Gamma-ray Burst 210531A

(All information courtesy of the instrument teams.)

Previous IAU Circulars

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Results of Observations

GCN NOTICE

TITLE:           GCN/FERMI NOTICE
NOTICE_DATE:     Mon 31 May 21 12:00:26 UT
NOTICE_TYPE:     Fermi-GBM Flight Position
RECORD_NUM:      49
TRIGGER_NUM:     644155206
GRB_RA:          145.200d {+09h 40m 48s} (J2000),
                 145.469d {+09h 41m 53s} (current),
                 144.571d {+09h 38m 17s} (1950)
GRB_DEC:          -4.383d {-04d 22' 59"} (J2000),
                  -4.481d {-04d 28' 52"} (current),
                  -4.156d {-04d 09' 19"} (1950)
GRB_ERROR:       4.38 [deg radius, statistical plus systematic]
GRB_INTEN:       895 [cnts/sec]
DATA_SIGNIF:     35.80 [sigma]
INTEG_TIME:      1.024 [sec]
GRB_DATE:        19365 TJD;   151 DOY;   21/05/31
GRB_TIME:        43201.65 SOD {12:00:01.65} UT
GRB_PHI:         293.00 [deg]
GRB_THETA:        80.00 [deg]
DATA_TIME_SCALE: 1.0240 [sec]
HARD_RATIO:      0.57
LOC_ALGORITHM:   3 (version number of)
MOST_LIKELY:      95%  GRB
2nd_MOST_LIKELY:   4%  Generic Transient
DETECTORS:       0,0,0, 1,1,0, 0,0,0, 0,0,0, 0,0,
SUN_POSTN:        68.64d {+04h 34m 35s}  +21.98d {+21d 59' 05"}
SUN_DIST:         79.55 [deg]   Sun_angle= -5.1 [hr] (East of Sun)
MOON_POSTN:      322.44d {+21h 29m 45s}  -19.94d {-19d 56' 14"}
MOON_DIST:       155.40 [deg]
MOON_ILLUM:      69 [%]
GAL_COORDS:      239.85, 34.25 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:      149.01,-17.25 [deg] ecliptic lon,lat of the burst (or transient)
LC_URL:          http://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2021/bn210531500/quicklook/glg_lc_medres34_bn210531500.gif
COMMENTS:        Fermi-GBM Flight-calculated Coordinates.  
COMMENTS:        This trigger occurred at longitude,latitude = 120.42,-22.37 [deg].  
COMMENTS:        The LC_URL file will not be created until ~15 min after the trigger.

GCN NOTICE

TITLE:           GCN/FERMI NOTICE
NOTICE_DATE:     Mon 31 May 21 12:00:35 UT
NOTICE_TYPE:     Fermi-GBM Flight Position
RECORD_NUM:      60
TRIGGER_NUM:     644155206
GRB_RA:          140.600d {+09h 22m 24s} (J2000),
                 140.866d {+09h 23m 28s} (current),
                 139.979d {+09h 19m 55s} (1950)
GRB_DEC:          -6.283d {-06d 16' 59"} (J2000),
                  -6.376d {-06d 22' 31"} (current),
                  -6.069d {-06d 04' 08"} (1950)
GRB_ERROR:       3.62 [deg radius, statistical plus systematic]
GRB_INTEN:       2791 [cnts/sec]
DATA_SIGNIF:     218.30 [sigma]
INTEG_TIME:      4.096 [sec]
GRB_DATE:        19365 TJD;   151 DOY;   21/05/31
GRB_TIME:        43201.65 SOD {12:00:01.65} UT
GRB_PHI:         298.00 [deg]
GRB_THETA:        80.00 [deg]
DATA_TIME_SCALE: 4.0960 [sec]
HARD_RATIO:      0.75
LOC_ALGORITHM:   3 (version number of)
MOST_LIKELY:      97%  GRB
2nd_MOST_LIKELY:   2%  Generic Transient
DETECTORS:       0,0,0, 1,1,0, 0,0,0, 0,0,0, 0,0,
SUN_POSTN:        68.64d {+04h 34m 35s}  +21.98d {+21d 59' 05"}
SUN_DIST:         76.12 [deg]   Sun_angle= -4.8 [hr] (East of Sun)
MOON_POSTN:      322.44d {+21h 29m 45s}  -19.94d {-19d 56' 12"}
MOON_DIST:       153.64 [deg]
MOON_ILLUM:      69 [%]
GAL_COORDS:      238.43, 29.44 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:      145.13,-20.57 [deg] ecliptic lon,lat of the burst (or transient)
LC_URL:          http://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2021/bn210531500/quicklook/glg_lc_medres34_bn210531500.gif
COMMENTS:        Fermi-GBM Flight-calculated Coordinates.  
COMMENTS:        This trigger occurred at longitude,latitude = 120.42,-22.37 [deg].  
COMMENTS:        The LC_URL file will not be created until ~15 min after the trigger.

GCN NOTICE

TITLE:           GCN/FERMI NOTICE
NOTICE_DATE:     Mon 31 May 21 12:00:44 UT
NOTICE_TYPE:     Fermi-GBM Ground Position
RECORD_NUM:      59
TRIGGER_NUM:     644155206
GRB_RA:          133.790d {+08h 55m 10s} (J2000),
                 134.074d {+08h 56m 18s} (current),
                 133.127d {+08h 52m 31s} (1950)
GRB_DEC:          +6.220d {+06d 13' 12"} (J2000),
                  +6.137d {+06d 08' 14"} (current),
                  +6.411d {+06d 24' 41"} (1950)
GRB_ERROR:       1.20 [deg radius, statistical only]
DATA_SIGNIF:     153.00 [sigma]
DATA_INTERVAL:   1.024 [sec]
GRB_DATE:        19365 TJD;   151 DOY;   21/05/31
GRB_TIME:        43201.65 SOD {12:00:01.65} UT
GRB_PHI:         300.00 [deg]
GRB_THETA:        94.00 [deg]
E_RANGE:         44.032 - 279.965 [keV]
LOC_ALGORITHM:   4173 (Gnd S/W Version number)
SUN_POSTN:        68.64d {+04h 34m 35s}  +21.98d {+21d 59' 05"}
SUN_DIST:         64.95 [deg]   Sun_angle= -4.4 [hr] (East of Sun)
MOON_POSTN:      322.44d {+21h 29m 46s}  -19.94d {-19d 56' 11"}
MOON_DIST:       163.98 [deg]
MOON_ILLUM:      69 [%]
GAL_COORDS:      222.03, 30.28 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:      134.44,-10.72 [deg] ecliptic lon,lat of the burst (or transient)
LC_URL:          http://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2021/bn210531500/quicklook/glg_lc_medres34_bn210531500.gif
POS_MAP_URL:     http://gcn.gsfc.nasa.gov/notices_f/gbm_gnd_loc_map_644155206.fits
COMMENTS:        Fermi-GBM Ground-calculated Coordinates.  
COMMENTS:        Bright hard burst in the GBM.  
COMMENTS:        This Notice was ground-generated -- not flight-generated.  
COMMENTS:        The LC_URL file will not be created/available until ~15 min after the trigger.  
COMMENTS:        The POS_MAP_URL file will not be created/available until ~1.5 min after the notice.

GCN NOTICE

TITLE:           GCN/FERMI NOTICE
NOTICE_DATE:     Mon 31 May 21 12:01:24 UT
NOTICE_TYPE:     Fermi-GBM Ground Position
RECORD_NUM:      3
TRIGGER_NUM:     644155206
GRB_RA:          135.790d {+09h 03m 10s} (J2000),
                 136.070d {+09h 04m 17s} (current),
                 135.136d {+09h 00m 33s} (1950)
GRB_DEC:          +3.810d {+03d 48' 36"} (J2000),
                  +3.724d {+03d 43' 28"} (current),
                  +4.008d {+04d 00' 30"} (1950)
GRB_ERROR:       1.00 [deg radius, statistical only]
DATA_SIGNIF:     180.60 [sigma]
DATA_INTERVAL:   5.120 [sec]
GRB_DATE:        19365 TJD;   151 DOY;   21/05/31
GRB_TIME:        43201.65 SOD {12:00:01.65} UT
GRB_PHI:         299.00 [deg]
GRB_THETA:        91.00 [deg]
E_RANGE:         44.032 - 279.965 [keV]
LOC_ALGORITHM:   41731 (Gnd S/W Version number)
SUN_POSTN:        68.64d {+04h 34m 35s}  +21.98d {+21d 59' 05"}
SUN_DIST:         67.69 [deg]   Sun_angle= -4.5 [hr] (East of Sun)
MOON_POSTN:      322.45d {+21h 29m 47s}  -19.93d {-19d 56' 04"}
MOON_DIST:       162.64 [deg]
MOON_ILLUM:      69 [%]
GAL_COORDS:      225.60, 30.87 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:      137.09,-12.46 [deg] ecliptic lon,lat of the burst (or transient)
LC_URL:          http://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2021/bn210531500/quicklook/glg_lc_medres34_bn210531500.gif
POS_MAP_URL:     http://gcn.gsfc.nasa.gov/notices_f/gbm_gnd_loc_map_644155206.fits
COMMENTS:        Fermi-GBM Ground-calculated Coordinates.  
COMMENTS:        This is likely a Long GRB.  
COMMENTS:        This Notice was ground-generated -- not flight-generated.  
COMMENTS:        The LC_URL file will not be created/available until ~15 min after the trigger.  
COMMENTS:        The POS_MAP_URL file will not be created/available until ~1.5 min after the notice.

GCN NOTICE

TITLE:           GCN/FERMI NOTICE
NOTICE_DATE:     Mon 31 May 21 12:43:52 UT
NOTICE_TYPE:     Fermi-GBM Final Position
RECORD_NUM:      0
TRIGGER_NUM:     644155206
GRB_RA:          135.790d {+09h 03m 10s} (J2000),
                 136.069d {+09h 04m 17s} (current),
                 135.137d {+09h 00m 33s} (1950)
GRB_DEC:          +3.520d {+03d 31' 12"} (J2000),
                  +3.434d {+03d 26' 04"} (current),
                  +3.718d {+03d 43' 06"} (1950)
GRB_ERROR:       1.00 [deg radius, statistical only]
GRB_DATE:        19365 TJD;   151 DOY;   21/05/31
GRB_TIME:        43201.65 SOD {12:00:01.65} UT
GRB_PHI:         299.12 [deg]
GRB_THETA:        90.67 [deg]
E_RANGE:         50.000 - 300.000 [keV]
LOC_ALGORITHM:   415 (Gnd S/W Version number)
SUN_POSTN:        68.67d {+04h 34m 42s}  +21.99d {+21d 59' 20"}
SUN_DIST:         67.78 [deg]   Sun_angle= -4.5 [hr] (East of Sun)
MOON_POSTN:      322.85d {+21h 31m 24s}  -19.82d {-19d 49' 23"}
MOON_DIST:       162.33 [deg]
MOON_ILLUM:      68 [%]
GAL_COORDS:      225.89, 30.72 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:      137.18,-12.74 [deg] ecliptic lon,lat of the burst (or transient)
LC_URL:          http://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2021/bn210531500/quicklook/glg_lc_medres34_bn210531500.gif
LOC_URL:         http://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2021/bn210531500/quicklook/glg_locplot_all_bn210531500.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.

GCN Circular #30105
B. Biltzinger, F. Kunzweiler, F. Berlato, J. Burgess & J. Greiner (all MPE Garching) report:
The public trigdat data of the Fermi Gamma-ray Burst Monitor (GBM) trigger 644155206 at 12:00:01 on 31 May 2021 were automatically fitted for spectrum and sky location with BALROG (Burgess et al. 2018, MNRAS 476, 1427; Berlato et al. 2019, ApJ 873, 60).
The best-fit position (1 sigma statistical errors) is:
```
RA(2000.0) = 140.9+/-0.5 deg
Decl.(2000.0) = 6.1+/-0.7 deg
```
We estimate an additional systematic error of 2 deg.
Further details are available at: https://grb.mpe.mpg.de/grb/GRB210531500/
The Healpix map can be downloaded from: https://grb.mpe.mpg.de/grb/GRB210531500/healpix
The location parameters are available as JSON at: https://grb.mpe.mpg.de/grb/GRB210531500/json
GCN Circular #30106
A. Ursi (INAF/IAPS), F. Longo (Univ. Trieste and INFN Trieste), M. Tavani (INAF/IAPS, and Univ. Roma Tor Vergata), A. Argan, M. Cardillo, C. Casentini, Y. Evangelista, G. Piano (INAF/IAPS), F. Lucarelli, C. Pittori, F. Verrecchia (SSDC, and INAF/OAR), A. Bulgarelli, A. Di Piano, V. Fioretti, F. Fuschino, N. Parmiggiani (INAF/OAS-Bologna), M. Marisaldi (INAF/OAS-Bologna, and Bergen University), M. Pilia, A. Trois (INAF/OA-Cagliari), I. Donnarumma (ASI), A. Giuliani (INAF/IASF-Mi), report on behalf of the AGILE Team:
The AGILE satellite detected the long GRB 210531A at T0 = 2021-05-31 12:00:02.66 +/- 0.01 s (UTC), reported by Fermi/GBM (Trigger no. 644155206) and BALROG (GCN #30105).
The burst is clearly visible in the AGILE scientific ratemeters of the SuperAGILE (SA; 20-60 keV), MiniCALorimeter (MCAL; 0.4-100 MeV), and AntiCoincidence (AC; 50-200 keV) detectors. The event lasted about 35 s and it released a total number of 9650 counts in the SA detector (above a background rate of 90 Hz), 53900 counts in the MCAL detector (above a background rate of 1400 Hz), and 151900 counts in the AC detector (above a background rate of 3780 Hz). The AGILE ratemeter light curves can be found at http://www.agilescienceapp.it/notices/GRB210531A_AGILE_RM.png .
The event also triggered a partial high time resolution MCAL data acquisition.
Additional analysis of AGILE data is in progress. Automatic MCAL GRB alert Notices can be found at: https://gcn.gsfc.nasa.gov/agile_mcal.html.
GCN Circular #30108
P. Sawant (IUCAA), G. Waratkar (IITB), A. Vibhute (IUCAA), S. Gupta (IUCAA), V. Bhalerao (IITB), D. Bhattacharya (IUCAA), A. R. Rao (IUCAA/TIFR), and S. Vadawale (PRL) report on behalf of the AstroSat CZTI collaboration:
Analysis of AstroSat CZTI data with the CIFT framework (Sharma et al, 2020, arxiv:2011.07067) showed detection of a long GRB 210531A, which was also detected by AGILE/MCAL (GCN #30106) and Fermi (GCN #30105).
The source was clearly detected in the 20-200 keV energy range. The light curve showed multiple peaks of emission with the strongest peak at 2021-05-31 12:00:04.5 UT. The measured peak count rate associated with the burst is 1948 (+77, -87) cts/s above the background in the combined data of four quadrants, with a total of 13005 (+281, -332) cts. The local mean background count rate was 532 (+3.0, -2.9) cts/s. Using cumulative rates, we measure a T90 of 20 (+0.2, -0.2)s.
It was also clearly detected in the CsI anticoincidence (Veto) detector in the 100-500 keV energy range. The light curve showed multiple peaks of emission with the strongest peak at 2021-05-31 12:00:04.9 UT. The measured peak count rate is 2541 (+104, -114) cts/s above the background in the combined Veto data of four quadrants, with a total of 16360 (+452, -552) cts. The local mean background count rate was 1729 (+5, -5) cts/s. We measure a T90 of 19 (+1, -2) s from the cumulative Veto light curve.
CZTI GRB detections are reported regularly on the payload site at http://astrosat.iucaa.in/czti/?q=grb [1]. CZTI is built by a TIFR-led consortium of institutes across India, including VSSC, ISAC, IUCAA, SAC and PRL. The Indian Space Research Organisation funded, managed and facilitated the project.
Links:
------
[1] http://astrosat.iucaa.in/czti/?q=grb
GCN Circular #30110
D. Svinkin, S. Golenetskii, D. Frederiks, A. Ridnaia, A. Lysenko, and T. Cline on behalf of the Konus-Wind team,
K. Hurley, on behalf of the IPN,
A. Goldstein, M. S. Briggs, and C. Wilson-Hodge on behalf of the Fermi GBM team,
A. von Kienlin, X. Zhang, A. Rau, V. Savchenko, E. Bozzo, and C. Ferrigno, on behalf of the INTEGRAL SPI-ACS GRB team, report:
The bright, long-duration GRB 210531A (BALROG localization: Biltzinger et al., GCN Circ. 30105; AGILE detection: Ursi et al., GCN Circ. 30106; AstroSat-CZTI detection: Sawant et al., GCN Circ. 30108) was detected by Fermi (GBM trigger 644155206), Konus-Wind, INTEGRAL (SPI-ACS), AGILE (MCAL, SA, and AC), and AstroSat (CZTI) at about 43201 s UT (12:00:01).
We have triangulated it to a preliminary, 3 sigma error box whose coordinates are:
```
  ---------------------------------------------
   RA(2000), deg                 Dec(2000), deg
  ---------------------------------------------
  Center:
   140.592 (09h 22m 22s)  +8.281 ( +8d 16' 50")
  Corners:
   141.277 (09h 25m 06s) +11.425 (+11d 25' 30")
   142.066 (09h 28m 16s) +10.564 (+10d 33' 51")
   139.800 (09h 19m 12s)  +5.254 ( +5d 15' 16")
   139.052 (09h 16m 12s)  +6.081 ( +6d 04' 51")
  ---------------------------------------------
```
The error box area is 5.9 sq. deg, and its maximum dimension is 6.3 deg (the minimum one is 1 deg). The Sun distance was 70 deg.
This box may be improved.
The IPN localization is consistent with, but reduces the area of, the Fermi final position and BALROG (GCN Circ. 30105) localizations.
A triangulation map is posted at http://www.ioffe.ru/LEA/GRBs/GRB210531_T43198/IPN/
The Konus-Wind time history and spectrum will be given in a forthcoming GCN Circular.

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Jochen Greiner, last update: 01-Jun-2021 [Disclaimer]