GCN Circular 41799
Subject
GRB 250910A / EP250910a: Swift-XRT afterglow detection
Event
Date
2025-09-11T16:29:52Z (a day ago)
From
Phil Evans at U of Leicester <pae9@star.le.ac.uk>
Via
email
S. Lanava (PSU), S. Dichiara (PSU), J.A. Kennea (PSU), J.P. Osborne (U.
Leicester), K.L. Page (U. Leicester), A.P. Beardmore (U. Leicester), M.
Perri (SSDC & INAF-OAR), V. D'Elia (SSDC & INAF-OAR), B. Sbarufatti
(INAF-OAB) and P.A. Evans (U. Leicester) reports on behalf of the
Swift-XRT team:
Swift-XRT has performed follow-up observations of GRB 250910A. We
searched for X-ray sources in 1.2 ks of Photon Counting (PC) mode
data. The total exposure at the position of the afterglow (see below)
is 1.2 ks, obtained between T0+29.5 ks and T0+30.7 ks.
An uncatalogued X-ray source is detected and is believed to be the
afterglow. Using 1195 s of PC mode data and 1 UVOT image, we find an
enhanced XRT position (using the XRT-UVOT alignment and matching UVOT
field sources to the USNO-B1 catalogue): RA, Dec = 39.80164, -39.69498
which is equivalent to:
RA (J2000): 02h 39m 12.39s
Dec(J2000): -39d 41' 41.9"
with an uncertainty of 8.4 arcsec (radius, 90% confidence). This source
is consistent with the position reported by EP/FXT (Liu et al., GCN
41776) and with the optical/NIR source detected with VLT (Schneider et
al., GCN 41794) and SVOM/VT (Li et al., GCN 41798). We cannot determine
at the present time whether the source is fading.
The results of the XRT-team automatic analysis are available at
http://www.swift.ac.uk/xrt_products/03000083.
The results of the full analysis of the XRT observations are available
at https://www.swift.ac.uk/SVOM/SVOM_FIELD00036.
This circular is an official product of the Swift-XRT team.