TITLE:   GCN CIRCULAR
NUMBER:  45832
SUBJECT: GRB 261007A: WINTER J-band observations
DATE:    26/10/07 10:54:56 GMT
FROM:    tanishk.mohan@iitb.ac.in


Tanishk Mohan (IITB), Benjamin Schneider (LAM), Geoffrey Mo (Caltech/Carnegie), Viraj Karambelkar (Columbia), Tomas Ahumada (NOIRLab), Robert Stein (UMD), Danielle Frostig (CfA), Nathan Lourie (MIT), Robert Simcoe (MIT), and Mansi Kasliwal (Caltech) report:

We observed the field of GRB 261007A (Goto et al., GCN 45824; also see Wen et al., GCN 45828 and Malacaria et al., 45830) in the near-infrared J band with the Palomar 1-m telescope, equipped with the 1.2-square degree WINTER camera (Lourie et al. 2020, Frostig et al. 2024).

Observations began on 2026-10-07 at 06:10:56.150 UTC in the J band (28.9 min after the SVOM/ECLAIRs trigger), consisting of 15*120 sec exposures. The images were processed using the WINTER data reduction pipeline implemented with mirar (https://github.com/winter-telescope/mirar, https://doi.org/10.5281/zenodo.13352565).

We detect a bright source present at the optical counterpart position (Zheng et al., GCN 45825; Saccardi et al., GCN 45829) in our stacked image. 
We obtain the following magnitude: J = 17.36 +- 0.06 mag (AB) in our stacked image.
We also note that the source has faded by ~0.5 mag between our first and last exposure during the observation (in about 28 min).

WINTER (Wide-field INfrared Transient ExploreR) is a partnership between MIT and Caltech, housed at Palomar Observatory, and funded by NSF MRI, NSF AAG, the David and Lucile Packard Foundation, and the MIT Kavli Institute for Astrophysics and Space Research.