TITLE: GCN CIRCULAR NUMBER: 36589 SUBJECT: GRB 240529A: 1.3m DFOT Optical observations DATE: 24/06/01 10:34:44 GMT FROM: Amit Kumar Ror at ARIES <mitturor77894@gmail.com> 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 36585. 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. View this GCN Circular online at https://gcn.nasa.gov/circulars/36589. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0LW...