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). View this GCN Circular online at https://gcn.nasa.gov/circulars/42919. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0LW...