TITLE:   GCN CIRCULAR
NUMBER:  36225
SUBJECT: GRB 240415A: Swift-XRT refined Analysis
DATE:    24/04/22 07:22:59 GMT
FROM:    Phil Evans at U of Leicester <pae9@star.le.ac.uk>

P.A. Evans (U. Leicester) reports on behalf of the Swift-XRT team:

We have analysed 5.4 ks of XRT data for GRB 240415A, from 3.3 ks to
26.8 ks after the  BAT trigger. The data comprise 281 s in Windowed
Timing (WT) mode 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=0.97 (+/-0.09).

A spectrum formed from the PC mode data can be fitted with an absorbed
power-law with a photon spectral index of 2.18 (+/-0.16). The
best-fitting absorption column is  2.2 (+/-0.5) x 10^21 cm^-2, in
excess of the Galactic value of 2.5 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 3.3 x 10^-11 (4.9 x 10^-11) erg
cm^-2 count^-1. 

A summary of the PC-mode spectrum is thus:
Total column:	     2.2 (+/-0.5) x 10^21 cm^-2
Galactic foreground: 2.5 x 10^20 cm^-2
Excess significance: 6.4 sigma
Photon index:	     2.18 (+/-0.16)

The results of the XRT-team automatic analysis are available at
http://www.swift.ac.uk/xrt_products/01221874.

This circular is an official product of the Swift-XRT team.