TITLE: GCN CIRCULAR NUMBER: 41498 SUBJECT: IPN triangulation of GRB 250821B (long/bright) DATE: 25/08/22 15:46:04 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, A. Goldstein, M. S. Briggs, C. Wilson-Hodge, and E. Burns on behalf of the Fermi GBM 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 250821B (Ferm-GBM detection: The Fermi GBM team, GCN 41473; Smith and Meegan, GCN 41477; BALROG localization: Preis and Greiner, GCN 41475; SVOM-GRM detection: Tan et al., GCN 41486) was detected by Fermi (GBM trigger 777485272), SVOM (GRM), Konus-Wind, and Mars-Odyssey (HEND), at about 58067 s UT (16:07:47). We have triangulated it to a preliminary, 3 sigma error box whose coordinates are: --------------------------------------------- RA(2000), deg Dec(2000), deg --------------------------------------------- Center: 29.373 (01h 57m 30s) -82.081 (-82d 04' 51") Corners: 26.171 (01h 44m 41s) -82.255 (-82d 15' 19") 32.420 (02h 09m 41s) -81.925 (-81d 55' 30") 32.427 (02h 09m 42s) -81.883 (-81d 52' 58") 26.212 (01h 44m 51s) -82.213 (-82d 12' 48") --------------------------------------------- The error box area is 127 sq. arcmin, and its maximum dimension is 56 arcmin (the minimum one is 2 arcmin). The Sun distance was 106 deg. This localization may be improved. The IPN localization is consistent with, but reduces the area of, the Fermi-GBM (GCN 41473) and BALROG (GCN 41475) localizations. A triangulation map and HEALPix FITS file are posted at http://www.ioffe.ru/LEA/GRBs/GRB250821_T58069/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. View this GCN Circular online at https://gcn.nasa.gov/circulars/41498. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0LW...