Toward detection of terrestrial planets in the habitable zone of our closest neighbor: Proxima Centauri

Abstract

The precision of radial velocity (RV) measurements to detect indirectly planetary companions of nearby stars has improved to enable the discovery of extrasolar planets in the Neptune and Super-Earth mass range. Discoveries of Earth-like planets by means of ground-based RV programs will help to determine the parameter Eta_Earth, the frequency of potentially habitable planets around other stars. In search of low-mass planetary companions we monitored Proxima Centauri (M5V) as part of our M dwarf program. In the absence of a significant detection, we use these data to demonstrate the general capability of the RV method in finding terrestrial planets. For late M dwarfs the classic liquid surface water habitable zone (HZ) is located close to the star, in which circumstances the RV method is most effective. We want to demonstrate that late M dwarfs are ideal targets for the search of terrestrial planets with the RV technique. We obtained differential RV measurements of Proxima Cen over a time span of 7 years with the UVES spectrograph at the ESO VLT. We determine upper limits to the masses of companions in circular orbits by means of numerical simulations. The RV data of Proxima Cen have a total rms scatter of 3.1 m/s and a period search does not reveal any significant signals. As a result of our companion limit calculations, we find that we successfully recover all test signals with RV amplitudes corresponding to planets with m sin i > 2 - 3 M_Earth residing inside the HZ of Proxima Cen with a statistical significance of >99%. Over the same period range, we can recover 50% of the test planets with masses of m sin i > 1.5 - 2.5 M_Earth. Based on our simulations, we exclude the presence of any planet in a circular orbit with m sin i > 1 M_Neptune at separations of a < 1 AU.

arXiv comment8 pages, 4 figures, accepted for publication in Astronomy & Astrophysics

References in corpus (18)

• Discovery of a Cool Planet of 5.5 Earth Masses Through Gravitational Microlensing
• A ~ 7.5 Earth-Mass Planet Orbiting the Nearby Star, GJ 876
• An extrasolar planetary system with three Neptune-mass planets
• Interferometric Astrometry of Proxima Centauri and Barnard's Star Using Hubble Space Telescope Fine Guidance Sensor 3: Detection Limits for sub-Stellar Companions
• The HARPS search for southern extra-solar planets XI. Super-Earths (5 & 8 M_Earth) in a 3-planet system
• Detailed Models of super-Earths: How well can we infer bulk properties?
• Detection of transits of the nearby hot Neptune GJ 436 b
• Detection Limits from the McDonald Observatory Planet Search Program
• A decreased probability of habitable planet formation around low-mass stars
• The low-level radial velocity variability in Barnard's star (=GJ 699). Secular acceleration, indications for convective redshift, and planet mass limits
• Meeting the Cool Neighbors VIII: A preliminary 20-parsec census from the NLTT catalogue
• Flares from small to large: X-ray spectroscopy of Proxima Centauri with XMM-Newton
• Planets Formed in Habitable Zones of M Dwarf Stars Probably are Deficient in Volatiles
• Photometry of Proxima Centauri and Barnard's Star Using HST Fine Guidance Sensor 3: A Search for Periodic Variations
• Could we identify hot Ocean-Planets with CoRoT, Kepler and Doppler velocimetry?
• Formation and Detectability of Terrestrial Planets Around Alpha Centauri B
• Are Proxima and Alpha Centauri Gravitationally Bound?
• A possible activity cycle in Proxima Centauri

Cited by in corpus (22)

• A terrestrial planet candidate in a temperate orbit around Proxima Centauri
• The HARPS search for southern extra-solar planets XXXI. The M-dwarf sample
• Stellar and substellar companions of nearby stars from Gaia DR2 - Binarity from proper motion anomaly
• The CRIRES Search for Planets Around the Lowest-Mass Stars. I. High-Precision Near-Infrared Radial Velocities with an Ammonia Gas Cell
• The M dwarf planet search programme at the ESO VLT + UVES. A search for terrestrial planets in the habitable zone of M dwarfs
• Optical, UV, and X-Ray Evidence for a 7-Year Stellar Cycle in Proxima Centauri
• MOST Observations of our Nearest Neighbor: Flares on Proxima Centauri
• Characterizing Habitable Exo-Moons
• Precision radial velocities of 15 M5 - M9 dwarfs
• Flaring activity of Proxima Centauri from TESS observations: quasi-periodic oscillations during flare decay and inferences on the habitability of Proxima b
• On the Method to Infer an Atmosphere on a Tidally-Locked Super Earth Exoplanet and Upper limits to GJ 876d
• X-Ray, FUV, and UV Observations of alpha Centauri B: Determination of Long-term Magnetic Activity Cycle and Rotation Period
• The Solar Neighborhood. XXXIV. A Search for Planets Orbiting Nearby M Dwarfs using Astrometry
• No Conclusive Evidence for Transits of Proxima b in MOST photometry
• ROPS: A New Search for Habitable Earths in the Southern Sky
• Proxima Centauri as a Benchmark for Stellar Activity Indicators in the Near Infrared
• Proxima Centauri b is not a transiting exoplanet
• On High-Contrast Characterization of Nearby, Short-Period Exoplanets with Giant Segmented-Mirror Telescopes
• Microlensing Events by Proxima Centauri in 2014 and 2016: Opportunities for Mass Determination and Possible Planet Detection
• The Mt John University Observatory Search For Earth-mass Planets In The Habitable Zone Of Alpha Centauri
• Upper limits for Mass and Radius of objects around Proxima Cen from SPHERE/VLT
• Searching for Faint Comoving Companions to the $\alpha$ Centauri system in the VVV Survey Infrared Images