TITLE:   GCN CIRCULAR
NUMBER:  39596
SUBJECT: EP250302a: Optical Observations at CrAO and SAO RAS
DATE:    25/03/05 12:52:41 GMT
FROM:    Nicolai Pankov at HSE, IKI RAS <colinsergesen@gmail.com>

N. Pankov (HSE, IKI), A. Moskvitin (SAO RAS), O. I. Spiridonova (SAO RAS), A. Pozanenko (IKI), V. Rumyantsev (CrAO), E. Klunko (ISTP) report on behalf of IKI-GRB-FuN:

We performed optical observations of the field of a fast X-Ray transient EP250302a (Dai et al., GCN 39556; Page et al., GCN 39557) in the R filter with the 2.6-meter telescope of the Crimean Astrophysical Observatory (CrAO) and the 1-meter Zeiss-1000 telescope of the Special Astrophysical Observatory of the RAS (SAO RAS). The observations began on 2025-03-03 (UT) 01:51:40, i.e. 1.42750 days since trigger. The optical source (Zhu et al., GCN 39550; Busmann et al., GCN 39551; Leonini et al., GCN 39553; Wu et al., GCN 39555; Xin et al., GCN 39558; Adami et al., GCN 39560; Yang et al., GCN 39561; Becerra et al., GCN 39562; Izzo et al., GCN 39564; Pankov et al., GCN 39565; Reguitti, GCN 39568; Komesh et al., GCN 39569; Shilling and Breeveld, GCN 39570; Aryan et al., GCN 39572; Moskvitin et. al, GCN 39576; Wu et. al, GCN 39578; Pankov et. al, GCN 39586; Gupta et. al, GCN 39593) is not detected in the stacked images from both telescopes. The preliminary upper limits are as follows:

Date       UT start t-T0        Exptime  Filter UL       Telescope
                    (mid, days) (s)             (3sigma)
2025-03-03 01:51:40 1.44460     9*300    Rc     22.7     Zeiss-1000/SAO RAS
2025-03-04 23:21:23 2.33286     14*120   R      23.3     ZTSh/CrAO

The photometry is based on nearby stars from the USNO-B1.0 catalog (R2 magnitudes) and has not been corrected for the Galactic extinction.