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The faintest stars: A study of white, red and brown dwarfs
Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Physics, Department of Astronomy and Space Physics, The Uppsala Astronomical Observatory.
1998 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The local space density of the faintest stars, including M dwarfs, white dwarfs and brown dwarfs has been studied by two different methods.

By using dark nebulae as opaque outer screens, the luminosity functions of M dwarfs and white dwarfs were studied as volume-limited and dynamically unbiassed foreground samples. The surveyed volume corresponds to 464 pc3 in the solar neighbourhood and contains 21 M dwarfs and 7 white dwarfs. The derived M-dwarf luminosity function is consistent with previous findings, showing no substantial upturnbeyond Mv = 16. The white dwarf space density is consistent with a 20% fraction of the dynamical matter in the solar neighbourhood residing in white dwarfs. This is in line with the most recent independent results obtained with different methods, making the white dwarfs the best explanation to the Milky Way dark matter at present.

The brown dwarfs were studied in the Pleiades open cluster. The distance and age of the Pleiades make the rapidly fading brown dwarfs still rather bright and easy to detect. 850 arcmin2 were covered in a deep RIJK survey. Nine new possible cluster members were discovered, four of which are below the brown dwarf limit. The faintest of these has an estimated mass of 0.040 M. and is thereby the lowest mass brown dwarf identified in the Pleiades cluster at present. The derived Pleiades substellar luminosity function is consistent with a mass function index between 0 and 1, making the brown dwarfs unlikely to contribute more than a few percent to the cluster mass, which is also consistent with recent dynamical results.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis , 1998. , 39 p.
Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1104-232X ; 342
Keyword [en]
Astronomy, brown dwarfs, white dwarfs, M dwarf, low luminosity, luminosity function, mass function, Pleiades
Keyword [sv]
National Category
Astronomy, Astrophysics and Cosmology
Research subject
URN: urn:nbn:se:uu:diva-145ISBN: 91-554-4146-7OAI: oai:DiVA.org:uu-145DiVA: diva2:160987
Public defence
1998-03-27, Lecture hall at the Uppsala Astronomical Observatory, Uppsala University, Uppsala, 14:00
Available from: 1998-03-06 Created: 1998-03-06Bibliographically approved

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