GRB 230509B
GCN Circular 39633
Subject
GRB 230509B: Tiled Swift observations
Date
2025-03-09T13:15:21Z (3 months ago)
Edited On
2025-03-09T19:31:27Z (3 months ago)
From
Phil Evans at U of Leicester <pae9@star.le.ac.uk>
Edited By
Judith Racusin at NASA/GSFC <judith.racusin@nasa.gov> on behalf of P.A. Evans at U. Leicester <pae9@leicester.ac.uk>
Via
email
P. A. Evans (U. Leicester) reports on behalf of the Swift team:
Swift has initiated a series of observations, tiled on the sky, of the
location of the Fermi/GBM GRB 250309B and IceCube-250309A. Automated analysis of
the XRT data will be presented online at
http://www.swift.ac.uk/xrt_products/TILED_GRB00134
Any uncatalogued X-ray sources detected in this analysis will be
reported on this website and via GCN COUNTERPART notices. The probability of finding
serendipitous sources, unrelated to the Fermi/GBM event is high: any X-ray source
considered to be a probable afterglow candidate will be reported via a GCN Circular
after manual consideration.
Details of the XRT automated analysis methods are detailed in Evans et
al. (2007, A&A, 469, 379; 2009, MNRAS, 397, 1177 and 2014, ApJS, 210, 8).
This circular is an official product of the Swift-XRT team.
GCN Circular 39679
Subject
GRB 230509B: 1.3m DFOT Optical observations
Date
2025-03-12T06:18:47Z (3 months ago)
From
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.