Ultracool Dwarf Rotation

Projected rotational velocity distribution for late-M, L, and T dwarfs (Hsu et al. 2021).

The rotation of ultracool dwarfs tells us their angular momentum evolution. Stellar and substellar objects experience different phases of angular momentum evolution, which can be constrained using their rotational period (through photometric light curves) and projected rotational velocities (vsini) through high-resolution spectroscopy.
Using the forward-modeling method, I found that the vsini trend of late-M, L, to T dwarfs goes up toward later spectral types, consistent with previous findings (while a much larger sample of T dwarfs), and showing that the angular momentum loss is less efficient for the lowest-mass regimes. The mechanism of releasing the angular momentum, thus spin-down during their field age, is less efficient for the fully convective ultracool dwarfs. You can check out my 2021 paper for more details. Stay tuned for my upcoming vsini analysis using SDSS/APOGEE!!