TITLE:   GCN CIRCULAR
NUMBER:  41773
SUBJECT: EP250908C: GROND observation of the fading optical counterpart
DATE:    25/09/10 08:48:05 GMT
FROM:    Arne Rau at MPE <arau@mpe.mpg.de>

Arne Rau (MPE) reports:

We observed the position of EP250908C (Zhang et al., GCN 41754) using the Gamma-Ray burst Optical Near-infrared Detector (GROND, Greiner et al. 2008) mounted to the MPG 2.2m telescope at ESO’s La Silla Observatory on 2025-09-10 07:24 UT, i.e. 31.5 hours after the Einstein Probe trigger.

The candidate optical counterpart reported by Malesani et al. (GCN 41760) was detected with

r’= 23.0+/-0.2
i’ = 22.8+/-0.2

indicating clear fading. The magnitudes are in the AB magnitude system and calibrated against nearby SkyMapper sources.

We acknowledge the excellent support of the 2.2m staff, in particular Angel Hempel.