GCN 43607: GRB 260131A: FTW optical and NIR observations

Ziyuan Zhu (LMU), Malte Busmann (LMU), Julius Gassert (LMU), Xander J. Hall (CMU), Brendan O’Connor (CMU), Daniel Gruen (LMU), and Antonella Palmese (CMU) report:

We observed the counterpart of GRB 260131A (Fermi/GBM Team, GCN 43579; Frederiks et al., GCN 43590; Luo et al., GCN 43591; Li et al., GCN 43605; Jayaraman et al., GCN 43606) with the Three Channel Imager (3KK) at the Fraunhofer Telescope at Wendelstein Observatory (FTW) in the r, i, and J bands for 15x 120s, starting at 2026-02-01T22:14:35 UT, (1.65 days after the trigger). We detect the counterpart in all bands and measure an r-band magnitude of 

r = 19.18 +/- 0.03 AB mag

The magnitude is calibrated against the PS1 catalog and not corrected for Galactic extinction.

We thank Christoph Ries from the Wendelstein Observatory for obtaining these observations.