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GCN Circular 35486

Subject
GRB 240101A: 1.3m DFOT optical observations
Date
2024-01-05T18:01:34Z (2 months ago)
From
Rahul Gupta at Aryabhatta Research Institute of Observational Sciences (ARIES) India <rahulbhu.c157@gmail.com>
Via
email
Rahul Gupta, Amit K. Ror, Amar Aryan, and Shashi B. Pandey (ARIES) report
on behalf of a larger collaboration:

We performed the optical follow-up observations of the field of new year
burst GRB 240101A detected by Swift (Cenko et al. 2024, GCN 35448),
utilizing the 1.3m Devasthal Fast Optical Telescope (DFOT) situated at the
Devasthal Observatory of the Aryabhatta Research Institute of Observational
Sciences (ARIES), India. Our observations started on 2024-01-01 at 15:37:15
UT, approximately 1.28 hours post-detection. Multiple frames were captured in
the R filter with an exposure time of 300 seconds each. Subsequently, we
aligned and stacked the images. In our stacked image, no optical afterglow
was detected within the enhanced Swift-XRT error box (Beardmore et al.
2024, GCN 35452), resulting in a preliminary 3-sigma upper limit of ~ 22.4
mag. This non-detection is consistent with the observations of Zheng et al.
2024, GCN 35453; Kuin et al. 2024, GCN 35457; and Volnova et al. 2024, GCN
35460.

Additionally, we observed a potential signature of very faint optical
emission at the position of the optical source reported by Volnova et al.
2024, GCN 35460. The detected faint optical source (if related) may
potentially represent a candidate afterglow or the associated host galaxy
of GRB 240101A. Further deep follow-up observations using larger telescopes
will help to unveil the true nature of the optical source.

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.

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