Angular Momentum Evolution of Young Stars in the Nearby Scorpius-Centaurus OB Association

Abstract

We report the results of a study of archival SuperWASP light curves for stars in Scorpius-Centaurus (Sco-Cen), the nearest OB association. We use SuperWASP time-series photometry to extract rotation periods for 189 candidate members of the Sco-Cen complex, and verify that 162 of those are members of the classic Sco-Cen subgroups of Upper Scorpius (US), Upper Centaurus-Lupus (UCL), and Lower Centaurus-Crux (LCC). This study provides the first measurements of rotation periods explicitly for large samples of pre-main sequence (pre-MS) stars spanning the UCL and LCC subgroups. Our final sample of 157 well-characterized pre-MS stars spans ages of $\sim$ 10 -- 20 Myr, spectral types of $\sim$ F3 -- M0, and masses of $M \simeq$ 0.3 -- 1.5 $\mathcal{M}^{\rm N}_{\odot}$. For this sample, we find a distribution of stellar rotation periods with a median of $P_{\textrm{rot}} \simeq$ 2.4 days, overall range of 0.2 $<$ $P_{\textrm{rot}}$ $<$ 8 days, and a fairly well-defined mass-dependent upper envelope of rotation periods. This distribution of periods is consistent with recently developed stellar angular momentum evolution models. These data are significant because they represent an undersampled age range and the number of measurable rotation periods is large compared to recent studies of other regions. We also search for new examples of eclipsing disk or ring systems analogous to 1SWASP J140747.93-394542.6 ("J1407", V1400 Cen), but find none. Our survey yielded five eclipsing binaries, but only one appears to be physically associated with the Sco-Cen complex. V2394 Oph is a heavily reddened (A$_V$ $\simeq$ 5 mag) massive contact binary in the LDN 1689 cloud whose Gaia astrometry is clearly consistent with kinematic membership with the Ophiuchus star-forming region.