TITLE: GCN CIRCULAR NUMBER: 38492 SUBJECT: GRB 241209A: REM optical/NIR observations DATE: 24/12/09 16:46:39 GMT FROM: Riccardo Brivio at INAF-OAB <riccardo.brivio@inaf.it> R.Brivio, M. Ferro, P. D’Avanzo, S. Covino, Y.-D. Hu, D. Fugazza (INAF-OAB) report on behalf of the REM team: We observed the field of GRB 241209A detected by Swift/BAT (Parsotan et al., GCN 38476) and Fermi/GBM (Fermi GBM team, GCN 38474) 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 2024 December 09 at 05:40:01 UT (i.e. 4.3 minutes after the Swift trigger), and lasting for about 2 hours. From preliminary photometry we do not detect any clear counterpart in the optical and NIR images at the Swift-XRT refined position (Evans et al., GCN 38486) down to the following 3sigma magnitude upper limits: r > 19.5 (AB; calibrated against the PanSTARRS catalogue) at a mid-time of t - t0 = 67.13 minutes after the trigger, J > 18.0 H > 16.1 (Vega; calibrated against the 2MASS catalogue) at a mid-time of t - t0 = 42.1 and 29.8 minutes after the trigger, respectively. View this GCN Circular online at https://gcn.nasa.gov/circulars/38492. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0LW...