TITLE: GCN CIRCULAR NUMBER: 41372 SUBJECT: GRB 250814A: J-band upper limit from WINTER DATE: 25/08/14 15:52:22 GMT FROM: Viraj Karambelkar at Indian Inst of Tech,Bombay <karambelkarvraj21197@gmail.com> Viraj Karambelkar (Caltech), Tomas Ahumada (Caltech), Benjamin Schneider (LAM), Robert Stein (UMD), Geoffrey Mo (MIT), Danielle Frostig (CfA), Nathan Lourie (MIT), Robert Simcoe (MIT), and Mansi Kasliwal (Caltech) report: We observed the field of the Fermi and Swift GRB 250814A (Fermi team, GCN Circ. 41357, Caputo et al. GCN Circ. 41358) coincident with the sub-threshold GW trigger S250814bg (GCN Circ. 41364) in the near-infrared with the Palomar 1-m telescope, equipped with the 1-square degree WINTER camera (Lourie et al. 2020, Frostig et al. 2024). Observations started on 2025-08-14 at 07:49:52 UT (15 min after the trigger) and consisted of 15 exposures of 120 s in the J-band. In the stacked image, we do not detect any new source at the X-ray afterglow position reported by Caputo et al, GCN 41358 down to the following 5-sigma AB magnitude: J > 19.3 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). The photometric calibration was performed using nearby stars from the 2MASS catalog and the magnitude is not corrected for Galactic extinction. 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. View this GCN Circular online at https://gcn.nasa.gov/circulars/41372. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0LW...