New periodograms separating orbital radial velocities and spectral shape variation

¹ Porter School of the Environment and Earth Sciences, Raymond and Beverly Sackler Faculty of Exact Sciences, Tel Aviv University, Tel Aviv 6997801, Israel
e-mail: avrahambinn@gmail.com
² Department of Particle Physics and Astrophysics, Weizmann Institute of Science, Rehovot 7610001, Israel
³ Institute of Physics, Laboratory of Astrophysics, École Polytechnique Fédérale de Lausanne (EPFL), Observatoire de Sauverny, 1290 Versoix, Switzerland
⁴ European Southern Observatory, Karl-Schwarzschild-Str. 2, 85748 Garching, Germany

Received: 27 May 2021
Accepted: 14 December 2021

Abstract

We present new periodograms that are effective in distinguishing Doppler shift from spectral shape variability in astronomical spectra. These periodograms, building upon the concept of partial distance correlation, separate the periodic radial velocity modulation induced by orbital motion from that induced by stellar activity. These tools can be used to explore large spectroscopic databases in search of targets in which spectral shape variations obscure the orbital motion; such systems include active planet-hosting stars or binary systems with an intrinsically variable component. We provide a detailed prescription for calculating the periodograms, demonstrate their performance via simulations and real-life case studies, and provide a public Python implementation.