GCN Circular 35798
Subject
GRB 240225B: AstroSat CZTI detection
Date
2024-02-26T09:04:31Z (9 months ago)
From
Gaurav Waratkar at IIT Bombay <gauravwaratkar24@gmail.com>
Via
Web form
J. Joshi (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 a long-duration GRB 240225B which was also detected by MAXI/GSC (M. Nakajima et al., GCN Circ. 35796). Inspection of INTEGRAL/SPI-ACS data also showed the detection of the burst. We note that the INTEGRAL/SPI-ACS detection time is consistent with our time which is about 3 min offset from the time reported in the MAXI/GSC detection (GCN 35796).
The source was clearly detected in the CZT detectors in the 20-200 keV energy range. The light curve showed multiple peaks of emission with the strongest peak at 2024-02-25 20:12:08.50 UTC. The measured peak count rate associated with the burst is 185 (+40, -22) counts/s above the background in the combined data of all quadrants, with a total of 1617 (+331, -224) counts. The local mean background count rate was 346 (+1, -5) counts/s. Using cumulative rates, we measure a T90 of 19 (+10, -5) s.
The source 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 2024-02-25 20:12:01.80 UTC. The measured peak count rate associated with the burst is 570 (+72, -69) counts/s above the background in the combined data of all quadrants, with a total of 5119 (+490, -666) counts. The local mean background count rate was 1539 (+7, -6) counts/s. We measure a T90 of 23 (+3, -4) 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