Back

GCN Circular 40938

Subject

GRB 250704A: REM detection of the optical afterglow

Event

GRB 250704A

Date

2025-07-04T07:59:57Z (13 days ago)

Edited On

2025-07-05T16:17:38Z (12 days 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UPDATE: this detection has been retracted (Brivio et al., GCN 40944Loading...
 
 ).

We observed the field of GRB 250704A detected by SVOM (Cao et al., GCN 40934Loading...
 
 ) 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.