Astron. J., 124, 1170-1189 (2002/August-0)
Astrometry and photometry for cool dwarfs and brown dwarfs.
DAHN C.C., HARRIS H.C., VRBA F.J., GUETTER H.H., CANZIAN B., HENDEN A.A., LEVINE S.E., LUGINBUHL C.B., MONET A.K.B., MONET D.G., PIER J.R., STONE R.C., WALKER R.L., BURGASSER A.J., GIZIS J.E., KIRKPATRICK J.D., LIEBERT J. and REID I.N.
Abstract (from CDS):
Trigonometric parallax determinations are presented for 28 late-type dwarfs and brown dwarfs, including eight M dwarfs with spectral types between M7 and M9.5, 17 L dwarfs with spectral types between L0 and L8, and three T dwarfs. Broadband photometry at CCD wavelengths (VRIz*) and/or near-IR wavelengths (JHK) is presented for these objects and for 24 additional late-type dwarfs. Supplemented with astrometry and photometry from the literature, including 10 L and two T dwarfs with parallaxes established by association with bright, usually Hipparcos primaries, this material forms the basis for studying various color-color and color-absolute magnitude relations. The I-J color is a good predictor of absolute magnitude for late M and L dwarfs. MJ becomes monotonically fainter with I-J color and with spectral type through late L dwarfs, then brightens for early T dwarfs. The combination of z*JK colors alone can be used to classify late M, early L, and T dwarfs accurately, as well as to predict their absolute magnitudes, but is less effective at untangling the scatter among mid- and late L dwarfs. The mean tangential velocity of these objects is found to be slightly less than that for dM stars in the solar neighborhood, consistent with a sample with a mean age of several Gyr. Using colors to estimate bolometric corrections and models to estimate stellar radii, effective temperatures are derived. The latest L dwarfs are found to have Teff∼1360 K.
Astrometry - Stars: Color-Magnitude Diagrams - Stars: Distances - Stars: Late-Type - Stars: Low-Mass, Brown Dwarfs
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