Seismic constraints on rotation of Sun-like star and mass of exoplanet

TL;DR

This study uses asteroseismology to determine the internal rotation and axis inclination of Sun-like star HD 52265, and refines the mass estimate of its exoplanet, confirming it as a planet rather than a brown dwarf.

Contribution

First application of asteroseismology to constrain the internal rotation and planetary mass of a Sun-like star with a known exoplanet.

Findings

Asteroseismic data agree with spectroscopic and star spot observations.

The exoplanet's true mass is estimated at approximately 1.85 Jupiter masses.

The star's rotation rate and axis inclination are constrained with high precision.

Abstract

Rotation is thought to drive cyclic magnetic activity in the Sun and Sun-like stars. Stellar dynamos, however, are poorly understood owing to the scarcity of observations of rotation and magnetic fields in stars. Here, inferences are drawn on the internal rotation of a distant Sun-like star by studying its global modes of oscillation. We report asteroseismic constraints imposed on the rotation rate and the inclination of the spin axis of the Sun-like star HD 52265, a principal target observed by the CoRoT satellite that is known to host a planetary companion. These seismic inferences are remarkably consistent with an independent spectroscopic observation (rotational line broadening) and with the observed rotation period of star spots. Furthermore, asteroseismology constrains the mass of exoplanet HD 52265b. Under the standard assumption that the stellar spin axis and the axis of the planetary orbit coincide, the minimum spectroscopic mass of the planet can be converted into a true mass of 1.85 (+0.52,-0.42) M_Jupiter, which implies that it is a planet, not a brown dwarf.