TITLE: GCN CIRCULAR NUMBER: 40828 SUBJECT: GRB 250625A: SAO RAS possible optical afterglow DATE: 25/06/25 21:47:40 GMT FROM: Alexander Moskvitin at SAO RAS mosk@sao.ru
A. Moskvitin, O. Spiridonova (SAO RAS), report on behalf of a GRB follow-up collaboration.
We observed the field of the GRB 250625A (The Fermi GBM team, GCN 40824; Ferro et al., GCN 40825) with SAO RAS 1-m telescope Zeiss-1000 equipped with CCD-photometer. We obtained 6 x 300 sec. exposures in Rc band on June 25, 20:39:03--21:12:11 UT (t_mid - T0 = 4.8447 hours).
Withtin the enhanced XRT error circle (Beardmore et al., GCN 40827) we detect single object with the coordinates: R.A. (J2000.0) = 17:26:02.1 Dec. (J2000.0) = +22:16:03.6 +/- 0".3 and brightness of R = 22.97 +/- 0.17, possible GRB OT. Observations are ongoing to confirm variability of the object.
Preliminary photometry is based on the nearby USNO-B1.0 and has not corrected for the Galactic extinction.
R.A. Dec. (2000) R2 17:26:06.4 +22:16:29.4 14.75 17:26:03.7 +22:15:09.9 15.42 17:26:10.0 +22:13:56.8 15.03 17:26:01.4 +22:18:39.0 14.59
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