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          Institute: MPI für Astronomie     Collection: Publikationen_mpia     Display Documents



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ID: 559071.0, MPI für Astronomie / Publikationen_mpia
Lucky Imaging survey for southern M dwarf binaries
Authors:Bergfors, C.; Brandner, W.; Janson, M.; Daemgen, S.; Geissler, K.; Henning, T.; Hippler, S.; Hormuth, F.; Joergens, V.; Köhler, R.
Date of Publication (YYYY-MM-DD):2010
Title of Journal:Astronomy and Astrophysics
Journal Abbrev.:A&A
Volume:520
Start Page:id.A54
Review Status:not specified
Audience:Experts Only
Abstract / Description:Context. While M dwarfs are the most abundant stars in the Milky Way, there is still large uncertainty about their basic physical properties (mass, luminosity, radius, etc.) as well as their formation environment. Precise knowledge of multiplicity characteristics and how they change in this transitional mass region, between Sun-like stars on the one side and very low mass stars and brown dwarfs on the other, provide constraints on low mass star and brown dwarf formation. <BR /> Aims: In the largest M dwarf binary survey to date, we search for companions to active, and thus preferentially young, M dwarfs in the solar neighbourhood. We study their binary/multiple properties, such as the multiplicity frequency and distributions of mass-ratio and separation, and identify short period visual binaries, for which orbital parameters and hence dynamical mass estimates can be derived in the near future. <BR /> Methods: The observations are carried out in the SDSS i' and z' band using the Lucky Imaging camera AstraLux Sur at the ESO 3.5 m New Technology Telescope. Lucky Imaging is a very efficient way of observing a large sample of stars at an angular resolution close to the diffraction limit. <BR /> Results: In the first part of the survey, we observed 124 M dwarfs of integrated spectral types M 0-M 6 and identified 34 new and 17 previously known companions to 44 stars. We derived relative astrometry and component photometry for these binary and multiple systems. More than half of the binaries have separations smaller than 1” and would have been missed in a simply seeing-limited survey. Correcting our sample for selection effects yields a multiplicity fraction of 32±6% for 108 M dwarfs within 52 pc and with angular separations of 0.1”-6.0”, corresponding to projected separations of 3-180 AU at median distance 30 pc. Compared to early-type M dwarfs (M ⪆ 0.3 Mȯ), later-type (and hence lower mass) M dwarf binaries appear to have closer separations, and more similar masses. Based on observations made with ESO Telescopes at La Silla or Paranal Observatories under programme ID 082.C-0053.Tables 1 and 2 are only available in electronic form at <A href="http://www.aanda.org">http://www.aanda.org</A>
Free Keywords:techniques: high angular resolution; binaries: visual; stars: low-mass; brown dwarfs
External Publication Status:published
Document Type:Article
Communicated by:N. N.
Affiliations:MPI für Astronomie
Identifiers:URL:http://cdsads.u-strasbg.fr/abs/2010A%26A...520A..5... [ID No:1]
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