GCN Circular 39557
Subject
EP250302a: Swift-XRT observations of a fading X-ray source
Date
2025-03-03T07:43:50Z (3 months ago)
From
K.L. Page at U Leicester <klp5@leicester.ac.uk>
Via
email
K.L. Page, P.A. Evans (U.Leicester) and J. DeLaunay (PSU) report on
behalf of the Swift XRT Team:
On 2025 March 02 at 16:36 UT, Swift started observing EP250302a, 3.6 ks
after the trigger (GCN Circ. 39556). A fading X-ray source was identified,
at a position of RA, Dec = 169.51508, +33.5858, which is equivalent to
RA (J2000): 11h 18m 03.62s
Dec (J2000): +33d 35′ 09.0″
with an uncertainty of 2.6 arcsec (radius, 90% confidence). This position
is consistent with the optical counterpart reported in GCNs 39550, 39551,
39553 and 39555.
The X-ray flux at the start of the observation was (5.0 +-/ 1.1) x 10^-11
erg cm^-2 s^-1 (0.3 - 10 keV), fading to a value of (7.1 +/- 0.9) x 10^-12
erg cm^-2 s^-1 at 8 ks post trigger. The decay can be fitted with a
power-law slope of alpha = 2.36 (+0.37/-0.32).