TITLE: GCN CIRCULAR NUMBER: 37406 SUBJECT: GRB 240905E: Swift-XRT refined Analysis DATE: 24/09/06 09:53:25 GMT FROM: Phil Evans at U of Leicester <pae9@star.le.ac.uk> M. Ferro (INAF-OAB), R. Brivio (INAF-OAB), A. D'Ai (INAF-IASFPA), M. A. Williams (PSU), S. Dichiara (PSU), J.A. Kennea (PSU), J.P. Osborne (U. Leicester), K.L. Page (U. Leicester), A.P. Beardmore (U. Leicester) and P.A. Evans report on behalf of the Swift-XRT team: We have analysed 7.6 ks of XRT data for GRB 240905E, from 96 s to 50.6 ks after the BAT trigger. The data comprise 146 s in Windowed Timing (WT) mode (the first 9 s were taken while Swift was slewing) with the remainder in Photon Counting (PC) mode. The refined XRT position is RA, Dec = 345.8021, +35.5227 which is equivalent to: RA (J2000): 23 03 12.51 Dec(J2000): +35 31 21.6 with an uncertainty of 4.1 arcsec (radius, 90% confidence). The light curve can be modelled with an initial power-law decay with an index of alpha=1.65 (+/-0.13), followed by a break at T+260 s to an alpha of 4.5 (+3.5, -0.4). A spectrum formed from the WT mode data can be fitted with an absorbed power-law with a photon spectral index of 1.25 (+/-0.10). The best-fitting absorption column is 1.3 (+0.5, -0.4) x 10^21 cm^-2, consistent with the Galactic value of 9.3 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 5.3 x 10^-11 (5.7 x 10^-11) erg cm^-2 count^-1. A summary of the WT-mode spectrum is thus: Total column: 1.3 (+0.5, -0.4) x 10^21 cm^-2 Galactic foreground: 9.3 x 10^20 cm^-2 Excess significance: <1.6 sigma Photon index: 1.25 (+/-0.10) If the light curve continues to decay with a power-law decay index of 4.5, the count rate at T+24 hours will be 3.0 x 10^-11 count s^-1, corresponding to an observed (unabsorbed) 0.3-10 keV flux of 1.6 x 10^-21 (1.7 x 10^-21) erg cm^-2 s^-1. The results of the XRT-team automatic analysis are available at http://www.swift.ac.uk/xrt_products/01252695. This circular is an official product of the Swift-XRT team. View this GCN Circular online at https://gcn.nasa.gov/circulars/37406. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0LW...