GCN Circular 41428
Subject
GRB 250818B: SAO RAS optical observations
Event
Date
2025-08-19T08:13:33Z (5 days ago)
From
Alexander Moskvitin at SAO RAS <mosk@sao.ru>
Via
Web form
A. Moskvitin, O. Spiridonova, V. Vlasyuk, Yu. Sotnikova (SAO RAS),
Tao An and Yuanqi Liu (Shanghai Astronomical Observatory) report
on behalf of a larger collaboration.
We observed the field of the SVOM short GRB 250818B (Wang et al.,
GCN 41405; also detected by Swift/XRT, Ferro et al., GCN 41407
and EP-FXT, Li et al., GCN 41424) with the 1-m SAO RAS telescope
Zeiss-1000 equipped with CCD-photometer. We obtained 13 x 300 sec.
images in Rc band on August 18, 23:15:02 -- August 19, 00:33:37 UT
(t_mid - T0 = 20.4196 hours = 0.85082 days).
The OT (Kumar et al., GCN 41406; Yao et al., GCN 41409; Zheng et al.,
GCN 41417; Fong et al., GCN 41419; Bendtsen et al., GCN 41426)
is clearly detected in the stacked image with the brightness of
R = 20.88 +/- 0.04 (R_lim = 23.0).
This preliminary photometry is based on nearby Pan-STARRS objects
(magnitudes were converted with the Lupton 2005 equations)
and not corrected for Galactic extinction.