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.

8 pages, 4 figures, accepted for publication in Astronomy & Astrophysics

References in corpus (8)

• 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 Limits from the McDonald Observatory Planet Search Program
• A decreased probability of habitable planet formation around low-mass stars
• 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 (10)

• A terrestrial planet candidate in a temperate orbit around Proxima Centauri
• 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
• 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
• Proxima Centauri as a Benchmark for Stellar Activity Indicators in the Near Infrared
• Proxima Centauri b is not a transiting exoplanet
• 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