Resolved Hubble space spectroscopy of ultracool binary systems

    Authors

    E. L. Martin; W. Brandner; H. Bouy; G. Basri; J. Davis; R. Deshpande;M. M. Montgomery

    Comments

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    Abbreviated Journal Title

    Astron. Astrophys.

    Keywords

    stars : low-mass, brown dwarfs; stars : late-type -techniques :; spectroscopic; stars : binaries : visual; Galaxy : solar neighbourhood; stars : fundamental parameters; LOW-MASS BINARY; DENIS-P J1228.2-1547; YOUNG BROWN DWARFS; KECK HIRES; SPECTRA; L FIELD DWARFS; ALL-SKY SURVEY; SOLAR NEIGHBORHOOD; UPPER-SCORPIUS; STAR-FORMATION; PROPER MOTION; Astronomy & Astrophysics

    Abstract

    Using the low-resolution mode of the Space Telescope Imaging Spectrograph (STIS) aboard the Hubble Space Telescope (HST), we obtain spectra from 20 spatially-resolved, ultracool dwarfs, eighteen of which belong to nine very low-mass binary systems with known angular separations in the range 0."37-0."098. For these dwarfs, we derive their spectral types to be in the range dM7.5 to dL6 by either obtaining their PC3 index value or by comparing our STIS spectra with ground-based spectra of similar spectral resolution from Martin et al. (1999b). We have searched for H-alpha emission in each object, but the emission is clearly detected in only two of them. We find that the distribution of H-alpha emission in our sample is statistically different from that of single field dwarfs, suggesting an intriguing anti-correlation between chromospheric activity and binarity for M7-M9.5 dwarfs. We provide strength measuments of the main photospheric features. We derive calibrations of spectral subclasses versus F814W and K-band absolute magnitudes for a subset of 10 dwarfs in 5 binaries that have known trigonometric parallaxes.

    Journal Title

    Astronomy & Astrophysics

    Volume

    456

    Issue/Number

    1

    Publication Date

    1-1-2006

    Document Type

    Article

    Language

    English

    First Page

    253

    Last Page

    U48

    WOS Identifier

    WOS:000240009800025

    ISSN

    0004-6361

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