Correcting for Telluric Absorption: Methods, Case Studies, and Release of the TelFit Code

Abstract

Ground-based astronomical spectra are contaminated by the Earth's atmosphere to varying degrees in all spectral regions. We present a Python code that can accurately fit a model to the telluric absorption spectrum present in astronomical data, with residuals of $\sim 3-5\%$ of the continuum for moderately strong lines. We demonstrate the quality of the correction by fitting the telluric spectrum in a nearly featureless A0V star, HIP 20264, as well as to a series of dwarf M star spectra near the 819 nm sodium doublet. We directly compare the results to an empirical telluric correction of HIP 20264 and find that our model-fitting procedure is at least as good and sometimes more accurate. The telluric correction code, which we make freely available to the astronomical community, can be used as a replacement for telluric standard star observations for many purposes.

7 pages, 5 figures, accepted to the Astronomical Journal. The TelFit code is available from github (https://github.com/kgullikson88/Telluric-Fitter) and my personal website (http://www.as.utexas.edu/~kgulliks/projects.html)