@article{33b03f73bdfc485d9d01902d26ca5f53,
title = "Insights on the Spectral Signatures of Stellar Activity and Planets from PCA",
abstract = "Photospheric velocities and stellar activity features such as spots and faculae produce measurable radial velocity signals that currently obscure the detection of sub-meter-per-second planetary signals. However, photospheric velocities are imprinted differently in a high-resolution spectrum than are Keplerian Doppler shifts. Photospheric activity produces subtle differences in the shapes of absorption lines due to differences in how temperature or pressure affects the atomic transitions. In contrast, Keplerian Doppler shifts affect every spectral line in the same way. With a high enough signal-to-noise (S/N) and resolution, statistical techniques can exploit differences in spectra to disentangle the photospheric velocities and detect lower-amplitude exoplanet signals. We use simulated disk-integrated time-series spectra and principal component analysis (PCA) to show that photospheric signals introduce spectral line variability that is distinct from that of Doppler shifts. We quantify the impact of instrumental resolution and S/N for this work.",
author = "Davis, {Allen B.} and Jessi Cisewski and Xavier Dumusque and Fischer, {Debra A.} and Ford, {Eric B.}",
note = "Funding Information: We are grateful to our referees for providing thoughtful and constructive feedback on this paper, which has greatly improved its presentation. We thank Jeff Valenti for providing Figure 1. We also acknowledge helpful conversations with Lars Buchhave. The authors acknowledge support from the NSF grant AST1616086. A.B.D. acknowledges support through the NSF Graduate Research Fellowship grant DGE1122492. X.D. acknowledges support from the Society in Science–The Branco Weiss Fellowship, and the Swiss National Science Foundation for funding through the National Centre for Competence in Research “PlanetS.” E.B.F. acknowledges support by the Pennsylvania State Office of Science Engagement and the Center for Exoplanets and Habitable Worlds, which is supported by The Pennsylvania State University, the Eberly College of Science, and the Pennsylvania Space Grant Consortium. E.B.F. also acknowledges support from NASA Exoplanets Research Program #NNX15AE21G. This work was partially supported by the NSF grant DMS-1127914 to the Statistical and Applied Mathematical Sciences Institute (SAMSI), and E.B.F. and D.F. acknowledge supporting collaborations within NASA{\textquoteright}s Nexus for Exoplanet System Science (NExSS). Publisher Copyright: {\textcopyright} 2017. The American Astronomical Society. All rights reserved.",
year = "2017",
month = sep,
day = "1",
doi = "10.3847/1538-4357/aa8303",
language = "English (US)",
volume = "846",
journal = "Astrophysical Journal",
issn = "0004-637X",
publisher = "IOP Publishing Ltd.",
number = "1",
}