TITLE: GCN CIRCULAR NUMBER: 44655 SUBJECT: GRB 260516D: GROWTH-India Telescope optical counterpart discovery DATE: 26/05/17 01:33:09 GMT FROM: V. Swain at IIT Bombay <vishwajeet.s@iitb.ac.in> T. Mohan (IITB), V. Swain (IITB), A.P. Saikia (IITB), S. Patil (IITB), V. Bhalerao (IITB), G.C. Anupama (IIA), S. Barway (IIA) and R. Norbu (IAO) report on behalf of the GIT team: We observed the field of GRB 260515D (Brunet et al., GCN 44649), with 0.7m GROWTH-India Telescope (GIT). We started the observation at 2026-05-16 22:19:57 (UTC), i.e., 1.67 hours after the trigger, and obtained multiple exposures in the r' filter. The observations were carried out at relatively high airmass (~2). We report the discovery of the possible counterpart whose coordinates are RA, Dec = 233.827989 (deg), 6.529308 (deg). No known minor planet was found at the source position during the time of observation. The photometric results are as follows: | MJD (mid) | Filter | tmid-t0 (minutes) | Exposure Time (sec) | Magnitude (AB) | | ------------ | ------ | ----------------- | ------------------- | -------------- | | 61176.93225 | r' | 102.62 | 1x300 | 19.17 +- 0.10 | | 61176.94497 | r' | 120.93 | 1x420 | 19.45 +- 0.09 | The measurement is calibrated against PanSTARRS DR1 (Chambers et al., 2016) and not corrected for Galactic extinction. Our results are consistent with other optical observations (Jelinek et al., GCN 44653) 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/44655. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0LW...