GCN Circular 39679
Subject
GRB 250309B: 1.3m DFOT Optical observations
Event
Date
2025-03-12T06:18:47Z (7 months ago)
Edited On
2025-08-11T15:38:03Z (2 months ago)
From
Amit Kumar Ror at ARIES <mitturor77894@gmail.com>
Edited By
Vidushi Sharma at NASA GSFC/UMBC <vidushi.sharma@nasa.gov> on behalf of Amit Kumar Ror at ARIES <mitturor77894@gmail.com>
Via
email
Amit K. Ror, Anshika Gupta, Pranshu, Shashi B. Pandey, Kuntal Mishra
(ARIES) report:
We observed the field of GRB 230509B detected by the Swift and Fermi (Evans
et al. 2025, GCN 39633; Fermi GBM team, GCN 39635, 39642) 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 2025-03-10 at 20:25:19 UT,
i.e., ~ 1.53 days after the Ferm-GBM trigger. We have taken multiple frames
with an exposure time of 300s in the R filter. We stacked the images after
the alignment. We detected an optical afterglow reported by Stein et al.
2025 (GCN 39639) in our stacked image. We obtain the following preliminary
magnitude in the stacked image:
Date Start_UT T_start-T0 (days) Filter Exp time (s) Magnitude
=========================================================
2025-03-10 20:25:19 ~1.53 R 300s*24 20.36 +/- 0.10
Our detection is consistent with Stein et al. 2025 (GCN 39639); Lipunov et
al. 2025 (GCN 39641); Pérez-Fournon et al. 2025 (GCN 39643); Stein et al.
2025 (GCN 39644); Moskvitin et al. 2025 (GCN 39645); Perley et al. 2025
(GCN 39646); Malesani et al. 2025 (GCN 39647); Ducoin et al. 2025 (GCN
39650); Shin et al. 2025 (GCN 39654); Moskvitin et al. 2025 (GCN 39658);
Wang et al. 2025 (GCN 39661) and Guiffreda et al. 2025 (GCN 39670).
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.