TITLE: GCN CIRCULAR NUMBER: 38694 SUBJECT: GRB241228B: GROWTH-India Telescope optical observations DATE: 24/12/28 19:49:02 GMT FROM: V. Swain at IIT Bombay vishwajeet.s@iitb.ac.in
T. Mohan, V. Swain, 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 GRB241228B (Fermi GRB, GCN 38682) with 0.7m GROWTH-India Telescope (GIT). We started the observation at 2024-12-28 17:37:04 UT, i.e., 13.39 hours after the Fermi trigger. We obtained multiple exposures in r' filter. We detected the optical afterglow in our stacked image at position reported by Kumar et al., GCN 38684. The photometry result follows as:
| MJD (mid) | Filter | Total Exposure Time (sec) | Magnitude (AB) | | ------------- | ------ | ------------------ | -------------- | | 60672.73893 | r' | 840 | 20.05 +/- 0.1 |
Our magnitude is consistent with other optical observations (Kumar et al., GCN 38684, An et al., GCN 38687, Kumar et al., GCN 38691, Ortega-Casas et al., GCN 38692).
The measurement is 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 the operations of the telescope. Telescope technical details are available at https://sites.google.com/view/growthindia/.
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