TITLE: GCN CIRCULAR NUMBER: 40618 SUBJECT: GRB 250603A: Swift-XRT refined Analysis DATE: 25/06/03 12:58:34 GMT FROM: Phil Evans at U of Leicester pae9@star.le.ac.uk
S. Campana (INAF-OAB), A. Melandri (INAF-OAR), T. Sbarrato (INAF-OAB), D.N. Burrows (PSU), M.A. Williams (PSU), S. Dichiara (PSU), J.P. Osborne (U. Leicester), K.L. Page (U. Leicester) and P.A. Evans report on behalf of the Swift-XRT team:
We have analysed 7.3 ks of XRT data for GRB 250603A, from 92 s to 34.7 ks after the trigger. The data comprise 3 s in Windowed Timing (WT) mode (taken while Swift was slewing), with the remainder in Photon Counting (PC) mode.
The light curve can be modelled with a power-law decay with a decay index of alpha=1.17 (+0.09, -0.08).
A spectrum formed from the PC mode data can be fitted with an absorbed power-law with a photon spectral index of 1.48 (+0.32, -0.30). The best-fitting absorption column is 1.6 (+0.5, -0.4) x 10^22 cm^-2, in excess of the Galactic value of 6.9 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 7.6 x 10^-11 (1.1 x 10^-10) erg cm^-2 count^-1.
A summary of the PC-mode spectrum is thus: Total column: 1.6 (+0.5, -0.4) x 10^22 cm^-2 Galactic foreground: 6.9 x 10^21 cm^-2 Excess significance: 3.3 sigma Photon index: 1.48 (+0.32, -0.30)
If the light curve continues to decay with a power-law decay index of 1.17, the count rate at T+24 hours will be 8.8 x 10^-4 count s^-1, corresponding to an observed (unabsorbed) 0.3-10 keV flux of 6.7 x 10^-14 (9.8 x 10^-14) erg cm^-2 s^-1.
The results of the XRT-team automatic analysis are available at http://www.swift.ac.uk/xrt_products/01320335.
This circular is an official product of the Swift-XRT team.
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