TITLE: GCN CIRCULAR NUMBER: 39872 SUBJECT: IPN triangulation of GRB 250322B DATE: 25/03/26 12:46:47 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,

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 bright, long-duration GRB 250322B (AstroSat-CZTI detection: Tembhurnikar et al., GCN 39848; NuSTAR CsI shield detection: Grefenstette et al., GCN 39857) was detected by AstroSat (CZTI), NuSTAR (CsI shield), Konus-Wind, Swift (BAT), and Mars-Odyssey (HEND) at about 72435 s UT (20:07:15). 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: 319.668 (21h 18m 40s) -24.964 (-24d 57' 51") Corners: 319.574 (21h 18m 18s) -23.375 (-23d 22' 29") 319.886 (21h 19m 33s) -26.698 (-26d 41' 53") 319.642 (21h 18m 34s) -26.204 (-26d 12' 13") 319.155 (21h 16m 37s) -22.325 (-22d 19' 29") --------------------------------------------- The error box area is 2638 sq. arcmin, and its maximum dimension is 4.4 deg (the minimum one is 12.2 arcmin). The Sun distance was 48 deg.

This localization may be improved.

A triangulation map and HEALPix FITS file are posted at http://www.ioffe.ru/LEA/GRBs/GRB250322_T72435/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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