GRB 250909B
GCN Circular 41797
Subject
GRB 250909B: Insight-HXMT detection
Date
2025-09-11T15:16:08Z (2 days ago)
From
Chenwei Wang at IHEP <cwwang@ihep.ac.cn>
Via
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Chen-Wei Wang, Shao-Lin Xiong, and Chao Zheng report on behalf of the Insight-HXMT team:
At 2025-09-09T17:49:10.200 (T0), Insight-HXMT/HE detected the burst GRB 250909B, which is also detected by AstroSat (M. Tembhurnikar et al., GCN#41775), SVOM/GRM (Wang et al., GCN#41796) and Konus-Wind.
The Insight-HXMT/HE light curve mainly consists of multi-pulses with a T90 of 12.9 +1.2/-1.7 s. The 1s peak rate, measured from T0+0.250 s, is 5422 cnts/sec. The total counts from this burst is 23044 counts.
The HXMT/HE light curve can be found here:
https://www.bursthub.cn//admin/static/hxmtgrb250909B.png
All measurements above are made with the CsI detectors operating in the regular mode with the energy range of about 60-900 keV (deposited energy). Only gamma-rays with energy greater than about 200 keV can penetrate the spacecraft and leave signals in the CsI detectors installed inside of the telescope.
Insight-HXMT is the first Chinese space X-ray telescope, which was funded jointly by the China National Space Administration (CNSA) and the Chinese Academy of Sciences (CAS). More information about it could be found at: http://www.hxmt.org.
GCN Circular 41796
Subject
GRB 250909B: SVOM/GRM observation
Date
2025-09-11T15:07:29Z (2 days ago)
From
Chenwei Wang at IHEP <cwwang@ihep.ac.cn>
Via
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SVOM/GRM team: Chen-Wei Wang, Shi-Jie Zheng, Yue Huang, Shao-Lin Xiong, Shuang-Nan Zhang (IHEP)
SVOM/ECLAIRs team: Jean-Luc Atteia (IRAP)
Report on behalf of the SVOM team:
SVOM/GRM was triggered on-ground by GRB 250909B at 2025-09-09T17:49:10.200 UTC (T0), which is also detected by AstroSat (M. Tembhurnikar et al., GCN#41775) and Konus-Wind.
With the event-by-event data downloaded through the X-band ground station, the GRM light curve shows that this burst consists of a multi-pulses with a T90 of 10.5 +3.5/-1.5 s in the 15-5000 keV band.
ECLAIRs was not collecting data at the time of this burst.
The SVOM/GRM light curve can be found here:
https://www.bursthub.cn//admin/static/svgrb250909B.png
The Space Variable Objects Monitor (SVOM) is a China-France joint mission led by the Chinese National Space Administration (CNSA, China), National Center for Space Studies (CNES, France) and the Chinese Academy of Sciences (CAS, China), which is dedicated to observing gamma-ray bursts and other transient phenomena in the energetic universe. GRM is developed by the Institute of High Energy Physics (IHEP) of CAS.
The SVOM point of contact for this burst is: Chen-Wei Wang (IHEP)(cwwang@ihep.ac.cn)
GCN Circular 41775
Subject
GRB 250909B: AstroSat CZTI detection of a long burst
Date
2025-09-10T08:58:31Z (3 days ago)
From
Anuraag Arya at IIT Bombay <aryaanuraag910@gmail.com>
Via
Web form
M. Tembhurnikar (IUCAA), Harsha K. H. (IUCAA), S. Salunke (IUCAA), A. Arya (IITB), A. Goyal (IITB), G. Waratkar (Caltech/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 and bright GRB 250909B which was also detected by Konus-Wind (IPN notices).
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 2025-09-09 17:49:11.50 UTC. The measured peak count rate associated with the burst is 701 (+50, -52) counts/s above the background in the combined data of all quadrants, with a total of 3971 (+218, -234) counts. The local mean background count rate was 282 (+4, -4) counts/s. Using cumulative rates, we measure a T90 of 10.1 (+0.9, -0.4) 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 2025-09-09 17:49:10.32 UTC. The measured peak count rate associated with the burst is 1432 (+86, -93) counts/s above the background in the combined data of all quadrants, with a total of 5850 (+337, -369) counts. The local mean background count rate was 1344 (+7, -8) counts/s. We measure a T90 of 9.4 (+0.5, -0.3) 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