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GCN Circular 35289

GRB 231205B: REM optical/NIR upper limits
2023-12-06T14:26:13Z (6 months ago)
Riccardo Brivio <>
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R. Brivio, M. Ferro, P. D'Avanzo, S. Covino, D. Fugazza (INAF-OAB) on behalf of the REM team, report:

We observed the field of GRB 231205B (Evans et al., GCN 35269) with the REM 60cm robotic telescope located at the ESO Observatory of La Silla (Chile). The observations were carried out in the g,r,i,z, J,H,K bands, starting on 2023 Dec 06 at 00:32:29 UT (i.e. about 7.81 hours after the Swift trigger) and lasted for about 1 hour.
From preliminary analysis, we do not find any source at the enhanced XRT position (Osborne et al., GCN 35275), down the the following 3 sigma upper limits:

r > 20.4 (AB; calibrated against the Pan-STARRS catalogue)
at a mid time of t-t0 ~ 8.54 h after the GRB trigger;

H > 17.8 (Vega; calibrated against the 2MASS catalogue)
at a mid time of t-t0 ~ 8.24 h after the GRB trigger.
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