Rotation of Low-mass Stars in Upper Centaurus-Lupus and Lower Centaurus-Crux with TESS

We present stellar rotation rates derived from Transiting Exoplanet Survey Satellite (TESS) light curves for stars in
Upper Centaurus–Lupus (UCL; ∼136 pc, ∼16 Myr) and Lower Centaurus–Crux (LCC; ∼115 pc, ∼17 Myr). We
find spot-modulated periods (P) for ∼90% of members. The range of light-curve and periodogram shapes echoes
that found for other clusters with K2, but fewer multiperiod stars may be an indication of the different noise
characteristics of TESS, or a result of the source selection methods here. The distribution of P as a function of color
as a proxy for mass fits nicely in between that for both older and younger clusters observed by K2, with fast
rotators being found among both the highest and lowest masses probed here, and a well-organized distribution of
M-star rotation rates. About 13% of the stars have an infrared excess, suggesting a circumstellar disk; this is well
matched to expectations, given the age of the stars. There is an obvious pileup of disked M stars at P ∼ 2 days, and
the pileup may move to shorter P as the mass decreases. There is also a strong concentration of disk-free M stars at
P ∼ 2 days, hinting that perhaps these stars have recently freed themselves from their disks. Exploring the rotation
rates of stars in UCL/LCC has the potential to help us understand the beginning of the end of the influence of disks
on rotation, and the timescale on which stars respond to unlocking.