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

¹ 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.