TITLE: GCN CIRCULAR NUMBER: 42411 SUBJECT: EP251023a: GROWTH-India Telescope optical observations DATE: 25/10/24 00:12:04 GMT FROM: V. Swain at IIT Bombay <vishwajeet.s@iitb.ac.in> T. Mohan (IITB), D. Eappachen (IIA), V. Swain (IITB), A.P. Saikia (IITB), V. Bhalerao (IITB), G.C. Anupama (IIA), S. Barway (IIA) and K. Angail (IAO) report on behalf of the GIT team: We observed the field of EP transient EP251023a (Wu et al., GCN 42388), with 0.7m GROWTH-India Telescope (GIT). We started the observation at 2025-10-23 20:05:36 UT, i.e., 17.57 hours after the EP trigger. We obtained multiple exposures in g', r', and i' filters. We detect the optical afterglow in our stacked images, at the position reported by GOTO (Wortley et al., GCN 42387). The photometry result follows as: | MJD (mid) | tmid - t0 (hours) | Filter | Exposure (s) | Magnitude (AB) | | --------- | ----------------- | ------ | ------------ | -------------- | |60971.87998| 18.60 | r' | 5 x 360 | 20.39+-0.09 | |60971.90145| 19.12 | i' | 5 x 360 | 20.24+-0.11 | |60971.92296| 19.63 | g' | 5 x 360 | 20.88+-0.10 | The measurement is calibrated against PanSTARRS DR1 (Chambers et al., 2016) and not corrected for Galactic extinction. Our magnitude is consistent with other optical observations (Wortley et al., GCN 42387; Li et al., GCN 42389; Liu et al., GCN 42391; Mandarakas et al., GCN 42400; Lipunov et al., GCN 42405; Selezneva et al., GCN 42406). The GROWTH India Telescope (GIT; Kumar et al. 2022) is a 70-cm telescope with a 0.7-degree field of view, set up by the Indian Institute of Astrophysics (IIA) and the Indian Institute of Technology Bombay (IITB) with funding from DST-SERB and IUSSTF. It is located at the Indian Astronomical Observatory (Hanle), operated by IIA. We acknowledge funding by the IITB alumni batch of 1994, which partially supports the operations of the telescope. Telescope technical details are available at https://sites.google.com/view/growthindia/. View this GCN Circular online at https://gcn.nasa.gov/circulars/42411. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0LW...