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GCN Circular 32956

Subject
GRB 221120A: GIT upper limits on optical afterglow
Date
2022-11-21T01:24:33Z (a year ago)
From
Varun Bhalerao at Indian Inst of Tech <varunb@iitb.ac.in>
V. Swain (IITB), H. Kumar (IITB), R. Norboo (IAO), V. Bhalerao (IITB), G. C. Anupama (IIA), S. Barway (IIA) report on behalf of the GIT team:

We observed the short GRB 221120A detected by Swift (R. A. J. Eyles-Ferris et al., GCN 32955Not found
 
 
), with the 0.7m GROWTH-India Telescope (GIT). The observations started at 22:31:28 UT on 2022-11-20, 62 mins after the Swift trigger. We obtained multiple 300-sec exposures in the g', r' and i' filters. We did not detect any new source in our stacked images within the 1.9 arcsec radius circle around R.A.= 02h 45m 21.24s, Dec.= +43d 14' 34.1". The obtained upper limits follow as:
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JD (mid) | T_mid-T0(hrs) | Exposure (sec) | Filter | Lim_mag (5-sigma) |
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2459904.44036416 | 1.08 | 3 x 300 (stacked) | g' | > 21.24 |
2459904.46842522 | 1.75 | 8 x 300 (stacked) | r' | > 21.37 |
2459904.46658235 | 1.70 | 3 x 300 (stacked) | i' | > 20.44 | 
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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 <https://iopscience.iop.org/article/10.3847/1538-3881/ac7bea <https://iopscience.iop.org/article/10.3847/1538-3881/ac7bea>>) 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 telescope���s operations. Telescope technical details are available at https://sites.google.com/view/growthindia/ <https://sites.google.com/view/growthindia/>.