The Palomar/Keck Adaptive Optics Survey of Young Solar Analogs: Evidence for a Universal Companion Mass Function

Metchev, Stanimir; Hillenbrand, Lynne A.

doi:10.1088/0067-0049/181/1/62

Cited by 238 publications

(284 citation statements)

References 160 publications

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“…Overall, our binary frequencies of a few percents are in agreement with the number of wide substellar companions to young solar analogues (0.5-6.3% for separations in the 28-1590 au range; Metchev & Hillenbrand 2009), M dwarfs (0.1-2.2% for separations larger than ∼120 au ; Radigan et al 2008), the frequency of 1 ± 1% of brown dwarf companions to GKM stars in the 75-300 au range (McCarthy & Zuckerman 2004) or the lack of planetary-mass objects more massive than 5-10 M Jup around young nearby stars beyond 36-65 au (Masciadri et al 2005). Similarly, Raghavan et al (2010) derived a stellar multiplicity of 7.3% and 2.2% among solar-type stars within 25 pc for projected separations in the 1000-10 000 au and 10 000-50 000 au ranges, respectively (their Fig.…”

Section: Multiplicity Of Planet-host Starssupporting

confidence: 86%

Binary frequency of planet-host stars at wide separations

Lodieu

Pérez‐Garrido

Béjar

et al. 2014

A&A

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Aims. The aim of the project is to improve our knowledge on the multiplicity of planet-host stars at wide physical separations. Methods. We cross-matched approximately 6200 square degree area of the southern sky imaged by the Visible Infrared Survey Telescope for Astronomy (VISTA) Hemisphere Survey (VHS) with the Two Micron All Sky Survey (2MASS) to look for wide common proper motion companions to known planet-host stars. We complemented our astrometric search with photometric criteria. Results. We confirmed spectroscopically the co-moving nature of seven sources out of 16 companion candidates and discarded eight, while the remaining one stays as a candidate. Among these new wide companions to planet-host stars, we discovered a T4.5 dwarf companion at 6.3 arcmin (∼9000 au) from HIP 70849, a K7V star which hosts a 9 Jupiter mass planet with an eccentric orbit. We also report two new stellar M dwarf companions to one G and one metal-rich K star. We infer stellar and substellar binary frequencies for our complete sample of 37 targets of 5.4 ± 3.8% and 2.7 ± 2.7% (1σ confidence level), respectively, for projected physical separations larger than ∼60-160 au assuming the range of distances of planet-host stars (24-75 pc). These values are comparable to the frequencies of non planet-host stars. We find that the period-eccentricity trend holds with a lack of multiple systems with planets at large eccentricities (e > 0.2) for periods less than 40 days. However, the lack of planets more massive than 2.5 Jupiter masses and short periods (<40 days) orbiting single stars is not so obvious due to recent discoveries by ground-based transit surveys and space missions.

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Section: Multiplicity Of Planet-host Starssupporting

confidence: 86%

Binary frequency of planet-host stars at wide separations

Lodieu

Pérez‐Garrido

Béjar

et al. 2014

A&A

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“…The BD distribution is normalized to the companion frequency, f BD , measured by Raghavan et al (2010) for stellar companions. If extrapolated to the BD mass regime (q = 0.012−0.072), it gives f BD = 1 +1 −0.6 % between 28-1590 AU, which is in agreement with the BD companion fraction presented by Metchev & Hillenbrand (2009), f BD = 3.2 +3.1 −2.7 %, over the same mass and separation ranges. Moreover, several physical mechanisms or observational constraints place upper and lower limits to the maximum and minimum mass (m max BD,pl , m min BD,pl ) and separation (a max BD,pl , a min BD,pl ) for these distributions.…”

Section: Model For the Substellar Cmfsupporting

confidence: 85%

“…In this context, we consider as BDs all objects that, having formed through a stellar-like mechanism, constitute the lower mass tail of the CMRD, assuming that it can be extrapolated into the BD regime as suggested by Metchev & Hillenbrand (2009). We define as planets, instead, all companions that formed in standard planet-formation scenarios and gave rise to the RV measured CMF but extrapolated to larger separations.…”

Section: Model For the Substellar Cmfmentioning

confidence: 99%

The VLT/NaCo large program to probe the occurrence of exoplanets and brown dwarfs at wide orbits

Reggiani

Meyer

Chauvin

et al. 2016

A&A

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Context. In recent years there have been many attempts to characterize the occurrence and distribution of stellar, brown dwarf (BD), and planetary-mass companions to solar-type stars with the aim of constraining formation mechanisms. From radial velocity observations a dearth of companions with masses between 10-40 M Jupiter has been noticed at close separations, suggesting the possibility of a distinct formation mechanism for objects above and below this range. Aims. We present a model for the substellar companion mass function (CMF). This model consists of the superposition of the planet and BD companion mass distributions, assuming that we can extrapolate the radial velocity measured CMF for planets to larger separations and the stellar companion mass-ratio distribution over all separations into the BD mass regime. By using both the results of the VLT/NaCo large program (NaCo-LP) and the complementary archive datasets, which probe the occurrence of planets and BDs on wide orbits around solar-type stars, we place some constraints on the planet and BD distributions. Methods. We developed a Monte Carlo simulation tool to predict the outcome of a given survey, depending on the shape of the orbital parameter distributions (mass, semimajor axis, eccentricity, and inclination). Comparing the predictions with the results of the observations, we calculate the likelihood of different models and which models can be ruled out. Results. Current observations are consistent with the proposed model for the CMF, as long as a sufficiently small outer truncation radius ( 100 AU) is introduced for the planet separation distribution. Some regions of parameter space can be excluded by the observations. Conclusions. We conclude that the results of the direct imaging surveys searching for substellar companions around Sun-like stars are consistent with a combined substellar mass spectrum of planets and BDs. This mass distribution has a minimum between 10 and 50 M Jupiter , in agreement with radial velocity measurements. In this picture the dearth of objects in this mass range would naturally arise from the shape of the mass distribution, without the introduction of any distinct formation mechanism for BDs. This kind of model for the CMF allows us to determine the probability for a substellar companion as a function of mass to have formed in a disk or from protostellar core fragmentation, as such mechanisms overlap in this mass range.

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“…If the follow-up observation is close in time to the first epoch and the displacement of the star on the sky due to proper motion is small, it may be challenging to determine with a high probability whether an object is bound. One example is given in Metchev & Hillenbrand (2009), where an object that was originally thought to be compatible with being bound, based on the proper motion test, was determined through spectroscopy to be a background M-star. Moreover, the case of the false positive object around IM Lupi (Mawet et al 2012) teaches that, when the distance determination is complex, it is possible to miscalculate the relative certainties of a bound versus unbound interpretation.…”

Section: Introductionmentioning

confidence: 99%

Astrophysical false positives in direct imaging for exoplanets: a white dwarf close to a rejuvenated star

Zurlo

Vigan

Hagelberg

et al. 2013

A&A

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Context. As is the case for all techniques involved in the research for exoplanets, direct imaging has to take into account the probability of so-called astrophysical false positives, which are phenomena that mimic the signature of the objects we are seeking. Aims. In this work we present the case of a false positive found during a direct-imaging survey conducted with VLT/NACO. A promising exoplanet candidate was detected around the K2-type star HD 8049 in July 2010. Its contrast of ∆H = 7.05 at 1.57 arcsec allowed us to assume a 35 M Jup companion at 50 projected AU, for the nominal system age and heliocentric distance. Methods. To check whether it was gravitationally bound to the host star, as opposed to an unrelated background object, we re-observed the system one year later and concluded a high probability of a bound system. We also used radial velocity measurements of the host star, spanning a time range of ∼30 yr, to constrain the companion's mass and orbital properties, as well as to probe the host star's spectral age indicators and general spectral energy distribution. We also obtained U-band imaging with EFOSC and near-infrared spectroscopy for the companion. Results. Combining all these information we conclude that the companion of HD 8049 is a white dwarf (WD) with temperature T eff = 18 800 ± 2100 K and mass M WD = 0.56 ± 0.08 M . The significant radial velocity trend combined with the imaging data indicates that the most probable orbit has a semi-major axis of about 50 AU. The discrepancy between the age indicators speaks against a bona-fide young star. The moderately high level of chromospheric activity and fast rotation, mimicking the properties of a young star, might be induced by the exchange of mass with the progenitor of the WD. This example demonstrates some of the challenges in determining accurate age estimates and identifications of faint companions.

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The Palomar/Keck Adaptive Optics Survey of Young Solar Analogs: Evidence for a Universal Companion Mass Function

Cited by 238 publications

References 160 publications

Binary frequency of planet-host stars at wide separations

Binary frequency of planet-host stars at wide separations

The VLT/NaCo large program to probe the occurrence of exoplanets and brown dwarfs at wide orbits

Astrophysical false positives in direct imaging for exoplanets: a white dwarf close to a rejuvenated star

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