TITLE:   GCN CIRCULAR
NUMBER:  37837
SUBJECT: GRB 241018A: 1.3m DFOT Optical upper limit
DATE:    24/10/22 09:30:43 GMT
FROM:    Amit Kumar Ror at ARIES <mitturor77894@gmail.com>

Amit K. Ror, Ansika Gupta, Arjun Dawn, Shashi B. Pandey, Kuntal Mishra
(ARIES) report:


We observed the field of GRB 241018A detected by SVOM (SVOM Team, GCN
37812, 37819, 37826), 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 2024-10-18 at 17:37:02 UT, i.e., ~ 0.24 days after the SVOM
trigger. We have taken multiple frames with an exposure time of 300 s in
the R filter. The observations were taken in the bright moon phase. We
stacked the images after the alignment. We did not detect any optical
afterglow (SVOM Team, GCN 37819) in our stacked image within the error box
of the improved burst position by SVOM (SVOM Team, GCN 37826). 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

=========================================================

2024-10-18 17:37:02     0.24     R     300s*12     > 20.9


Our non-detection is consistent with Turpin et al. 2024, GCN 37818; SVOM
Team, GCN 37819; Malesani et al. 2024, GCN 37821; Ferro et al. 2024, GCN
37822; Song et al. 2024, GCN 37824; Mohan et al. 2024, GCN 37825; Pankov et
al. 2024, GCN 37827; Garcia et al. 2024, GCN 37828; and Liu et al. 2024,
GCN 37830.


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.