Physical properties of young brown dwarfs and very low mass stars inferred from high-resolution model spectra

Emily L. Rice, T. Barman, Ian S. McLean, L. Prato, J. Davy Kirkpatrick

Research output: Contribution to journalArticle

66 Scopus citations

Abstract

By comparing near-infrared spectra with atmospheric models, we infer the effective temperature, surface gravity, projected rotational velocity, and radial velocity for 21 very low mass stars and brown dwarfs. The unique sample consists of two sequences in spectral type from M6-M9, one of 5-10 Myr objects and one of >1 Gyr field objects. A third sequence is comprised of only ∼ M6 objects with ages ranging from <1 Myr to >1 Gyr. Spectra were obtained in the J band at medium (R ∼ 2000) and high (R ∼ 20,000) resolutions with NIRSPEC on the Keck II telescope. Synthetic spectra were generated from atmospheric structures calculated with the PHOENIX model atmosphere code. Using multi-dimensional least-squares fitting and Monte Carlo routines we determine the best-fit model parameters for each observed spectrum and note which spectral regions provide consistent results. We identify successes in the reproduction of observed features by atmospheric models, including pressure-broadened K I lines, and investigate deficiencies in the models, particularly missing FeH opacity, that will need to be addressed in order to extend our analysis to cooler objects. The precision that can be obtained for each parameter using medium- and high-resolution near-infrared spectra is estimated and the implications for future studies of very low mass stars and brown dwarfs are discussed.

Original languageEnglish (US)
Pages (from-to)63-84
Number of pages22
JournalAstrophysical Journal, Supplement Series
Volume186
Issue number1
DOIs
StatePublished - Feb 5 2010

Keywords

  • Infrared: stars
  • Open clusters and associations: individual (Upper Scorpius, TW Hydrae Association)
  • Stars: atmospheres
  • Stars: low-mass, brown dwarfs
  • Techniques: spectroscopic

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science

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