2013ApJ...768..122W

A Chandra spectrum of the moderately active nearby F6 V star π³ Ori is used to study the coronal properties of mid-F dwarfs. We find that π³ Ori's coronal emission measure distribution is very similar to those of moderately active G and K dwarfs, with an emission measure peak near log T = 6.6 seeming to be ubiquitous for such stars. In contrast to coronal temperature, coronal abundances are known to depend on spectral type for main sequence stars. Based on this previously known relation, we expected π³ Ori's corona to exhibit an extremely strong "first ionization potential (FIP) effect," a phenomenon first identified on the Sun where elements with low FIP are enhanced in the corona. We instead find that π³ Ori's corona exhibits a FIP effect essentially identical to that of the Sun and other early G dwarfs, perhaps indicating that the increase in FIP bias toward earlier spectral types stops or at least slows for F stars. We find that π³ Ori's coronal characteristics are significantly different from two previously studied mid-F stars, Procyon (F5 IV-V) and τ Boo (F7 V). We believe π³ Ori is more representative of the coronal characteristics of mid-F dwarfs, with Procyon being different because of luminosity class, and τ Boo being different because of the effects of one of two close companions, one stellar (τ Boo B: M2 V) and one planetary.