GRB 261024C

Jin-Ye Luo, Chen-Wei Wang, Chao Zheng, Yue Wang, Zheng-Hang Yu, Shao-Lin Xiong (IHEP) report on behalf of GECAM team: 

GECAM-B was triggered on-ground by GRB 261024C at 2026-10-24T18:24:11.250 UTC (denoted as T0), which is also detected by AstroSat/CZTI (Harsha K. H. et al., GCN #46039
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 ) and NuSTAR (G. Waratkar et al., GCN #46050
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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 39.0 +13/-5 s.

The on-ground calculated location, using the GECAM-B trigger data, is RA = 30.4 deg, Dec = 46.5 deg, with a statistical uncertainty of 1.8 deg.

The GECAM-B light curve can be found here:
https://www.bursthub.cn/gcn/2026/gecambgrb261024C.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).

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 261024C in both the NuSTAR CsI anti-coincidence shields. This GRB was identified through a blind search using the CsI shield rates. Details of the search algorithm will be described in a future paper.

The NuSTAR SINGS algorithm triggered at 2026-10-24T18:24:12.000 UTC shows a detection of GRB 261024C, also detected by KONUS-Wind (GCN Notices) and AstroSat-CZTI (GCN 46039
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 ).

The NuSTAR CsI shield data are recorded at 1 Hz. We detect a double-peaked burst lasting for about 40-s. The peak count rate is ~1800-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/2026/261024C 

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.

Harsha K. H. (IUCAA), S. Salunke (IUCAA), A. Arya (IITB), S. Puri (IITB), A. Goyal (IITB), G. Waratkar (Caltech/IITB), V. Bhalerao (IITB),  A. Vibhute (IUCAA), 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 GRB 261024C which was also detected by KONUS-Wind (via IPN notices).

The source was detected in the CsI anticoincidence (Veto) detector in the 100-500 keV energy range. The light curve showed multiple peaks with the strongest peak at 2026-10-24 18:24:33.89 UTC. The measured peak count rate associated with the burst is 347 (+58, -27) counts/s above the background in the combined data of all four quadrants, with a total of 5461 (+472, -514) counts. The local mean background count rate was 796 (+3, -3) counts/s. We measure a T90 of 32 (+3, -3) s from the cumulative Veto light curve.

The source was also detected in the CZT detectors in the 20-200 keV energy range.

CZTI data products like interactive and downloadable light curves for this GRB can be found at: 
https://astrosat.iucaa.in/cift/cift_products/530562236.39/S530562236.39_details.html

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