Kinematic Age of the Tucana-Horologium Association

Dominic Couture ( Université de Montréal )

Exoplanets around M-dwarfs within nearby young associations (NYA) are prime targets for planetary characterization, due to the better contrast of nearby, young, directly imaged exoplanets, and the greater transit depth of transiting exoplanets orbiting dim, low-mass stars. NYAs also present the opportunity to obtain more reliable stellar ages as opposed to isolated systems. By tracing back the individual Galactic orbits of stars within NYAs up to the epoch of minimal association size, it is possible to find a kinematic age for the NYA, independent of any stellar evolution models. This approach, however, has faced challenges in the past, as a result of the limited, low-quality kinematic data, needed to compute 3D space velocities. The Gaia DR3 Catalog, with its millions of radial velocity (RV) measurements, has changed this field dramatically since its release, and has allowed for precise backward Galactic orbit computations of large samples of stars. Still, systematics plague RV measurements: gravitational redshift, and convective blueshift, which can offset RV measurements by ~ 0.6 km/s, have a significant impact on the final kinematic age. Furthermore, measurement errors can bias ages towards younger values. By correcting for these systematics, and using the best available kinematic data, we are able to derive traceback ages that are more precise, and reliable than ever before. Our method has already been applied successfully to the β Pictoris Moving Group, for which we found a kinematic age in agreement with other age-dating methods for the first time. In this presentation, I will show the results of application of our traceback method to the Tucana-Horologium Association. This ~ 45 Myr-old association, is among the largest, and closest to the Sun, and several directly imaged exoplanets have been detected in orbit around some of its members.