GCN Circular 37422
Subject
GRB 240905E: GIT optical upper limit
Event
Date
2024-09-07T16:13:58Z (a year ago)
From
vishwajeet.s@iitb.ac.in
Via
Web form
T. Mohan, Y. Wagh, R. Kumar, V. Swain, 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 the Swift GRB 240905E (Dichiara et al., GCN 37397) with the 0.7m GROWTH-India Telescope (GIT). The observations started at 2024-09-05 20:13:28 UT, about 1.78 hours after the Swift BAT trigger. We obtained multiple images of 360s each in r', i' and z' filters respectively. We did not detect any new source in our stacked image around the coordinates reported by Swift-XRT (Dichiara et al., GCN 37397). Additionally, we examined the coordinates of the potential OT candidate reported in GCN 37415 by Belkin et al., but we did not detect the source at that location. While our upper limits are comparable to the reported detection magnitude, deeper observations are encouraged to track the source’s evolution. The obtained upper limits are:
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| JD (mid) | t-t0 (hours) | Filter | Exposure (s) | Limiting Magnitude (AB) |
| ----------------- | ------------ | ------ | ------------ | ----------------------- |
| 2460559.437685 | 2.28 | r' | 8x360 | 22.4 |
| 2460559.460185 | 2.82 | z' | 1x360 | 18.6 |
| 2460559.476852 | 3.22 | i' | 4x360 | 20.4 |
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Our upper limits are consistent with others (Lipunov et al., GCN 37398; An et al., GCN 37399; Moskvitin et al., GCN 37401; Swift/UVOT team, GCN 37402; Strausbaugh et al., GCN 37403; Brivio et al., GCN 37408; Fu et al., GCN 37409, GCN 37412; Adami et al., GCN 37413; WU et al., GCN 37414; Odeh et al., GCN 37419; Maksut et al., GCN 37420; Fu et al.). The magnitude 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 the operations of the telescope. Telescope technical details are available at https://sites.google.com/view/growthindia/.