A robust, template-free approach to precise radial velocity extraction

Abstract

Doppler spectroscopy is a powerful tool for discovering and characterizing exoplanets. For decades, the standard approach to extracting radial velocities (RVs) has been to cross-correlate observed spectra with a weighted template mask. While still widely used, this approach is known to suffer numerous drawbacks, and so in recent years increasing attention has been paid to developing new and improved ways of extracting RVs. In this proof-of-concept paper we present a simple yet powerful approach to RV extraction. We use Gaussian processes to model and align all pairs of spectra with each other; without constructing a template, we combine pairwise RV shifts to produce accurate differential stellar RVs. Doing this on a highly-localized basis enables a data-driven approach to identifying and mitigating spectral contamination, even without the input of any prior astrophysical knowledge. We show that a crude implementation of this method applied to an inactive standard star yields RVs with comparable precision to and significantly lower rms variation than RVs from industry-standard pipelines. Though amenable to numerous improvements, even in its basic form presented here our method could facilitate the study of smaller planets around a wider variety of stars than has previously been possible.

27 pages, 16 figures. Accepted for publication in MNRAS

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Cited by in corpus (9)

• The EXPRES Stellar Signals Project II. State of the Field in Disentangling Photospheric Velocities
• Statistical methods for exoplanet detection with radial velocities
• A HARPS-N mass for the elusive Kepler-37d: a case study in disentangling stellar activity and planetary signals
• SOAP-GPU: Efficient Spectral Modelling of Stellar Activity Using Graphical Processing Units
• Applications of a Gaussian Process Framework for Modelling of High-Resolution Exoplanet Spectra
• Multi-Mask Least-Squares Deconvolution: Extracting RVs using tailored masks
• Spectral Line Depth Variability in Radial Velocity Spectra
• HiFLEx -- a highly flexible package to reduce cross-dispersed echelle spectra
• A Hermite-Gaussian Based Radial Velocity Estimation Method