Young L Dwarf Variability in the Mid-IR

We present Spitzer variability monitoring of three young, low-gravity L dwarfs known to be variable in the near-IR. We detect significant variability in two of our targets at [3.6] and [4.5] micron. Compiling the entire sample of brown dwarfs with mid-IR variability detections, we find no enhancement in amplitude for young, early-L dwarfs compared to the field dwarf population. We find a possible enhancement in amplitude of low-gravity late-L dwarfs at [4.5]. We do not find correlation between amplitude ratio and spectral type for field dwarfs or young population. We calculate the inclination angles of both variable objects and find that they are consistent with the tentative relations between inclination, amplitude and color anomaly previously reported. Finally, we compile the rotation periods of a large sample of brown dwarfs with ages 1 Myr to 1 Gyr and compare the rotation rates predicted by evolutionary models assuming angular momentum conservation. We find that the rotation rates of the current sample of brown dwarfs generally falls within the limits set by evolutionary models and breakup limits.