GCN Circular 39807
Subject
EP250321a: REM optical/NIR afterglow detection
Date
2025-03-21T09:16:29Z (5 days ago)
From
Riccardo Brivio at INAF-OAB <riccardo.brivio@inaf.it>
Via
Web form
R. Brivio, M. Ferro, P. D'Avanzo, S. Covino, D. Fugazza (INAF-OAB) report on behalf of the REM team:
We observed the field of EP250321a (Hu et al., GCN 39800) with the REM 60cm robotic telescope located at the ESO observatory of La Silla (Chile). The observations were carried in the g, r, i, z, J, H, K bands, starting on 2025 March 21 at 07:05:26 UT (i.e. ~0.92 hr after the EP trigger), and lasting for about 2 hours.
From preliminary photometry we detect the counterpart in the optical and NIR images at the position of the optical afterglow (Fu et al., GCN 39804; Perez-Garcia et al., GCN 39805) with the following magnitudes:
r = 19.9 +/- 0.2 (AB; calibrated against the Pan-STARRS catalogue)
at a mid-time of t - t0 = 1.78 hr after the trigger;
H = 15.3 +/- 0.2 (Vega; calibrated against the 2MASS catalogue)
at a mid-time t - t0 = 1.06 hr after the trigger.