TITLE: GCN CIRCULAR NUMBER: 40987 SUBJECT: GRB 250704B: Swift-XRT refined Analysis DATE: 25/07/06 11:00:24 GMT FROM: Phil Evans at U of Leicester <pae9@star.le.ac.uk> C. Salvaggio (INAF-OAB), M. Ferro (INAF-OAB), R. Brivio (INAF-OAB), S. Dichiara (PSU), J.A. Kennea (PSU), D.N. Burrows (PSU), K.L. Page (U. Leicester), A.P. Beardmore (U. Leicester), E. Ambrosi (INAF-IASF PA) and P.A. Evans (U. Leicester) reports on behalf of the Swift-XRT team: We have analysed 3.3 ks of XRT data for GRB 250704B, from 2.0 ks to 97.7 ks after the Einstein Probe/WXT trigger. The data are entirely in Photon Counting (PC) mode. Using 1717 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 = 300.87238, +12.02301 which is equivalent to: RA (J2000): 20h 03m 29.37s Dec(J2000): +12d 01' 22.9" with an uncertainty of 2.7 arcsec (radius, 90% confidence). The light curve can be modelled with a power-law decay with a decay index of alpha=0.9 (+0.4, -0.3). A spectrum formed from the PC mode data can be fitted with an absorbed power-law with a photon spectral index of 1.96 (+0.16, -0.13). The best-fitting absorption column is consistent with the Galactic value of 1.5 x 10^21 cm^-2 (Willingale et al. 2013). The counts to observed (unabsorbed) 0.3-10 keV flux conversion factor deduced from this spectrum is 3.6 x 10^-11 (4.3 x 10^-11) erg cm^-2 count^-1. A summary of the PC-mode spectrum is thus: Total column: 1.47 (+/-0.25) x 10^21 cm^-2 Galactic foreground: 1.5 x 10^21 cm^-2 Excess significance: <1.6 sigma Photon index: 1.96 (+0.16, -0.13) The results of the XRT-team automatic analysis are available at http://www.swift.ac.uk/xrt_products/00019908. This circular is an official product of the Swift-XRT team. View this GCN Circular online at https://gcn.nasa.gov/circulars/40987. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0LW...