The corona and upper transition region of epsilon Eridani

TL;DR

This study analyzes multi-instrument observations of epsilon Eridani to determine its coronal properties, element abundances, and emission measure distribution, providing insights into stellar coronae and elemental composition.

Contribution

It offers a comprehensive analysis of epsilon Eridani's coronal temperature, density, and abundances using combined data from multiple space telescopes, improving understanding of stellar coronae.

Findings

Coronal temperature of 3.4 million K

Ne/O abundance ratio of 0.30

No evidence for low-FIP element enhancement

Abstract

We present analyses of observations of epsilon Eridani (K2 V) made with the Low Energy Transmission Grating Spectrometer on Chandra and the Extreme Ultraviolet Explorer, supplemented by observations made with the Space Telescope Imaging Spectrograph, the Far Ultraviolet Spectroscopic Explorer and the Reflection Grating Spectrometer on XMM-Newton. The observed emission lines are used to find relative element abundances, to place limits on the electron densities and pressures and to determine the mean apparent emission measure distribution. As in the previous paper by Sim & Jordan (2003a), the mean emitting area as a function of the electron temperature is derived by comparisons with a theoretical emission measure distribution found from energy balance arguments. The final model has a coronal temperature of 3.4 x 10^6 K, an electron pressure of 1.3 x 10^16 cm^-3 K at T_e = 2 x 10^5 K and an area filling factor of 0.14 at 3.2 x 10^5 K. We discuss a number of issues concerning the atomic data currently available. Our analyses are based mainly on the latest version of CHIANTI (v5.2). We conclude that the Ne/O relative abundance is 0.30, larger than that recommended from solar studies, and that there is no convincing evidence for enhanced coronal abundances of elements with low first ionization potentials.