TITLE: GCN CIRCULAR NUMBER: 40831 SUBJECT: GRB 250625A: NOT z-band upper limit DATE: 25/06/26 00:25:21 GMT FROM: Daniele Bjørn Malesani at Cosmic Dawn Center, Niels Bohr Institute daniele.malesani@nbi.ku.dk
D. B. Malesani (DAWN/NBI and Radboud), A. Martin-Carrillo (UCD), A. de Ugarte Postigo (LAM), G. Corcoran (UCD), B. P. Gompertz (Birmingham), D. Xu (NAOC), M. A. Diaz Teodori (NOT and Turku Univ.), report on behalf of a larger collaboration:
We observed the position of the X-ray and optical afterglow (Beardmore et al., GCN 40827; Moskvitin & Spiridonova, GCN 40828) of GRB 250625A (Ferro et al., GCN 40825; Fermi GBM team, GCN 40824) using the Nordic Optical Telescope, using the “standby” StanCam instrument.
In a sequence of 3 exposures of 200 s each, with mean time 2025 Jun 25.948 UT (6.67 hr after the trigger), we detect no object consistent with the X-ray afterglow, down to a limiting magnitude z > 21 AB, calibrated against the Pan-STARRS catalog.
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