Simulating the Environment Around Planet-Hosting Stars - I. Coronal Structure

TL;DR

This paper uses advanced MHD simulations driven by Zeeman Doppler Imaging data to model the coronal structures of exoplanet-hosting stars, revealing insights into their high-energy emissions and magnetic activity.

Contribution

It introduces a detailed numerical simulation approach incorporating Alfvén wave dissipation for coronal heating, based on observational magnetic field maps, to study stellar coronae.

Findings

Coronal structures are qualitatively and quantitatively characterized.

Simulated high-energy emission maps match observed trends.

Rotational modulation of emissions can reach up to 15%.

Abstract

We present the results of a detailed numerical simulation of the circumstellar environment around three exoplanet-hosting stars. A state-of-the-art global magnetohydrodynamic (MHD) model is considered, including Alfv\'en wave dissipation as a self-consistent coronal heating mechanism. This paper contains the description of the numerical set-up, evaluation procedure, and the simulated coronal structure of each system (HD 1237, HD 22049 and HD 147513). The simulations are driven by surface magnetic field maps, recovered with the observational technique of Zeeman Doppler Imaging (ZDI). A detailed comparison of the simulations is performed, where two different implementations of this mapping routine are used to generate the surface field distributions. Quantitative and qualitative descriptions of the coronae of these systems are presented, including synthetic high-energy emission maps in the Extreme Ultra-Violet (EUV) and Soft X-rays (SXR) ranges. Using the simulation results, we are able to recover similar trends as in previous observational studies, including the relation between the magnetic flux and the coronal X-ray emission. Furthermore, for HD 1237 we estimate the rotational modulation of the high-energy emission due to the various coronal features developed in the simulation. We obtain variations, during a single stellar rotation cycle, up to 15\% for the EUV and SXR ranges. The results presented here will be used, in a follow-up paper, to self-consistently simulate the stellar winds and inner astrospheres of these systems.