Response of Hinode XRT to quiet Sun, active region and flare plasma

Department of Applied Mathematics and Theoretical Physics, Wilberforce Road, Cambridge CB3 0WA, UK
e-mail: B.O-Dwyer@damtp.cam.ac.uk; G.Del-Zanna@damtp.cam.ac.uk; H.E.Mason@damtp.cam.ac.uk

Received: 17 December 2010
Accepted: 28 October 2013

Abstract

Aims. We examine the response of the Hinode X-Ray Telescope (XRT), using simultaneous observations with the Hinode Extreme-ultraviolet Imaging Spectrometer (EIS), for a flare, an active region and a quiet Sun region. We also examine the relative intensity calibration of EIS and XRT.

Methods. EIS differential emission measure distribution (DEM) curves were used to create synthetic spectra with the CHIANTI atomic database. The contribution of spectral lines and continuum emission to each of the XRT channels was determined from the synthetic spectra, which were then convolved with the effective area of each XRT channel. The predicted total count rates for each channel were compared with the observed count rates. The effects of varying elemental abundances and the temperature range for the inversion were investigated. DEMs obtained from the XRT bands were also computed and compared to those obtained with EIS.

Results. For the active region observations, the observed XRT count rates for most of the channels are in reasonable agreement with those predicted using EIS observations, but are dependent on the elemental abundances chosen. Significant discrepancies between predicted and observed count rates were found and are discussed for the adjacent quiet Sun region and also for the flare. Synthetic spectra and continuum emission contributing to the XRT channels are presented and discussed for the active region, quiet Sun and flare observations.