GCN 43601: GRB 260131A/B (AT2026bwg): J-band observations by SYSU 80cm infrared telescope

Yun Shi, Jin-Ji Li, Pu Lin, Hao-Nan Yang, Zhong-Nan Dong, Yan Yu, Jia-Qi Lin, Wei-Sen Huang, Chun Chen, Duo-Le Cao, P H Thomas Tam, Rong-Feng Shen, Bin Ma (Sun Yat-sen University) report on behalf of the SYSU 80cm infrared telescope team:

We observed the field of GRB 260131A/B (Fermi/GBM Team, GCN 43579; Sugai et al., GCN 43580; Roberts et al., GCN 43585; Frederiks et al., GCN 43590; Luo et al., GCN 43591), using the Sun Yat-sen University (SYSU) 80cm infrared telescope. Our observations were carried out on 2026 Feb 01 14:39 UT, 31.99 hours after the GRB trigger, using stacked images in the J band.

We clearly detect an infrared counterpart at the position of the optical afterglow candidate AT2026bwg / GOTO26akj (Gompertz et al., GCN 43586; Lee et al., GCN 43587; Saccardi et al., GCN 43595; García García et al., GCN 43599). The preliminary photometric results are summarized in the table below. The photometry was calibrated against nearby stars from the 2MASS catalog and is reported in the Vega system, without correction for Galactic extinction.

Start Time (UTC)  |Band | Exp  | Mag (Vega)
-------------------------|-------|---------|------------------
2026/2/1 14:39:25  | J   | 600s  | 16.9+/-0.2
2026/2/1 14:49:48  | J   | 600s  | 17.0+/-0.2
2026/2/1 15:00:10  | J   | 600s  | 17.1+/-0.2
2026/2/1 15:10:33  | J   | 840s  | 17.0 +/-0.2

The SYSU 80cm infrared telescope is operated and managed by the Department of Astronomy, Sun Yat-sen University.