Detection Limits of Low-mass, Long-period Exoplanets Using Gaussian Processes Applied to HARPS-N Solar RVs. (arXiv:2008.05970v1 [astro-ph.EP])
<a href="http://arxiv.org/find/astro-ph/1/au:+Langellier_N/0/1/0/all/0/1">N. Langellier</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Milbourne_T/0/1/0/all/0/1">T. W. Milbourne</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Phillips_D/0/1/0/all/0/1">D. F. Phillips</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Haywood_R/0/1/0/all/0/1">R. D. Haywood</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Saar_S/0/1/0/all/0/1">S. H. Saar</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Mortier_A/0/1/0/all/0/1">A. Mortier</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Malavolta_L/0/1/0/all/0/1">L. Malavolta</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Thompson_S/0/1/0/all/0/1">S. Thompson</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Cameron_A/0/1/0/all/0/1">A. Collier Cameron</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Dumusque_X/0/1/0/all/0/1">X. Dumusque</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Cegla_H/0/1/0/all/0/1">H. M. Cegla</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Latham_D/0/1/0/all/0/1">D. W. Latham</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Maldonado_J/0/1/0/all/0/1">J. Maldonado</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Watson_C/0/1/0/all/0/1">C. A. Watson</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Cecconi_M/0/1/0/all/0/1">M. Cecconi</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Charbonneau_D/0/1/0/all/0/1">D. Charbonneau</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Cosentino_R/0/1/0/all/0/1">R. Cosentino</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Ghedina_A/0/1/0/all/0/1">A. Ghedina</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Gonzalez_M/0/1/0/all/0/1">M. Gonzalez</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Li_C/0/1/0/all/0/1">C-H. Li</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Lodi_M/0/1/0/all/0/1">M. Lodi</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Lopez_Morales_M/0/1/0/all/0/1">M. L&#xf3;pez-Morales</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Micela_G/0/1/0/all/0/1">G. Micela</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Molinari_E/0/1/0/all/0/1">E. Molinari</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Pepe_F/0/1/0/all/0/1">F. Pepe</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Poretti_E/0/1/0/all/0/1">E. Poretti</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Rice_K/0/1/0/all/0/1">K. Rice</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Sasselov_D/0/1/0/all/0/1">D. Sasselov</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Sozzetti_A/0/1/0/all/0/1">A. Sozzetti</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Udry_S/0/1/0/all/0/1">S. Udry</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Walsworth_R/0/1/0/all/0/1">R. L. Walsworth</a>

Radial velocity (RV) searches for Earth-mass exoplanets in the habitable zone
around Sun-like stars are limited by the effects of stellar variability on the
host star. In particular, suppression of convective blueshift and brightness
inhomogeneities due to photospheric faculae/plage and starspots are the
dominant contribution to the variability of such stellar RVs. Gaussian process
(GP) regression is a powerful tool for modeling these quasi-periodic
variations. We investigate the limits of this technique using 800 days of RVs
from the solar telescope on the HARPS-N spectrograph. These data provide a
well-sampled time series of stellar RV variations. Into this data set, we
inject Keplerian signals with periods between 100 and 500 days and amplitudes
between 0.6 and 2.4 m s$^{-1}$. We use GP regression to fit the resulting RVs
and determine the statistical significance of recovered periods and amplitudes.
We then generate synthetic RVs with the same covariance properties as the solar
data to determine a lower bound on the observational baseline necessary to
detect low-mass planets in Venus-like orbits around a Sun-like star. Our
simulations show that discovering such planets using current-generation
spectrographs using GP regression will require more than 12 years of densely
sampled RV observations. Furthermore, even with a perfect model of stellar
variability, discovering a true exo-Venus with current instruments would take
over 15 years. Therefore, next-generation spectrographs and better models of
stellar variability are required for detection of such planets.

Radial velocity (RV) searches for Earth-mass exoplanets in the habitable zone
around Sun-like stars are limited by the effects of stellar variability on the
host star. In particular, suppression of convective blueshift and brightness
inhomogeneities due to photospheric faculae/plage and starspots are the
dominant contribution to the variability of such stellar RVs. Gaussian process
(GP) regression is a powerful tool for modeling these quasi-periodic
variations. We investigate the limits of this technique using 800 days of RVs
from the solar telescope on the HARPS-N spectrograph. These data provide a
well-sampled time series of stellar RV variations. Into this data set, we
inject Keplerian signals with periods between 100 and 500 days and amplitudes
between 0.6 and 2.4 m s$^{-1}$. We use GP regression to fit the resulting RVs
and determine the statistical significance of recovered periods and amplitudes.
We then generate synthetic RVs with the same covariance properties as the solar
data to determine a lower bound on the observational baseline necessary to
detect low-mass planets in Venus-like orbits around a Sun-like star. Our
simulations show that discovering such planets using current-generation
spectrographs using GP regression will require more than 12 years of densely
sampled RV observations. Furthermore, even with a perfect model of stellar
variability, discovering a true exo-Venus with current instruments would take
over 15 years. Therefore, next-generation spectrographs and better models of
stellar variability are required for detection of such planets.

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