.97} UT,   282.7 [sec] since BAT Trigger Time
  FILTER:          7, U
  EXPOSURE_ID:     648850759
  X_OFFSET:        974 [pixels]
  Y_OFFSET:        962 [pixels]
  WIDTH:           160 [pixels]
  HEIGHT:          160 [pixels]
  X_GRB_POS:       1134
  Y_GRB_POS:       1122
  BINNING_INDEX:   1
  IM_URL:          sw01061482000msuni0310.fits
  SUN_POSTN:       124.42d {+08h 17m 41s}  +19.68d {+19d 40' 36"}
  SUN_DIST:        104.62 [deg]   Sun_angle= -6.9 [hr] (East of Sun)
  MOON_POSTN:      315.85d {+21h 03m 23s}  -21.54d {-21d 32' 19"}
  MOON_DIST:        85.94 [deg]
  MOON_ILLUM:      99 [%]
  GAL_COORDS:      353.06, 42.73 [deg] galactic lon,lat of the pointing direction
  ECL_COORDS:      226.75, 10.98 [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:     Sat 24 Jul 21 20:30:15 UT
  NOTICE_TYPE:     Swift-XRT Position UPDATE
  TRIGGER_NUM:     1061482,   Seg_Num: 0
  GRB_RA:          227.4139d {+15h 09m 39.33s} (J2000),
                   227.7000d {+15h 10m 48.00s} (current),
                   226.7512d {+15h 07m 00.29s} (1950)
  GRB_DEC:          -6.2910d {-06d 17' 27.6"} (J2000),
                    -6.3720d {-06d 22' 19.2"} (current),
                    -6.1014d {-06d 06' 05.1"} (1950)
  GRB_ERROR:       1.9 [arcsec radius, statistical plus systematic, 90% containment]
  GRB_INTEN:       1.00e-10 [erg/cm2/sec]
  GRB_SIGNIF:      10.00 [sigma]
  IMG_START_DATE:  19419 TJD;   205 DOY;   21/07/24
  IMG_START_TIME:  73029.00 SOD {20:17:09.00} UT,   179.8 [sec] since BAT Trigger Time
  TAM[0-3]:        100.00 100.00 100.00 100.00
  AMPLIFIER:       1
  WAVEFORM:        31
  SUN_POSTN:       124.42d {+08h 17m 41s}  +19.68d {+19d 40' 36"}
  SUN_DIST:        104.62 [deg]   Sun_angle= -6.9 [hr] (East of Sun)
  MOON_POSTN:      315.84d {+21h 03m 21s}  -21.54d {-21d 32' 26"}
  MOON_DIST:        85.94 [deg]
  MOON_ILLUM:      99 [%]
  GAL_COORDS:      353.07, 42.73 [deg] galactic lon,lat of the burst
  ECL_COORDS:      226.75, 10.99 [deg] ecliptic lon,lat of the burst
  COMMENTS:        SWIFT-XRT Coordinates.  
  COMMENTS:        This Notice was ground-generated -- not flight-generated.  
  COMMENTS:        This is an Update Notice -- the RA,Dec values herein supersede the previous XRT_POS Notice.  
  COMMENTS:        TAM values, flux and significance fields are not valid.  
  COMMENTS:        This position was automatically generated on the ground using  
  COMMENTS:        Photon Counting data telemetered via TDRSS (SPER data).  
  COMMENTS:        See http://www.swift.ac.uk/sper/docs.php for details.  
  COMMENTS:        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:     Sat 24 Jul 21 20:30:06 UT
  NOTICE_TYPE:     Swift-UVOT Processed Source List
  TRIGGER_NUM:     1061482,   Seg_Num: 0
  POINT_RA:        227.415d {+15h 09m 40s} (J2000)
  POINT_DEC:        -6.301d {-06d 18' 02"} (J2000)
  POINT_ROLL:      288.734d
  IMG_START_DATE:  19419 TJD;   205 DOY;   21/07/24
  IMG_START_TIME:  73131.97 SOD {20:18:51.97} UT,   282.7 [sec] since BAT Trigger Time
  FILTER:          7, U
  BKG_MEAN:        0.655
  N_STARS:         53
  X_OFFSET:        415 [pixels]
  Y_OFFSET:        403 [pixels]
  X_MAX:           1854 [pixels]
  Y_MAX:           1842 [pixels]
  DET_THRESH:      7
  PHOTO_THRESH:    3
  SL_URL:          sw01061482000msufc0282.fits
  SUN_POSTN:       124.42d {+08h 17m 41s}  +19.68d {+19d 40' 36"}
  SUN_DIST:        104.62 [deg]   Sun_angle= -6.9 [hr] (East of Sun)
  MOON_POSTN:      315.84d {+21h 03m 21s}  -21.54d {-21d 32' 27"}
  MOON_DIST:        85.93 [deg]
  MOON_ILLUM:      99 [%]
  GAL_COORDS:      353.06, 42.73 [deg] galactic lon,lat of the pointing direction
  ECL_COORDS:      226.75, 10.98 [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 24 Jul 21 20:31:03 UT
  NOTICE_TYPE:     Swift-UVOT Processed Image
  TRIGGER_NUM:     1061482,   Seg_Num: 0
  POINT_RA:        227.415d {+15h 09m 40s} (J2000)
  POINT_DEC:        -6.301d {-06d 18' 02"} (J2000)
  ROLL:            288.734d
  IMG_START_DATE:  19419 TJD;   205 DOY;   21/07/24
  IMG_START_TIME:  73131.97 SOD {20:18:51.97} UT,   282.7 [sec] since BAT Trigger Time
  FILTER:          7, U
  EXPOSURE_ID:     648850759
  X_OFFSET:        974 [pixels]
  Y_OFFSET:        962 [pixels]
  WIDTH:           160 [pixels]
  HEIGHT:          160 [pixels]
  X_GRB_POS:       1134
  Y_GRB_POS:       1122
  BINNING_INDEX:   1
  IM_URL:          sw01061482000msuni0310.fits
  SUN_POSTN:       124.42d {+08h 17m 41s}  +19.68d {+19d 40' 36"}
  SUN_DIST:        104.62 [deg]   Sun_angle= -6.9 [hr] (East of Sun)
  MOON_POSTN:      315.85d {+21h 03m 23s}  -21.54d {-21d 32' 19"}
  MOON_DIST:        85.94 [deg]
  MOON_ILLUM:      99 [%]
  GAL_COORDS:      353.06, 42.73 [deg] galactic lon,lat of the pointing direction
  ECL_COORDS:      226.75, 10.98 [deg] ecliptic lon,lat of the pointing direction
  COMMENTS:        SWIFT-UVOT Processed Image.  
  COMMENTS:        The GRB Position came from the Window Position in the Mode Command.  
  COMMENTS:        The image has 2x2 binning (compression).  
  COMMENTS:        All 4 attachments are included.  
  

  
• GCN Circular #30496
  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 GRB210724.84 (trigger No 1061482,15h 09m 37.68s , -06d 16m 26.4s, R=0.05) errorbox 21 sec after notice time and 566 sec after trigger time at 2021-07-24 20:23:35 UT, with upper limit up to 17.2 mag. The observations began at zenith distance = 46 deg. The sun altitude is -56.0 deg.
  MASTER-Tavrida robotic telescope located in Russia (Lomonosov MSU, SAI Crimea astronomical station) was pointed to the Swift GRB210724.84 errorbox 28 sec after notice time and 573 sec after trigger time at 2021-07-24 20:23:42 UT, with upper limit up to 15.3 mag. The observations began at zenith distance = 71 deg. The sun altitude is -23.3 deg.
  The galactic latitude b = 42 deg., longitude l = 354 deg.
  Real time updated cover map and OT discovered available here: https://master.sai.msu.ru/site/master2/observ.php?id=1669395
  We obtain a following upper limits.

  Tmid-T0  |          Site       |Filt.| Expt. | Limit| Comment
  _________|_____________________|_____|_______|______|________
  
       621 |         MASTER-SAAO | P\  |   110 | 17.1 |        
       629 |      MASTER-Tavrida |  P\ |   110 | 15.3 |        
       758 |         MASTER-SAAO | P\  |   140 | 17.2 |        
       773 |      MASTER-Tavrida |  P\ |   140 | 15.3 |        
  

  The observation and reduction will continue. The message may be cited.
• GCN Circular #30497
  P. D'Avanzo (INAF-OAB), M. G. Bernardini (INAF-OAB), J. A. Kennea (PSU), N. J. Klingler (GSFC/UMBC/CRESSTII), A. Y. Lien (GSFC/UMBC), F. E. Marshall (NASA/GSFC), A. Melandri (INAF-OAB), D. M. Palmer (LANL) and T. Sbarrato (INAF-OAB) report on behalf of the Neil Gehrels Swift Observatory Team:
  At 20:14:09 UT, the Swift Burst Alert Telescope (BAT) triggered and located GRB 210724A (trigger=1061482). Swift slewed immediately to the burst. The BAT on-board calculated location is RA, Dec 227.407d, -6.274d which is

     RA(J2000) = 15h 09m 38s
     Dec(J2000) = -06d 16' 27"
  

  with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). Due to a telemetry outage the BAT lightcurve is not immediately available. However, the trigger information indicates a duration of at least 4 seconds.
  The XRT began observing the field at 20:17:09.0 UT, 179.8 seconds after the BAT trigger. Using promptly downlinked data we find a fading, uncatalogued X-ray source with an enhanced position: RA, Dec 227.4118, -6.2911 which is equivalent to:

     RA(J2000)  = 15h 09m 38.83s
     Dec(J2000) = -06d 17' 27.8"
  

  with an uncertainty of 1.9 arcseconds (radius, 90% containment). This position may be improved as more data are received; the latest position is available at https://www.swift.ac.uk/sper.
  A power-law fit to a spectrum formed from promptly downlinked event data gives a column density consistent with the Galactic value of 8.23 x 10^20 cm^-2 (Willingale et al. 2013).
  UVOT took a finding chart exposure of 150 seconds with the White filter starting 124 seconds after the BAT trigger. No credible afterglow candidate has been found in the initial data products. The 2.7'x2.7' sub-image covers 100% of the XRT error circle. The typical 3-sigma upper limit has been about 19.6 mag. The 8'x8' region for the list of sources generated on-board covers 100% of the XRT error circle. The list of sources is typically complete to about 18 mag. No correction has been made for the expected extinction corresponding to E(B-V) of 0.097.
  Burst Advocate for this burst is P. D'Avanzo (paolo.davanzo AT inaf.it). Please contact the BA by email if you require additional information regarding Swift followup of this burst. In extremely urgent cases, after trying the Burst Advocate, you can contact the Swift PI by phone (see Swift TOO web site for information: http://www.swift.psu.edu/)
• GCN Circular #30498
  S. de Wet (UCT), P.J. Groot (Radboud/UCT/SAAO), A.J. Levan (Radboud), P.M. Vreeswijk (Radboud), report on behalf of the MeerLICHT consortium:
  Following the detection of GRB210724A by Swift and its X-ray counterpart (D'Avanzo et al., GCN30497), the 0.6m MeerLICHT telescope, located at Sutherland, South Africa obtained a repeating series of 60s images in the q,u,q,g,q,r,q,i,q,z bands. Observations began at 2021-07-24, 20:25:18.02 UT, 11 minutes after the Swift detection, and 2 minutes after the distribution of the BAT alert, and continued untill 21:27:36 UT.
  We detect no optical afterglow at the XRT position (D’Avanzo et al. GCN30497) in our first u,g,q,r,i,z exposures to 5-sigma limiting magnitudes of:

  u > 18.59 at 20:27:37 UT
  g > 19.40 at 20:31:01 UT
  q > 19.77 at 20:25:49 UT
  r > 19.38 at 20:34:31 UT
  i > 19.26 at 20:37:45 UT
  z > 18.14 at 20:59:12 UT
  

  Full moon conditions limited the depth of our exposures.
  We do note that an r=21.5 object is visible within the XRT localisation in PanSTARRS imaging of the field, and is a plausible host galaxy.
  MeerLICHT is built and run by a consortium consisting of Radboud University, University of Cape Town, the South African Astronomical Observatory, the University of Oxford, the University of Manchester and the University of Amsterdam. Disclaimer - University of Cape Town This email is subject to UCT policies and email disclaimer published on our website at http://www.uct.ac.za/main/email-disclaimer or obtainable from +27 21 650 9111. If this email is not related to the business of UCT, it is sent by the sender in an individual capacity. Please report security incidents or abuse via https://csirt.uct.ac.za/page/report-an-incident.php.
• GCN Circular #30511
  A. de Ugarte Postigo (HETH/IAA-CSIC,DARK/NBI), C. C. Thoene, D. A. Kann, M. Blazek, J. F. Agui Fernandez (all HETH/IAA-CSIC), J. P. U. Fynbo (DAWN/NBI), L. Izzo (DARK/NBI), N. R. Tanvir (U. Leicester), N. Castro-Rodriguez, and A. Marante (GRANTECAN, IAC) report:
  We observed the field of GRB 210724A (D'Avanzo et al. GCN 30497) with OSIRIS mounted on the 10.4 m GTC telescope at the Roque de los Muchachos observatory (La Palma, Spain). Observations started at 22:07 UT (1.88 hr after the burst). Observations were affected by strong calima and the full Moon, which resulted in bad transparency and very high background. In a series of short images in r', i' and z' bands we detect a new source, not present in the PanSTARRS catalogue images. The object is located at (J2000 +/- 0.5"):

  RA: 15:09:39.44
  Dec.: -06:17:26.0
  

  This object had a magnitude of r' = 22.00 +/- 0.15 mag as compared to PanSTARRS field stars. We note that this source is within the early XRT alert error circles but outside the refined one (D'Avanzo et al. GCN 30497). There is no new source detected within this refined error circle. Due to the fact that this source is significantly brighter than the PanSTARRS limit, we propose it as the optical counterpart of GRB 210724A.
• GCN Circular #30513
  S. Laha (GSFC/UMBC), S. D. Barthelmy (GSFC), P. D'Avanzo (INAF-OAB), 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+962 sec from the recent telemetry downlink, we report further analysis of BAT GRB 210724A (trigger #1061482) (D'Avanzo et al., GCN Circ. 30497). The BAT ground-calculated position is RA, Dec = 227.425, -6.279 deg which is

     RA(J2000)  =  15h 09m 41.9s
     Dec(J2000) = -06d 16' 42.9"
  

  with an uncertainty of 1.9 arcmin, (radius, sys+stat, 90% containment). The partial coding was 34%.
  The mask-weighted light curve shows a multi-peaked structure that starts at ~T-40 s and ends at ~T+25 s. The main peak occurs at ~T0. T90 (15-350 keV) is 50.57 +- 9.54 sec (estimated error including systematics).
  The time-averaged spectrum from T-38.55 to T+25.50 sec is best fit by a simple power-law model. The power law index of the time-averaged spectrum is 2.30 +- 0.28. The fluence in the 15-150 keV band is 1.8 +- 0.2 x 10^-6 erg/cm2. The 1-sec peak photon flux measured from T-0.51 sec in the 15-150 keV band is 2.5 +- 0.8 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/1061482/BA/
• GCN Circular #30515
  P.A. Evans (U. Leicester), M. Capalbi (INAF-IASFPA), M. Perri (SSDC & INAF-OAR), V. D'Elia (SSDC & INAF-OAR), A. Tohuvavohu (U. Toronto), B. Sbarufatti (PSU), D.N. Burrows (PSU), J.P. Osborne (U. Leicester), K.L. Page (U. Leicester) and P. D'Avanzo report on behalf of the Swift-XRT team:
  We have analysed 2.5 ks of XRT data for GRB 210724A (D'Avanzo et al. GCN Circ. 30497), from 123 s to 84.6 ks after the BAT trigger. The data comprise 263 s in Windowed Timing (WT) mode with the remainder in Photon Counting (PC) mode. Using 331 s of PC mode data and 1 UVOT image, we find an enhanced XRT position (using the XRT-UVOT alignment and matching UVOT field sources to the USNO-B1 catalogue): RA, Dec = 227.41131, -6.29009 which is equivalent to:

  RA (J2000): 15h 09m 38.72s
  Dec(J2000): -06d 17' 24.3"
  

  with an uncertainty of 2.0 arcsec (radius, 90% confidence).
  The light curve can be modelled with a power-law decay with a decay index of alpha=1.17 (+0.10, -0.09).
  A spectrum formed from the WT mode data can be fitted with an absorbed power-law with a photon spectral index of 2.48 (+/-0.08). The best-fitting absorption column is 2.08 (+0.23, -0.22) x 10^21 cm^-2, in excess of the Galactic value of 8.2 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 2.8 x 10^-11 (4.9 x 10^-11) erg cm^-2 count^-1.
  A summary of the WT-mode spectrum is thus:

  Total column:	     2.08 (+0.23, -0.22) x 10^21 cm^-2
  Galactic foreground: 8.2 x 10^20 cm^-2
  Excess significance: 9.5 sigma
  Photon index:	     2.48 (+/-0.08)
  

  The results of the XRT-team automatic analysis are available at http://www.swift.ac.uk/xrt_products/01061482.
  This circular is an official product of the Swift-XRT team.
• GCN Circular #30518
  S. Belkin (IKI), A. Novichonok (Petrozavodsk State University, KIAM), A. Pozanenko (IKI), A. Zhornichenko (KIAM), N. Pankov (HSE) report on behalf of IKI GRB FuN:
  We observed the field of GRB 210724A (D'Avanzo et al. GCN 30497) with Zeiss-1000 telescope of Koshka observatory starting on July 24 (UT) 20:39:32. We do not detect any object XRT error circle (D'Avanzo et al. GCN 30497). We also not detect the object at the position of the afterglow candidate (Ugarte Postigo et al., GCN 30511).
  Preliminary photometry of the field is following

  Date       UT start   t-T0       Filter Exp.    OT   Err.  UL(3sigma)
                         (mid, days)        (s)
  
  2021-07-24 20:39:32   0.024919    R     21*60   n/d  n/d   18.6
  

  The photometry is based on the nearby USNO-B1.0 stars

  USNO-B1.0_id R2
  0837-0267865 15.24
  0836-0268753 16.95
  0837-0267827 15.54
  

• GCN Circular #30529
  GRB 210724A: Swift/UVOT Upper Limits
  S. J. LaPorte (PSU) and P. D'Avanzo (INAF-OAB) report on behalf of the Swift/UVOT team:
  The Swift/UVOT began settled observations of the field of GRB 210724A 125 s after the BAT trigger (D'Avanzo et al., GCN Circ. 30497). No optical afterglow consistent with the XRT position (D'Avanzo et al. GCN Circ. 30497) is detected in the initial UVOT exposures. Preliminary 3-sigma upper limits using the UVOT photometric system (Breeveld et al. 2011, AIP Conf. Proc. 1358, 373) for the first finding chart (FC) exposure and subsequent exposures are:

  Filter         T_start(s)   T_stop(s)      Exp(s)         Mag
  
  white_FC           125          275          147         >20.8
  u_FC               283          513          226         >20.1
  white              125          275          147         >20.8
  u                  283          513          227         >20.1
  

  The magnitudes in the table are not corrected for the Galactic extinction due to the reddening of E(B-V) = 0.097 in the direction of the burst (Schlegel et al. 1998).
• GCN Circular #30547
  P.A. Evans (U. Leicester) and P. D'Avanzo (INAF-OAB) report on behalf of the Swift-XRT team.
  The XRT position of GRB 210724A reported in GCN Circ. 30515 was 11" from the position of the optical candidate found by de Ugarte Postigo et al. (GCN Circ. 30511). Unusually, this position underwent significant variation during the normal revisions after each data downlink. Investigation has revealed a rare local minimum issue during the first XRT image, which has now been fixed.
  The best XRT position is RA, Dec = 227.41461, -6.29070 which is equivalent to:

  RA (J2000): 15h 09m 39.51s
  Dec(J2000): -06d 17' 26.5"
  

  with an uncertainty of 3.0 arcsec (radius, 90% confidence). This position is 1.1" from the optical position of de Ugarte Postigo et al.
  We apologise for the confusion caused by this rare glitch, which coincided with the author's vacation (Murphy et al).
  As ever, the most recent version of the position can be found online at: https://www.swift.ac.uk/xrt_positions/01061482/
  This circular is an official product of the Swift-XRT team.
• GCN Circular #30551
  D. A. Kann (HETH/IAA-CSIC), A. de Ugarte Postigo (HETH/IAA-CSIC, DARK/NBI), C. Thoene, M. Blazek, J. F. Agui Fernandez (all HETH/IAA-CSIC), A. Gardini, and I. Hermelo (both CAHA) report:
  We observed the in-flight XRT afterglow position (revised in Evans et al., GCN #30547) of GRB 210724A (D'Avanzo et al., GCN #30497) with CAFOS mounted at the 2.2m Calar Alto telescope (Almeria, Spain), under very adverse conditions (high airmass, strong Calima, clouds, bad seeing, strong moonlight - the works). We obtained 10 x 180 s images in r', starting on July 24, 21:07:08 UT (0.8831 h after the burst).
  At the position of the GTC afterglow candidate (de Ugarte Postigo et al., GCN #30511), we detect no source down to r' > 22.0 mag (AB magnitude) against PanSTARRS comparison stars, at midtime 0.0482 d (1.1569 h) after the burst. This is of similar depth as the detection by de Ugarte Postigo et al., GCN #30511, perhaps indicating a slowly rising afterglow, or at least one that is not steeply decaying.