Gamma-ray Burst 251129B

(All information courtesy of the instrument teams.)

Previous IAU Circulars

• none

• GCN Circular #42958
  S. Salunke (IUCAA), M. Tembhurnikar (IUCAA), Harsha K. H. (IUCAA), A. Arya (IITB), A. Goyal (IITB), 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 short-duration GRB 251129B which was also detected by Konus Wind (IPN Notices).
  The source was clearly detected in the CZT detectors in the 20-200 keV energy range. The light curve showed a peak of emission with the strongest peak at 2025-11-29T09:51:34 UTC. The measured peak count rate associated with the burst is 1480 (+927, -83) counts/s above the background in the combined data of three quadrants (out of four), with a total of 128 (+30, -29) counts. The local mean background count rate was 212 (+20, -44)) counts/s. Using cumulative rates, we measure a T90 of 0.14 (+0.04, -0.03) s.
  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
• GCN Circular #42960
  A.S. Kozyrev, D.V. Golovin, M.L. Litvak, I.G. Mitrofanov, and A.B. Sanin on behalf of the HEND/Mars Odyssey team,
  D. Svinkin, D. Frederiks, A. Lysenko, A. Ridnaia, and T. Cline on behalf of the Konus-Wind team,
  E. Burns on behalf of the IPN,
  S. Barthelmy, J. Cummings, H. Krimm, D. Palmer, A. Tohuvavohu, and J. DeLaunay on behalf of the Swift-BAT team,
  and
  W. Boynton, C. Fellows, K. Harshman, H. Enos, R. Starr, and A.S. Gardner on on behalf of the GRS-Odyssey GRB team, report:
  The short-duration GRB 251129B (AstroSat-CZTI detection: Salunke et al., GCN 42958) was detected by Konus-Wind, Swift(BAT), Mars-Odyssey (HEND), and AstroSat (CZTI), at about 35494 s UT (09:51:34). The burst was outside the coded field of view of the BAT.
  We have triangulated it to a preliminary, 3 sigma error box whose coordinates are:

   ---------------------------------------------
    RA(2000), deg                 Dec(2000), deg
   ---------------------------------------------
   Center:
    124.862 (08h 19m 27s) +76.391 (+76d 23' 28")
   Corners:
    118.469 (07h 53m 53s) +78.048 (+78d 02' 53")
    119.970 (07h 59m 53s) +77.774 (+77d 46' 26")
    129.621 (08h 38m 29s) +74.606 (+74d 36' 22")
    128.692 (08h 34m 46s) +74.931 (+74d 55' 51")
   ---------------------------------------------
  

  The error box area is 617 sq. arcmin, and its maximum dimension is 4.32 deg (the minimum one is 2.6 arcmin). The Sun distance was 117 deg.
  The localization may be improved.
  A triangulation map and HEALPix FITS file are posted at http://www.ioffe.ru/LEA/GRBs/GRB251129_T35496/IPN/ The HEALPix triangulation map is the multi-order HEALPix in units of probability density.
  The Konus-Wind time history and spectrum will be given in a forthcoming GCN Circular.
• GCN Circular #42984
  Xue-Yuan Zao, Yue Wang, Zheng-Hang Yu, Chen-Wei Wang, Chao Zheng, Shao-Lin Xiong (IHEP) report on behalf of GECAM team:
  GECAM-B was triggered in-flight and on-ground by a short/hard burst GRB 251129B at 2025-11-29T09:51:34.250 UTC (denoted as T0). According to the GECAM-B light curves in about 70-6000 keV, this burst mainly consists of a single pulse main emission with a duration (T90) of 0.25 +0.10/-0.15 s.
  The GECAM-B light curve can be found here: https://www.bursthub.cn//admin/static/gecambgrb251129B.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).
  
• GCN Circular #42992
  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, confirms the detection of the short GRB 251129B, which was detected by AstroSat/CZTI (GCN 42958), Konus-Wind, Swift/BAT, Mars-Odyssey/HEND (GCN 42960), and GECAM-B (GCN 42984). The light curve comprises a single peak at 2025-11-29 09:51:33.20 with a duration of 0.16s.
  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 telescopes 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
  [2] Woolf, R.S. et al. 2022, Proc. SPIE, 12181, id. 121811O
  [3] Woolf, R.S. et al. 2024, Proc. SPIE, 13151, id. 1315108
  

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