TITLE: GCN CIRCULAR NUMBER: 39924 SUBJECT: GRB 250329A: Swift-XRT afterglow detection DATE: 25/03/29 12:53:30 GMT FROM: P.A. Evans at U. Leicester pae9@leicester.ac.uk
S. Dichiara (PSU), K.L. Page (U. Leicester), A.P. Beardmore (U. Leicester), C. Salvaggio (INAF-OAB), M. Ferro (INAF-OAB), R. Brivio (INAF-OAB), J.A. Kennea (PSU), D.N. Burrows (PSU) and P.A. Evans (U. Leicester) reports on behalf of the Swift-XRT team:
We have analysed 1.6 ks of XRT data for the SVOM/ECLAIRs-detected burst GRB 250329A, from 6.8 ks to 13.1 ks after the SVOM/ECLAIRs trigger. The data are entirely in Photon Counting (PC) mode. Using 1005 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 = 197.44646, +9.49619 which is equivalent to:
RA (J2000): 13h 09m 47.15s Dec(J2000): +09d 29' 46.3"
with an uncertainty of 4.7 arcsec (radius, 90% confidence). This position is 51 arcsec from the SVOM/ECLAIRs position, and 3.3 arcsec from the optical candidate first reported by Watson et al., (GCN. Circ 39915).
The source has a mean count rate of 3.0e-02 ct/sec and shows weak (1.4-sigma) indications of fading.
The results of the XRT-team automatic analysis are available at http://www.swift.ac.uk/xrt_products/00019666.
This circular is an official product of the Swift-XRT team.
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