Rotation of Low-mass Stars in Taurus with K2

Abstract

We present an analysis of K2 light curves (LCs) from Campaigns 4 and 13 for members of the young (∼3 Myr) Taurus association, in addition to an older (∼30 Myr) population of stars that is largely in the foreground of the Taurus molecular clouds. Out of 156 of the highest-confidence Taurus members, we find that 81% are periodic. Our sample of young foreground stars is biased and incomplete, but nearly all stars (37/38) are periodic. The overall distribution of rotation rates as a function of color (a proxy for mass) is similar to that found in other clusters: the slowest rotators are among the early M spectral types, with faster rotation toward both earlier FGK and later M types. The relationship between period and color/mass exhibited by older clusters such as the Pleiades is already in place by Taurus age. The foreground population has very few stars but is consistent with the USco and Pleiades period distributions. As found in other young clusters, stars with disks rotate on average slower, and few with disks are found rotating faster than ∼2 days. The overall amplitude of the LCs decreases with age, and highermass stars have generally lower amplitudes than lower-mass stars. Stars with disks have on average larger amplitudes than stars without disks, though the physical mechanisms driving the variability and the resulting LC morphologies are also different between these two classes.

The magnetic obliquity of accreting T Tauri stars

“…The variability of the radial velocity of the He I line is consistent with a period of 4.6 days, found in the literature (Percy et al 2010;Artemenko et al 2012) and in this star's K2 light curve (Rebull et al 2020). There is no clear trend in veiling or in the Hα and Hβ line profiles with this period, even though the variability of the line profiles is very strong.…”

“…The radial velocity of this star's He I NC is very well modulated with a period of 2.7±0.4 days, while the radial velocity of the Li I line gives a similar period of 2.86 days. These periods coincide well with the photometric period of 2.81 days measured by Artemenko et al (2012) and in its K2 light curve (Rebull et al 2020). The top two panels of Fig.…”

“…This star's K2 light curve clearly shows a spot-like behaviour, with two distinct periods, one of which agrees with this period found in the Li I line (see Fig. A4 and Rebull et al 2020). It is likely that one of these periods represents the star's rotation while the other may be due to a companion.…”

Even More Rapidly Rotating Pre-main-sequence M Dwarfs with Highly Structured Light Curves: An Initial Survey in the Lower Centaurus-Crux and Upper Centaurus-Lupus Associations

“…In a series of papers, we have recently used light curves from the K2 mission (Howell et al 2014) to conduct an extensive survey of the rotational evolution of low-mass stars (Rebull et al 2016a(Rebull et al , 2016b(Rebull et al , 2017(Rebull et al , 2018(Rebull et al , 2020Stauffer et al 2017Stauffer et al , 2018a. In the process of conducting that survey, the two lead authors (L.M.R.…”

Pleiades or Not? Resolving the Status of the Lithium-rich M Dwarfs HHJ 339 and HHJ 430

“…The member list for Group 29 comes from Oh et al (2017) and the member list for the 32 Ori group comes from Bell et al (2017). The Taurus member list is based on Rebull et al (2020), which in turn heavily relies on the list from Luhman (2018) and Esplin & Luhman (2019), and the Taurus radial velocities are from Galli et al (2019).…”