Ages for Illustrative Field Stars Using Gyrochronology: Viability, Limitations, and Errors

Abstract

We here develop an improved way of using a rotating star as a clock, set it\nusing the Sun, and demonstrate that it keeps time well. This technique, called\ngyrochronology, permits the derivation of ages for solar- and late-type main\nsequence stars using only their rotation periods and colors. The technique is\nclarified and developed here, and used to derive ages for illustrative groups\nof nearby, late-type field stars with measured rotation periods. We first\ndemonstrate the reality of the interface sequence, the unifying feature of the\nrotational observations of cluster and field stars that makes the technique\npossible, and extends it beyond the proposal of Skumanich by specifying the\nmass dependence of rotation for these stars. We delineate which stars it cannot\ncurrently be used on. We then calibrate the age dependence using the Sun. The\nerrors are propagated to understand their dependence on color and period.\nRepresentative age errors associated with the technique are estimated at ~15%\n(plus possible systematic errors) for late-F, G, K, & early-M stars. Ages\nderived via gyrochronology for the Mt. Wilson stars are shown to be in good\nagreement with chromospheric ages for all but the bluest stars, and probably\nsuperior. Gyro ages are then calculated for each of the active main sequence\nfield stars studied by Strassmeier and collaborators where other ages are not\navailable. These are shown to be mostly younger than 1Gyr, with a median age of\n365Myr. The sample of single, late-type main sequence field stars assembled by\nPizzolato and collaborators is then assessed, and shown to have gyro ages\nranging from under 100Myr to several Gyr, and a median age of 1.2Gyr. Finally,\nwe demonstrate that the individual components of the three wide binaries\nXiBooAB, 61CygAB, & AlphaCenAB yield substantially the same gyro ages.\n