Journal Article

A new benchmark T8-9 brown dwarf and a couple of new mid-T dwarfs from the UKIDSS DR5+ LAS*

B. Goldman, S. Marsat, T. Henning, C. Clemens and J. Greiner

in Monthly Notices of the Royal Astronomical Society

Published on behalf of The Royal Astronomical Society

Volume 405, issue 2, pages 1140-1152
Published in print June 2010 | ISSN: 0035-8711
Published online June 2010 | e-ISSN: 1365-2966 | DOI:
A new benchmark T8-9 brown dwarf and a couple of new mid-T dwarfs from the UKIDSS DR5+ LAS*

More Like This

Show all results sharing this subject:

  • Astronomy and Astrophysics


Show Summary Details


Benchmark brown dwarfs are those objects for which fiducial constraints are available, including effective temperature, parallax, age and metallicity. We searched for new cool brown dwarfs in 186 deg2 of the new area covered by the data release DR5+ of the UKIRT Deep Infrared Sky Survey (UKIDSS) Large Area Survey. Follow-up optical and near-infrared broad-band photometry, and methane imaging of four promising candidates, revealed three objects with distinct methane absorption, typical of mid- to late-T dwarfs and one possibly T4 dwarf. The latest-type object, classified as T8–9, shares its large proper motion with Ross 458 (BD+13o2618), an active M0.5 binary which is 102 arcsec away, forming a hierarchical low-mass star + brown dwarf system. Ross 458C has an absolute J-band magnitude of 16.4, and seems overluminous, particularly in the K band, compared to similar field brown dwarfs. We estimate the age of the system to be less than 1 Gyr, and its mass to be as low as 14 Jupiter masses for the age of 1 Gyr. At 11.4 pc, this new late-T benchmark dwarf is a promising target to constrain the evolutionary and atmospheric models of very low-mass brown dwarfs. We present proper motion measurements for our targets and for 13 known brown dwarfs. Two brown dwarfs have velocities typical of the thick disc and may be old brown dwarfs.

Keywords: binaries: general; brown dwarfs; stars: individual: Ross 458C

Journal Article.  9366 words.  Illustrated.

Subjects: Astronomy and Astrophysics

Full text: subscription required

How to subscribe Recommend to my Librarian

Users without a subscription are not able to see the full content. Please, subscribe or login to access all content.