GCN Circular 40938
Subject
GRB 250704A: REM detection of the optical afterglow
Event
Date
2025-07-04T07:59:57Z (a day ago)
Edited On
2025-07-05T16:17:38Z (4 hours ago)
From
Riccardo Brivio at INAF-OAB <riccardo.brivio@inaf.it>
Edited By
Judith Racusin at NASA/GSFC <judith.racusin@nasa.gov> on behalf of Riccardo Brivio at INAF-OAB <riccardo.brivio@inaf.it>
Via
Web form
R. Brivio, M. Ferro (INAF-OAB), S. D. Vergani (LUX-Paris Obs.), A. Melandri (INAF-OAR), P. D'Avanzo, S. Covino, D. Fugazza (INAF-OAB) report on behalf of the REM team:
UPDATE: this detection has been retracted (Brivio et al., GCN 40944).
We observed the field of GRB 250704A detected by SVOM (Cao et al., GCN 40934) 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, z, J, H, and K bands, started on 2025 July 04 at 05:19:02 UT (i.e. 1.6 hr after the burst), and lasted for about 2 hours.
From preliminary inspection, we detect the optical afterglow within the SVOM/MXT error region at the coordinates (J2000):
RA = 01:08:46.5
Dec = -17:19:28.0
and with the following magnitude:
r = 17.6 +/- 0.2 (AB; calibrated against the Pan-STARRS catalogue),
at a mid-time of 1.7 hr after the trigger.
No NIR counterpart is detected down to the following 3sigma upper limit:
H > 15.6 (Vega; calibrated against the 2MASS catalogue),
at a mid-time of 1.8 hr after the trigger.