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 ) are presented for these objects and for 24 additional late-type dwarfs .
Supplemented with astrometry and photometry from the literature , including ten 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 . M _ { J } 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 , and 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 T _ { eff } \sim 1360 K .