THE LUMINOSITY FUNCTION OF MASSIVE WHITE-DWARFS

The obtention of the star formation rate in the solar neighborhood fro m the white dwarf luminosity function has been recently considered by different authors. However, the white dwarf luminosity function has co ntributions of white dwarfs of all masses. Thus, at any luminosity, ex tremely different evolutionary times are involved. As a consequence, d econvolving the SFR from the white dwarf luminosity function becomes a difficult task. Here we present a method to obtain the star formation rate in the solar neighborhood from the luminosity function of massiv e white dwarfs, whose progenitors have very short main sequence lifeti mes. This allows us to overcome the difficulties in deconvolving the S FR. For this purpose cooling sequences for C+O white dwarfs with masse s ranging from 0.7 to 1.2 M. have been computed. We also present a pre liminary observational luminosity function for massive white dwarfs wh ich allows us to discuss our method. The usefulness of this method see ms to be promising since observations of white dwarfs should only indi cate if a white dwarf is massive and not the exact value of its mass.