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GCN Circular 36589

GRB 240529A: 1.3m DFOT Optical observations
2024-06-01T10:34:44Z (12 days ago)
Amit Kumar Ror at ARIES <>
Amit K. Ror, Anshika Gupta, Rishi C., Shashi B. Pandey, and Kuntal Misra
(ARIES) report:

We observed the field of GRB 240529A detected by Swift (Eyles-Ferris et
al., 2024 GCN 36556) 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
2024-05-30 at 21:11:46 UT, i.e., ~ 1.76 days after the BAT trigger. We have
taken multiple frames with an exposure time of 300 s in the R filter. A
similar set of observations was also performed on 2024-05-31 at 20:34:36
UT, i.e., ~ 2.734 days after the BAT trigger. We stacked the images after
the alignment. We clearly detected an optical afterglow in our final
stacked image within the error box of enhanced Swift-XRT and UVOT
observations (Osborne et al., 2024, GCN 36557; Shilling et al., 2024, GCN
36562). The estimated preliminary magnitude is as follows:

Date Start_UT T_start-T0 (days) Filter  Exp time (s)  Magnitude
2024-05-30 21:11:46 UT    1.76     R     300*20     20.15 +/- 0.04

The detection of the GRB afterglow is consistent with the observations of
Kumar et al., 2024, GCN 36559; Fu et al., 2024, GCN 36561; Shilling et al.,
2024, GCN 36562; Perez-Garcia et al., 2024, GCN 36563; Dutton et al., 2024,
GCN 36568; Mo et al., 2024, GCN 36569; Odeh et al., 2024, GCN 36573;
Postigo et al., 2024, GCN 36574; Adami et al., 2024, GCN 36575; Mohan et
al., 2024, GCN 36576; Vinko et al., 2024, GCN 36577; Lim et al., 2024, GCN
36579; Moskvitin et al., 2024, GCN 36582; and Pankov et al., 2024, GCN

By combining our magnitudes with the observations of Moskvitin et al.
(2024, GCN 36582) and Pankov et al. (2024, GCN 36585), we have calculated
the decay index ~ 1.44 of the R-band light curve at late time.

The given magnitude value is not corrected for the Galactic and host
extinctions in the direction of the GRB afterglow. Photometric calibration
is performed using the standard stars from the USNO-B1.0 catalog. This
circular may be cited.

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