TITLE: GCN CIRCULAR NUMBER: 38853 SUBJECT: GRB 250108A: Swift-XRT afterglow detection DATE: 25/01/08 16:18:44 GMT FROM: Phil Evans at U of Leicester pae9@star.le.ac.uk
E. Ambrosi (INAF-IASFPA) , M. Capalbi (INAF-IASFPA), J.A. Kennea (PSU), D.N. Burrows (PSU), M. A. Williams (PSU), A.P. Beardmore (U. Leicester), J.P. Osborne (U. Leicester), M. Perri (SSDC & INAF-OAR) 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 250108A. 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 3.2 ks, obtained between T0+16.1 ks and T0+34.4 ks.
An uncatalogued X-ray source is detected within the estimated 3-sigma SVOM/MXTs error region (98 arcsec) and is above the LSXPS 3-sigma upper limit at this position, and is therefore likely the GRB afterglow. Using 2670 s of PC mode data and 2 UVOT images, we find an enhanced XRT position (using the XRT-UVOT alignment and matching UVOT field sources to the USNO-B1 catalogue): RA, Dec = 207.92093, +26.21642 which is equivalent to:
RA (J2000): 13h 51m 41.02s Dec(J2000): +26d 12' 59.1"
with an uncertainty of 4.1 arcsec (radius, 90% confidence). This position is 73 arcsec from the SVOM/MXTs position. The source has a mean count rate of 1.7e-02 ct/sec; we cannot determine at the present time whether it is fading.
The results of the XRT-team automatic analysis are available at http://www.swift.ac.uk/xrt_products/00021755. The results of the full analysis of the XRT observations are available at https://www.swift.ac.uk/ToO_GRBs/00021755.
This circular is an official product of the Swift-XRT team.
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