GCN Circular 45623
Subject
GRB 260915A: Swift-XRT afterglow detection
Event
Date
2026-09-18T06:26:48Z (a day ago)
From
Phil Evans at U of Leicester <pae9@star.le.ac.uk>
Via
email
K.L. Page (U. Leicester), M. Perri (SSDC & INAF-OAR), V. D'Elia (SSDC &
INAF-OAR), J.A. Kennea (PSU), S. Lanava (PSU), A.P. Beardmore (U.
Leicester), J.P. Osborne (U. Leicester), 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 the
SVOM/ECLAIRs-detected burst GRB 260915A. We searched for X-ray sources
in 2.7 ks of Photon Counting (PC) mode data. The total exposure at the
position of the afterglow (see below) is 2.7 ks, obtained between
T0+174.4 ks and T0+246.9 ks.
An uncatalogued X-ray source is detected within the estimated 3-sigma
SVOM/MXT error region (49 arcsec). While the source does not fade
during the Swift-XRT observation, the measured flux of 2.0 (+7.4,
-1.4)e-13 erg cm^-2 s^-1 (0.3-10 keV) is more than an order of
magnitude below the EP value of 7.8 (+/- 0.4)e-12 erg cm^-2 s^-1
(0.5-10 keV) at T0+6 ks, reported in GCN Circ. 45587. This source is
therefore believed to be the afterglow. The position of this source is
RA, Dec=8.1546, +8.2487 which is equivalent to:
RA (J2000): 00h 32m 37.11s
Dec(J2000): +08d 14' 55.5"
with an uncertainty of 8.5 arcsec (radius, 90% confidence). This
position is 23 arcsec from the SVOM/MXT position, and 11 arcsec from
the EP-FXT position.
The results of the XRT-team automatic analysis are available at
https://www.swift.ac.uk/xrt_products/00021912.
The results of the full analysis of the XRT observations are available
at https://www.swift.ac.uk/ToO_GRBs/00021912.
This circular is an official product of the Swift-XRT team.