Astrophys. J., 879, 49-49 (2019/July-1)
A temporary epoch of stalled spin-down for low-mass stars: insights from NGC 6811 with Gaia and Kepler.
CURTIS J.L., AGUEROS M.A., DOUGLAS S.T. and MEIBOM S.
Abstract (from CDS):
Stellar rotation was proposed as a potential age diagnostic that is precise, simple, and applicable to a broad range of low-mass stars (≤ 1 M☉). Unfortunately, rotation period (Prot) measurements of low-mass members of open clusters have undermined the idea that stars spin down with a common age dependence (i.e., Prot∝ \sqrtage): K dwarfs appear to spin down more slowly than F and G dwarfs. Agueros et al. interpreted data for the ≃1.4 Gyr-old cluster NGC 752 differently, proposing that after having converged onto a slow-rotating sequence in their first 600-700 Myr (by the age of Praesepe), K dwarf Prot stall on that sequence for an extended period of time. We use data from Gaia DR2 to identify likely single-star members of the ≃1 Gyr-old cluster NGC 6811 with Kepler light curves. We measure Prot for 171 members, more than doubling the sample relative to the existing catalog and extending the mass limit from ~0.8 to ≃0.6 M☉. We then apply a gyrochronology formula calibrated with Praesepe and the Sun to 27 single G dwarfs in NGC 6811 to derive a precise gyrochronological age for the cluster of 1.04 ± 0.07 Gyr. However, when our new low-mass rotators are included, NGC 6811's color-Prot sequence deviates away from the naive 1 Gyr projection down to Teff~4295 K (K5V, 0.7 M☉), where it clearly overlaps with Praesepe's. Combining these data with Prot for other clusters, we conclude that the assumption that mass and age are separable dependencies is invalid. Furthermore, the cluster data show definitively that stars experience a temporary epoch of reduced braking efficiency where Prot stall, and that the duration of this epoch lasts longer for lower-mass stars.
© 2019. The American Astronomical Society.
open clusters and associations: individual: (NGC 6811, Pleiades, Praesepe) - stars: evolution - stars: rotation - stars: solar-type
Status in Simbad:
waiting for electronic table
View the reference in ADS
To bookmark this query, right click on this link: simbad:2019ApJ...879...49C and select 'bookmark this link' or equivalent in the popup menu