TITLE:   GCN CIRCULAR
NUMBER:  38815
SUBJECT: GRB 241228A: 1.3m DFOT upper limit
DATE:    25/01/04 05:40:01 GMT
FROM:    Amit Kumar Ror at ARIES <mitturor77894@gmail.com>

Amit K. Ror, Anshika Gupta, Pranshu, Shashi B. Pandey, Kuntal Mishra
(ARIES) report:


We observed the field of GRB 241228A detected by Swift (Swift Observatory
Team, D'Elia et al. 2024, GCN 38681) 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 2024-12-30 at 13:16:07 UT, i.e., ~ 2.38 days
after the Swift-BAT trigger. We have taken multiple frames with an exposure
time of 300 s in the R filter. We stacked the images after the alignment.
We could not detect the optical emission reported by Volnova et al. (2024,
GCN 38709) in our stacked image within the error box enhanced Swift-XRT
position (GCN 38683). We obtain the following 3-sigma upper limit in the
stacked image:


Date Start_UT T_start-T0 (days) Filter  Exp time (s)  Magnitude

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

2024-12-30 13:16:07    ~ 2.38     R     300s*12     >21.2


The non-detection of the burst is consistent with the upper limits reported
by Kuin et al. 2024, GCN 38685; Mohan et al. 2024, GCN 38689; Lipunov et
al. 2024, GCN 38693; Zhu et al. 2024, GCN 38703.


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 catalogue. This circular may be cited.