GRB 210812A
GCN Circular 30633
Subject
GRB 210812A: Fermi GBM Final Real-time Localization
Date
2021-08-12T18:12:27Z (4 years ago)
From
Fermi GBM Team at MSFC/Fermi-GBM <do_not_reply@GIOC.nsstc.nasa.gov>
The Fermi GBM team reports the detection of a likely LONG GRB
At 16:47:01 UT on 12 Aug 2021, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 210812A (trigger 650479626.014242 / 210812699).
The on-ground calculated location, using the Fermi GBM trigger data, is RA = 39.7, Dec = 69.6 (J2000 degrees, equivalent to J2000 02h 38m, 69d 35'), with a statistical uncertainty of 1.1 degrees.
The angle from the Fermi LAT boresight is 149.0 degrees.
The skymap can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2021/bn210812699/quicklook/glg_skymap_all_bn210812699.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/bn210812699/quicklook/glg_healpix_all_bn210812699.fit
The GBM light curve can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2021/bn210812699/quicklook/glg_lc_medres34_bn210812699.gif
GCN Circular 30634
Subject
GRB 210812A: BALROG localization (Fermi Trigger 650479626 / GRB 210812699)
Date
2021-08-12T18:14:44Z (4 years ago)
From
Jochen Greiner at MPE,Garching <jcg@mpe.mpg.de>
F. Kunzweiler, B. Biltzinger, F. Berlato, J. Burgess & J. Greiner (all MPE Garching) report:
The public trigdat data of the Fermi Gamma-ray Burst Monitor (GBM) trigger
650479626 at 16:47:01 on 12 Aug. 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) = 62.1+/-4.2 deg
Decl.(2000.0) = 71.7+/-0.8 deg
We estimate an additional systematic error of 1 deg.
Further details are available at:
https://grb.mpe.mpg.de/grb/GRB210812699/
The Healpix map can be downloaded from:
https://grb.mpe.mpg.de/grb/GRB210812699/healpix
The location parameters are available as JSON at:
https://grb.mpe.mpg.de/grb/GRB210812699/json
GCN Circular 30636
Subject
Fermi GRB 210812A: Global MASTER-Net observations report
Date
2021-08-12T19:15:10Z (4 years ago)
From
Vladimir Lipunov at Moscow State U/Krylov Obs <lipunov@xray.sai.msu.ru>
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-Kislovodsk robotic telescope (Global MASTER-Net: http://observ.pereplet.ru, Lipunov et al., 2010, Advances in Astronomy, vol. 2010, 30L) located in Russia (Lomonosov MSU, Kislovodsk Solar Station of Pulkovo observatory) started inspect of the Fermi GRB 210812A ( Fermi GBM team, GCN 30633) errorbox 3906 sec after notice time and 3934 sec after trigger time at 2021-08-12 17:52:35 UT, with upper limit up to 18.0 mag. Observations started at twilight. The observations began at zenith distance = 63 deg. The sun altitude is -15.8 deg.
MASTER-Tavrida robotic telescope located in Russia (Lomonosov MSU, SAI Crimea astronomical station) started inspect of the Fermi GRB 210812A errorbox 3968 sec after notice time and 3996 sec after trigger time at 2021-08-12 17:53:37 UT, with upper limit up to 16.9 mag. Observations started at twilight. The observations began at zenith distance = 63 deg. The sun altitude is -10.7 deg.
The galactic latitude b = 9 deg., longitude l = 132 deg.
Real time updated cover map and OT discovered available here:
https://master.sai.msu.ru/site/master2/observ.php?id=1688546
We obtain a following upper limits.
Tmid-T0 | Date Time | Site | Coord (J2000) |Filt.| Expt. | Limit| Comment
_________|_____________________|_____________________|____________________________________|_____|_______|_______|________
3965 | 2021-08-12 17:52:35 | MASTER-Kislovodsk | (02h 39m 39.55s , +67d 43m 23.0s) | C | 60 | 17.1 |
3965 | 2021-08-12 17:52:35 | MASTER-Kislovodsk | (02h 49m 52.81s , +67d 17m 41.9s) | C | 60 | 18.0 |
4027 | 2021-08-12 17:53:37 | MASTER-Tavrida | (03h 00m 15.85s , +69d 33m 20.0s) | C | 60 | 14.1 |
4045 | 2021-08-12 17:53:56 | MASTER-Kislovodsk | (02h 23m 17.82s , +71d 30m 31.7s) | C | 60 | 16.6 |
4045 | 2021-08-12 17:53:56 | MASTER-Kislovodsk | (02h 35m 30.22s , +71d 04m 38.3s) | C | 60 | 17.6 |
4250 | 2021-08-12 17:57:21 | MASTER-Tavrida | (02h 16m 36.54s , +69d 38m 13.4s) | C | 60 | 14.2 |
4866 | 2021-08-12 18:07:37 | MASTER-Tavrida | (02h 37m 13.34s , +69d 37m 48.2s) | C | 60 | 16.1 |
4927 | 2021-08-12 18:08:37 | MASTER-Kislovodsk | (02h 39m 44.39s , +67d 43m 18.2s) | C | 60 | 17.1 |
4927 | 2021-08-12 18:08:37 | MASTER-Kislovodsk | (02h 50m 00.20s , +67d 17m 36.6s) | C | 60 | 18.0 |
5175 | 2021-08-12 18:12:46 | MASTER-Tavrida | (02h 16m 39.00s , +69d 38m 21.4s) | C | 60 | 13.4 |
6543 | 2021-08-12 18:35:34 | MASTER-Tavrida | (02h 37m 17.68s , +69d 39m 33.3s) | C | 60 | 13.5 |
6623 | 2021-08-12 18:36:53 | MASTER-Tavrida | (03h 00m 13.68s , +69d 36m 38.3s) | C | 60 | 16.2 |
6781 | 2021-08-12 18:39:31 | MASTER-Tavrida | (02h 16m 35.36s , +69d 40m 00.6s) | C | 60 | 16.9 |
Filter C is a clear (unfiltred) band.
The observation and reduction will continue.
The message may be cited.
GCN Circular 30645
Subject
GRB 210812A is consistent with being a lensed GRB
Date
2021-08-13T20:34:35Z (4 years ago)
From
Peter Veres at UAH <veresp@gmail.com>
P. Veres (UAH) reports on behalf of the Fermi-GBM team:
"
Fermi GBM triggered on GRB 210812A at 16:47:01 UT on 12 Aug 2021 (trigger
650479626 / 210812699). Location information can be found in the Fermi GBM
team GCN 30633.
The lightcurve of GRB 210812A consists of two pulses, separated by about 33
s. The two pulses have similar shapes, the first pulse being approximately
5 times brighter.
The best fitting spectral shapes are consistent between the pulses. The
hardness ratio as a function of time also shows a consistent evolution.
These observations suggest that the two pulses are gravitationally lensed
manifestations of a single pulse.
Assuming a point mass lens model (e.g. Mao 1992, ApJL, 839, 41), the mass
of the lens is about 10^6 Msun.
GRB 210812A was also detected by INTEGRAL/SPI-ACS.
This analysis is preliminary, further analysis is ongoing. We encourage
follow-up observations.
"
GCN Circular 30842
Subject
GRB 210812A is not a compelling example of a lensed GRB
Date
2021-09-15T23:50:45Z (4 years ago)
From
Robert Nemiroff at Michigan Tech. <nemiroff@mtu.edu>
Oindabi Mukherjee (Michigan Tech U.) & Robert J. Nemiroff (Michigan Tech
U.) report:
A preliminary light curve and hardness comparison between the two main
pulses of GRB 210812A has been done using Fermi GBM data to test for
gravitational lensing (as suggested by Veres et al. 2021, GCN 30645).
First, an amplitude-equalized light curve comparison of combined energy
bands 3 through 7 in detectors 2, 7, 8, 9, 10, 11, and 12 shows a chi^2
difference of 2.796 sigma, so that there is only a 0.52% chance of the two
pulses being randomly drawn from the same pulse.
Additionally, a hardness analysis shows that in energy channels 4 and 5,
the hardness difference between the two pulses differs at the 2.24 sigma
level, with the second pulse being softer.
These preliminary results suggest that although the case of GRB 210812A is
interesting, it is not a compelling example of a GRB gravitational lens.
A more thorough analysis is ongoing.