TITLE: GCN CIRCULAR NUMBER: 42447 SUBJECT: GRB 251025B: GROWTH-India Telescope optical observations DATE: 25/10/25 20:34:06 GMT FROM: V. Swain at IIT Bombay <vishwajeet.s@iitb.ac.in> T. Mohan, V. Swain, S. Patil, A.P. Saikia, V. Bhalerao (IITB), G.C. Anupama, S. Barway (IIA) and K. Angail (IAO) report on behalf of the GIT team: We observed the field of SVOM GRB 251025B (Hussein et al., GCN 42437), with 0.7m GROWTH-India Telescope (GIT). We started the observation at 2025-10-25 15:47:08 UT, i.e., 1.38 hours after the SVOM trigger. Multiple exposures were obtained in the r′-filter, and we detect the optical counterpart in our stacked image. The photometry result follows as: | MJD (mid) | tmid - t0 (hours) | Filter | Exposure (s) | Magnitude (AB) | | --------- | ----------------- | ------ | ------------ | -------------- | |60973.68833| 2.12 | r' | 4 x 360 | 20.41 +- 0.11 | The measurement is calibrated against PanSTARRS DR1 (Chambers et al., 2016) and not corrected for Galactic extinction. Our result is consistent with other optical observations (WU et al., GCN 42438; Gress et al., GCN 42439; Wu et al., GCN 42440). Further multiband optical observations are ongoing. 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/42447. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0LW...