Simulating the environment around planet-hosting stars - II. Stellar winds and inner astrospheres

TL;DR

This paper presents detailed 3D simulations of stellar winds and astrospheres around exoplanet-host stars, analyzing their properties, interactions with planets, and implications for planetary atmospheres and radio emissions.

Contribution

It introduces a comprehensive simulation framework for stellar winds around exoplanet hosts, including magneto-hydrodynamical properties and mass loss rates, and compares results with solar activity levels.

Findings

Stellar wind properties vary significantly among the studied stars.

Particle injection into planetary atmospheres is dominated by density distribution.

Predicted exoplanetary radio emission can reach up to 12 mJy at 40 MHz.

Abstract

We present the results of a comprehensive numerical simulation of the environment around three exoplanet-host stars (HD 1237, HD 22049, and HD 147513). Our simulations consider one of the latest models currently used for space weather studies in the Heliosphere. Large-scale magnetic field maps, recovered with two implementations of the tomographic technique of Zeeman-Doppler imaging, serve to drive steady-state solutions in each system. This paper contains the description of the stellar wind and inner astrosphere, while the coronal structure was previously discussed in Alvarado-G\'omez et al. (2016). The analysis includes the magneto-hydrodynamical properties of the stellar wind, the associated mass and angular momentum loss rates, as well as the topology of the astrospheric current sheet in each system. A systematic comparison among the considered cases is performed, including two reference solar simulations covering activity minimum and maximum. For HD 1237, we investigate the interactions between the structure of the developed stellar wind, and a possible magnetosphere around the Jupiter-mass planet in this system. We find that the process of particle injection into the planetary atmosphere is dominated by the density distribution rather than velocity profile of the stellar wind. In this context, we predict a maximum exoplanetary radio emission of 12 mJy at 40 MHz in this system, assuming the crossing of a high-density streamer during periastron passage. Furthermore, in combination with the analysis performed in Alvarado-G\'omez et al. (2016), we obtain for the first time a fully simulated mass loss-activity relation, which is compared and discussed in the context of the relation based on astrospheric detections proposed by Wood et al. (2005a). Finally, we provide a characterisation of the 3D properties of the stellar wind of these systems, at the inner edges of their habitable zones.