Stellar signal components seen in HARPS and HARPS-N solar radial velocities

Abstract

Context. Radial velocity (RV) measurements induced by the presence of planets around late-type stars are contaminated by stellar signals that are of the order of a few meters per second in amplitude, even for the quietest stars. Those signals are induced by acoustic oscillations, convective granulation patterns, active regions co-rotating with the stellar surface, and magnetic activity cycles. Aims. This study investigates the properties of all coherent stellar signals seen on the Sun on timescales up to its sidereal rotational period. By combining HARPS and HARPS-N solar data spanning several years, we are able to clearly resolve signals on timescales from minutes to several months. Methods. We use a Markov Chain Monte Carlo (MCMC) mixture model to determine the quality of the solar data based on the expected airmass-magnitude extinction law. We then fit the velocity power spectrum of the cleaned and heliocentric RVs with all known variability sources, to recreate the RV contribution of each component. Results. After rejecting variations caused by poor weather conditions, we are able to improve the average intra-day root mean square (RMS) value by a factor of ~1.8. On sub-rotational timescales, we are able to fully recreate the observed RMS of the RV variations. In order to also include rotational components and their strong alias peaks introduced by nightly sampling gaps, the alias powers are accounted for by being redistributed to the central frequencies of the rotational harmonics. Conclusions. In order to enable a better understanding and mitigation of stellar activity sources, their respective impact on the total RV must be well-measured and characterized. We are able to recreate RV components up to rotational timescales, which can be further used to analyse the impact of each individual source of stellar signals on the detectability of exoplanets.

Accepted for publication in A&A

References in corpus (18)

• The generalised Lomb-Scargle periodogram. A new formalism for the floating-mean and Keplerian periodograms
• Radial velocity planets de-aliased. A new, short period for Super-Earth 55 Cnc e
• SOAP 2.0: A tool to estimate the photometric and radial velocity variations induced by stellar spots and plages
• Three years of Sun-as-a-star radial-velocity observations on the approach to solar minimum
• Three Years of HARPS-N High-Resolution Spectroscopy and Precise Radial Velocity Data for the Sun
• Radial-Velocity Fitting Challenge. II. First results of the analysis of the data set
• Separating planetary reflex Doppler shifts from stellar variability in the wavelength domain
• Filtering solar-like oscillations for exoplanet detection in radial velocity observations
• HARPS-N Solar Radial-Velocity Variations Are Dominated By Large, Bright Magnetic Regions
• Radial Velocity Fitting Challenge. I. Simulating the data set including realistic stellar radial-velocity signals
• Stellar Surface Magneto-Convection as a Source of Astrophysical Noise III. Sun-as-a-star Simulations and Optimal Noise Diagnostics
• Measuring precise radial velocities on individual spectral lines. III. Dependence of stellar activity signal on line formation temperature
• Variations of the solar granulation motions with height using the GOLF/SoHO experiment
• Temporal evolution and correlations of optical activity indicators measured in Sun-as-a-star observations
• Detection Limits of Low-mass, Long-period Exoplanets Using Gaussian Processes Applied to HARPS-N Solar RVs
• Activity time series of old stars from late F to early K. I. Simulating radial velocity, astrometry, photometry, and chromospheric emission
• Estimating Magnetic Filling Factors From Simultaneous Spectroscopy and Photometry: Disentangling Spots, Plage, and Network
• Leveraging space-based data from the nearest Solar-type star to better understand stellar activity signatures in radial velocity data

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