TATOO: Tidal-chronology standalone tool to estimate the age of massive close-in planetary systems

F Gallet

doi:10.1051/0004-6361/202038058

Abstract

Context. The presence of a massive close-in planet with an orbital period of a few days or less around a low-mass star can possibly result in a strong variation in the properties of the central star. Indeed, star-planet tidal interactions generate exchanges of angular momentum that can result in tidal spin-up. This effect could then lead to gyrochronological ages biased towards younger ages. Aims. This article provides the community with TATOO, a standalone tool based on tidal-chronology, with which to estimate the age of a massive close-in planetary system using only its observed properties: mass of the planet and the star, stellar rotation, and planetary orbital periods. Methods. I used a star-planet tidal evolution numerical code to create a large multi-parametric grid of the evolution of synthetic star-planet systems. Furthermore, using the tidal-chronology technique, I employed a 3D interpolation method to provide a fairly precise age estimate of any given planetary system composed of one massive close-in planet. Results. About half of the planetary systems investigated in this work are subject to tidal spin-up bias. I pointed out that this bias linearly scales with the ratio between rotation and orbital period, making this quantity a useful proxy to rapidly investigate whether tidal-chronology needs to be used. Moreover, while being model dependent, TATOO can also be used even if no rotational departure is present. In that case, it gives results in agreement with the classical gyrochronological analysis. Conclusions. TATOO is a useful tool specifically designed for massive close-in planetary systems that can also be used as a classical gyrochronological tool. For now it is the only publicly available software to estimate the age of massive close-in planetary systems subject to tidal spin-up. In that sense, tidal-chronology can be seen as a first order correction of the impact of tidal interaction on gyrochronology.

Highlights

Together with rotation, radius, and luminosity, age is a fundamental physical parameter for both stellar and exoplanetary fields, and its determination for a given star or planetary system is currently a key issue in astrophysics
In Gallet & Delorme (2019) we demonstrated that the observed pair composed of the stellar rotation period (Prot,obs) and planetary orbital period (Porb,obs) of a given star and massive close-in planet system is only retrieved at a unique age or during a short range of time
Gallet: TATOO: Tidal-chronology standalone tool to estimate the age of massive close-in planetary systems dissipation formalism described in Bolmont & Mathis (2016) that is parametrized following the simplified model by Ogilvie (2013)

Summary

Introduction

Radius, and luminosity, age is a fundamental physical parameter for both stellar and exoplanetary fields, and its determination for a given star or planetary system is currently a key issue in astrophysics. In Gallet & Delorme (2019) we used a tailored model grid matching the specific observed properties of WASP-43 to perform this estimation Since this process is time consuming because of the large initial parameter space of planetary systems to be explored, I decided to provide the community with a standalone tool dedicated to the estimation of the age of planetary systems (composed of one low-mass star and one massive close-in planet). In the case of WASP-43 that we investigated in Gallet & Delorme (2019), we used a 0.71 M stellar model and a 2.052 Mjup mass planet for which we explored the initial conditions of the stellar rotation rate and orbital period This tailored gird is only valid for planetary systems that are identical to the WASP-43 ones. I reiterate the general principles of the tidalchronology technique and how age estimation can be performed using such a technique

Basic principle of tidal-chronology

Gallet: TATOO

Findings

Discussion

Conclusion