TITLE: GCN CIRCULAR NUMBER: 36069 SUBJECT: GRB 240411B: 1.3m DFOT Optical observations DATE: 24/04/12 10:52:24 GMT FROM: Amit Kumar Ror at ARIES <mitturor77894@gmail.com> Amit K. Ror, Anshika Gupta, Rahul Gupta, Amar Aryan, Saurabh, and Shashi B. Pandey (ARIES) report: We observed the field of GRB 240411B detected by Swift (Parsotan et al., 2024 GCN 36063) 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 2024-04-11 at 19:06:28 UT, i.e., ~ 3.56 hours after the 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 clearly detected an optical afterglow (Izzo et al., 2024, GCN 36064; Schneider et al., 2024, GCN 36067) in our final stacked image within the error box of enhanced Swift-XRT observation (Goad et al., 2024, GCN 36065). The estimated preliminary magnitude is as follows: Date Start_UT T_start-T0 (hours) Filter Exp time (s) Limiting magnitude ======================================================= 2024-04-11 19:06:28 UT 3.56 R 300*15 22.34 +/- 0.11 The detection of the afterglow is consistent with the observations of Izzo et al. 2024, GCN 36064, and Schneider et al. 2024, GCN 36067. 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/36069. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0LW...