GCN Circular 33415
Subject
GRB 230307A: AstroSat CZTI detection
Date
2023-03-08T06:17:52Z (a year ago)
From
Gaurav Waratkar at IIT,Bombay <gauravwaratkar@iitb.ac.in>
P K. Navaneeth (IUCAA), G. Waratkar (IITB), A. Vibhute (IUCAA), V.
Bhalerao (IITB), D. Bhattacharya (Ashoka University/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.,
2021, JApA, 42, 73) showed the detection of the extremely bright long
GRB 230307A which was also detected by Fermi-GBM (Fermi GBM team, GCN
33405), GECAM (Xiong et al., GCN 33406), Solar Orbiter STIX (Xiao et
al., GCN 33410), AGILE/MCAL (Casentini et al., GCN 33412) and IPN
(Kozyrev et al., GCN 33413).
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
2023-03-07 15:44:10.0 UTC. The measured peak count rate associated with
the burst is 4041 (+33, -37) counts/s above the background in the
combined data of all quadrants, with a total of 90900 (+758, -850)
counts. The local mean background count rate was 453 (+1, -1) counts/s.
Using cumulative rates, we measure a T90 of 33 (+1, -1) s. In the
preliminary analysis, we find 5484 Compton events associated with this
event.
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 2023-03-07 15:44:15.17 UTC. The
measured peak count rate is 276156 (+268, -300) counts/s above the
background in the combined Veto data of all quadrants, with a total of
5571313 (+4953, -6044) counts. The local mean background count rate was
14750 (+7, -6) counts/s. We measure a T90 of 40 (+0.2, -0.2) s from the
cumulative Veto light curve.
CZTI is built by a TIFR-led consortium of institutes across India,
including VSSC, URSC, IUCAA, SAC, and PRL. The Indian Space Research
Organisation funded, managed, and facilitated the project. CZTI GRB
detections are reported regularly on the payload site at:
http://astrosat.iucaa.in/czti/?q=grb