GRB 251009A
GCN Circular 42190
Subject
GRB 251009A: GECAM-B detection of a short burst
Date
2025-10-10T16:22:21Z (13 days ago)
From
Chenwei Wang at IHEP <cwwang@ihep.ac.cn>
Via
Web form
Chen-Wei Wang, Shao-Lin Xiong (IHEP) report on behalf of GECAM team:
GECAM-B was triggered on-ground by the short burst GRB 251009A at 2025-10-09T15:58:56.300 UTC (denoted as T0), which is also detected by Fermi/GBM (Fermi GBM team, GCN#42179), SVOM/GRM (Wang et al., GCN#42185) and Insight-HXMT (Wang et al., GCN#42189). According to the GECAM-B light curves in about 40-6000 keV, this burst mainly consists of a single pulse with a duration (T90) of 0.14 +0.08/-0.08 s.
The GECAM-B light curve can be found here:
https://www.bursthub.cn//admin/static/gecambgrb251009A.png
Using the automatic on-ground localization pipeline, GECAM-B localized this burst to the following position (J2000):
Ra: 103.2 deg
Dec: 34.2 deg
Err: 21.4 deg (1-sigma, statistical only)
Gravitational wave high-energy Electromagnetic Counterpart All-sky Monitor (GECAM) mission originally consists of two micro-satellites (GECAM-A and GECAM-B) launched in Dec. 2020. As the third member of GECAM constellation, GECAM-C was launched onboard SATech-01 experimental satellite in July 2022. GECAM mission is funded by the Chinese Academy of Sciences (CAS).
GCN Circular 42189
Subject
GRB 251009A: Insight-HXMT detection of a short burst
Date
2025-10-10T16:17:00Z (13 days ago)
From
Chenwei Wang at IHEP <cwwang@ihep.ac.cn>
Via
Web form
Chen-Wei Wang, Cheng-Kui Li, Shao-Lin Xiong, and Chao Zheng report on behalf of the Insight-HXMT team:
At 2025-10-09T15:58:56.350 (T0), Insight-HXMT/HE detected the burst GRB 251009A, which is also detected by Fermi/GBM (Fermi GBM team, GCN#42179) and SVOM/GRM (Wang et al., GCN#42185).
The Insight-HXMT/HE light curve mainly consists of a single pulse with a T90 of 0.65 +0.31/-0.28 s. The total counts from this burst is 998 counts.
The HXMT/HE light curve can be found here:
https://www.bursthub.cn//admin/static/hxmtgrb251009A.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 42185
Subject
GRB 251009A: SVOM/GRM observation of short GRB with possible tail emission
Date
2025-10-10T13:32:03Z (13 days ago)
From
Chenwei Wang at IHEP <cwwang@ihep.ac.cn>
Via
Web form
SVOM/GRM team: Chen-Wei Wang, Shu-Xu Yi, Shi-Jie Zheng, Yue Huang, Shao-Lin Xiong, Shuang-Nan Zhang (IHEP)
SVOM/ECLAIRs team: Frédéric Piron (LUPM)
Report on behalf of the SVOM team:
SVOM/GRM was triggered in-flight by a short burst GRB 251009A (SVOM trigger reference: sb25100902) at 2025-10-09T15:58:56.500 UTC (T0), which is also detected by Fermi/GBM (Fermi GBM team, GCN#42179).
With the event-by-event data downloaded through the X-band ground station, the GRM light curve shows that this burst consists of a narrow spike followed by a weak tail emission with a T90 of 0.32 +0.05/-0.11 s in the 15-5000 keV band, which is somewhat similar to extragalactic magnetar giant flare.
The SVOM/GRM light curve can be found here:
https://www.bursthub.cn//admin/static/svgrb251009A.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 42179
Subject
GRB 251009A: Fermi GBM Final Localization
Date
2025-10-10T00:04:26Z (13 days ago)
From
Matt Godwin <msg0028@uah.edu>
Via
Web form
The Fermi GBM team reports the detection of a likely SHORT GRB
"At 15:58:56.61 UT on 09 October 2025, the Fermi Gamma-ray Burst Monitor (GBM)
triggered and located GRB 251009A (trigger 781718341/251009666).
The on-ground calculated location, using the Fermi GBM trigger data,
is RA = 72.05, Dec = -25.84 (J2000 degrees, equivalent to J2000 4h 48m, -25d 50'),
with a statistical uncertainty of 25.22 degrees.
The angle from the Fermi LAT boresight is 86 degrees.
The skymap can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn251009666/quicklook/glg_skymap_all_bn251009666.png
The HEALPix FITS file, including the estimated localization systematic, can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn251009666/quicklook/glg_healpix_all_bn251009666.fit
The GBM light curve can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn251009666/quicklook/glg_lc_medres34_bn251009666.gif"