TITLE: GCN CIRCULAR NUMBER: 41377 SUBJECT: GRB 250814A: Possible afterglow candidate from P200/WIRC DATE: 25/08/14 19:35:32 GMT FROM: Viraj Karambelkar at Indian Inst of Tech,Bombay karambelkarvraj21197@gmail.com

Viraj Karambelkar (Caltech), Mansi Kasliwal (Caltech), Steven Giacalone (Caltech), Emily Gilbert (IPAC), Matt Lastovka (UMD), Vishwajeet Swain (IITB), Gaurav Waratkar (IITB), Tomas Ahumada (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 J and Ks bands with the Wide-field infrared Camera (WIRC, Wilson et al. 2003) on the Palomar 200-inch telescope. Observations started on 2025-08-14 at 11:31:29 UT and lasted for 1665 seconds in the J-band, and started at 12:09:12 UT and lasted for 810 seconds in the Ks-band.

We marginally detect a faint source in the Ks-band image at RA=20:25:13.9, Dec=48:23:55.9 (J2000), ~0.6 arcsec from the enhanced position of the X-ray counterpart reported by Caputo et al (GCN 41358). We also detect a marginal source at this location in the more sensitive J-band image, however, it is blended with several faint sources and is near the detection limit of the image. We performed aperture photometry at the location of this source and measured the following magnitudes

Ks ~ 21.2 +/- 0.35 mag (AB),

J ~ 21.6 mag +/- 0.4 mag (AB)

We encourage deep NIR observations to trace the brightness evolution and confirm the nature of this source.

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