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GCN Circular 40282

Subject

EP250428b: SAO RAS optical upper limit

Date

2025-04-29T23:39:13Z (16 hours ago)

From

Alexander Moskvitin at SAO RAS <mosk@sao.ru>

Via

Web form

A. S. Moskvitin, O. I. Spiridonova (SAO RAS)
report on behalf of the GRB follow-up team.

We observed the field of the X-ray transient EP250428b (Liu et al.,
GCN 40277Loading...
 
 ) with the SAO RAS 1-m telescope Zeiss-1000 on April 29,
20:47:38--21:28:24 UT (t_mid - T0 = 1.6267 days).
We obtained 7 x 300 sec. images in Rc band.

Within the FXT error circle we detect several sources which are presented
in the PanSTARRS images:
     R.A.         Decl.         R_mag +/- err
#1   14:41:50.4   +02:06:18.0   20.20 +/- 0.10
#2   14:41:50.7   +02:06:13.4   22.86 +/- 0.21
#3   14:41:49.8   +02:05:55.9   22.57 +/- 0.17

Within the FXT error circle we did not detect any new sources
down to the limiting magnitude of R_lim = 23.2 (calibrated against R2
magnitudes of nearby UNSO-B1 stars and not corrected for the MW
extinction).