A&A 473, 257-264 (2007)
DOI: 10.1051/0004-6361:20065386

Spectral analysis of high resolution near-infrared spectra of ultra cool dwarfs

Y. Lyubchik¹, H. R. A. Jones², Y. V. Pavlenko^{1, 2}, E. Martin^{3, 4}, I. S. McLean⁵, L. Prato⁶, R. J. Barber⁷, and J. Tennyson<sup>7

1</sup>  Main Astronomical Observatory of Academy of Sciences of Ukraine, Zabolotnoho, 27, Kyiv 03680, Ukraine
    e-mail: lyu@mao.kiev.ua
²  Center for Astrophysics Research, University of Hertfordshire, College Lane, Hatfield, Hertfordshire AL10 9AB, UK
³  Instituto de Astrofísica de Canarias, La Laguna, Tenerife 38200, Spain
⁴  University of Central Florida, Department of Physics, PO Box 162385, Orlando, FL 32816, USA
⁵  Department of Physics and Astronomy, UCLA, Los Angeles, CA 90095, USA
⁶  Lowell Observatory, 1400 West Mars Hill Road, Flagstaff, AZ 86001, USA
⁷  Department of Physics and Astronomy, University College London, Gower Street, London WC1E 6BT, UK

(Received 7 April 2006 / Accepted 11 July 2007)

Abstract
Aims.We present an analysis of high resolution spectra in the J band of five ultra cool dwarfs from M6 to L0.
Methods.We make use of a new ab initio water vapour line list and existing line lists of FeH and CrH for modelling the observations.
Results.We find a good fit for the Mn I 12 899.76 Å line. This feature is one of the few for which we have a reliable oscillator strength. Other atomic features are present but most of the observed features are FeH and H₂O lines. While we are uncertain about the quality of many of the atomic line parameters, the FeH and CrH line lists predict a number of features which are not apparent in our observed spectra. We infer that the main limiting factor in our spectral analysis is the FeH and CrH molecular spectra.

Key words: line: identification -- stars: atmospheres -- stars: low-mass, brown dwarfs -- stars: late-type

© ESO 2007

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