GRB 260308A
GCN Circular 43983
Subject
GRB 260308A: Insight-HXMT/HE detection
Date
2026-03-13T11:02:02Z (8 days ago)
From
Xinghao Luo at IHEP <2952704891@qq.com>
Via
Web form
Xing-Hao Luo, Chen-Wei Wang, Chao Zheng, Hao-Xuan Guo, Xiao-Bo Li and Shao-Lin Xiong (IHEP) report on behalf of the Insight-HXMT team:
At 2026-03-08T20:05:53.000 (T0), Insight-HXMT/HE detected the burst GRB 260308A, which is also detected by Fermi/GBM (Fermi GBM Team, GCN #43949) and SVOM/GRM (Xing-Hao Luo et.al., GCN#43960).
The Insight-HXMT/HE light curve mainly consists of a single pulse with a T90 of 0.3 +0.2/-0.1 s. The 1s peak rate, measured from T0-0.65 s, is 625 cnts/sec. Insight-HXMT/HE detected a total of 512 counts form this burst.
The HXMT/HE light curve can be found here:
https://www.bursthub.cn//admin/static/hxmtgrb260308A.png
All measurements above are made with the CsI detectors of Insight-HXMT/HE 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://hxmten.ihep.ac.cn/
GCN Circular 43960
Subject
GRB 260308A: SVOM/GRM observation of a short GRB
Date
2026-03-11T14:33:12Z (10 days ago)
From
Xinghao Luo at IHEP <2952704891@qq.com>
Via
Web form
SVOM/GRM team: Xing-Hao Luo, Chen-Wei Wang, Zheng-Hang Yu, Yue Huang, Shi-Jie Zheng, Shao-Lin Xiong, Shuang-Nan Zhang (IHEP)
SVOM/ECLAIRs team: Olivier GODET (IRAP)
Report on behalf of the SVOM team:
SVOM/GRM was triggered in-flight by GRB 260308A (SVOM trigger reference: sb26030801) at 2026-03-08T20:05:53.100 UTC (T0), which is also detected by Fermi/GBM (Fermi GBM team, GCN #43949).
With the event-by-event data downloaded through the X-band ground station, the GRM light curve shows that this burst consists of multiple pulses with a T90 of 1.50 +/-0.4 s in the 15-5000 keV band.
The SVOM/GRM light curve can be found here:
https://www.bursthub.cn//admin/static/svgrb260308A.png
In addition, the position of this burst, as determined by Fermi/GBM (RA=250.2 , DEC=-32.6, Fermi GBM team, GCN #43949), is located at about 62 degrees form the SVOM optical axis, which is outside the ECLAIRs field of view.
With this localization, the time-averaged spectrum from T0-0.8 to T0+0.4 s is best fitted by a power law function with an exponential high-energy cutoff. The power law index is -0.86 +0.18/-0.16 and the cutoff energy, parameterized as Epeak, is 643 +346/-180 keV.
The localization of GRB 260308A in the 'Amati' relation diagram is shown at:
https://www.bursthub.cn//admin/static/svgrb260308A_amati.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: Xing-Hao Luo (luoxh@ihep.ac.cn)
GCN Circular 43949
Subject
GRB 260308A: Fermi GBM Final Real-time Localization
Date
2026-03-08T20:16:13Z (13 days ago)
From
Fermi GBM Team at MSFC/Fermi-GBM <do_not_reply@GIOC.nsstc.nasa.gov>
Via
email
The Fermi GBM team reports the detection of a likely SHORT GRB
At 20:05:52 UT on 8 Mar 2026, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 260308A (trigger 794693157.451346 / 260308837).
The on-ground calculated location, using the Fermi GBM trigger data, is RA = 250.2, Dec = -32.6 (J2000 degrees, equivalent to J2000 16h 40m, -32d 36'), with a statistical uncertainty of 3.6 degrees.
The angle from the Fermi LAT boresight is 108.0 degrees.
The skymap can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260308837/quicklook/glg_skymap_all_bn260308837.png
The HEALPix FITS file, including the estimated localization systematic, can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260308837/quicklook/glg_healpix_all_bn260308837.fit
The GBM light curve can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260308837/quicklook/glg_lc_medres34_bn260308837.gif