GCN Circular 40106

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, and A. Tohuvavohu
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 bright, short-duration GRB 250406B
was detected by Konus-Wind, Mars-Odyssey (HEND), and Swift (BAT)
at about 21400 s UT (05:56:40).
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:
  316.521 (21h 06m 05s) +45.187 (+45d 11' 13")
 Corners:
  317.243 (21h 08m 58s) +45.058 (+45d 03' 28")
  315.809 (21h 03m 14s) +45.386 (+45d 23' 10")
  315.796 (21h 03m 11s) +45.310 (+45d 18' 36")
  317.227 (21h 08m 55s) +44.981 (+44d 58' 53")
 ---------------------------------------------
The error box area is 289 sq. arcmin, and its maximum
dimension is 1.078 deg (the minimum one is 4.53 arcmin).
The Sun distance was 63 deg.

This localization may be improved.

A triangulation map and HEALPix FITS file are posted at
http://www.ioffe.ru/LEA/GRBs/GRB250406_T21401/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.