Constraining the age of young stellar clusters via the amplitude of photometric variability

Abstract

Context. The determination of stellar age is a crucial task in astrophysics research. At present, the various methods employed in such studies are either model-dependent or based on calibrated empirical relations. The most reliable results are generally obtained when different methods are applied in a complementary manner. Aims. We propose a new method for the age determination of young stellar associations and open clusters (ages ≲ 125 Myr), which may allow for the placement of further constraints on the age when used in tandem with other methods. Methods. We explore the amplitude of the photometric variability in bins of color and rotation period of five young associations and clusters spanning an interval of ages from ∼1−3 Myr to ∼ 625 Myr (Taurus, ρ Ophiuchi, Upper Scorpius, Pleiades, and Praesepe), which all have high-quality time-series photometry from Kepler K2 campaigns. Results. In the low-mass regime, we find that stars with similar color and rotation periods but different ages exhibit a range of amplitudes for their photometric variability, with younger stars showing a larger photometric variability than older stars. Conclusions. The decline of photometric variability amplitude versus age in stars with similar color and rotation period may, in principle, be calibrated and adopted as an additional empirical relation for constraining the age of young associations and open clusters, provided that time-series photometry is available for their low-mass members.