Confronting substellar theoretical models with stellar ages

Trent J. Dupuy*, Michael C. Liu, Michael J. Ireland

*Corresponding author for this work

Research output: Chapter in Book/Report/Conference proceedingConference proceeding contributionpeer-review

Abstract

By definition, brown dwarfs never reach the main-sequence, cooling and dimming over their entire lifetime, thus making substellar models challenging to test because of the strong dependence on age. Currently, most brown dwarfs with independently determined ages are companions to nearby stars, so stellar ages are at the heart of the effort to test substellar models. However, these models are only fully constrained if both the mass and age are known. We have used the Keck adaptive optics system to monitor the orbit of HD 130948BC, a brown dwarf binary that is a companion to the young solar analog HD 130948A. The total dynamical mass of 0.109 +/- 0.003 M(circle dot) is the most precise mass measurement (3%) for any brown dwarf binary to date and shows that both components are substellar for any plausible mass ratio. The ensemble of available age indicators from the primary star suggests in age comparable to the Hyades, with the most precise age being 0.79(-0.15)(+0.22) Cyr based on gyrochronology. Therefore, HD 130948BC is unique among field L and T dwarfs as it possesses a well-determined mass, luminosity, and age. Our results indicate that substellar evolutionary models may underpredict the luminosity of brown dwarfs by as much as a factor of approximate to 2-3x. The implications of such a, systematic error in evolutionary models would be far-reaching, for example, affecting determinations of the initial mass function and predictions of the radii of extrasolar gas-giant, planets. This result is largely based on the reliability of stellar age estimates, and the case study of HD 130948A highlights the difficulties in determining the age of an arbitrary field star, even with the most up-to-date chromospheric activity and gyrochronology relations. In order to better assess the, potential systematic errors present in substellar models, more refined age estimates for HD 130948A and other stars with binary brown dwarf companions (e.g., epsilon Ind Bab) are critically needed.

Original languageEnglish
Title of host publicationAges of stars
EditorsEE Mamajek, DR Soderblom, RFG Wyse
Place of PublicationCambridge
PublisherCambridge University Press
Pages337-344
Number of pages8
ISBN (Print)978-0-521-88989-6
DOIs
Publication statusPublished - 2009
Externally publishedYes
Event258th Symposium of the International-Astronomical-Union - Baltimore, Moldova, Republic of
Duration: 13 Oct 200817 Oct 2008

Publication series

NameIAU Symposium Proceedings Series
PublisherCAMBRIDGE UNIV PRESS
Volume4
ISSN (Print)1743-9213

Conference

Conference258th Symposium of the International-Astronomical-Union
CountryMoldova, Republic of
CityBaltimore
Period13/10/0817/10/08

Keywords

  • stars: brown dwarfs
  • techniques: high angular resolution
  • binaries: close, visual
  • infrared: stars
  • SOLAR-TYPE STARS
  • BINARY BROWN DWARF
  • LOW-MASS STARS
  • LITHIUM ABUNDANCES
  • MULTIPLE SYSTEM
  • DYNAMICAL MASS
  • NEARBY STARS
  • COOL STARS
  • EVOLUTION
  • EMISSION

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