Precise Modeling of Atmospheric Absorption Features in High-Resolution Astronomical Spectra

We present the latest results in modeling atmospheric absorption features in highresolution astronomical spectra, both, in the optical and near infrared at spectral resolutions of R=30,000 - 100,000. By using a variety of meteorological input parameters to build realistic atmospheric profiles and by modeling the instrumental profile of our spectrographs, we achieve a fit to telluric lines at the 1% level. While this is often sufficient for the removal of such lines from stellar spectra, we outline the range for further improvements and identify the most likely reasons for the current limitations. We will further emphasize the prospects for using telluric lines as a restframe for precise radial velocity measurements in the near infrared, which may facilitate the detection of very low mass extrasolar planets around late type stars and brown dwarfs. Finally, we will give an outlook how telluric features in astronomical spectra may be used for monitoring climate changes by precise measurements of the column density of CO2 and CH4.Session I: Astrophysics. June 22, 2008