The limit of the gyrochronology - A new age determination technique: the tidal-chronology

Abstract

While the number of detected planets is continuously increasing since 1995, their impact on their central star still remain poorly understood. Yet, the presence of a massive close-in planet can strongly modify the surface angular velocity evolution of the star. In these circumstances, age estimation techniques based on rotation, such as the gyrochronology, can't be applied to stars that experienced significant star-planet magnetic and tidal interactions during their evolution. With the use of a numerical model that combines an angular momentum evolution and an orbital evolution code, we investigated the evolution of initial distribution of star-planet systems, in which the orbital evolution of the planet is driven by the tidal dissipation formalism. Based on these initial distributions we highlighted the limits of applicability of the gyrochronology analysis and proposed a new age determination technique based on the observation of the couple $\rm P_{rot,\star}$-$a$, where $\rm P_{rot,\star}$ is the stellar rotational period and $a$ the planetary semi-major axis. This technique called tidal-chronology can be very helpful for planetary system composed of a star between 0.3 and 1.2 $\rm M_{\odot}$ and a planet more massive than 1 $\rm M_{jup}$ initially located at few hundredth au of the host star.