Simulating the environment around planet-hosting stars

I. Coronal structure

¹ European Southern Observatory, Karl-Schwarzschild-Str. 2, 85748 Garching bei München, Germany
e-mail: jalvarad@eso.org
² Universitäts-Sternwarte München, Ludwig-Maximilians-Universität, Scheinerstr. 1, 81679 München, Germany
³ Institut de Recherche en Astrophysique et Planétologie, Université de Toulouse, UPS-OMP, 31400 Toulouse, France
⁴ Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138, USA
⁵ Center for Space Environment Modeling, University of Michigan, 2455 Hayward St., Ann Arbor, MI 48109, USA

Received: 25 November 2015
Accepted: 17 January 2016

Abstract

We present the results of a detailed numerical simulation of the circumstellar environment around three exoplanet-hosting stars. A modern global magnetohydrodynamic model is considered that includes Alfvén 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. 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 ultraviolet (EUV) and soft X-ray (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 that is due to the various coronal features developed in the simulation. We obtain variations during a single stellar rotation cycle of 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.