TITLE: GCN CIRCULAR NUMBER: 42526 SUBJECT: GRB 251031A: BALROG localization (Fermi Trigger 783588065 / GRB 251031306) DATE: 25/10/31 07:43:38 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 783588065 at 07:21:00 on 31 Oct. 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) = 188.3 deg Decl.(2000.0) = -17.9 deg The 1 sigma statistical error radius is 2.8 deg. We estimate an additional systematic error of 1 deg.

Further details are available at: https://grb.mpe.mpg.de/grb/GRB251031306/

The Healpix map can be downloaded from: https://grb.mpe.mpg.de/grb/GRB251031306/healpix

The location parameters are available as JSON at: https://grb.mpe.mpg.de/grb/GRB251031306/json

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