TITLE: GCN CIRCULAR NUMBER: 35391 SUBJECT: GRB 231216A: Swift-XRT refined Analysis DATE: 23/12/17 19:18:04 GMT FROM: Phil Evans at U of Leicester <pae9@star.le.ac.uk> B. Sbarufatti (INAF-OAB), C. Salvaggio (INAF-OAB), M. Ferro (INAF-OAB), J. D. Gropp (PSU), S. Dichiara (PSU), J.A. Kennea (PSU), A.P. Beardmore (U. Leicester), J.P. Osborne (U. Leicester) and P.A. Evans report on behalf of the Swift-XRT team: We have analysed 6.1 ks of XRT data for GRB 231216A, from 115 s to 68.0 ks after the BAT trigger. The data comprise 8 s in Windowed Timing (WT) mode (taken while Swift was slewing), with the remainder in Photon Counting (PC) mode. The refined XRT position is RA, Dec = 39.7727, +33.5764 which is equivalent to: RA (J2000): 02 39 05.45 Dec(J2000): +33 34 35.0 with an uncertainty of 3.9 arcsec (radius, 90% confidence). The light curve can be modelled with a power-law decay with a decay index of alpha=0.7 (+nan, -nan). A spectrum formed from the PC mode data can be fitted with an absorbed power-law with a photon spectral index of 2.1 (+0.4, -0.3). The best-fitting absorption column is 3.2 (+1.7, -1.4) x 10^21 cm^-2, in excess of the Galactic value of 8.4 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 3.7 x 10^-11 (5.7 x 10^-11) erg cm^-2 count^-1. A summary of the PC-mode spectrum is thus: Total column: 3.2 (+1.7, -1.4) x 10^21 cm^-2 Galactic foreground: 8.4 x 10^20 cm^-2 Excess significance: 2.8 sigma Photon index: 2.1 (+0.4, -0.3) The results of the XRT-team automatic analysis are available at http://www.swift.ac.uk/xrt_products/01202749. This circular is an official product of the Swift-XRT team. View this GCN Circular online at https://gcn.nasa.gov/circulars/35391. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0LW...