TITLE: GCN CIRCULAR NUMBER: 39079 SUBJECT: GRB 250129A: REM optical/NIR afterglow detection DATE: 25/01/29 11:27:01 GMT FROM: Riccardo Brivio at INAF-OAB <riccardo.brivio@inaf.it> R. Brivio, M. Ferro, P. D’Avanzo (INAF-OAB), D.B. Malesani (DAWN/NBI and Radboud Univ.), M. De Pasquale (Univ. of Messina), L. Izzo (INAF-OACn and DARK/NBI), A. Melandri (INAF-OAR), G. Tagliaferri, S. Covino, D. Fugazza (INAF-OAB) report on behalf of the REM team: We observed the field of GRB 250129A detected by Swift (Beardmore et al., GCN 39066) 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 2025 January 29 at 04:47:12 UT (i.e. 123 s after the Swift trigger), and lasting for about 4 hours. From preliminary photometry we detect the counterpart in the optical and NIR images at the position of the optical afterglow (Francile et al., GCN 39065; Schneider et al., GCN 39071; Belkin et al., GCN 39072; Izzo et al., GCN 39073; Izzo & Malesani, GCN 39074; Gosh et al., GCN 39077; Schneider et al., GCN 39078) with the following early-time magnitudes: r = 17.7 +/- 0.3 (AB; calibrated against the Pan-STARRS catalogue) at a mid-time of t - t0 = 128 s after the trigger. H = 15.3 +/- 0.3 (Vega; calibrated against the 2MASS catalogue) at a mid-time t - t0 = 175 s after the trigger. Our light curve spans between t0 + 128 s and t0+15120 s. It peaks around t0+2300 s and shows a rebrightening around t0+14300 s. View this GCN Circular online at https://gcn.nasa.gov/circulars/39079. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0LW...