{
  "submitter": "Dmitry Svinkin at Ioffe Institute <svinkin@mail.ioffe.ru>",
  "bibcode": "2025GCN.39652....1K",
  "body": "A.S. Kozyrev, D.V. Golovin, M.L. Litvak, I.G. Mitrofanov, and A.B. Sanin\non behalf of the HEND/Mars Odyssey team,\n\nD. Svinkin, D. Frederiks, A. Lysenko, A. Ridnaia,\nand T. Cline on behalf of the Konus-Wind team,\n\nA. Goldstein, M. S. Briggs, C. Wilson-Hodge,\nand E. Burns on behalf of the Fermi GBM team, \n\nand\n\nW. Boynton, C. Fellows, K. Harshman, H. Enos, R. Starr,\nand A.S. Gardner on on behalf of the GRS-Odyssey GRB team,\nreport:\n\nThe long-duration GRB 250309B\n(Fermi-GBM BALROG localization: Preis and Greiner, GCN 39629;\nFermi-GBM detection: The Fermi GBM team, GCN 39635;\nMcDermott et al., GCN 39642;\nGECAM-B detection: Wang et al., GCN 39648)\nwas detected by Fermi (GBM trigger 763198715), Konus-Wind,\nMars-Odyssey (HEND), and GECAM-B at about 27510 s UT (07:38:30).\n\nWe have triangulated it to a preliminary, 3 sigma error box\nwhose coordinates are:\n-------------------------------\n  RA(2000), deg  Dec(2000), deg\n ------------------------------\n Center:\n  208.8101       -12.9141\n Corners:\n  204.1541       -23.3442\n  204.3621       -23.0319\n  213.4312        -2.9483\n  213.5345        -2.5970\n -------------------------------\nThe error box area is 1.3 sq. deg, and its maximum\ndimension is 23 deg (the minimum one is 3.5 arcmin).\nThe Sun distance was 135 deg.\n\nThis localization may be improved.\n\nThe IPN localization is consistent with, but reduces the area of,\nthe final Fermi-GBM (GCN 39635) and BALROG (GCN 39629) localizations.\n\nA triangulation map and HEALPix FITS file are posted at\nhttp://www.ioffe.ru/LEA/GRBs/GRB250309_T27513/IPN/\nThe HEALPix triangulation map is the multi-order HEALPix in units of\nprobability density.\n\nThe localization of IceCube-250309A (IceCube Collaboration, GCN 39631) is inconsistent with the IPN localization. The optical transient ZTF25aaitvjt/AT2025dws (Stein  et al., GCN 39639) is inside the IPN box, which further strengthen the interpretation of transient as the burst afterglow.\n\nThe Konus-Wind time history and spectrum will be given\nin a forthcoming GCN Circular. ",
  "circularId": 39652,
  "eventId": "GRB 250309B",
  "format": "text/plain",
  "subject": "IPN triangulation of GRB 250309B",
  "createdOn": 1741612654455,
  "submittedHow": "web"
}