TITLE:   GCN CIRCULAR
NUMBER:  37352
SUBJECT: GRB 240828B: J-band upper limit from WINTER
DATE:    24/08/30 19:23:34 GMT
FROM:    Benjamin Schneider at MIT <bschn@mit.edu>

Benjamin Schneider (MIT), Geoffrey Mo (MIT), Robert Stein (Caltech), Viraj Karambelkar (Caltech), Nathan Lourie (MIT), Danielle Frostig (MIT), Tomas Ahumada (Caltech), Robert Simcoe (MIT), and Mansi Kasliwal (Caltech) report:

We observed the field of the SVOM/ECLAIRs GRB 240828B (Le Provost et al, GCN 37318) in the near-infrared J-band with the Palomar 1-m telescope, equipped with the 1-square degree WINTER camera (Lourie et al. 2020).

Our observations began at 2024-08-29T09:00:15 UTC (~20 hours after the GRB trigger) and consisted of 30x120s exposures. The images were processed using the WINTER data reduction pipeline (https://github.com/winter-telescope/mirar, https://doi.org/10.5281/zenodo.10888436), with image subtraction performed relative to J-band images from the UKIRT Hemisphere survey (Dye et al., 2017).

In our stacked and subtracted images, we do not detect any new source within the Swift/XRT error circle (Page et al., GCN 37334) down to a 5-sigma depth of J ~ 19.2 mag (AB). 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.