GCN Circular 41948
Subject
GRB 250920B: SAO RAS optical observations
Event
Date
2025-09-22T22:46:39Z (a year ago)
From
Alexander Moskvitin at SAO RAS <mosk@sao.ru>
Via
Web form
A. Moskvitin, O. Spiridonova (SAO), N. Pankov (HSE), A. Pozanenko
(IKI) report on behalf of GRB follow-up collaboration and IKI-GRB-FuN.
We observed the field of the GRB 250920B (Fermi GBM Team, GCN 41897;
Gupta et al., GCN 41898; Page et al., GCN 41909; Evans et al.,
GCN 41910; Sonawane and Meegan, GCN 41919; Sakamoto et al., GCN 41923;
Cheung et al., GCN 41937; Svinkin et al., GCN 41942) with the 1-m
SAO RAS telescope Zeiss-1000 equipped with CCD-photometer.
We obtained 10 x 300 sec. images Rc band on September 22,
16:22:43--17:17:34 (t_mid - T0 = 2.33586 days).
The optical transient (Gupta et al., GCN 41898; Wu et al., GCN 41908;
Hall et al., GCN 41914; Kuin and Gupta, GCN 41915; Reguitti et al.,
GCN 41932) is clearly detected in the stacked frame
with the brightness of R = 21.7 +/- 0.1.
Date UT start t-T0 Exp. Filter OT Err. UL (3sigma)
(mid, d) (s)
2025.09.22 16:22:43 2.33586 10 x 300 Rc 21.7 +/- 0.1 23.2
Preliminary photometry is based on the nearby stars from USNO-B1
(R2 magnitudes) and not corrected for the Galactic extinction.