Insights on the Spectral Signatures of Stellar Activity and Planets from PCA
(Aug 1, 2017)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
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 high enough S/N and high
enough 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 Doppler shifts. We quantify the impact
of instrumental resolution and S/N for this work.