TITLE: GCN CIRCULAR NUMBER: 39629 SUBJECT: GRB 250309B: BALROG localization (Fermi Trigger 763198715 / GRB 250309318) DATE: 25/03/09 08:04:59 GMT FROM: Jochen Greiner at MPE jcgrog@mpe.mpg.de

T. Preis (University of Innsbruck) & J. Greiner (MPE Garching) report:

The public trigdat data of the Fermi Gamma-ray Burst Monitor (GBM) trigger 763198715 at 07:38:30 on 09 March 2025 were automatically fitted for spectrum and sky location with BALROG (Burgess et al. 2018, MNRAS 476, 1427; Berlato et al. 2019, ApJ 873, 60).

The best-fit position is: RA(2000.0) = 210.5 deg Decl.(2000.0) = -7.6 deg The 1 sigma statistical error radius is 1.3 deg. We estimate an additional systematic error of 1 deg.

Further details are available at: https://grb.mpe.mpg.de/grb/GRB250309318/

The Healpix map can be downloaded from: https://grb.mpe.mpg.de/grb/GRB250309318/healpix

The location parameters are available as JSON at: https://grb.mpe.mpg.de/grb/GRB250309318/json

View this GCN Circular online at https://gcn.nasa.gov/circulars/39629. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0LW...