Telluric-line subtraction in high-accuracy velocimetry: a PCA-based approach

TL;DR

This paper introduces a PCA-based method for removing telluric lines in near-infrared high-precision radial velocity measurements, improving accuracy and efficiency in exoplanet detection around cooler stars.

Contribution

A novel PCA-based approach for telluric line subtraction in near-infrared velocimetry, enhancing RV precision and observational efficiency.

Findings

Improved RV accuracy by excluding minimal spectral regions.

Utilized entire spectrum for better RV measurements.

Achieved higher telescope time efficiency using archival telluric standards.

Abstract

Optical velocimetry has led to the detection of more than 500 planets to date and there is a strong effort to push m/s velocimetry to the near-infrared to access cooler and lighter stars. The presence of numerous telluric absorption lines in the nIR brings an important challenge. As the star's barycentric velocity varies through the year, the telluric absorption lines effectively varies in velocity relative to the star's spectrum by the same amount leading to important systematic RV offsets. We present a novel principal component analysis-based approach for telluric line subtraction and demonstrated its effectiveness with archival HARPS data for GJ436 and {\tau} Ceti, over parts of the R-band that contain strong telluric absorption lines. The main results are: 1) a better RV accuracy with excluding only a few percentage of the domain, 2) better use of the entire spectrum to measure RV and 3) a higher telescope time efficency by using A0V telluric standard from telescope archive.