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Raassen, AJJ; Kaastra, JS; van der meer, RLJ; Mewe, R; Audard, M; Gudel, M; Ness, J-U; and Behar, E Abstract We have obtained the spectra of the coronae of &alpha Centauri and Procyon using the Reflection Grating Spectrometer (RGS) on board XMM-Newton and the Lowe Energy Transmission Grating Spectrometer (LETGS) on board Chandra. From measured line fluxes of H- and He-like 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, &alpha Cen (G2V), and &alpha Cen (K1V)) the temperatures are the the regime of 1-2 MK. The emission measure for Procyon is about 1 x 1050 cm-3 and for both components of &alpha Cen about 8 x 1048 cm-3. Global fits to the total spectrum using SPEX show significant temperature components around 1 and 2 MK. Self-consistent continuous emission measures have been constructed. The &alpha Cen (K1V) is somewhat hotter than its (G2V) companion. I used this article mainly to gain insight into the details of emission measure calcualtion. This paper directly gives the definition of emission measure as where ne is the electron density, nH is the hydrogen density, and V is the emitting volume. The authors give |