TITLE: GCN CIRCULAR NUMBER: 17818 SUBJECT: GRB 150514A: Swift-XRT afterglow detection DATE: 15/05/15 09:52:17 GMT FROM: Phil Evans at U of Leicester J.A. Kennea (PSU), B. Sbarufatti (INAF-OAB/PSU), K.L. Page (U. Leicester), C. Pagani (U. Leicester), A.P. Beardmore (U. Leicester), A. Maselli (INAF-IASFPA), A. Melandri (INAF-OAB), P. D'Avanzo (INAF-OAB), D.N. Burrows (PSU) and P.A. Evans (U. Leicester) report on behalf of the Swift-XRT team: Swift-XRT has performed follow-up observations of the Fermi/LAT-detected burst GRB 150514A (Kocevski et al. GCN Circ. 17816), collecting 1.3 ks of Photon Counting (PC) mode data between T0+40.8 ks and T0+42.2 ks. Three uncatalogued X-ray sources are detected, of which one ("Source 1") is above the RASS limit, and is therefore likely the GRB afterglow. The position of this source is RA, Dec=74.8750, -60.9691 which is equivalent to: RA (J2000): 04:59:30.00 Dec(J2000): -60:58:08.8 with an uncertainty of 3.9 arcsec (radius, 90% confidence). This position is 3.6 arcmin from the Fermi/LAT position. The light curve is consistent with a constant source of mean count rate 5.4e-02 ct/sec. A power-law fit gives an index of 3.17 (+0.05, -4.47). A spectrum formed from the PC mode data can be fitted with an absorbed power-law with a photon spectral index of 2.2 (+0.7, -0.4). The best-fitting absorption column is 3 (+11, -1) x 10^20 cm^-2, consistent with the Galactic value of 2.0 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 2.9 x 10^-11 (3.3 x 10^-11) erg cm^-2 count^-1. A summary of the PC-mode spectrum is thus: Total column: 3 (+11, -1) x 10^20 cm^-2 Galactic foreground: 2.0 x 10^20 cm^-2 Excess significance: <1.6 sigma Photon index: 2.2 (+0.7, -0.4) The results of the XRT-team automatic analysis of the likely afterglow are at http://www.swift.ac.uk/ToO_GRBs/00020510/index_1.php. The results of the full analysis of the XRT observations are available at http://www.swift.ac.uk/ToO_GRBs/00020510. This circular is an official product of the Swift-XRT team.