Title:Age determination of pre-main sequence stars by high-resolution near-infrared spectroscopy
Author(s):Yuhei Takagi, Yoichi Itoh, Yumiko Oasa
Abstract:

We present a new method to determine the age of pre-main sequence stars with high-resolution near-infrared spectroscopy. The age determined by the general method, which is estimated by deriving the luminosity of young star, is inaccurate since their luminosity is contaminated by the effect of distance uncertainty, extinction, and veiling. Therefore, we created a new age-determining method by estimating the surface gravity of young star. Since a star contracts in the early evolutional stage, its age is able to be estimated by deriving its surface gravity. We used the �gequivalent width ratio�h of the nearby absorption lines to estimate the surface gravity, which is free from the distance uncertainty, the effect of veiling, and also the difference of metal abundance. However, a fine pair which indicates the surface gravity is not established yet. We observed high-resolution near-infrared spectra of dwarfs, T Tauri, and giants of which effective temperature are almost equal. We found that the Sc/Na in K-band is a good indicator of surface gravity. It is expected that the age determination of pre-main sequence star can be determined with a precision of the factor of 1.5 by our new method.