TITLE: GCN CIRCULAR NUMBER: 28876 SUBJECT: ZTF20acozryr (GRB 201103B): GROWTH-India Telescope optical observations DATE: 20/11/10 15:25:55 GMT FROM: Harsh Kumar at Indian Inst of Tech,Bombay K. Sharma (IITB), H. Kumar (IITB), P. Dorjay (IAO), J. Stanzin (IAO), U. Stanzin (IAO), V. Bhalerao (IITB), G. C. Anupama (IIA), S. Barway (IIA), report on behalf of the GROWTH-India collaboration: We followed-up the optical afterglow ZTF20acozryr (Michael Coughlin et. al., GCN #28841) of GRB 201103B, detected by the AGILE (GCN #28831) and IPN (D. Svinkin et. al. GCN #28844), with 0.7 m GROWTH-India telescope. We obtained 300-sec exposures in the SDSS r' filter over multiple nights. Here are the photometric results from GIT observations:- -------------------------------------------------- JD (mid) | Filter | Exposure | mag | e_mag | -------------------------------------------------- 2459160.322200 | r' | 300 x 20 | 21.08 | 0.08 | 2459163.145455 | r' | 300 x 30 | 21.91 | 0.06 | -------------------------------------------------- Combining our photometric results with r/r' band measurements of Michael Coughlin et. al., GCN #28841; D. Xu et. al., GCN #28846; D. Xu et. al., GCN #28847; S. Belkin et. al., GCN #28862; we conclude that the source is fading with a power-law index of 1.16 +/- 0.07. The magnitudes are calibrated against PanSTARRs PS1 data release, (Flewelling et al., 2018) and are not corrected for galactic extinction. The GROWTH India Telescope (GIT) is a 70-cm telescope with a 0.7 degree field of view, set up by the Indian Institute of Astrophysics and the Indian Institute of Technology Bombay with support from the Indo-US Science and Technology Forum (IUSSTF) and the Science and Engineering Research Board (SERB) of the Department of Science and Technology (DST), Government of India (https://sites.google.com/view/growthindia/). It is located at the Indian Astronomical Observatory (Hanle), operated by the Indian Institute of Astrophysics (IIA).