Stellar magnetic activity produces time-varying distortions in the
photospheric line profiles of solar-type stars. The changing shape of the
profile produces systematic errors in high-precision radial-velocity
measurements, which limit efforts to discover and measure the masses of
low-mass exoplanets with orbital periods of more than a few tens of days. We
present a new data-driven method for separating Doppler shifts of dynamical
origin from apparent velocity variations arising from variability-induced
changes in the stellar spectrum. It uses the invariance to translation in the
velocity domain of the autocorrelation function of the spectrum (and of its
cross-correlation function). By projecting the measured velocity time series
onto the principal components of the autocorrelation function, we isolate the
velocity perturbations caused by solar magnetic activity. Dynamical shifts are
preserved when we subtract the projected perturbations from the original
velocity measurements. We demonstrate its effectiveness using a 5-year time
sequence of 880 daily-averaged cross-correlation functions of the solar
spectrum from the HARPS-N instrument and solar-telescope feed on the 3.58-m
Telescopio Nazionale Galileo, reduced with a new version of the HARPS-N
data-reduction pipeline. We inject synthetic low-mass planet signals with
amplitude $K=40$ cm s$^-1$ into the solar observations at a wide range of
orbital periods. We find that our method isolates these signals effectively
from solar activity signals. Their semi-amplitudes are recovered with a
precision of $4.4$ cm~s$^-1$, opening the door to Doppler detection and
characterization of terrestrial-mass planets around well-observed, bright
main-sequence stars across a wide range of orbital periods.
Description
Separating planetary reflex Doppler shifts from stellar variability in the wavelength domain
%0 Generic
%1 cameron2020separating
%A Cameron, A. Collier
%A Ford, E. B.
%A Shahaf, S.
%A Aigrain, S.
%A Dumusque, X.
%A Haywood, R. D.
%A Mortier, A.
%A Phillips, D. F.
%A Buchhave, L.
%A Cecconi, M.
%A Cegla, H.
%A Cosentino, R.
%A Cretignier, M.
%A Ghedina, A.
%A Gonzalez, M.
%A Latham, D. W.
%A Lodi, M.
%A Lopez-Morales, M.
%A Micela, G.
%A Molinari, E.
%A Pepe, F.
%A Piotto, G.
%A Poretti, E.
%A Queloz, D.
%A Juan, J. San
%A Segransan, D.
%A Sozzetti, A.
%A Szentgyorgyi, A.
%A Thompson, S.
%A Udry, S.
%A Watson, C.
%D 2020
%K astrophysics
%T Separating planetary reflex Doppler shifts from stellar variability in
the wavelength domain
%U http://arxiv.org/abs/2011.00018
%X Stellar magnetic activity produces time-varying distortions in the
photospheric line profiles of solar-type stars. The changing shape of the
profile produces systematic errors in high-precision radial-velocity
measurements, which limit efforts to discover and measure the masses of
low-mass exoplanets with orbital periods of more than a few tens of days. We
present a new data-driven method for separating Doppler shifts of dynamical
origin from apparent velocity variations arising from variability-induced
changes in the stellar spectrum. It uses the invariance to translation in the
velocity domain of the autocorrelation function of the spectrum (and of its
cross-correlation function). By projecting the measured velocity time series
onto the principal components of the autocorrelation function, we isolate the
velocity perturbations caused by solar magnetic activity. Dynamical shifts are
preserved when we subtract the projected perturbations from the original
velocity measurements. We demonstrate its effectiveness using a 5-year time
sequence of 880 daily-averaged cross-correlation functions of the solar
spectrum from the HARPS-N instrument and solar-telescope feed on the 3.58-m
Telescopio Nazionale Galileo, reduced with a new version of the HARPS-N
data-reduction pipeline. We inject synthetic low-mass planet signals with
amplitude $K=40$ cm s$^-1$ into the solar observations at a wide range of
orbital periods. We find that our method isolates these signals effectively
from solar activity signals. Their semi-amplitudes are recovered with a
precision of $4.4$ cm~s$^-1$, opening the door to Doppler detection and
characterization of terrestrial-mass planets around well-observed, bright
main-sequence stars across a wide range of orbital periods.
@misc{cameron2020separating,
abstract = {Stellar magnetic activity produces time-varying distortions in the
photospheric line profiles of solar-type stars. The changing shape of the
profile produces systematic errors in high-precision radial-velocity
measurements, which limit efforts to discover and measure the masses of
low-mass exoplanets with orbital periods of more than a few tens of days. We
present a new data-driven method for separating Doppler shifts of dynamical
origin from apparent velocity variations arising from variability-induced
changes in the stellar spectrum. It uses the invariance to translation in the
velocity domain of the autocorrelation function of the spectrum (and of its
cross-correlation function). By projecting the measured velocity time series
onto the principal components of the autocorrelation function, we isolate the
velocity perturbations caused by solar magnetic activity. Dynamical shifts are
preserved when we subtract the projected perturbations from the original
velocity measurements. We demonstrate its effectiveness using a 5-year time
sequence of 880 daily-averaged cross-correlation functions of the solar
spectrum from the HARPS-N instrument and solar-telescope feed on the 3.58-m
Telescopio Nazionale Galileo, reduced with a new version of the HARPS-N
data-reduction pipeline. We inject synthetic low-mass planet signals with
amplitude $K=40$ cm s$^{-1}$ into the solar observations at a wide range of
orbital periods. We find that our method isolates these signals effectively
from solar activity signals. Their semi-amplitudes are recovered with a
precision of $\sim 4.4$ cm~s$^{-1}$, opening the door to Doppler detection and
characterization of terrestrial-mass planets around well-observed, bright
main-sequence stars across a wide range of orbital periods.},
added-at = {2020-11-03T22:16:13.000+0100},
author = {Cameron, A. Collier and Ford, E. B. and Shahaf, S. and Aigrain, S. and Dumusque, X. and Haywood, R. D. and Mortier, A. and Phillips, D. F. and Buchhave, L. and Cecconi, M. and Cegla, H. and Cosentino, R. and Cretignier, M. and Ghedina, A. and Gonzalez, M. and Latham, D. W. and Lodi, M. and Lopez-Morales, M. and Micela, G. and Molinari, E. and Pepe, F. and Piotto, G. and Poretti, E. and Queloz, D. and Juan, J. San and Segransan, D. and Sozzetti, A. and Szentgyorgyi, A. and Thompson, S. and Udry, S. and Watson, C.},
biburl = {https://www.bibsonomy.org/bibtex/20e817a8250b82b75d05a3004cd2bc292/zechmeister},
description = {Separating planetary reflex Doppler shifts from stellar variability in the wavelength domain},
interhash = {2406cf9a0b2e72157fb044afa9c6fa1e},
intrahash = {0e817a8250b82b75d05a3004cd2bc292},
keywords = {astrophysics},
note = {cite arxiv:2011.00018Comment: 17 pages, 12 figures, submitted to MNRAS},
timestamp = {2020-11-03T23:40:11.000+0100},
title = {Separating planetary reflex Doppler shifts from stellar variability in
the wavelength domain},
url = {http://arxiv.org/abs/2011.00018},
year = 2020
}