TITLE:   GCN CIRCULAR
NUMBER:  37822
SUBJECT: GRB 241018A: REM optical/NIR upper limits
DATE:    24/10/19 11:12:34 GMT
FROM:    Matteo Ferro at INAF-OAB <matteo.ferro@inaf.it>


M. Ferro, P. D’Avanzo, M. G. Bernardini, D. Fugazza, R. Brivio, Y.-D. Hu, and S. Covino  (INAF-OAB), report on behalf of the REM team:

We observed the field of GRB 241018A detected by SVOM (Atteia et al., GCN 37812; Maggi et al., GCN 37814; Qiu et al., GCN 37819), 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, H bands, starting on 2024 October 19 at 07:08:55 UT (i.e. 19.2 hours after the Fermi trigger), and lasting for about 40 minutes.

From preliminary photometry at the best candidate afterglow position (Qiu et al., GCN 37819; Malesani et al., GCN 37821) we did not detect any optical/NIR counterpart down to the following 3sigma magnitude upper limits:

H > 17.5 (Vega; calibrated against the 2MASS catalogue)
r > 18.9  (AB; calibrated against the PS1 catalogue)
at a mid-time of t - t0 = 19.5 hours after the trigger.