TITLE: GCN CIRCULAR NUMBER: 42442 SUBJECT: GRB 251024A: Swift-XRT refined Analysis DATE: 25/10/25 18:09:15 GMT FROM: Phil Evans at U of Leicester pae9@star.le.ac.uk
S. Dichiara (PSU), K.L. Page (U. Leicester), A.P. Beardmore (U. Leicester), V. D'Elia (SSDC & INAF-OAR), B. Sbarufatti (INAF-OAB), C. Salvaggio (INAF-OAB), J.A. Kennea (PSU), D.N. Burrows (PSU) and P.A. Evans report on behalf of the Swift-XRT team:
We have analysed 4.4 ks of XRT data for GRB 251024A, from 113 s to 56.4 ks after the trigger. The data comprise 30 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 late-time light curve (from T0+4.5 ks) is consistent with a constant source of mean count rate 4.5e-01 ct/sec. A power-law fit gives an index of -0.14 (+0.15, -0.14).
A spectrum formed from the PC mode data can be fitted with an absorbed power-law with a photon spectral index of 2.06 (+0.16, -0.11). The best-fitting absorption column is consistent with the Galactic value of 3.7 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 3.2 x 10^-11 (3.6 x 10^-11) erg cm^-2 count^-1.
A summary of the PC-mode spectrum is thus: Total column: 3.7 (+/-2.8) x 10^20 cm^-2 Galactic foreground: 3.7 x 10^20 cm^-2 Excess significance: <1.6 sigma Photon index: 2.06 (+0.16, -0.11)
The results of the XRT-team automatic analysis are available at https://www.swift.ac.uk/xrt_products/01406589.
This circular is an official product of the Swift-XRT team.
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