Revisiting the multi-planetary system of the nearby star HD 20794: Confirmation of a low-mass planet in the habitable zone of a nearby G-dwarf

Abstract

Close-by Earth analogs and super-Earths are of primary importance because they will be preferential targets for the next generation of direct imaging instruments. Bright and close-by G-to-M type stars are preferential targets in radial velocity surveys to find Earth analogs. We present an analysis of the RV data of the star HD 20794, a target whose planetary system has been extensively debated in the literature. The broad time span of the observations makes it possible to find planets with signal semi-amplitudes below 1 m/s in the habitable zone. We monitored the system with ESPRESSO. We joined ESPRESSO data with the HARPS data, including archival data and new measurements from a recent program. We applied the post-processing pipeline YARARA to HARPS data to correct systematics, improve the quality of RV measurements, and mitigate the impact of stellar activity. Results. We confirm the presence of three planets, with periods of 18.3142 +/- 0.0022 d, 89.68 +/- 0.10 d, and 647.6 +/- 2.6 d, along with masses of 2.15 +/- 0.17 MEarth, 2.98 +/- 0.29 MEarth, and 5.82 +/- 0.57 MEarth respectively. For the outer planet, we find an eccentricity of 0.45 +/- 0.10, whereas the inner planets are compatible with circular orbits. The latter is likely to be a rocky planet in the habitable zone of HD 20794. From the analysis of activity indicators, we find evidence of a magnetic cycle with a period around 3000 d, along with evidence pointing to a rotation period around 39 d. We have determined the presence of a system of three planets orbiting the solar-type star HD 20794. This star is bright (V=4.34 mag) and close (d = 6.04 pc), and HD 20794 d resides in the stellar habitable zone, making this system a high-priority target for future atmospheric characterization with direct imaging facilities.

References in corpus (33)

• The NumPy array: a structure for efficient numerical computation
• The generalised Lomb-Scargle periodogram. A new formalism for the floating-mean and Keplerian periodograms
• The K2 Mission: Characterization and Early results
• Habitable Zones Around Main-Sequence Stars: Dependence on Planetary Mass
• Spectroscopic parameters for 451 stars in the HARPS GTO planet search program. Stellar [Fe/H] and the frequency of exo-Neptunes
• ESPRESSO@VLT -- On-sky performance and first results
• Planets and Stellar Activity: Hide and Seek in the CoRoT-7 system
• The Hipparcos-Gaia Catalog of Accelerations: Gaia EDR3 Edition
• SOAP 2.0: A tool to estimate the photometric and radial velocity variations induced by stellar spots and plages
• Stellar and substellar companions from Gaia EDR3 -- Proper motion anomaly and resolved common proper motion pairs
• Revisited Mass-Radius relations for exoplanets below 120 Earth masses
• ARES v2 - new features and improved performance
• Magnetic Cycles and Rotation Periods of Late Type Stars from photometric time series
• Search for exoplanets with the radial-velocity technique: quantitative diagnostics of stellar activity
• Large Interferometer For Exoplanets (LIFE): I. Improved exoplanet detection yield estimates for a large mid-infrared space-interferometer mission
• Atmospheric characterization of Proxima b by coupling the Sphere high-contrast imager to the Espresso spectrograph
• A candidate short-period sub-Earth orbiting Proxima Centauri
• Revisiting Proxima with ESPRESSO
• Cold Jupiters and improved masses in 38 Kepler and K2 small planet systems from 3661 HARPS-N radial velocities. No excess of cold Jupiters in small planet systems
• Warm terrestrial planet with half the mass of Venus transiting a nearby star
• Filtering solar-like oscillations for exoplanet detection in radial velocity observations
• YARARA: Significant improvement of RV precision through post-processing of spectral time-series
• The Na I D resonance lines in main sequence late-type stars
• The Impact of Stellar Oscillations on Doppler Velocity Planet Searches
• Two temperate Earth-mass planets orbiting the nearby star GJ1002
• Efficient modeling of correlated noise. III. Scalable methods for jointly modeling several observables' time series with Gaussian processes
• The Extremely Large Telescope
• YARARA V2: Reaching sub m/s precision over a decade using PCA on line-by-line RVs
• Stellar activity correction using PCA decomposition of shells
• Improving exoplanet detection capabilities with the false inclusion probability. Comparison with other detection criteria in the context of radial velocities
• Evidence for at least three planet candidates orbiting HD20794
• A quarter century of spectroscopic monitoring of the nearby M dwarf Gl 514. A super-Earth on an eccentric orbit moving in and out of the habitable zone
• An Integrative Analysis of the Rich Planetary System of the Nearby Star e Eridani: Ideal Targets For Exoplanet Imaging and Biosignature Searches

Cited by in corpus (5)

• Luminaries in the Sky: The TESS Legacy Sample of Bright Stars. I. Asteroseismic detections in naked-eye main-sequence and sub-giant solar-like oscillators
• Rethinking Habitability using Biogenic Precursors: Formaldehyde in Millimeter Molecular Clouds of the Inner Galaxy
• Closing the Evidence Gap: reddemcee, a Fast Adaptive Parallel Tempering Sampler
• SPORES-HWO. II. Companion Mass Limits and Updated Planet Properties for 120 Future Exoplanet Imaging Targets from 35 yr of Precise Doppler Monitoring
• A Theoretical Study of the Structure and Elemental Abundances of HD 20794