Exoplanet Radio Transits as a Probe for Exoplanetary Magnetic Fields -- Time-dependent MHD Simulations

TL;DR

This study uses time-dependent MHD simulations of the star-planet system HD 189733 to predict radio transit signals caused by planetary magnetic fields, suggesting radio observations could reveal exoplanet magnetic properties.

Contribution

It introduces a dynamic simulation approach combining stellar wind models with planetary magnetospheres to predict radio transit features linked to magnetic field strength.

Findings

Radio light curves show clear planetary motion signatures.

Transit features depend on planetary magnetic field strength.

Simulations suggest radio transits can inform about exoplanet magnetism.

Abstract

We perform a series of time dependent Magnetohydrodynamic simulations of the HD 189733 star-planet system in order to predict radio transit modulations due to the interaction between the stellar wind and planetary magnetic field. The simulation combines a model for the stellar corona and wind with an exoplanet that is orbiting the star in a fully dynamic, time-dependent manner. Our simulations generate synthetic radio images that enable us to obtain synthetic radio lightcurves in different frequencies. We find a clear evidence for the planetary motion in the radio light curves. Moreover, we find specific repeated features in the light curves that are attributed to the passage of the planetary magnetosphere in front of the star during transit. More importantly, we find a clear dependence in the magnitude and phase of these lightcurve features on the strength of the planetary magnetic field. Our work demonstrates that if radio transits could be observed, they could indeed provide information about the magnetic field strength of the transiting exoplanet. Future work to parameterize these lightcurve features and their dependence on the planetary field strength would provide tools to search for these features in radio observations datasets. As we only consider the thermal radio emission from the host star for our study, very sensitive radio interferometers are necessary to detect these kinds of planetary transit in radio.