TITLE:   GCN CIRCULAR
NUMBER:  39927
SUBJECT: GRB250329A: REM optical afterglow detection
DATE:    25/03/29 16:25:26 GMT
FROM:    Matteo Ferro at INAF-OAB <matteo.ferro@inaf.it>

M. Ferro, R. Brivio, P. D'Avanzo, S. Covino, D. Fugazza (INAF-OAB), and A. Melandri (INAF-OAR) report on behalf of the REM team:

We observed the field of GRB250329A (Wang et al., GCN 39916) 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 29 at 04:19:30 UT (i.e. 96 s after the SVOM trigger), and lasting for about 3 hours.

From preliminary photometry we detect the counterpart in the optical images at the position of the optical afterglow (Watson et al., GCN 39915; Wang et al., GCN 39917; Schneider et al., GCN 39918; Ghosh et al., GCN 39922) with the following magnitude:

r = 17.2 +/- 0.1 (AB; calibrated against the Pan-STARRS catalogue)
at a mid-time of t - t0 = 165 s after the trigger.