Gamma-ray Burst 210605A

(All information courtesy of the instrument teams.)

Previous IAU Circulars

none

Results of Observations

GCN Circular #30127
The Fermi GBM team reports the detection of a likely SHORT GRB
At 05:08:58 UT on 5 Jun 2021, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 210605A (trigger 644562543.389178 / 210605215).
The on-ground calculated location, using the Fermi GBM trigger data, is RA = 21.7, Dec = -41.5 (J2000 degrees, equivalent to J2000 01h 26m, -41d 30'), with a statistical uncertainty of 2.0 degrees.
The angle from the Fermi LAT boresight is 128.0 degrees.
The skymap can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2021/bn210605215/quicklook/glg_skymap_all_bn210605215.png
The HEALPix FITS file, including the estimated localization systematic, can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2021/bn210605215/quicklook/glg_healpix_all_bn210605215.fit
The GBM light curve can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2021/bn210605215/quicklook/glg_lc_medres34_bn210605215.gif
GCN Circular #30128
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-OAFA robotic telescope (Global MASTER-Net: http://observ.pereplet.ru, Lipunov et al., 2010, Advances in Astronomy, vol. 2010, 30L) located in Argentina (OAFA observatory of San Juan National University) started inspect of the Fermi GRB 210605A ( Fermi GBM team, GCN 30127) errorbox 571 sec after notice time and 600 sec after trigger time at 2021-06-05 05:18:58 UT, with upper limit up to 17.2 mag. The observations began at zenith distance = 86 deg. The sun altitude is -76.8 deg.
The galactic latitude b = -74 deg., longitude l = 277 deg.
Real time updated cover map and OT discovered available here: https://master.sai.msu.ru/site/master2/observ.php?id=1628580
We obtain a following upper limits.
```
Tmid-T0  |      Date Time      |          Site       |             Coord (J2000)          |Filt.| Expt. | Limit| Comment
_________|_____________________|_____________________|____________________________________|_____|_______|_______|________

     661 | 2021-06-05 05:18:58 |         MASTER-OAFA | (01h 24m 45.07s , -42d 19m 00.9s) |   C |   120 | 17.0 |        
    1023 | 2021-06-05 05:24:31 |         MASTER-OAFA | (01h 24m 38.95s , -42d 20m 23.9s) |   C |   180 | 17.3 |        
```
Filter C is a clear (unfiltred) band.
The observation and reduction will continue. The message may be cited.
GCN Circular #30143
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,
and
S. Barthelmy, J. Cummings, H. Krimm, D. Palmer, and A. Tohuvavohu on behalf of the Swift-BAT team, report:
The bright, short-duration GRB 210605A (Fermi-GBM detection: The Fermi GBM team, GCN Circ. 30127) was detected by Fermi (GBM trigger 644562543), Konus-Wind, INTEGRAL (SPI-ACS), and Swift (BAT) at about 18538 s UT (05:08:58). The burst was outside the coded field of view of the BAT.
We have triangulated it to a preliminary, 3 sigma error box whose coordinates are:
```
  ---------------------------------------------
   RA(2000), deg                 Dec(2000), deg
  ---------------------------------------------
  Center:
    21.609 (01h 26m 26s) -45.089 (-45d 05' 19")
  Corners:
    24.666 (01h 38m 40s) -49.385 (-49d 23' 08")
    19.468 (01h 17m 52s) -41.356 (-41d 21' 22")
    19.355 (01h 17m 25s) -41.513 (-41d 30' 47")
    24.633 (01h 38m 32s) -49.663 (-49d 39' 47")
  ---------------------------------------------
```
The error box area is 1.2 sq. deg, and its maximum dimension is 9.0 deg (the minimum one is 8.4 arcmin). The Sun distance was 81 deg.
This box may be improved.
The IPN localization is consistent with, but reduces the area of, the Fermi RoboBA and BALROG localizations.
A triangulation map is posted at http://www.ioffe.ru/LEA/GRBs/GRB210605_T18539/IPN
The Konus-Wind time history and spectrum will be given in a forthcoming GCN Circular.
GCN Circular #30144
D. Frederiks, S. Golenetskii, A.Lysenko, A. Ridnaia, D. Svinkin, A. Tsvetkova, M. Ulanov, and T. Cline, on behalf of the Konus-Wind team, report:
The short/hard GRB 210605A (Fermi GBM Final Real-time Localization: Fermi GBM team, GCN 30127; IPN localization: Svinkin et al., GCN 30143) triggered Konus-Wind (KW) at T0=18539.058 s UT (05:08:59.058).
The burst light curve shows a single, hard-spectrum pulse, which starts at ~T0-0.038 s, peaks at ~T0-0.032 s, and has the total duration of ~0.35 s (T100, 20-1500 keV). The emission in this pulse is seen up to ~10 MeV. In the soft 20-100 keV KW band, we note a hint for an extended emission up to ~T0+25 s.
The Konus-Wind light curve of this GRB is available at http://www.ioffe.ru/LEA/GRBs/GRB210605_T18539/
As observed by Konus-Wind, the burst had a fluence of (4.2 ą 1.1)x10^-6 erg/cm^2 and a 16-ms peak energy flux, measured from T0-0.032, of (5.7 ą 1.4)x10^-5 erg/cm^2/s (both in the 20 keV - 10 MeV energy range).
The time-averaged spectrum of the burst (measured from T0 to T0+0.256 s) is best fit in the 20 keV - 15 MeV range by a power law with exponential cutoff (CPL) model: dN/dE ~ (E^alpha)*exp(-E*(2+alpha)/Ep) with alpha = -0.75(-0.18,+0.21) and Ep = 2079(-614,+986) keV (chi2 = 23/44 dof). Fitting this spectrum by a Band function yields the same alpha and Ep, and an upper limit on the high energy photon index: beta < -2.1 (chi2 = 23/43 dof).
All the quoted errors are estimated at the 90% confidence level. All the presented results are preliminary.
GCN Circular #30158
S. Sugita, A. Yoshida, T. Sakamoto, V. Pal'shin (AGU), Y. Kawakubo (LSU), K. Yamaoka (Nagoya U), S. Nakahira (RIKEN), Y. Asaoka (ICRR), S. Torii, Y. Akaike, K. Kobayashi (Waseda U), Y. Shimizu, T. Tamura (Kanagawa U), N. Cannady (GSFC/UMBC), M. L. Cherry (LSU), S. Ricciarini (U of Florence), P. S. Marrocchesi (U of Siena), and the CALET collaboration:
The short GRB 210605A (Fermi GBM Final Real-time Localization: Fermi GBM team, GCN Circ. 30127; IPN localization: Svinkin et al., GCN Circ. 30143; Konus-Wind detection: Frederiks et al., GCN Circ. 30144; https://gcn.gsfc.nasa.gov/other/210605A.gcn3) triggered the CALET Gamma-ray Burst Monitor (CGBM) at 05:08:58.441 UTC on 5 June 2021. The burst signal was seen by all CGBM detectors. No real-time CGBM GCN notice was distributed about this trigger because the real-time communication from the ISS was off (loss of signal).
The burst light curve shows a multi-peaked pulse which starts at T-0.096 sec, peaks at -0.032 sec and ends at T+0.240 sec. The T90 and T50 durations measured by the SGM data are 0.304 +- 0.051 sec and 0.144 +- 0.045 sec (40-1000 keV), respectively.
The ground processed light curve is available at
http://cgbm.calet.jp/cgbm_trigger/ground/1306904781/
The CALET data used in this analysis are provided by the Waseda CALET Operation Center located at the Waseda University.

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Jochen Greiner, last update: 09-Jun-2021 [Disclaimer]