Disentangling the Effects of Temperature, Clouds, and Gravity on K I doublet in L dwarfs

Abstract: We investigate the effects of surface gravity, effective temperature, and cloudiness on the potassium doublet (\ion{K}{1}) at 1.17 {\mu}m in brown dwarf spectra. Using pseudo-Voigt profiles to fit the \ion{K}{1} doublet in Sonora Diamondback atmospheric model spectra, we find that gravity and cloudiness affect the spectra differently in mid to late-L dwarfs. The full-width at half-maximum (FWHM) is strongly correlated with surface gravity, while the maximum depth strongly correlates with cloudiness. This method allows us to separate the effects of clouds and surface gravity on the \ion{K}{1} 1.17 {\mu}m doublet. We also find that the FWHM and maximum depth of the doublet can help to estimate the effective temperature and surface gravity in early to mid-L dwarfs.