Age determination of the HR8799 planetary system using asteroseismology

TL;DR

This paper uses asteroseismology of gamma Doradus pulsations to more accurately estimate the age of HR8799, which is crucial for understanding the masses of its directly imaged planets.

Contribution

It develops a comprehensive asteroseismic modeling approach to determine the star's age, addressing uncertainties in previous methods and highlighting the importance of stellar rotation and inclination.

Findings

Previous age estimates ([30,160] Myr) are unlikely.

The star's age is likely closer to 1 Gyr.

An older age suggests the orbiting objects are brown dwarfs.

Abstract

Discovery of the first planetary system by direct imaging around HR8799 has made the age determination of the host star a very important task. This determination is the key to derive accurate masses of the planets and to study the dynamical stability of the system. The age of this star has been estimated using different procedures. In this work we show that some of these procedures have problems and large uncertainties, and the real age of this star is still unknown, needing more observational constraints. Therefore, we have developed a comprehensive modeling of HR8799, and taking advantage of its gamma Doradus-type pulsations, we have estimated the age of the star using asteroseismology. The accuracy in the age determination depends on the rotation velocity of the star, and therefore an accurate value of the inclination angle is required to solve the problem. Nevertheless, we find that the age estimate for this star previously published in the literature ([30,160] Myr) is unlikely, and a more accurate value might be closer to the Gyr. This determination has deep implications on the value of the mass of the objects orbiting HR8799. An age around $\approx$ 1 Gyr implies that these objects are brown dwarfs.