TITLE: GCN CIRCULAR NUMBER: 33536 SUBJECT: GRB 230328B: GIT optical follow-up DATE: 23/03/29 14:22:27 GMT FROM: Varun Bhalerao at Indian Inst of Tech varunb@iitb.ac.in
A. Suresh (IITB), V. Swain (IITB), H. Kumar (IITB), P. Dorjay (IAO), V. Bhalerao (IITB), G. C. Anupama(IIA), S. Barway (IIA) report on behalf of the GIT team:
We observed GRB 230328B detected by Swift-BAT and optical afterglow discovered by Swift-UVOT (GCN 33527), with the 0.7m GROWTH-India Telescope (GIT). The observations started at 16:51:27.896 UT on 2023-03-28, 116.66 mins after the Swift-BAT trigger. We obtained multiple 300s exposures in the g', r', i', and z' filters. In stacked images for two bands, we clearly detected the afterglow at R.A.= 19h 24m 01.8s, DEC.= 80d 00' 34.5", consistent with the enhanced Swift-XRT position (GCN 33533). The photometric results follow as: ------------------------------------------------------------------- JD (mid) | T_mid-T0(hrs) | Filter| Total Exposure (s) | Magnitude (AB) | ------------------------------------------------------------------- 2460032.22721302 | 2.539 | r' | 1200 |20.181 +/- 0.054 | 2460032.23485986 | 2.723 | i' | 1200 |19.672 +/- 0.078 | 2460032.23490645 | 2.724 | g' | 600 |>20.089 | 2460032.24251012 | 2.906 | z' | 1200 |>18.503 | -------------------------------------------------------------------
These magnitudes are consistent with the reported optical afterglow detections (N. Pankov et al., GCN #33528; S. Belkin et al., GCN #33530; T.H. Lu et al., GCN #33534; A. Catapano et al., GCN #33535).
The magnitudes are calibrated against PanSTARRS DR1 (Chambers et al., 2016) and not corrected for Galactic extinction.
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 operations of the telescope. Telescope technical details are available at https://sites.google.com/view/growthindia/.