The HARPS search for Earth-like planets in the habitable zone - I. Very low-mass planets around HD 20794, HD 85512, and HD 192310

By F. Pepe, C. Lovis, Damien Ségransan, W. Benz, F. Bouchy, Xavier Dumusque, M. Mayor, D. Queloz, Nuno C. Santos, S. Udry. 2011

263 citations recorded by the source corpus.

Context. In 2009 we started an intense radial-velocity monitoring of a few nearby, slowly-rotating and quiet solar-type stars within the dedicated HARPS-Upgrade GTO program. Aims. The goal of this campaign is to gather very-precise radial-velocity data with high cadence and continuity to detect tiny signatures of very-low-mass stars that are potentially present in the habitable zone of their parent stars. Methods. Ten stars were selected among the most stable stars of the original HARPS high-precision program that are uniformly spread in hour angle, such that three to four of them are observable at any time of the year. For each star we recorded 50 data points spread over the observing season. The data points consist of three nightly observations with a total integration time of 10 min each and are separated by two hours. This is an observational strategy adopted to minimize stellar pulsation and granulation noise. Results. We present the first results of this ambitious program. The radial-velocity data and the orbital parameters of five new and one confirmed low-mass planets around the stars HD 20794, HD 85512, and HD 192310 are reported and discussed, among which is a system of three super-Earths and one that harbors a 3.6 M⊕-planet at the inner edge of the habitable zone. Conclusions. This result already confirms previous indications that low-mass planets seem to be very frequent around solar-type stars and that this may occur with a frequency higher than 30%.

Subfields: Astronomy and Astrophysics, Instrumentation

View Paper: https://www.semanticscholar.org/paper/4452ed6bef44259aeaead5e76c15766fe29cf26e

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In Astronomy and Astrophysics

1. D. Charbonneau
2. Timothy Morton
3. J. Johnson
4. G. Marcy
5. Andrew W. Howard
6. Jon Fortney
7. J. Winn
8. D. Fabrycky

In Instrumentation

1. D. Charbonneau
2. Timothy Morton
3. Andrew W. Howard
4. J. Johnson
5. G. Marcy
6. J. Southworth
7. B. Fulton
8. J. Winn

Citations in the corpus

• 3D climate modeling of close-in land planets: Circulation patterns, climate moist bistability and habitability (2013, background): “As shown hereafter, this could be the case for Gl 581 c (Udry et al. 2007; Mayor et al. 2009; Forveille et al. 2011) and HD 85512 b (Pepe et al. 2011), the only two confirmed planets having masses that are compatible with a terrestrial planet (M p <∼ 7−8 M⊕; although defining such a mass limit is…”
• TRANSIT TIMING OBSERVATIONS FROM KEPLER. IV. CONFIRMATION OF FOUR MULTIPLE-PLANET SYSTEMS BY SIMPLE PHYSICAL MODELS (2012, background): “…of architecture has been building on several different fronts: radial velocity detections (HD 40307: Mayor et al. 2009; GJ 876: Rivera et al. 2010; HD 20794: Pepe et al. 2011), and a dramatic 4-planet system discovered by direct imaging (HR 8799: Fabrycky & Murray-Clay 2010b; Marois et al. 2010).”
• THE MUSCLES TREASURY SURVEY. I. MOTIVATION AND OVERVIEW (2016, background): “HD 85512 b is a super-Earth mass planet (3.6 M⊕) orbiting with a semi-major axis of 0.26 AU (Pepe et al. 2011).”
• AN ANCIENT EXTRASOLAR SYSTEM WITH FIVE SUB-EARTH-SIZE PLANETS (2015, background): “Some of these planets may even be found in the habitable zones around their parent stars (Pepe et al. 2011; Quintana et al. 2014).”
• HABITABLE ZONES AROUND MAIN-SEQUENCE STARS: NEW ESTIMATES (2013, background): “We have included a ‘?’ for Gl 581 system of planets in the plot, indicating that there is an active ongoing discussion in the literature about the number of planets in this system and their exact orbital parameters (Vogt et al. 2010; Pepe et al. 2011b; Vogt et al. 2012; Baluev 2012).”
• The planet search programme at the ESO CES and HARPS - IV. The search for Jupiter analogues around solar-like stars (2012, methodology): “For τ Cet (GJ 71, HIP 8102, HR 509, HD 10700) which is known as an RV constant star (the HARPS data have an rms scatter of∼1.1 m/s HARPS data, Pepe et al. 2011, this work), we achieve with the CES+VLC a long-term precision of 8.1 m/s (Fig.”
• The GALAH survey: scientific motivation (2015, methodology): “A set of five exposures were taken with HERMES over six nights for the velocity-stable star, HD 1581, which has radial velocity variations of 1.26 m s−1 over a time span of 2566 d as confirmed by HARPS spectra (Pepe et al. 2011).”
• STABILIZING CLOUD FEEDBACK DRAMATICALLY EXPANDS THE HABITABLE ZONE OF TIDALLY LOCKED PLANETS (2013, background): “This brings already detected planets, such as HD85512b and GJ 163 c, into the HZ, and dramatically increases estimates of the frequency of habitable planets.”
• SOAP 2.0: A TOOL TO ESTIMATE THE PHOTOMETRIC AND RADIAL VELOCITY VARIATIONS INDUCED BY STELLAR SPOTS AND PLAGES (2014, background): “Optimal observational strategies can be used to mitigate the effect of oscillations and granulation phenomena when observing solar-type stars (Dumusque et al. 2011a), which enables the detection of tiny planetary signals (Dumusque et al. 2012; Pepe et al. 2011).”
• A REVISED ESTIMATE OF THE OCCURRENCE RATE OF TERRESTRIAL PLANETS IN THE HABITABLE ZONES AROUND KEPLER M-DWARFS (2013, background): “…recent exoplanet surveys have discovered terres- trial planets in the habitable zone (HZ) of their parent star (Udry et al. 2007; Vogt et al. 2010; Pepe et al. 2011a; Borucki et al. 2011; Bonfils et al. 2011; Borucki et al. 2012; Vogt et al. 2012; Tuomi et al. 2012b; Anglada-Escudé et al.…”
• HABITABLE ZONES AROUND MAIN-SEQUENCE STARS: DEPENDENCE ON PLANETARY MASS (2014, background): “Recent observational surveys have discovered several potential habitable zone (HZ) planet candidates (Udry et al. 2007; Vogt et al. 2010; Pepe et al. 2011a; Borucki et al. 2011; Bonfils et al. 2011; Borucki et al. 2012; Vogt et al. 2012; ?”
• 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).”
• The Habitability of Planets Orbiting M-dwarf Stars (2016, methodology): “While the semi-amplitude of Proxima b at 1.4 m s−1 is not especially small (Pepe et al., 2011), it eluded detection for years because of the sparse radial velocity time sampling coupled with the long stellar activity cycle (Anglada-Escudé et al., 2016).”
• SOPHIE velocimetry of Kepler transit candidates VII. A false-positive rate of 35% for Kepler close-in giant candidates (2012, methodology): “…HARPS-N radial velocity uncertainty for a 1-h exposure as a function of stellar magnitude based on our experiment with HARPS for the CoRoT follow-up (Santerne et al. 2011a) and assuming a non-rotating and non-active solar-type star and a systematic error of 50 cm s−1 at high S/N (Pepe et al. 2011).”
• High-cadence spectroscopy of M-dwarfs. I. Analysis of systematic effects in HARPS-N line profile measurements on the bright binary GJ 725A+B (2016, background): “…more Doppler variable than this limit, it is unlikely that the 0.8 - 0.9 m s−1 (reported lower noise limit in HARPS-ESO observations by Pepe et al. 2011, and of a handful of very quiet M dwarfs, e.g. GJ 699 and GJ 588, by Anglada-Escudé & Butler 2012) is an universal limit for…”
• Limits on Planetary Companions from Doppler Surveys of Nearby Stars (2016, methodology): “For example, HD 88512 b was detected with RVs whose pernight measurement uncertainties are <0.3 m s−1and the data set has an rms of 0.75m s−1after subtracting the single planet model with K=0.77 m s−1(Pepe et al. 2011).”
• Multiplicity among Solar-type Stars (2017, methodology): “With respect to the FEROS radial velocities of faint commonproper-motion sources or candidates with V< 15mag, we adopt the PopulationII star 82 Eri as the velocity standard with vr=+87.953 km s −1 (Pepe et al. 2011).”