Exploring coronal abundances of M dwarfs at moderate activity levels

¹ Leibniz Institute for Astrophysics, An der Sternwarte 16, 14482 Potsdam, Germany
² University of Potsdam, Institute of Physics and Astronomy, Potsdam-Golm 14476, Germany
³ Université Paris Cité, Université Paris-Saclay, CEA, CNRS, AIM, 91191 Gif-sur-Yvette, France
⁴ Naval Research Laboratory, Space Science Division, Washington, DC 20375, USA

^★ Corresponding author; judy.chebly@cea.fr

Received: 2 April 2024
Accepted: 10 February 2025

Abstract

Context. Main sequence stars of spectral types F, G, and K with low to moderate activity levels exhibit a recognizable pattern known as the first ionization potential effect (FIP effect), where elements with lower first ionization potentials are more abundant in the stellar corona than in the photosphere. In contrast, high activity main sequence stars such as AB Dor (K0), active binaries, and M dwarfs exhibit an inverse pattern known as iFIP.

Aims. We aim to determine whether or not the iFIP pattern persists in moderate-activity M dwarfs.

Methods. We used XMM-Newton to observe the moderately active M dwarf HD 223889 that has an X-ray surface flux of log F_X,surf = 5.26, the lowest for an M dwarf studied so far for coronal abundance patterns. We used low-resolution CCD spectra of the star to calculate the strength of the FIP effect quantified by the FIP bias (F_bias) to assess the persistence of the iFIP effect in M dwarfs.

Results. Our findings reveal an iFIP effect similar to that of another moderately active binary star, GJ 338 AB, with a comparable error margin. The results hint at a possible plateau in the T_eff -F_bias diagram for moderately active M dwarfs.

Conclusions. Targeting stars with low coronal activity that have a coronal temperature between 2 MK and 4 MK is essential for refining our understanding of (i)FIP patterns and their causes.