TITLE: GCN CIRCULAR NUMBER: 42284 SUBJECT: GRB 251014D: Swift-XRT afterglow detection DATE: 25/10/15 10:20:16 GMT FROM: Phil Evans at U of Leicester <pae9@star.le.ac.uk> K.L. Page (U. Leicester), A.P. Beardmore (U. Leicester), S. Campana (INAF-OAB), A. Melandri (INAF-OAR), T. Sbarrato (INAF-OAB), S. Dichiara (PSU), J.A. Kennea (PSU), D.N. Burrows (PSU) and P.A. Evans (U. Leicester) reports on behalf of the Swift-XRT team: Swift-XRT has performed follow-up observations of GRB 251014D. We searched for X-ray sources in 2.9 ks of Photon Counting (PC) mode data. The total exposure at the position of the afterglow (see below) is 5.0 ks, obtained between T0+159.4 s and T0+22.3 ks. An uncatalogued X-ray source is detected within the estimated 3-sigma Swift-BAT error region (296 arcsec) and is fading with >3-sigma significance, and is therefore likely the GRB afterglow. Using 1351 s of PC mode data and 3 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 = 323.92080, -41.85533 which is equivalent to: RA (J2000): 21h 35m 40.99s Dec(J2000): -41d 51' 19.2" with an uncertainty of 3.4 arcsec (radius, 90% confidence). The light curve can be modelled with a power-law decay with a decay index of alpha=1.71 (+0.12, -0.11). A spectrum formed from the WT mode data can be fitted with an absorbed power-law with a photon spectral index of 1.64 (+/-0.06). The best-fitting absorption column is 9.7 (+1.9, -1.8) x 10^20 cm^-2, in excess of the Galactic value of 2.1 x 10^20 cm^-2 (Willingale et al. 2013). The counts to observed (unabsorbed) 0.3-10 keV flux conversion factor deduced from this spectrum is 4.1 x 10^-11 (4.6 x 10^-11) erg cm^-2 count^-1. A summary of the WT-mode spectrum is thus: Total column: 9.7 (+1.9, -1.8) x 10^20 cm^-2 Galactic foreground: 2.1 x 10^20 cm^-2 Excess significance: 6.8 sigma Photon index: 1.64 (+/-0.06) The results of the XRT-team automatic analysis are available at https://www.swift.ac.uk/xrt_products/01404126. The results of the full analysis of the XRT observations are available at https://www.swift.ac.uk/ToO_GRBs/01404126. This circular is an official product of the Swift-XRT team. View this GCN Circular online at https://gcn.nasa.gov/circulars/42284. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0LW...