Follow-up observations of binary ultra-cool dwarfs

    Authors

    H. Bouy; E. L. Martin; W. Brandner; T. Forveille; X. Delfosse; N. Huelamo; G. Basri; J. Girard; M. R. Z. Osorio; M. Stumpf; A. Ghez; L. Valdivielso; F. Marchis; A. J. Burgasser;K. Cruz

    Comments

    Authors: contact us about adding a copy of your work at STARS@ucf.edu

    Abbreviated Journal Title

    Astron. Astrophys.

    Keywords

    stars : low-mass; brown dwarfs; binaries : visual; techniques : high; angular resolution; LOW-MASS STARS; HUBBLE-SPACE-TELESCOPE; ALL-SKY SURVEY; ADAPTIVE OPTICS; SURVEY; YOUNG BROWN DWARFS; DYNAMICAL MASS; T-DWARFS; ACCURATE MASSES; MAIN-SEQUENCE; MULTIPLICITY; Astronomy & Astrophysics

    Abstract

    Context. Astrometric observations of resolved binaries provide estimates of orbital periods and will eventually lead to measurement of dynamical masses. Only a few very low mass star and brown dwarf masses have been measured to date, and the mass-luminosity relation still needs to be calibrated. Aims. We have monitored 14 very low mass multiple systems for several years to confirm their multiplicity and, for those with a short period, derive accurate orbital parameters and dynamical mass estimates. Methods. We have used high spatial resolution images obtained at the Paranal, Lick and HST observatories to obtain astrometric and photometric measurements of the multiple systems at several epochs. The targets have periods ranging from 5 to 200 years, and spectral types in the range M7.5-T5.5. Results. All of our 14 multiple systems are confirmed as common proper motion pairs. One system (2MASSW J0920122+351742) is not resolved in our new images, probably because the discovery images were taken near maximum elongation. Six systems have periods short enough to allow dynamical mass measurements within the next 15 to 20 years. We estimate that only 8% of the ultracool dwarfs in the solar neighborhood are binaries with separations large enough to be resolved, and yet periods short enough to derive astrometric orbital fits over a reasonable time frame with current instrumentation. A survey that doubles the number of ultracool dwarfs observed with high angular resolution is called for to discover enough binaries for a first attempt to derive the mass-luminosity relationship for very low-mass stars and brown dwarfs.

    Journal Title

    Astronomy & Astrophysics

    Volume

    481

    Issue/Number

    3

    Publication Date

    1-1-2008

    Document Type

    Article

    Language

    English

    First Page

    757

    Last Page

    767

    WOS Identifier

    WOS:000254754200021

    ISSN

    0004-6361

    Share

    COinS