Novel gyrochronology tests with wide-separation binaries
Gyrochronology is the technique that uses rotation periods to derive stellar ages via age-rotation relations. If properly calibrated, its potential applications to Galactic, stellar and exoplanetary astrophysics are far-reaching. Thanks to the exquisite high-precision photometry provided by space-based missions such as Kepler, TESS, and the upcoming PLATO, the number of stars with measured rotation periods will continue to drastically increase in the coming years. Accordingly, it has become imperative to comprehensively test gyrochronology, so its remarkable applications can be fully exploited, and its limits well understood. This work presents a novel technique that tests the state-of-the-art age-rotation relations in under-explored domains using wide binary stars. The components of a given binary are co-eval and taken together they can provide exquisite assessments of gyrochronology. The results of a dedicated test on a sample of Kepler-field binaries and star clusters show that: 1) statistically, the commonly used age-rotation relations do have predictive power in identifying co-eval populations of field stars; 2) they achieve the best results when used in the members of young clusters (ages < 1 Gyr); 3) their performance decreases when used in field wide binaries, as well as in older clusters. All in all, the existing relations need better calibrations, particularly in the regime of ages older than a few Gyr. This work sets up the stage for decisive gyrochronology assessments in the era of ever-expanding space-based photometry.