GCN Circular 42919
Subject
EP251130a: SAO RAS optical observations
Event
Date
2025-12-01T14:03:05Z (10 months ago)
From
Alexander Moskvitin at SAO RAS <mosk@sao.ru>
Via
Web form
A. S. Moskvitin and O. I. Spiridonova (SAO RAS)
report on behalf of GRB follow-up team.
We observed the field of the X-ray transient EP251130a (Wu et al.,
GCN 42903; Zhang et al., GCN 42915), also detected by Swift-XRT
(Evans et al., GCN 42908) with the Zeiss-1000 1m telescope
of the SAO RAS on December 1, 01:29:21--03:08:47 UT
(t_mid - T0 = 0.63281 days). We obtained 11 * 300 images in Rc band
under mediocre weather conditions.
The optical counterpart (Dornic et al., GCN 42904; He et al. GCN 42914;
Gupta et al. GCN 42916; Zheng et al. GCN 42917; van Dalen et al.,
GCN 42918) is clearly detected in our stacked image
with the brightness of R = 20.11 +/- 0.07 (R_lim = 21.8).
This preliminary photometry is based on nearby stars from the USNO-B1
catalogue (R2 magnitudes) and is not corrected for the Galactic
extinction.
USNO-B1 star RA DEC R2
1173-00161316 101.000000 +27.372589 16.26
1173-00161485 101.071981 +27.375787 16.76
1173-00161417 101.045348 +27.394953 16.04
In comparison with the OT brightness from 1.3m DFOT data
(Gupta et al., GCN 42916) we noted a brightening between
two epochs (also reported by Zheng et al. GCN 42917
and van Dalen et al., GCN 42918).