The Coronal Abundances of Mid-F Dwarfs

TL;DR

This study analyzes the coronal properties of the mid-F dwarf Pi3 Ori using Chandra data, revealing similarities with G and K dwarfs in emission measure distribution and a solar-like FIP effect, contrasting with previous mid-F star observations.

Contribution

It provides the first detailed coronal abundance analysis of a typical mid-F dwarf, showing a solar-like FIP effect and highlighting differences from other mid-F stars due to luminosity class and companions.

Findings

Pi3 Ori's emission measure peaks near log T=6.6.

Pi3 Ori exhibits a solar-like FIP effect.

Coronal properties differ from other mid-F stars like Procyon and Tau Boo.

Abstract

A Chandra spectrum of the moderately active nearby F6 V star Pi3 Ori is used to study the coronal properties of mid-F dwarfs. We find that Pi3 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 Pi3 Ori's corona to exhibit an extremely strong "FIP effect," a phenomenon first identified on the Sun where elements with low "First Ionization Potential" (FIP) are enhanced in the corona. We instead find that Pi3 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 towards earlier spectral types stops or at least slows for F stars. We find that Pi3 Ori's coronal characteristics are significantly different from two previously studied mid-F stars, Procyon (F5 IV-V) and Tau Boo (F7 V). We believe Pi3 Ori is more representative of the coronal characteristics of mid-F dwarfs, with Procyon being different because of luminosity class, and Tau Boo being different because of the effects of one of two close companions, one stellar (Tau Boo B: M2 V) and one planetary.