TITLE: GCN CIRCULAR NUMBER: 40205 SUBJECT: EP250421a: REM optical upper limit DATE: 25/04/22 09:22:46 GMT FROM: Riccardo Brivio at INAF-OAB riccardo.brivio@inaf.it
R. Brivio, M. Ferro, D. Fugazza, P. D'Avanzo, S. Covino (INAF-OAB) report on behalf of the REM team:
We observed the field of EP250421a (Zhao et al., GCN 40198) with the REM 60 cm robotic telescope located at the ESO observatory of La Silla (Chile). The observations were carried in the g, r, i, and z bands, started on 2025 April 21 at 23:08:27 UT (i.e. 6.9 hr after the burst), and lasted for about 1 hour.
From preliminary inspection, we do not detect any counterpart at the position of the optical afterglow (Lee et al., GCN. 40192; Fu et al., GCN 40193; Liu et al., GCN 40197) down to the following 3sigma limit:
r > 20.6 (AB; calibrated against the Pan-STARRS catalogue), at a mid-time of 7.4 hours after the trigger.
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