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GCN Circular 34460

Subject
GRB230816A: Possible host and GIT detection of optical counterpart
Date
2023-08-16T22:08:37Z (8 months ago)
From
Vishwajeet Swain at IIT Bombay <vishwajeet.s@iitb.ac.in>
Via
Web form
R. Kumar (IITB), R. Sharma (IITB), V. Swain (IITB), A. Salgundi (IITB), H. Kumar (IITB), G. Waratkar(IITB), V. Bhalerao (IITB), G. C. Anupama(IIA), S. Barway (IIA) and K. Angail (IAO) report on behalf of the GIT team:

We observed the field of GRB 230816A detected by SWIFT (Siegel  et al., GCN 34450) with 0.7m GROWTH-India Telescope (GIT). We started observations at 16:40:00 UT, i.e., 31.2 mins after the Swift/BAT trigger. We obtained 5 frames in the r' band of 300 sec each. After image subtraction, we detected a source in our stacked image at RA 21:53:46.96, Dec: +37:51:16.08 with an uncertainty of 0.67 arcsec - coincident with the reported afterglow (Jiang et al., GCN 34453), and 3.75 arsec away from center of the XRT error circle (Siegel et al., GCN 34450). 

We note that there is a faint source (m_r ~ 23.0) nearly coincident with the counterpart in the Pan-STARRS1 images, which could be a host of this GRB. Our image subtraction ensures that this source flux does not affect out photometric measurements. There is no minor planet present at this position. The photometric results are as follows:

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 JD (mid) | T_mid-T0 (mins) | Exposure (sec) | Filter | Magnitude (AB) |

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 2460173.202193 | 42.35  | 5 x 300 | r' | 20.61 +/- 0.06  |

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Our results are consistent with other reports (Jiang et al. GCN 34453, Moskvitin et al., GCN 34456, Pankov et al., GCN 34457, Odeh et al., GCN 34458, Klose et al., GCN 34459). We encourage photometric for further confirmation and spectroscopic follow-up for redshift measurement. The magnitudes are calibrated against PanSTARRS DR1 (Chambers et al., 2016) and are 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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