TITLE:   GCN CIRCULAR
NUMBER:  42919
SUBJECT: EP251130a: SAO RAS optical observations
DATE:    25/12/01 14:03:05 GMT
FROM:    Alexander Moskvitin at SAO RAS <mosk@sao.ru>

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).