GRB 260210A

SVOM/GRM team: Hao-Xuan Guo, Chen-Wei Wang, Shi-Jie Zheng, Yue Huang, Shao-Lin Xiong, Shuang-Nan Zhang (IHEP)

SVOM/ECLAIRs team: Feliu Lacreu (IAP), Olivier GODET (IRAP)
Report on behalf of the SVOM team:

SVOM/GRM was triggered in-flight by GRB 260210A at 2026-02-10T11:27:37.300 (T0), which is also detected by KONUS-Wind, AstroSat CZTI (Arya et al., GCN #43686
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 ) and Glowbug (Cheung et al., GCN #43689
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 ).

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 34.4 +8.8/-5.2 s in the 15-5000 keV band.

The SVOM/GRM light curve can be found here:
https://www.bursthub.cn//admin/static/svgrb260210A.png

In addition, the position of this burst, as determined by on-ground trigger (RA = 254, Dec = 19, Error = 57), is located at about 72 degrees from the SVOM optical axis, which is outside the ECLAIRs field of view. But this burst is still detected by ECLAIRs through the shield.

With this localization, the time-averaged spectrum from T0-30 to T0+62 s is best fitted by a power law function with an exponential high-energy cutoff. The power law index is -1.33 +0.15/-0.14 and the cutoff energy, parameterized as Epeak, is 182 +65/-36 keV. The event fluence (10-1000 keV) in this time interval is (1.67 +0.17/-0.15)E-05 erg/cm^2.

The 1s peak spectrum, measured from T0+0.7 to T0+1.7 s, is also best fitted by a power law function with an exponential high-energy cutoff. The power law index is -0.74 +0.17/-0.16 and the cutoff energy, parameterized as Epeak, is 207 +33/-24 keV. The flux (10-1000 keV) in this time interval is (1.34 +0.11/-0.10)E-06 erg/cm^2/s.

The localization of GRB 260210A in the 'Amati' relation diagram is shown at:
https://www.bursthub.cn//admin/static/svgrb260210A_amati.png
And the localization in the 'Yonetoku' relation diagram is shown at:
https://www.bursthub.cn//admin/static/svgrb260210A_yonetoku.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/GRM point of contact for this burst is: Hao-Xuan Guo (IHEP) (guohx@ihep.ac.cn)

C.C. Cheung, R. Woolf, M. Kerr, J.E. Grove (NRL), A. Goldstein (USRA), C.A. Wilson-Hodge, D. Kocevski (MSFC), and M.S. Briggs (UAH) report:

The Glowbug gamma-ray telescope [1,2,3], operating on the International Space Station, reports the detection of GRB 260210A, which was also detected by AstroSat/CZTI, SVOM/GRM, and Konus-Wind (GCN 43686
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 ).

Using an adaptive window with a resolution of 32-ms, the burst onset is determined to be 2026-02-10 11:27:33.624 with a duration of 27.6 s and a total significance of about 49 sigma.  The Glowbug light curve comprises three main peaks at ~T0+4s, +16s, and +26s.

The analysis results presented here are preliminary and use a response function that lacks a detailed characterization of the surrounding passive structure of the ISS.

Glowbug is a NASA-funded technology demonstrator for sensitive, low-cost gamma-ray transient developed, built, and operated by the U.S. Naval Research Laboratory (NRL) with support from the University of Alabama in Huntsville, USRA, and NASA MSFC.  It was launched on 2023 March 15 aboard the Department of Defense Space Test Program’s STP-H9 to the ISS and operated until 2024 April when it was put in safe storage on orbit. Glowbug was removed from storage and resumed operation on 2025 September 12.

[1] Grove, J.E. et al. 2020, Proc. Yamada Conf. LXXI, arXiv:2009.11959
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[2] Woolf, R.S. et al. 2022, Proc. SPIE, 12181, id. 121811O
[3] Woolf, R.S. et al. 2024, Proc. SPIE, 13151, id. 1315108

Distribution Statement A: Approved for public release.  Distribution is unlimited.

A. Arya (IITB), A. Goyal (IITB), M. Tembhurnikar (IUCAA), S. Salunke (IUCAA), Harsha K. H. (IUCAA), G. Waratkar (Caltech/IITB), A. Vibhute (IUCAA), V. Bhalerao (IITB), 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 long GRB 260210A which was also detected by SVOM/GRM (via GCN notices), and KONUS-Wind (via IPN notices).

The source was clearly detected in the CsI anticoincidence (Veto) detector in the 100-500 keV energy range. The light curve showed multiple peaks of emission with the strongest peak at 2026-02-10 11:27:38.52 UTC. The measured peak count rate associated with the burst is 292 (+76, -33) counts/s above the background in the combined data of all quadrants, with a total of 3215 (+487, -705) counts. The local mean background count rate was 1390 (+5, -5) counts/s. We measure a T90 of 34 (+2, -9) s from the cumulative Veto light curve.

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