The Empirical Limits of Gyrochronology
Abstract
The promise of gyrochronology is that, given a star's rotation period and mass, its age can be inferred. The reality of gyrochronology is complicated by effects other than ordinary magnetized braking that alter stellar rotation periods. In this work, we present an interpolationbased gyrochronology framework that reproduces the time and massdependent spindown rates implied by the latest open cluster data, while also matching the rate at which the dispersion in initial stellar rotation periods decreases as stars age. We validate our technique for stars with temperatures of 38006200 K and ages of 0.082.6 gigayears (Gyr), and use it to reexamine the empirical limits of gyrochronology. In line with previous work, we find that the uncertainty floor varies strongly with both stellar mass and age. For Sunlike stars (≈5800 K), the statistical age uncertainties improve monotonically from ±38% at 0.2 Gyr to ±12% at 2 Gyr, and are caused by the empirical scatter of the cluster rotation sequences combined with the rate of stellar spindown. For lowmass K dwarfs (≈4200 K), the posteriors are highly asymmetric due to stalled spindown, and ±1σ age uncertainties vary nonmonotonically between 10% and 50% over the first few gigayears. Highmass K dwarfs (5000 K) older than ≈1.5 Gyr yield the most precise ages, with limiting uncertainties currently set by possible changes in the spindown rate (12% systematic), the calibration of the absolute age scale (8% systematic), and the width of the slow sequence (4% statistical). An opensource implementation, gyrointerp, is available online at github.com/lgbouma/gyrointerp.
 Publication:

The Astrophysical Journal
 Pub Date:
 April 2023
 DOI:
 10.3847/20418213/acc589
 arXiv:
 arXiv:2303.08830
 Bibcode:
 2023ApJ...947L...3B
 Keywords:

 Stellar ages;
 Stellar rotation;
 Field stars;
 Bayesian statistics;
 1581;
 1629;
 2103;
 1900;
 Astrophysics  Solar and Stellar Astrophysics;
 Astrophysics  Instrumentation and Methods for Astrophysics
 EPrint:
 ApJL accepted. Data behind Fig1 are uploaded. Code documentation is at https://gyrointerp.readthedocs.io/