The HARPS search for southern extra-solar planets - XXXI. The M-dwarf sample

By X. Bonfils, X. Delfosse, S. Udry, T. Forveille, M. Mayor, C. Perrier, F. Bouchy, M. Gillon, C. Lovis, F. Pepe and 4 more. 2011

545 citations recorded by the source corpus.

Searching for planets around stars with different masses helps us to assess the outcome of planetary formation for different initial conditions. The low-mass M dwarfs are also the most frequent stars in our Galaxy and potentially therefore, the most frequent planet hosts. Aims. We present observations of 102 southern nearby M dwarfs, using a fraction of our guaranteed time on the ESO/HARPS spectrograph. We observed for 460 h and gathered 1965 precise (~1-3 m/s) radial velocities (RVs), spanning the period from Feb. 11, 2003 to Apr. 1, 2009. Methods. For each star observed, we derive a time series and its precision as well as its variability. We apply systematic searches for long-term trends, periodic signals, and Keplerian orbits (from one to four planets). We analyze the subset of stars with detected signals and apply several diagnostics to discriminate whether the observed Doppler shifts are caused by either stellar surface inhomogeneities or the radial pull of orbiting planets. To prepare for the statistical view of our survey, we also compute the limits on possible unseen signals, and derive a first estimate of the frequency of planets orbiting M dwarfs. Results. We recover the planetary signals of 9 planets announced by our group (Gl 176 b, Gl 581 b, c, d & e, Gl 674 b, Gl 433 b, Gl 667C b, and Gl 667C c). We present radial velocities confirming that GJ 849 hosts a Jupiter-mass planet, plus a long-term radial-velocity variation. We also present RVs that precise the planetary mass and period of Gl 832b. We detect long-term RV changes for Gl 367, Gl 680, and Gl 880, which are indicative of yet unknown long-period companions. We identify candidate signals in the radial-velocity time series of 11 other M dwarfs. Spectral diagnostics and/or photometric observations demonstrate however that these signals are most probably caused by stellar surface inhomogeneities. Finally, we find that our survey is sensitive to a few Earth-mass planets for periods up to several hundred days. We derive a first estimate of the occurrence of M-dwarf planets as a function of their minimum mass and orbital period. In particular, we find that giant planets (msini = 100 − 1000 M⊕) have a low frequency (e.g. f ≲ 1% for P = 1 − 10 d and f = 0.02+0.03-0.01 for P = 10 − 100 d), whereas super-Earths (msini = 1 − 10 M⊕) are likely very abundant (f = 0.36+0.25-0.10 for P = 1 − 10 d and f = 0.52+0.50-0.16 for P = 10 − 100 d). We also obtained η⊕ = 0.41+0.54-0.13, which is the frequency of habitable planets orbiting M dwarfs (1 ≤ msini ≤ 10 M⊕). For the first time, η⊕ is a direct measure and not a number extrapolated from the statistics of more massive and/or shorter-period planets.

Subfields: Astronomy and Astrophysics, Instrumentation

View Paper: https://www.semanticscholar.org/paper/025532f9d19c8c0e00570567a34cf730420a0a3a

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In Astronomy and Astrophysics

1. B. Bowler
2. Jon Fortney
3. D. Charbonneau
4. M. Perryman
5. Michael C. Liu
6. M. Marley
7. N. Madhusudhan
8. E. Gaidos

In Instrumentation

1. Jon Fortney
2. B. Bowler
3. D. Charbonneau
4. E. Gaidos
5. A. Mann
6. J. Johnson
7. Timothy Morton
8. Michael C. Liu

Citations in the corpus

• The Habitability of Planets Orbiting M-dwarf Stars (2016, background): “Such a star would present a 5 m s−1 peak-to-peak reflex motion over 7 years at the median inclination, challenging but detectable for radial velocity surveys like the California Planet Survey (CPS) and for HARPS (Clanton & Gaudi, 2014b; Johnson et al., 2010a; Bonfils et al., 2013).”
• TERRESTRIAL PLANET OCCURRENCE RATES FOR THE KEPLER GK DWARF SAMPLE (2015, unknown): “…Field, CA 94035, USA 2005; Naef et al. 2005; Gould et al. 2006; Sahu et al. 2006; Cumming et al. 2008; Bowler et al. 2010; Howard et al. 2010; Bayliss & Sackett 2011; Mayor et al. 2011; van Saders & Gaudi 2011; Wright et al. 2012; Bonfils et al. 2013; Meibom et al. 2013; Clanton & Gaudi 2014).”
• State of the Field: Extreme Precision Radial Velocities (2016, unknown): “Several exoplanet programs are carried out with HARPS, including a search of metal-rich and metalpoor stars (Santos et al. 2014), an M dwarf exoplanet search (Bonfils et al. 2013), and a search for super-Earth and Neptune mass planets around FGK stars (Pepe et al. 2011).”
• A STEEPER THAN LINEAR DISK MASS–STELLAR MASS SCALING RELATION (2016, background): “…positive correlation between stellar mass and the occurrence rate of Jovian planets within a few au (e.g., Johnson et al. 2010; Howard et al. 2012; Bonfils et al. 2013), although no correlation is present for the population of hot Jupiters within a 10-day period (Obermeier et al. 2016); and (ii)…”
• The Occurrence and Architecture of Exoplanetary Systems (2014, background): “One secure result is that they have fewer giant planets with P <∼ 1 yr than FGK dwarfs (Butler et al. 2004, Endl et al. 2006, Johnson et al. 2007, Bonfils et al. 2013).”
• ALMA SURVEY OF LUPUS PROTOPLANETARY DISKS. I. DUST AND GAS MASSES (2016, background): “…and M∗ in Lupus supports the suggestion by Andrews et al. (2013) that such a relation fundamentally explains the correlation between giant planet frequency and host star mass identified in the exoplanet population (Endl et al. 2006; Johnson et al. 2007; Bonfils et al. 2013; Bowler et al. 2010).”
• How to Characterize Habitable Worlds and Signs of Life (2017, unknown): “…solar twin 0.34 ± 0.14 0.5 ≤ r ≤ 2.0 Traub 2011 Host stars: F, G, K HZ: empirical, nominal, narrow (Kopparapu et al. 2014) 0.41+0.54−0.13 Mass range: 1 ≤ m∗sin(i) ≤ 10 M⊕ Bonfils et al. 2013 Host stars: RV M dwarfs HZ: Selsis et al. 2007 0.46 (95% confidence interval: 0.31–0.64) 0.8 ≤ r ≤ 2.0…”
• Predictions of the WFIRST Microlensing Survey. I. Bound Planet Detection Rates (2018, background): “…et al. 2016; Clanton & Gaudi 2016; Suzuki et al. 2016), and near it from transits (e.g., Burke et al. 2015), radial velocity (e.g., Cumming et al. 2008; Johnson et al. 2010; Bonfils et al. 2013; Montet et al. 2014) and direct imaging (Nielsen & Close 2010; Chauvin et al. 2015; Bowler et al. 2015).”
• PASTIS: Bayesian extrasolar planet validation. I. General framework, models, and performance (2014, background): “…about the target being studied is combined with the global prior knowledge on planet occurrence rate and statistics for different types of host star (e.g. Howard et al. 2010b, 2012; Mayor et al. 2011; Bonfils et al. 2013; Fressin et al. 2013), and stellar multiple system (Raghavan et al. 2010).”
• ASTROMETRIC EXOPLANET DETECTION WITH GAIA (2014, background): “…of host stars for more detailed consideration, given their large numbers at relatively small distances from the Sun, their low stellar mass resulting in large astrometric displacements for a given planet mass, and their topical interest as habitable zone host stars (e.g. Bonfils et al. 2013).”
• The Gemini Planet Imager Exoplanet Survey: Giant Planet and Brown Dwarf Demographics from 10 to 100 au (2019, background): “While Keplerʼs transiting planets greatly outnumber RV-detected planets, the RV method does not suffer as much bias toward longer periods, especially with precision RV surveys operating for multiple decades (e.g., Bonfils et al. 2013; Fischer et al. 2014; Astudillo-Defru et al. 2017).”