A candidate short-period sub-Earth orbiting Proxima Centauri

Abstract

Proxima Centauri is the closest star to the Sun. This small, low-mass, mid M dwarf is known to host an Earth-mass exoplanet with an orbital period of 11.2 days within the habitable zone, as well as a long-period planet candidate with an orbital period of close to 5 years. We report on the analysis of a large set of observations taken with the ESPRESSO spectrograph at the VLT aimed at a thorough evaluation of the presence of a third low-mass planetary companion, which started emerging during a previous campaign. Radial velocities (RVs) were calculated using both a cross-correlation function (CCF) and a template matching approach. The RV analysis includes a component to model Proxima's activity using a Gaussian process (GP). We use the CCF's full width at half maximum to help constrain the GP, and we study other simultaneous observables as activity indicators in order to assess the nature of any potential RV signals. We detect a signal at 5.12 $\pm$ 0.04 days with a semi-amplitude of 39 $\pm$ 7 cm/s. The analysis of subsets of the ESPRESSO data, the activity indicators, and chromatic RVs suggest that this signal is not caused by stellar variability but instead by a planetary companion with a minimum mass of 0.26 $\pm$ 0.05 $M_{\oplus }$ (about twice the mass of Mars) orbiting at 0.029 au from the star. The orbital eccentricity is well constrained and compatible with a circular orbit.

arXiv comment17 pages, 13 figures

References in corpus (55)

• Gaia Data Release 1. Summary of the astrometric, photometric, and survey properties
• Habitable Zones Around Main-Sequence Stars: New Estimates
• A terrestrial planet candidate in a temperate orbit around Proxima Centauri
• How to Constrain Your M Dwarf: measuring effective temperature, bolometric luminosity, mass, and radius
• Stellar Diameters and Temperatures II. Main Sequence K & M Stars
• ESPRESSO@VLT -- On-sky performance and first results
• Planets and Stellar Activity: Hide and Seek in the CoRoT-7 system
• Spectrum radial velocity analyser (SERVAL). High-precision radial velocities and two alternative spectral indicators
• The HARPS-TERRA project I. Description of the algorithms, performance and new measurements on a few remarkable stars observed by HARPS
• State of the Field: Extreme Precision Radial Velocities
• Parametrizing the exoplanet eccentricity distribution with the Beta distribution
• Nightside condensation of iron in an ultra-hot giant exoplanet
• The habitability of Proxima Centauri b II. Possible climates and Observability
• CHEOPS: A Transit Photometry Mission for ESA's Small Mission Programme
• The habitability of Proxima Centauri b. I. Irradiation, rotation and volatile inventory from formation to the present
• 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
• The Habitable-Zone Planet Finder: A Stabilized Fiber-Fed NIR Spectrograph for the Hobby-Eberly Telescope
• TAPAS, a web-based service of atmospheric transmission computation for astronomy
• Determining the Mass of Kepler-78b With Nonparametric Gaussian Process Estimation
• Three years of Sun-as-a-star radial-velocity observations on the approach to solar minimum
• A candidate super-Earth planet orbiting near the snow line of Barnard's star
• AMD-stability and the classification of planetary systems
• The Space Weather of Proxima Centauri b
• The HARPS search for southern extra-solar planets XXXV. The interesting case of HD41248: stellar activity, no planets?
• Revisiting Proxima with ESPRESSO
• Optical, UV, and X-Ray Evidence for a 7-Year Stellar Cycle in Proxima Centauri
• Warm terrestrial planet with half the mass of Venus transiting a nearby star
• Detecting extrasolar planets from stellar radial velocities using Bayesian evidence
• MOST Observations of our Nearest Neighbor: Flares on Proxima Centauri
• A temperate exo-Earth around a quiet M dwarf at 3.4 parsecs
• Evidence against the young hot-Jupiter around BD +20 1790
• The CARMENES search for exoplanets around M dwarfs. Radial velocities and activity indicators from cross-correlation functions with weighted binary masks
• Planetary system LHS 1140 revisited with ESPRESSO and TESS
• Planet-induced radio emission from the coronae of M dwarfs: the case of Prox Cen and AU Mic
• Characterisation of the radial velocity signal induced by rotation in late-type dwarfs
• ACTIN: A tool to calculate stellar activity indices
• Flaring activity of Proxima Centauri from TESS observations: quasi-periodic oscillations during flare decay and inferences on the habitability of Proxima b
• kima: Exoplanet detection in radial velocities
• Catalog for the ESPRESSO blind radial velocity exoplanet survey
• AMD-stability in presence of first order Mean Motion Resonances
• The large-scale magnetic field of Proxima Centauri near activity maximum
• The SOPHIE search for northern extrasolar planets. XIV. A temperate ($T_{\mathrm{eq}}\sim 300$ K) super-earth around the nearby star Gliese 411
• Orbital inclination and mass of the exoplanet candidate Proxima c
• A multiple planet system of super-Earths orbiting the brightest red dwarf star GJ887
• The Solar Neighborhood XXXI: Discovery of an Unusual Red+White Dwarf Binary at ~25 Parsecs via Astrometry and UV Imaging
• Improving exoplanet detection capabilities with the false inclusion probability. Comparison with other detection criteria in the context of radial velocities
• Auto-correlation functions of astrophysical processes, and their relation to Gaussian processes; Application to radial velocities of different starspot configurations
• Proxima Centauri b is not a transiting exoplanet
• Beyond the exoplanet mass-radius relation
• Recovering planet radial velocity signals in the presence of starspot activity in fully convective stars
• Flare activity and photospheric analysis of Proxima Centauri
• HD22496b: the first ESPRESSO standalone planet discovery
• Searching for the near infrared counterpart of Proxima c using multi-epoch high contrast SPHERE data at VLT
• Expectations for the confirmation of Proxima c from a long-term radial velocity follow-up

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• The CARMENES search for exoplanets around M dwarfs: Stable radial-velocity variations at the rotation period of AD~Leonis -- A test case study of current limitations to treating stellar activity
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• Two super-Earths at the edge of the habitable zone of the nearby M dwarf TOI-2095
• Behind the Mask: can HARMONI@ELT detect biosignatures in the reflected light of Proxima b?
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• FIESTA II. Disentangling stellar and instrumental variability from exoplanetary Doppler shifts in Fourier domain
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• 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
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• Using Doppler Imaging to model stellar activity and search for planets around Sun-like stars
• A Case Study of Interstellar Material Delivery: α Centauri
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• The SPIRou Legacy Survey: near-infrared and optical radial velocity analysis of Gl 480 and Gl 382 using SPIRou, HARPS and CARMENES spectrographs
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• TILARA: Template-Independent Line-by-line Algorithm for Radial velocity Analysis. I. Description of the code and application on a Sun-like star
• The SPIRou Legacy Survey: Detection of a nearby world orbiting in the habitable zone of Gl725B achieved by correcting strong telluric contamination in near-infrared radial velocities with WAPITI
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• $\mathtt{KOBEsim}$: a Bayesian observing strategy algorithm for planet detection in radial velocity blind-search surveys
• Inferring planet occurrence rates from radial velocities
• Refined M-type Star Catalog from LAMOST DR10: Measurements of Radial Velocities, $T_{\text{eff}}$, log $g$, [M/H] and [$\alpha$/M]
• Assessing the Climate and Habitability of Tidally Locked Rocky Exoplanets