GRB 250814C

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,

Y. Zhang, C. Wang, S. Xiong, J. Wei, and B. Cordier
on behalf of the SVOM-GRM team,

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 250814C
(SVOM-GRM detection: Wang et al., GCN 41385
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was detected by Konus-Wind, SVOM (GRM), Swift (BAT),
and Mars-Odyssey (HEND) at about 12263 s UT (03:24:23).
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:
  164.655 (10h 58m 37s) +47.526 (+47d 31' 35")
 Corners:
  164.814 (10h 59m 15s) +47.549 (+47d 32' 56")
  164.789 (10h 59m 09s) +47.597 (+47d 35' 48")
  164.497 (10h 57m 59s) +47.504 (+47d 30' 13")
  164.521 (10h 58m 05s) +47.456 (+47d 27' 21")
 ---------------------------------------------
The error box area is 39 sq. arcmin, and its maximum
dimension is 14 arcmin (the minimum one is 3 arcmin).
The Sun distance was 37 deg.

A triangulation map and HEALPix FITS file are posted at
http://www.ioffe.ru/LEA/GRBs/GRB250814_T12259/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.

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

SVOM/ECLAIRs team: Hui Yang (IRAP), Stéphane Schanne (CEA)

Report on behalf of the SVOM team:

SVOM/GRM was triggered in-flight by a short burst GRB 250814C (SVOM trigger reference: sb25081402) at 2025-08-14T03:24:23.000 UTC (T0), which is also detected by Konus-Wind and Swift/BAT.

With the event-by-event data downloaded through the X-band ground station, the GRM light curve shows that this burst consists of multi-pulses with a T90 of 1.20 +0.20/-0.30 s in the 15-5000 keV band.

The SVOM/GRM light curve can be found here:
https://www.bursthub.cn//admin/static/svgrb250814C.png

There is no indication of any subthreshold target from both CRT and IMT triggers onboard ECLAIRs close to the time of this event, suggesting that it is either too weak to be detected or outside the FoV of ECLAIRs.

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)