E. Ambrosi (INAF-IASFPA) , S. Dichiara (PSU), J.A. Kennea (PSU), A.
Tohuvavohu (U. Toronto), A.P. Beardmore (U. Leicester), P.A. Evans (U.
Leicester), J.P. Osborne (U. Leicester), M. Capalbi (INAF-IASFPA), M.
Perri (SSDC & INAF-OAR) and report on behalf of the Swift-XRT team:
We have analysed 7.2 ks of XRT data for GRB 230420A, from 98 s to 84.8
ks after the BAT trigger. The data comprise 102 s in Windowed Timing
(WT) mode with the remainder in Photon Counting (PC) mode.
The light curve can be modelled with an initial power-law decay with an
index of alpha=4.13 (+0.26, -0.18), followed by a break at T+316 s to
an alpha of 0.83 (+0.10, -0.07).
A spectrum formed from the WT mode data can be fitted with an absorbed
power-law with a photon spectral index of 1.59 (+/-0.09). The
best-fitting absorption column is 4.6 (+2.5, -2.3) x 10^20 cm^-2, in
excess of the Galactic value of 1.7 x 10^20 cm^-2 (Willingale et al.
2013). The PC mode spectrum has a photon index of 1.82 (+0.21, -0.11)
and a best-fitting absorption column consistent with the Galactic
value. The counts to observed (unabsorbed) 0.3-10 keV flux conversion
factor deduced from this spectrum is 3.5 x 10^-11 (3.6 x 10^-11) erg
A summary of the PC-mode spectrum is thus:
Total column: 1.7 (+4.0, -0.0) x 10^20 cm^-2
Galactic foreground: 1.7 x 10^20 cm^-2
Excess significance: <1.6 sigma
Photon index: 1.82 (+0.21, -0.11)
The results of the XRT-team automatic analysis are available at
This circular is an official product of the Swift-XRT team.