TITLE:   GCN CIRCULAR
NUMBER:  38816
SUBJECT: GRB 241228B: 1.3m DFOT Optical observations
DATE:    25/01/04 05:44:27 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 241228B detected by the Fermi Gamma-ray Burst
Monitor (Fermi GBM team, GCN 38682), 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 17:50:12 UT, i.e., ~ 2.5 days
after the Fermi GBM 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 detected an optical emission in our stacked image at the position of the
optical counterpart candidate by GOTO collaboration (Amit et al. 2024, GCN
38684). We obtain the following preliminary magnitude in the stacked image:


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

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

2024-12-30 17:50:12     ~2.56     R     300s*24     21.23 +/- 0.05


Our detection is consistent with Amit et al. 2024, GCN 38684; An et al.
2024, GCN 38687; Kumar et al. 2024, GCN 38691; Ortega-Casas et al. 2024,
GCN 38692; Ghosh et al. 2024, GCN 38702; An et al. 2024, GCN 38704; Volnova
et al. 2024, GCN 38709; Strobl et al. 2024, GCN 38715; Moskvitin et al.
2024, GCN 38733; Kumar et al. 2024, GCN 38739.


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.