Stellar Coronal Abundances. V. Evidence for the First Ionization Potential Effect in α Centauri

We present an analysis of the EUV spectrum of the nearby binary a Cen AB (G2 V, K0 V), observed by the Extreme Ultraviolet Explorer satellite (EUV E). Emission measure curves are constructed for elements with high and low rst ionization potential (FIP) in order to investigate the coronal composition and determine whether or not a solar-like compositional fractionation mechanism ("" FIP e ect ) is operating in the corona of a Cen. As pointed out in the recent analysis of the a Cen EUV E spectra by Mewe et al., the emission measure distribution is very much like that of the Sun. It peaks at log T D 6.3, has a minimum near log T D 5.5, and has a slope between these points of approximately 1.75 (EM P T 7@4). The emission measure results for the di erent elements are not consistent with the underlying photospheric composition and indicate that the low-FIP elements are overabundant relative to the high-FIP elements by a factor of about 2. This result represents the rst evidence of the FIP e ect in solar-like stars with similar activity to that of the Sun.