TITLE: GCN CIRCULAR NUMBER: 40615 SUBJECT: GRB 250603A: Swift-XRT position and confirmation of GRB nature DATE: 25/06/03 05:40:03 GMT FROM: K.L. Page at U Leicester klp5@leicester.ac.uk
K.L. Page and P.A. Evans (U. Leicester) report on behalf of the Swift-XRT team:
The XRT began observing the field of GRB 250603A (GCN Circ. 40613) at 01:12:04.7 UT, 101.7 seconds after the BAT trigger. Using promptly-collected data (although downlinked after a delay), we find a fading, uncatalogued X-ray source with an enhanced position: RA, Dec 129.93750, -39.29289 which is equivalent to: RA(J2000) = 08h 39m 45.00s Dec(J2000) = -39d 17' 34.4" with an uncertainty of 1.9 arcseconds (radius, 90% containment). This location is 104 arcseconds from the BAT onboard position, within the BAT error circle.
Given the nature of the fading X-ray light-curve, we confirm this trigger as GRB 250603A, and not a new Galactic transient.
This circular is an official product of the Swift-XRT team.
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