TITLE: GCN CIRCULAR NUMBER: 41446 SUBJECT: IPN triangulation of GRB 250804B (short) DATE: 25/08/20 14:44:09 GMT FROM: Dmitry Svinkin at Ioffe Institute svinkin@mail.ioffe.ru

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 41229; Insight-HXMT detection: Wang et al., GCN 41284) 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 41231, 41239). 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.

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