GRB 210424B
GCN Circular 29943
Subject
GRB 210424B: AstroSat CZTI detection
Date
2021-05-05T04:55:36Z (5 years ago)
From
Varun Bhalerao at Indian Inst of Tech <varunb@iitb.ac.in>
P. Sawant (IUCAA), G. Waratkar (IITB), A. Vibhute (IUCAA), S. Gupta (IITB), 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 a strong detection of a short GRB 210424B, which was also detected by IPN (GCN #29909) and Konus-Wind (GCN #29911).
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 2021-04-24 08:01:55.150 UT. The measured peak count rate associated with the burst is 2260 (+322, -98) cts/s above the background using 0.1s bins in the combined data of four quadrants, with a total of 1380 (+96, -118) cts. The local mean background count rate was 530 (+9, -11) cts/s. Using cumulative rates, we measure a T90 of 1.24 (+0.13, -0.40)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 2021-04-24 08:01:54.535 UT. The measured peak count rate is 1244 (+89, -98) cts/s above the background in the combined Veto data of four quadrants, with a total of 1822 (+351, -377) cts. The local mean background count rate was 1895 (+5, -6) cts/s. We measure a T90 of 7 (+4, -5) s from the cumulative Veto light curve, though this is most likely an overestimate due to the intrinsic 1s binning of veto data.
CZTI GRB detections are reported regularly on the payload site at http://astrosat.iucaa.in/czti/?q=grb. 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.
GCN Circular 29920
Subject
GRB 210424B: MITSuME Akeno optical upper limits
Date
2021-05-01T12:26:07Z (5 years ago)
From
Katsuhiro L. Murata at Nagoya U <murata@u.phys.nagoya-u.ac.jp>
R. Hosokawa, Y. Imai, K. L. Murata, M. Niwano, N. Ito, H. Takamatsu, S.
Sato, M. Takaku, R. Noto, R. Yamaguchi, Y. Yatsu, and N. Kawai (TokyoTech)
report on behalf of the MITSuME collaboration:
We observed the field of GRB 210424B (IPN triangulation: Hurley et al. GCN
Circular #29909, Konus-Wind detection: Svinkin et al. GCN Circular #29911,
CALET Gamma-Ray Burst Monitor detection: Yoshida et al. GCN Circular
#29913) 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 2021-04-29
16:49:39 UT (5.35 days after the triggers). We stacked the images with good
conditions. We did not detect any uncatalogued sources within the IPN
triangulation error box (Hurley et al. GCN Circular #29909) in all three
bands. We obtained the 5-sigma limits of the stacked images as follows.
T0+[day] MID-UT T-EXP[sec] 5-sigma limits
------------------------------------------------------------------------------------------------
5.35 2021-04-29 17:05 1020 g'>18.5, Rc>18.4, Ic>17.8
------------------------------------------------------------------------------------------------
T0+ : Elapsed time after the burst
T-EXP: Total Exposure time
We used the 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 29913
Subject
GRB 210424B: CALET Gamma-Ray Burst Monitor detection
Date
2021-04-30T12:32:09Z (5 years ago)
From
Valentin Pal'shin at AGU <val@phys.aoyama.ac.jp>
A. Yoshida, T. Sakamoto, V. Pal'shin, S. Sugita (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 210424B (IPN triangulation: Hurley, GCN Circ. 29909;
Konus-Wind detection: Svinkin et al., GCN Circ. 29911) triggered the CALET
Gamma-ray Burst Monitor (CGBM) at 08:01:55.115 UTC on 24 April 2021
(http://cgbm.calet.jp/cgbm_trigger/flight/1303286436/). The burst signal
was seen mainly by the SGM detector.
The burst light curve shows a multi-peaked structure which starts
at T+0.40 sec, peaks at 1.28 sec and ends at T+1.42 sec.
The T90 and T50 durations measured by the SGM data are 1.04 +- 0.16 sec
and 0.56 +- 0.15 sec (40-1000 keV), respectively.
The ground processed light curve is available at
http://cgbm.calet.jp/cgbm_trigger/ground/1303286436/
The CALET data used in this analysis are provided by
the Waseda CALET Operation Center located at the Waseda University.
GCN Circular 29911
Subject
Konus-Wind detection of GRB 210424B
Date
2021-04-29T12:54:06Z (5 years ago)
From
Dmitry Svinkin at Ioffe Institute <svinkin@mail.ioffe.ru>
D. Svinkin, S. Golenetskii, D. Frederiks, M. Ulanov,
A. Tsvetkova, A. Lysenko, A. Ridnaia, and T. Cline
on behalf of the Konus-Wind team, report:
The short-duration, very bright GRB 210424B
(IPN triangulation: Hurley et al., GCN Circ. 29909)
triggered Konus-Wind at T0=28916.081 s UT (08:01:56.081).
The burst light curve shows a multi-peaked structure
which starts at ~T0-0.1 s and has a total duration of ~1.6 s.
The emission is seen up to ~10 MeV.
The Konus-Wind light curve of this GRB is available at
http://www.ioffe.ru/LEA/GRBs/GRB210424_T28916/
As observed by Konus-Wind, the burst
had a fluence of 8.91(-0.83,+0.93)x10^-6 erg/cm2,
and a 16-ms peak flux, measured from T0+0.800 s,
of 3.13(-0.52,+0.54)x10^-5 erg/cm2/s
(both in the 20 keV - 10 MeV energy range).
The time-averaged spectrum of the burst
(measured from T0 to T0+1.024 s)
is best fit in the 20 keV - 15 MeV range
by the GRB (Band) model with the following parameters:
the low-energy photon index alpha = -0.39(-0.17,+0.20),
the high energy photon index beta = -2.76(-0.45,+0.25),
the peak energy Ep = 198(-21,+23) keV
(chi2 = 62/55 dof).
All the quoted errors are at the 90% confidence level.
All the quoted values are preliminary.
GCN Circular 29909
Subject
IPN triangulation of GRB 210424B (short/hard)
Date
2021-04-28T16:20:26Z (5 years ago)
From
Dmitry Svinkin at Ioffe Institute <svinkin@mail.ioffe.ru>
K. Hurley, on behalf of the IPN,
I. G. Mitrofanov, D. V. Golovin, A. S. Kozyrev, M. L. Litvak,
and A. B. Sanin, on behalf of the HEND-Odyssey GRB team,
D. Svinkin, S. Golenetskii, D. Frederiks, A. Ridnaia,
A. Lysenko, and T. Cline on behalf of the Konus-Wind 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
W. Boynton, C. Fellows, K. Harshman, H. Enos, and R. Starr,
on behalf of the GRS-Odyssey GRB team, report:
The short-duration, very bright GRB 210424B
was detected by Konus-Wind, INTEGRAL (SPI-ACS), CALET (GBM),
and Mars-Odyssey (HEND) at about 28916 s UT (08:01:56).
We have triangulated it to a preliminary, 3 sigma error box
whose coordinates are:
---------------------------------------------
RA(2000), deg Dec(2000), deg
---------------------------------------------
Center:
284.716 (18h 58m 52s) +16.172 (+16d 10' 20")
Corners:
284.892 (18h 59m 34s) +16.078 (+16d 04' 42")
284.882 (18h 59m 32s) +16.153 (+16d 09' 09")
284.540 (18h 58m 10s) +16.265 (+16d 15' 55")
284.550 (18h 58m 12s) +16.191 (+16d 11' 28")
---------------------------------------------
The error box area is 84 sq. arcmin, and its maximum
dimension is 23 arcmin (the minimum one is 4 arcmin).
The Sun distance was 102 deg.
This box may be improved.
A triangulation map is posted at
http://www.ioffe.ru/LEA/GRBs/GRB210424_T28916/IPN
The time history and spectrum will be given in forthcoming
GCN Circulars.