TITLE:   GCN CIRCULAR
NUMBER:  33090
SUBJECT: GRB 221218A: 3.6m DOT optical upper limit
DATE:    22/12/21 21:44:51 GMT
FROM:    Rahul Gupta at ARIES, India  <rahulbhu.c157@gmail.com>

Rahul Gupta, Amit K. Ror, S. B. Pandey, A. Aryan, A. Ghosh, Dimple, and K.
Misra (ARIES) report:


We observed the field of GRB 221218A detected by INTEGRAL (Mereghetti et al.,
GCN 33082) using the 4Kx4K CCD Imager (Pandey et al. 2017,
arXiv:1711.05422v1) mounted at the axial port of the 3.6m Devasthal Optical
Telescope of ARIES Nainital. We have taken multiple frames having an
exposure time of 300 sec in the R filter. We stacked the images after the
alignment. We do not find any evidence of an afterglow candidate inside the
INTEGRAL error circle, consistent with other non-detections (Lipunov et al.,
GCN 33081; Zheng et al., GCN 33085; Hu et al., GCN 33086; and Takahashi et
al., GCN 33087). We obtained the limiting mag of ~ 22.8 mag at ~ 2.3 days
post-detection. Despite early to late time deep optical follow-up
observations, the non-detection of the optical counterpart of GRB 221218A
indicates the dark nature of the burst, although more detailed analysis is
needed to confirm.

The limiting magnitudes quoted are not corrected for the Galactic and host
extinction in the direction of the burst. Photometric calibration is
performed using the standard stars from the USNO-B1.0 catalogue.

This circular may be cited. 3.6m Devasthal Optical Telescope (DOT) is
the recently commissioned facility in the Northern Himalayan region of
India (long:79 41 04E, lat:29 21 40N, alt:2540m) owned and operated by the
Aryabhatta Research Institute of Observational Sciences (ARIES), Nainital (
https://www.aries.res.in). Authors of this GCN circular thankfully
acknowledge consistent support from the staff members to run and maintain
the 3.6m DOT.