GCN Circular 34853
Subject
GRB 231017A: 1.3m DFOT Optical upper limit
Date
2023-10-20T17:12:08Z (a year ago)
From
Amit Kumar Ror at ARIES <mitturor77894@gmail.com>
Via
email
Amit K. Ror, Rahul Gupta, Amar Aryan, Shashi B. Pandey, Rishi C., and
Neelam Panwar (ARIES) report:
We observed the field of Fermi, and Swift detected GRB 231017A (Fermi GCM
Team GCN 34822; Mangan et al. 2023, GCN 34830; DeLaunay et al. 2023, GCN
34824; and Swift team GCN 34825) with the 1.3m Devasthal Fast Optical
Telescope (DFOT), located at the Devasthal Observatory of the Aryabhatta
Research Institute of Observational Sciences (ARIES), India. The
observations were started on 2023-10-18 at 22:19:07 UT, i.e., ~ 1.6 days
after the GBM trigger. We have taken multiple frames with an exposure time
of 100 s in the R filter. We stacked the images after the alignment. We did
not detect any optical afterglow in our stacked image within the error box
of Swift-XRT observation (Dichiara et al., 2023, GCN 34829). We obtain the
following preliminary 3-sigma upper limit in the stacked image:
Date Start_UT T_start-T0 (days) Filter Exp time (s) Limiting magnitude
=========================================================
2023-10-18 22:19:07 1.6 R 100*36 > 21.6
Our non-detection is consistent with Kumar et al. 2023, GCN 34833;
Strausbaugh et al. 2023, GCN 34834; Shrestha et al. 2023, GCN 34836; Xu et
al. 2023, GCN 34840; and Belkin et al. 2023, GCN 34841.
The magnitude is not corrected for the Galactic extinction in the direction
of the burst. Photometric calibration is performed using the standard stars
from the USNO-B1.0 catalog. This circular may be cited.