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Astron. Astrophys. 336, 883-894 (1998)

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The luminosity function of white dwarfs and M dwarfs using dark nebulae as opaque outer screens *

L. Festin

Astronomical Observatory, Box 515, S-751 20 Uppsala, Sweden (leif@astro.uu.se)

Received 28 January 1998 / Accepted 9 June 1998

Abstract

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 [FORMULA] Oph cloud complexes were observed, covering a volume corresponding to 464 pc3 in the solar neighbourhood, complete to [FORMULA]. 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 [FORMULA]. The 7 white dwarfs imply a local density of 0.013 ([FORMULA]) [FORMULA] pc-3 ([FORMULA]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

* Based on observations collected at the European Southern Observatory (ESO), La Silla, Chile and at the Nordic Optical Telescope (NOT), La Palma

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© European Southern Observatory (ESO) 1998

Online publication: July 27, 1998
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