GRB 260830A

Zheng-Hang Yu, Shao-Lin Xiong (IHEP) report on behalf of GECAM team:

GECAM-B was triggered in-flight by a burst GRB 260830A at 2026-08-30T19:32:11.800 UTC (denoted as T0), which is also detected by NuSTAR (G. Waratkar et al., GCN #45483
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 ) and Insight-HXMT/HE (Yu et al., GCN #45511
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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 11 +/-1 s. 

The on-ground localization of GECAM-B is:
Ra: 245.5 deg   
Dec: -61.1 deg
Err: 3.4 deg (1-sigma, statistical only)

The GECAM-B light curve can be found here:
https://www.bursthub.cn/gcn/2026/gecambgrb260830A.png

The time-averaged spectrum from T0-5.0 to T0+10.0 s is best fitted by a power law function with an exponential high-energy cutoff. The power law index is -1.13 +0.30/-0.28 and the cutoff energy, parameterized as Epeak, is 190 +23/-14 keV. The event fluence (10-1000 keV) in this time interval is (1.85 +0.25/-0.18) E-05 erg/cm^2.

The localization of GRB 260830A in the 'Amati' relation diagram is shown at: 
https://www.bursthub.cn/gcn/2026/gecambgrb260830A_amati.png

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).

Zheng-Hang Yu and Shao-Lin Xiong (IHEP) report on behalf of the Insight-HXMT team:
 
At 2026-08-30T19:32:13.02 (T0), Insight-HXMT/HE detected GRB 260830A, which is also detected by NuSTAR (G. Waratkar et al., GCN #45483
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 ).
 
The Insight-HXMT/HE light curve mainly consists of multiple pulses with a T90 of 9 +7/-3 s. The 1 s peak rate, measured from T0+5.5 s, is 552 cnts/sec. Insight-HXMT/HE detected a total of 3815 counts from this burst.
 
The Insight-HXMT/HE light curve can be found here:
https://www.bursthub.cn/gcn/2026/hxmtgrb260830A.png
 
All measurements above are made with the CsI detectors of Insight-HXMT/HE operating in the Normal 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

G. Waratkar (Caltech) and B. Grefenstette (Caltech) report on behalf of the NuSTAR Search for INteresting Gamma-ray Signals (SINGS) working group:

The NuSTAR SINGS working group reports the detection of prompt emission from the long-duration GRB 260830A in both the NuSTAR CsI anti-coincidence shields. Details of the search algorithm will be described in a future paper.

The NuSTAR SINGS algorithm, triggered at 2026-08-30T19:32:13.02 UTC, shows a detection of GRB 260830A, also detected by Konus-Wind (GCN notices).

The NuSTAR CsI shield data are recorded at 1 Hz. We detect a single episode with two peaks lasting for about 10-s. The peak count rate is ~1500-cps with a baseline rate of ~1000-cps during this time period. We do not see any evidence in the signal above 100 keV in the CZT detectors.

Lightcurves and analysis for this GRB can be found here:
https://nustarsoc.caltech.edu/NuSTAR_Public/grbs/reports/2026/260830A  

Information on NuSTAR SINGS can be found here: 
https://nustarsoc.caltech.edu/NuSTAR_Public/grbs/     

NuSTAR is a NASA Small Explorer mission led by Caltech and managed by JPL for NASA's Science Mission Directorate in Washington.