TITLE: GCN CIRCULAR NUMBER: 38831 SUBJECT: GRB 250101A: REM optical/NIR counterpart detection DATE: 25/01/06 15:58:24 GMT FROM: Matteo Ferro at INAF-OAB matteo.ferro@inaf.it
M. Ferro, R.Brivio, P. D’Avanzo, S. Covino, D. Fugazza (INAF-OAB) report on behalf of the REM team:
We observed the field of GRB 250101A, detected by Swift (Page et al., GCN 38752) 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 02 at 00:47:33 UT (i.e. 11.4 hours after the Swift trigger), and lasting for about 1 hour. From preliminary photometry we detect the counterpart in the optical and NIR images at the position of the optical afterglow (e.g., Page et al., GCN 38752; Li et al., GCN 38753; Mohan et al., GCN 38754; Zhu et al., GCN 38755; Wu et al., GCN 38758), in agreement with the rebrightening reported by Moskvitin et al., GCN 38765, with the following magnitudes:
r = 19.3 +- 0.1 (AB; calibrated against the PanSTARRS catalogue) at a mid-time of t - t0 = 11.9 hr after the trigger,
H = 17.2 +- 0.2 (Vega; calibrated against the 2MASS catalogue) at a mid-time of t - t0 = 11.9 hr after the trigger.
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