Summary: Temperature determination and emission measure modeling of the
coronae of ff Centauri and Procyon
A.J.J. Raassen 1;2 , J.S. Kaastra 2 , R.L.J. van der Meer 2 , R. Mewe 2 , M. Audard 3 ,
M. G˜udel 3 , J.­U. Ness 4 , E. Behar 5
Abstract.
We have obtained the spectra of the coronae of ff Centauri and Procyon
using the Reflection Grating Spectrometer (RGS) on board XMM­Newton and
the Low Energy Transmission Grating Spectrometer (LETGS) on board Chan­
dra. From measured line fluxes of H­ and He­like lines of Carbon, Nitrogen
and Oxygen and of strong lines of Fe IX and Fe X temperature estimates and
emission measures EM have been obtained. For all three stars (Procyon, ff Cen
(G2V), and ff Cen (K1V)) the temperatures are in the regime of 1­2 MK. The
emission measure for Procyon is about 1\Theta 10 50 cm \Gamma3 and for both components
of ff Cen about 8 \Theta 10 48 cm \Gamma3 . Global fits to the total spectrum using SPEX
show significant temperature components around 1 and 2 MK. Self­consistent
continuous emission measures have been constructed. The ff Cen (K1V) is
somewhat hotter than its G2V companion.
1. Introduction
Solar­type stars of spectral classes F­M show considerable hot outer atmospheres (coro­
nae). From the solar corona we know that there is a variety of processes with rich de­

Source: Audard, Marc - INTEGRAL Science Data Centre & Observatory of Geneva, Université de Genève
Guedel, Manuel - Institut für Astronomie, Universität Wien

Collections: Physics