GCN Circular 40630

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,

G. Waratkar, J.Joshi, V. Bhalerao, D. Bhattacharya,
and S. Vadawale, on behalf of the Astrosat-CZTI 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 250404B
(AstroSat CZTI detection: Salunke et al., GCN Circ. 40078
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was detected by Konus-Wind, Swift (BAT), AstroSat (CZTI),
and Mars-Odyssey (HEND) at about 66970 s UT (18:36:10).
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:
  273.629 (18h 14m 31s)  -2.251 ( -2d 15' 03")
 Corners:
  273.108 (18h 12m 26s)  -2.676 ( -2d 40' 35")
  274.127 (18h 16m 31s)  -1.659 ( -1d 39' 32")
  274.151 (18h 16m 36s)  -1.842 ( -1d 50' 30")
  273.131 (18h 12m 31s)  -2.866 ( -2d 51' 58")
 ---------------------------------------------
The error box area is 768 sq. arcmin, and its maximum
dimension is 1.6 deg (the minimum one is 9 arcmin).
The Sun distance was 100 deg.

This localization may be improved.

A triangulation map and HEALPix FITS file are posted at
http://www.ioffe.ru/LEA/GRBs/GRB250404_T66970/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.