TITLE: GCN CIRCULAR NUMBER: 35469 SUBJECT: GRB 240102A: Swift-XRT refined Analysis DATE: 24/01/03 07:00:54 GMT FROM: Phil Evans at U of Leicester <pae9@star.le.ac.uk> J. D. Gropp (PSU), J.P. Osborne (U. Leicester), K.L. Page (U. Leicester), A. Melandri (INAF-OAR), T. Sbarrato (INAF-OAB), P. D'Avanzo (INAF-OAB), S. Dichiara (PSU), J.A. Kennea (PSU) and P.A. Evans report on behalf of the Swift-XRT team: We have analysed 6.6 ks of XRT data for GRB 240102A, from 113 s to 28.3 ks after the BAT trigger. The data comprise 91 s in Windowed Timing (WT) mode (the first 10 s were taken while Swift was slewing) with the remainder in Photon Counting (PC) mode. The best available XRT position (using the promptly downlinked event data, the XRT-UVOT alignment and matching UVOT field sources to the USNO-B1 catalogue) is RA, Dec = 96.83800, -20.04076 which is equivalent to: RA (J2000): 06 27 21.12 Dec(J2000): -20 02 26.7 with an uncertainty of 1.9 arcsec (radius, 90% confidence). The late-time light curve (from T0+4.7 ks) can be modelled with a power-law decay with a decay index of alpha=0.5 (+/-0.3). A spectrum formed from the WT mode data can be fitted with an absorbed power-law with a photon spectral index of 1.74 (+0.11, -0.10). The best-fitting absorption column is 3.3 (+0.6, -0.5) x 10^21 cm^-2, in excess of the Galactic value of 2.3 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 4.3 x 10^-11 (5.7 x 10^-11) erg cm^-2 count^-1. A summary of the WT-mode spectrum is thus: Total column: 3.3 (+0.6, -0.5) x 10^21 cm^-2 Galactic foreground: 2.3 x 10^21 cm^-2 Excess significance: 3.1 sigma Photon index: 1.74 (+0.11, -0.10) If the light curve continues to decay with a power-law decay index of 0.5, the count rate at T+24 hours will be 9.8 x 10^-3 count s^-1, corresponding to an observed (unabsorbed) 0.3-10 keV flux of 4.2 x 10^-13 (5.6 x 10^-13) erg cm^-2 s^-1. The results of the XRT-team automatic analysis are available at http://www.swift.ac.uk/xrt_products/01205899. This circular is an official product of the Swift-XRT team. View this GCN Circular online at https://gcn.nasa.gov/circulars/35469. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0LW...