Spectra, colors, luminosities and motions of the white dwarfs . (original) (raw)

Abstract

Spectroscopic and photometric data, most of which are new, are given for 166 white dwarfs in Table 1 together with the available astrometric data. An (Mv, U - V) diagram is constructed for 19 stars with trigonometric parallaxes greater than O.OS , 16 stars in the Pleiades, Hyades, and Praesepe clusters, and 34 stars in wide binary systems. The red components in many of the wide binaries have been observed in the (R - I) as well as in the (UB V) system; low-dispersion spectra of some of these objects are also discussed. The white dwarfs are divided into two groups: (1) those that cluster, with very little dispersion,about the relation Mv = +11.65 + 0.85 (U - V), and (2) those that show a somewhat larger dispersion about a similar, but steeper, relation with a zero-point approximately 1.5 fainter. This well-marked separation is also reflected in the nature of the spectral lines, with those in group (1) showing appreciably sharper absorption lines than the fainter stars. Group 1 stars are mainly sharp-lined DA objects, whereas the "peculiar" (i.e., non-DA) stars fall in group 2. Many stars of individual interest, as well as various correlations involving the equivalent widths of H in the DA stars and the colors and the departure of the stars from black bodies, are discussed in detail. Spectroscopically some of the most interesting stars include the DK and DM objects which are available for the first time in many numbers. The four known 4670 stars, which includes one new member of this class, may form a moving group, as previously suggested by Bell (1962). This group, called the W219 group, may also include two stars of type DC and one of type DK.