GCN Circular 41446

Subject
IPN triangulation of GRB 250804B (short)
Event
GRB 250804B
Date
2025-08-20T14:44:09Z (a year ago)
From
Dmitry Svinkin at Ioffe Institute <svinkin@mail.ioffe.ru>
Via
Web form
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 250804B
(SVOM-GRM detection: Wang et al., GCN 41229Loading...
 
 ;
Insight-HXMT detection: Wang et al., GCN 41284Loading...
 
 )
was detected by Konus-Wind, Swift (BAT), SVOM (GRM), Insight (HXMT),
and Mars-Odyssey (HEND) at about 17092 s UT (04:44:52).
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:
   40.607 (02h 42m 26s) -46.768 (-46d 46' 04")
 Corners:
   40.397 (02h 41m 35s) -46.987 (-46d 59' 12")
   40.852 (02h 43m 24s) -46.590 (-46d 35' 25")
   40.815 (02h 43m 16s) -46.548 (-46d 32' 52")
   40.360 (02h 41m 26s) -46.944 (-46d 56' 39")
 ---------------------------------------------
The error box area is 84 sq. arcmin, and its maximum
dimension is 31 arcmin (the minimum one is 3 arcmin).
The Sun distance was 105 deg.

This localization may be improved.

A Swift ToO has been requested for this burst (GCN 41231Loading...
 
 , 41239Loading...
 
 ).
Only source #8 detected by Swift-XRT (https://www.swift.ac.uk/xrt_products/TILED_GRB00138/) 
is inside the IPN box.

A triangulation map and HEALPix FITS file are posted at
http://www.ioffe.ru/LEA/GRBs/GRB250804_T17091/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.