GRB 260103A

Xing-hao Luo, Chen-Wei Wang, Chao Zheng, and Shao-Lin Xiong (IHEP) report on behalf of the Insight-HXMT team:

At 2026-01-03T01:46:53.800 (T0), Insight-HXMT/HE detected the long burst GRB 260103A, which is also detected by SVOM/GRM (Chen-Wei Wang et.al., GCN #43314
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 ) , GECAM-B (Xing-Hao Luo et.al., GCN #43317
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 )
	
The Insight-HXMT/HE light curve mainly consists of multiple pulses with a T90 of 4.6 +1.8/-1.0 s. The 1s peak rate, measured from T0-0.25 s, is 1848 cnts/sec. Insight-HXMT/HE detected a total of 4704 counts form this burst.

The HXMT/HE light curve can be found here:
https://www.bursthub.cn//admin/static/hxmtgrb260103A.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://www.hxmt.org

Xing-Hao Luo, Chen-Wei Wang, Shao-Lin Xiong, Yue Huang (IHEP) report on behalf of GECAM team:

GECAM-B was triggered in-flight by GRB 260103A, at 2026-01-03T01:46:53.950 UTC (denoted as T0), which is also detected by SVOM/GRM (Chen-Wei Wang et.al., GCN #43314
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 ).

According to the GECAM-B light curves in about 70-6000 keV, this burst mainly consists of multiple pulses with a duration (T90) of  9.0 +7.0/-3.6 s.

The GECAM-B light curve can be found here:
https://www.bursthub.cn//admin/static/gecambgrb260103A.png

GECAM-B on-ground localization of this burst is (J2000): 
Ra: 269.0 deg 
Dec: 46.7 deg
Err: 4.6 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).

SVOM/GRM team: Chen-Wei Wang, Yue Huang, Shi-Jie Zheng, 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 burst GRB 260103A (SVOM trigger reference: sb26010302) at 2026-01-03T01:46:54.000 UTC (T0). 

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 8.0 +3.8/-1.8 s in the 15-5000 keV band. 

The SVOM/GRM light curve can be found here:
https://www.bursthub.cn//admin/static/svgrb260103A.png

We note that the burst occurred near the end of a C class solar flare as detected by the GOES satellites. So the solar flare origin cannot be excluded although this burst has a typical brightness, duration, and hardness of a long GRB.

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)