期刊
ASTROPHYSICAL JOURNAL
卷 542, 期 1, 页码 464-472出版社
UNIV CHICAGO PRESS
DOI: 10.1086/309513
关键词
Hertzsprung-Russell; stars : evolution; stars : low-mass brown dwarfs; stars : luminosity function, mass function
We present evolutionary calculations for very low-mass stars and brown dwarfs based on synthetic spectra and nongray atmosphere models which include dust formation and opacity, i.e., objects with T-eff less than or similar to 2800 K. The interior of the most massive brown dwarfs is shown to develop a conductive core after similar to2 Gyr which slows down their cooling. Comparison is made in optical and infrared color-magnitude diagrams with recent late-M and L dwarf observations. The saturation in optical colors and the very red near-infrared colors of these objects are well explained by the onset of dust formation in the atmosphere. Comparison of the faintest presently observed L dwarfs with these dusty evolutionary models suggests that dynamical processes such as turbulent diffusion and gravitational settling are taking place near the photosphere. As the effective temperature decreases below T-eff approximate to 1300-1400 K, the colors of these objects move to very blue near-infrared colors, a consequence of the ongoing methane absorption in the infrared. We suggest the possibility of a brown dwarf dearth in J, H, and K color-magnitude diagrams around this temperature.
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