TITLE:   GCN CIRCULAR
NUMBER:  39763
SUBJECT: GRB 250317B: Swift-XRT observations
DATE:    25/03/17 15:05:53 GMT
FROM:    Andrea Melandri at INAF-OAR <andrea.melandri@inaf.it>

A. Melandri (INAF-OAR), V. D'Elia (SSDC & INAF-OAR), E. Ambrosi, A. D'Ai (INAF-IASFPA) , J.A. Kennea (PSU) 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 GRB 250317B (Zhao et al., GCN circ. 39752 and GCN circ. 39753) and SVOM/MXT (Götz et al., GCN circ. 39756), collecting  1.7 ks of Photon Counting (PC) mode data between T0+10.0 ks and T0+12.9 ks (SVOM burst-id sb25031701). 

One uncatalogued X-ray source has been detected within the estimated 3-sigma SVOM/MXT error region (Götz et al., GCN circ. 39756), consistent with the optical counterpart (Watson et al., GCN 39754). The source is fading with 3.0-σ significance. Details of this source are given below:

Source 1:
  RA (J2000.0):  211.6427  =  14:06:34.3
  Dec (J2000.0): +40.0796  =  +40:04:46.7
  Error: 3.0 arcsec (radius, 90% conf. [Enhanced position])
  Count-rate: 0.19 (±0.04) ct s-1   
  Flux: 3.7 (±0.4) ×10-12 erg cm-2 s-1 (observed, 0.3-10 keV)

The results of the XRT-team automatic analysis of the XRT observations, including a position-specific upper limit calculator, are available at https://www.swift.ac.uk/SVOM/SVOM_FIELD00003/.

This circular is an official product of the Swift-XRT team.