TITLE: GCN CIRCULAR NUMBER: 38322 SUBJECT: LIGO/Virgo/KAGRA S241125n: HCT upper limit DATE: 24/11/26 14:31:18 GMT FROM: V. Swain at IIT Bombay <vishwajeet.s@iitb.ac.in> V. Swain (IITB), R.S. Teja (IIA), T. Mohan (IITB), V. Bhalerao (IITB), G. C. Anupama (IIA), S. Barway (IIA), D.K. Sahu (IIA), Surya Prakash (IAO): We observed field of LIGO/Virgo/KAGRA S241125n event (GCN Circ. 38305, 38309, 38312, 38313, 38315) with the 2.0m Himalayan Chandra Telescope (HCT) of the Indian Astronomical Observatory (IAO), FOV: 10 x 10 arcmin and scale: 0.296 arcsec/pixel. We obtained multiple exposures in the SDSS r’ filter and performed image subtraction on individual images with a limiting magnitude of ~22.5. No new transient was detected in the subtracted images at the coordinate reported by DeLaunay et al., GCN 38308. Furthermore, after stacking the images and conducting catalog matching, no new source was identified. The derived upper limit is as follows: | JD (mid) | t-t0 (hours) | Filter | Exposure (s) | Upper limit (AB) | | ----------------- | ------------ | ------ | ------------------ | ---------------- | | 2460640.466157639 | 22.16 | r' | 3 x 1200 | 23 | Our result is consistent with (Watson et al., GCN 38317; Chen et al., GCN 38314). The image subtraction was performed using the ZOGY algorithm, with the PanSTARRS-1 survey used as the reference image. The magnitudes are calibrated against PanSTARRS DR1 (Chambers et al., 2016) and not corrected for Galactic extinction. These observations were carried out under the ToO program HCT-2024-C3-P38. We thank the HCT staff for their support during the observations. The Indian Astronomical Observatory is operated by the Indian Institute of Astrophysics, Bengaluru, India. View this GCN Circular online at https://gcn.nasa.gov/circulars/38322. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0LW...