TITLE: GCN CIRCULAR NUMBER: 39855 SUBJECT: GRB 250322A: Swift-XRT refined Analysis DATE: 25/03/23 16:54:19 GMT FROM: Phil Evans at U of Leicester pae9@star.le.ac.uk
M. Perri (SSDC & INAF-OAR), J.A. Kennea (PSU), D.N. Burrows (PSU), M. A. Williams (PSU), A.P. Beardmore (U. Leicester), J.P. Osborne (U. Leicester), V. D'Elia (SSDC & INAF-OAR), B. Sbarufatti (INAF-OAB) and P.A. Evans report on behalf of the Swift-XRT team:
We have analysed 3.7 ks of XRT data for GRB 250322A, from 58 s to 22.2 ks after the BAT trigger. The data comprise 7 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=2.28 (+0.18, -0.17).
A spectrum formed from the PC mode data can be fitted with an absorbed power-law with a photon spectral index of 2.09 (+0.49, -0.26). The best-fitting absorption column is consistent with the Galactic value of 2.7 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 3.6 x 10^-11 (5.4 x 10^-11) erg cm^-2 count^-1.
A summary of the PC-mode spectrum is thus: Total column: 2.7 (+/-2.3) x 10^21 cm^-2 Galactic foreground: 2.7 x 10^21 cm^-2 Excess significance: <1.6 sigma Photon index: 2.09 (+0.49, -0.26)
If the light curve continues to decay with a power-law decay index of 2.28, the count rate at T+24 hours will be 2.2 x 10^-7 count s^-1, corresponding to an observed (unabsorbed) 0.3-10 keV flux of 7.9 x 10^-18 (1.2 x 10^-17) erg cm^-2 s^-1.
The results of the XRT-team automatic analysis are available at http://www.swift.ac.uk/xrt_products/01297832.
This circular is an official product of the Swift-XRT team.
View this GCN Circular online at https://gcn.nasa.gov/circulars/39855. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0LW...