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GCN Circular 32662

Subject
GRB 221009A / Swift J1913.1+1946: GIT detection of the optical afterglow
Date
2022-10-10T15:38:59Z (2 years ago)
From
Harsh Kumar at Indian Inst of Tech,Bombay <harshkosli13@gmail.com>
H. Kumar (IITB), V. Swain (IITB), G. Waratkar (IITB), K. Angail (IAO), V.
Bhalerao (IITB), G. C. Anupama(IIA), S. Barway (IIA) report on behalf of
the GIT team:

We observed Swift J1913.1+1946/GRB 221009A detected by Swift (S. Dichiara
et al., GCN #32632), Fermi (P. Veres et al., GCN #32636), INTEGRAL
(SPI-ACS) (Gotz et al., GCN #32660), and Konus-Wind (D. Svinkin et al., GCN
#32641), with 0.7m GROWTH-India Telescope (GIT). We obtained 200-sec
exposures in the g' and r' filters. We clearly detected the afterglow
candidate in our images at the position of Swift J1913.1+1946/GRB 221009A.
The photometric results follow as:

-------------------------------------------------------------------

 JD (mid) | T_mid-T0(hrs) | Filter | Magnitude (AB) |

-------------------------------------------------------------------

2459862.18181 | 2.19 | g' | 17.66 +/- 0.07 |

2459862.18451 | 2.25 | r' | 16.16 +/- 0.07 |

-------------------------------------------------------------------
The results are consistent with Lipunov et al., GCN #. 32634 and 32639;
Perley GCN #32638;  Broens, GCN #32640; Hu et al., GCN #32644; Belkin et
al. GCN #32645; de Wet et al. GCN #32646; Xu et al. GCN #32647; Odeh, GCN
#32649; Brivio et al. GCN # 32652. The magnitudes are calibrated against
PanSTARRS DR1 (Chambers et al., 2016) and not corrected for Galactic
extinction.

The GROWTH India Telescope (GIT) 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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