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The luminosity function of white dwarfs and M dwarfs using dark nebulae as opaque outer screens *
Received 28 January 1998 / Accepted 9 June 1998
By using dark nebulae as opaque outer screens, the luminosity function of white dwarfs and M dwarfs has been studied. High-extinction areas towards the Orion A, Serpens and Oph cloud complexes were observed, covering a volume corresponding to 464 pc3 in the solar neighbourhood, complete to . Foreground stars were selected by VRI photometry and photometric parallaxes.
The resulting foreground sample consists of 21 M dwarfs and 7 white dwarfs. The derived M-dwarf luminosity function is consistent with previous studies, showing no substantial upturn beyond . The 7 white dwarfs imply a local density of 0.013 () pc-3 (15 % of the dynamical mass in the solar neighbourhood) supporting other recent results but obtained with a completely different method.
For the clouds, foreground-star data were used to derive independent cloud distances, while the background stars and a simple model of the Milky Way gave reliable cloud extinctions.
Key words: stars: late-type; low-mass; brown dwarfs; luminosity function; mass function; white dwarfs Galaxy: solar neighbourhood; stellar content
Send offprint requests to: L. Festin
Online publication: July 27, 1998