Astron. J., 155, 196-196 (2018/May-0)
Rotation of low-mass stars in Upper Scorpius and ρ Ophiuchus with K2.
REBULL L.M., STAUFFER J.R., CODY A.M., HILLENBRAND L.A., DAVID T.J. and PINSONNEAULT M.
Abstract (from CDS):
We present an analysis of K2 light curves (LCs) for candidate members of the young Upper Sco (USco) association (∼8 Myr) and the neighboring ρ Oph embedded cluster (∼1 Myr). We establish ∼1300 stars as probable members, ∼80% of which are periodic. The phased LCs have a variety of shapes which can be attributed to physical causes ranging from stellar pulsation and stellar rotation to disk-related phenomena. We identify and discuss a number of observed behaviors. The periods are ∼0.2-30 days with a peak near 2 days and the rapid period end nearing breakup velocity. M stars in the young USco region rotate systematically faster than GK stars, a pattern also present in K2 data for the older Pleiades and Praesepe systems. At higher masses (types FGK), the well-defined period-color relationship for slowly rotating stars seen in the Pleiades and Praesepe systems is not yet present in USco. Circumstellar disks are present predominantly among the more slowly rotating M stars in USco, with few disks in the subday rotators. However, M dwarfs with disks rotate faster on average than FGK systems with disks. For four of these disked M dwarfs, we provide direct evidence for disk locking based on the K2 LC morphologies. Our preliminary analysis shows a relatively mass-independent spin-up by a factor of ∼3.5 between USco and the Pleiades, then mass-dependent spin-down between Pleiades and Praesepe.
© 2018. The American Astronomical Society. All rights reserved.
stars: low-mass - stars: pre-main sequence
VizieR on-line data:
<Available at CDS (J/AJ/155/196): table1.dat table3.dat>
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