Astrophys. J., 839, 92-92 (2017/April-3)
Rotation of late-type stars in Praesepe with K2.
REBULL L.M., STAUFFER J.R., HILLENBRAND L.A., CODY A.M., BOUVIER J., SODERBLOM D.R., PINSONNEAULT M. and HEBB L.
Abstract (from CDS):
We have Fourier-analyzed 941 K2 light curves (LCs) of likely members of Praesepe, measuring periods for 86% and increasing the number of rotation periods (P) by nearly a factor of four. The distribution of P versus (V-Ks), a mass proxy, has three different regimes: (V-Ks) < 1.3, where the rotation rate rapidly slows as mass decreases; 1.3 < (V-Ks) < 4.5, where the rotation rate slows more gradually as mass decreases; and (V-Ks) > 4.5, where the rotation rate rapidly increases as mass decreases. In this last regime, there is a bimodal distribution of periods, with few between ∼2 and ∼10 days. We interpret this to mean that once M stars start to slow down, they do so rapidly. The K2 period-color distribution in Praesepe (∼790 Myr) is much different than that in the Pleiades (∼125 Myr) for late F, G, K, and early-M stars; the overall distribution moves to longer periods and is better described by two line segments. For mid-M stars, the relationship has a similarly broad scatter and is steeper in Praesepe. The diversity of LCs and of periodogram types is similar in the two clusters; about a quarter of the periodic stars in both clusters have multiple significant periods. Multi-periodic stars dominate among the higher masses, starting at a bluer color in Praesepe ((V-Ks) ∼ 1.5) than in the Pleiades ((V-Ks) ∼ 2.6). In Praesepe, there are relatively more LCs that have two widely separated periods, ΔP 6 days. Some of these could be examples of M star binaries where one star has spun down but the other has not.
© 2017. The American Astronomical Society. All rights reserved.
stars: rotation - stars: variables: general - stars: variables: general
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<Available at CDS (J/ApJ/839/92): table1.dat table4.dat table5.dat table6.dat table7.dat table8.dat table9.dat table10.dat table11.dat table12.dat>
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