Dust in the Photospheric Environment: Unified Cloudy Models of M, L, and T Dwarfs

摘要: We report an attempt to construct unified cloudy models of M, L, and T dwarfs. For this purpose, we first discuss opacities as well thermochemical properties the cool dense matter. Below about 2000 K, refractory material condenses, dust will play a major role source opacity. Then problem in modeling photospheres very dwarfs is how treat and, especially, could be sustained static photosphere for long time. Under high density dwarfs, forms easily at condensation temperature, Tcond, but soon grow larger than its critical radius rcr (at which Gibbs free energy attains maximum) temperature Tcr. Such large grains with rgr segregate from gas precipitate below photosphere. reason, exists effectively only limited region Tcr Tcond photosphere, means that cloud formed deep rather cooler surface region. With simple model cloud, show nongray radiative-convective equilibrium can extended Teff values low 800 K. Since ≈ K condensates such corundum iron, warm necessarily located deeper (τ > 1) objects (note τ 1). This explains why apparently shows little observable effect warmer objects, always same range nearer < 1), L appear dusty. recently proposed spectral classification consistently interpreted by single grid our thin