We have obtained high-resolution spectra (R~25,000) of an A star over varying air mass to determine the effectiveness of telluric removal within the limit of a high signal-to-noise ratio. The near-infrared line He I at 2.058 μm, which is a sensitive indicator of physical conditions in massive stars, supergiants, H II regions, and YSOs, resides among pressure-broadened telluric absorption from CO2 and water vapor that varies with both time and observed air mass. Our study shows that in the limit of bright stars at high resolution, accuracies of 5% are typical for high-air-mass observations (greater than 1.9), improving to a photon-limited accuracy of 2% at smaller air masses (less than 1.15). We find that by using the continuum between telluric absorption lines of a rovibrational fan, a photon-limited 1% accuracy is achievable.
Publications of the Astronomical Society of the Pacific
- Pub Date:
- January 2004
- Methods: Data Analysis;
- Techniques: Spectroscopic;
- 14 pages, 7 figures. Accepted for publication in PASP