AAS 203rd Meeting, January 2004
Session 74 Young Substellar Objects
Invited, Tuesday, January 6, 2004, 3:40-5:10pm, Centennial I/II

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[74.02] Brown Dwarfs: Up Close and Physical

G.B. Basri (Univ. of California, Berkeley)

I review what has now been nearly a decade of progress in the study of brown dwarfs as physical objects. The definition of brown dwarfs as distinct from stars or planets has some subtlety, and is an amalgam of considerations. I briefly discuss their internal structure, and the evolution of luminosity sources within them. Deuterium and lithium can be used as external probes of their internal state. I next discuss the effective temperature scale for the new L and T spectral classes. Formation of dust in the atmospheres of these objects is a crucial determinant of their spectral appearance, as is the conversion of typical molecules from oxides to hydrides. Not only is the chemical formation of dust important, but proper treatment of cloud formation and dust settling is clearly important (``meteorology'' becomes a consideration). This can strongly affect the colors of the objects, and the visibility of spectral features. Finally, I summarize results on other physical properties which can be studied using high spectral and angular resolution, including angular momentum, magnetic activity, surface gravity, and binarity.

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Bulletin of the American Astronomical Society, 35#5
© 2003. The American Astronomical Soceity.