The Astralux Large M-Dwarf Multiplicity Survey

Janson, Markus; Hormuth, F.; Bergfors, C.; Brandner, W.; Hippler, S.; Daemgen, S.; Kudryavtseva, N.; Schmalzl, Eva; Schnupp, C.; Henning, Thomas

doi:10.1088/0004-637x/754/1/44

Cited by 245 publications

(400 citation statements)

References 108 publications

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“…This continuity across the mass-limit between stars and BDs was apparently supported by recent investigations of the late M-dwarf binary population in the Galactic field. In a lucky-imaging survey, the AstraLux survey for earlier (Janson et al 2012) and later M-dwarfs (the two studies overlap somewhat in mass) showed separation distributions significantly narrower than that for solar-type stars, confirming results from a previous lucky-imaging survey (Bergfors et al 2010). For the late M-dwarfs the separation distribution lies remarkably close to the one for BDs in the Galactic field, suggesting a common origin.…”

Section: Width Of the Separation Distributions Of Galactic Field Binasupporting

confidence: 70%

“…The binary-fraction and width of the observed log-normal separation distributions in the Galactic field decline continuously with decreasing mass of the primary component (Duquennoy & Mayor 1991;Fischer & Marcy 1992;Delfosse et al 2004;Bergfors et al 2010;Raghavan et al 2010;Janson et al 2012;Jódar et al 2013;Tokovinin 2014;Duchêne & Kraus 2013;Reipurth et al 2014;Ward-Duong et al 2015;Cortés-Contreras et al 2017). This continuity across the mass-limit between stars and BDs was apparently supported by recent investigations of the late M-dwarf binary population in the Galactic field.…”

Section: Width Of the Separation Distributions Of Galactic Field Binamentioning

confidence: 99%

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Using binary statistics in Taurus-Auriga to distinguish between brown dwarf formation processes

Marks¹,

Martín

Béjar

et al. 2017

A&A

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Context. Whether brown dwarfs (BDs) form just as stars directly from the gravitational collapse of a molecular cloud core ("star-like") or whether BDs and some very low-mass stars (VLMSs) constitute a separate population which form alongside stars comparable to the population of planets, e.g. through circumstellar disk ("peripheral") fragmentation, is one of the key questions of the star-formation problem. Aims. For young stars in Taurus-Auriga the binary fraction has been shown to be large with little dependence on primary mass above ≈ 0.2M⊙, while for BDs it is < 10%. Here we investigate a case in which BDs in Taurus formed dominantly, but not exclusively, through peripheral fragmentation, which naturally results in low binary fractions. The decline of the binary frequency in the transition region between star-like formation and peripheral formation is modelled. Methods. A dynamical population synthesis model is employed in which stellar binary formation is universal with a large binary fraction close to unity. Peripheral objects form separately in circumstellar disks with a distinctive initial mass function (IMF), own orbital parameter distributions for binaries and a low binary fraction according to observations and expectations from smoothed particle hydrodynamics (SPH) and grid-based computations. A small amount of dynamical processing of the stellar component is accounted for as appropriate for the low-density Taurus-Auriga embedded clusters. Results. The binary fraction declines strongly in the transition region between star-like and peripheral formation, exhibiting characteristic features. The location of these features and the steepness of this trend depend on the masslimits for star-like and peripheral formation. Such a trend might be unique to low density regions like Taurus which host dynamically largely unprocessed binary populations in which the binary fraction is large for stars down to M-dwarfs and low for BDs. Conclusions. The existence of a strong decline in the binary fraction -primary mass diagram will become verifiable in future surveys on BD and VLMS binarity in the Taurus-Auriga star forming region. It is a test of the (non-)continuity of star formation along the mass-scale, the separateness of the stellar and BD populations and the dominant formation channel for BDs and BD binaries in regions of low stellar density hosting dynamically unprocessed populations.

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Section: Width Of the Separation Distributions Of Galactic Field Binasupporting

confidence: 70%

Section: Width Of the Separation Distributions Of Galactic Field Binamentioning

confidence: 99%

Using binary statistics in Taurus-Auriga to distinguish between brown dwarf formation processes

Marks¹,

Martín

Béjar

et al. 2017

A&A

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“…(a) Some other publications and meta-archives that we have searched for potential CARMENES targets are Kirkpatrick et al (1991), Gizis (1997), Gizis & Reid (1997), Gizis et al (2000b), Henry et al (2002Henry et al ( , 2006, Mochnacki et al (2002), Gray et al (2003), Bochanski et al (2005), Crifo et al (2005), Lodieu et al (2005), Scholz et al (2005), Phan-Bao & Bessell (2006), Reylé et al (2006), Riaz et al (2006), Caballero (2007Caballero ( , 2009Caballero ( , 2012, Gatewood & Coban (2009), Shkolnik et al (2009, 2012, Bergfors et al (2010), Johnson et al (2010), Boyd et al (2011), Irwin et al (2011), West et al (2011, Avenhaus et al (2012), Deacon et al (2012), Janson et al (2012, 2014), Frith et al (2013, Jódar et al (2013), Malo et al (2013), Aberasturi et al (2014), Dieterich et al (2014), Riedel et al (2014), Yi et al (2014), , and the DwarfArchive at http://dwarfarchive.org. (b) PMSU: Reid et al (1995Reid et al ( , 2002; Hawley et al (1996); Gizis et al (2002).…”

Section: Carmenes Samplementioning

confidence: 99%

CARMENES input catalogue of M dwarfs

Alonso-Floriano¹,

Morales²,

Caballero³

et al. 2015

A&A

195

178

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Context. CARMENES is a stabilised, high-resolution, double-channel spectrograph at the 3.5 m Calar Alto telescope. It is optimally designed for radial-velocity surveys of M dwarfs with potentially habitable Earth-mass planets. Aims. We prepare a list of the brightest, single M dwarfs in each spectral subtype observable from the northern hemisphere, from which we will select the best planet-hunting targets for CARMENES. Methods. In this first paper on the preparation of our input catalogue, we compiled a large amount of public data and collected lowresolution optical spectroscopy with CAFOS at the 2.2 m Calar Alto telescope for 753 stars. We derived accurate spectral types using a dense grid of standard stars, a double least-squares minimisation technique, and 31 spectral indices previously defined by other authors. Additionally, we quantified surface gravity, metallicity, and chromospheric activity for all the stars in our sample. Results. We calculated spectral types for all 753 stars, of which 305 are new and 448 are revised. We measured pseudo-equivalent widths of Hα for all the stars in our sample, concluded that chromospheric activity does not affect spectral typing from our indices, and tabulated 49 stars that had been reported to be young stars in open clusters, moving groups, and stellar associations. Of the 753 stars, two are new subdwarf candidates, three are T Tauri stars, 25 are giants, 44 are K dwarfs, and 679 are M dwarfs. Many of the 261 investigated dwarfs in the range M4.0-8.0 V are among the brightest stars known in their spectral subtype. Conclusions. This collection of low-resolution spectroscopic data serves as a candidate target list for the CARMENES survey and can be highly valuable for other radial-velocity surveys of M dwarfs and for studies of cool dwarfs in the solar neighbourhood.

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“…The distribution of q values for a sample of binaries is the companion mass-ratio distribution (CMRD). Several surveys in the past decades focused on the detection of stellar binaries with the purpose of characterizing the occurrence of companions and their mass distribution both in the field (e.g., Raghavan et al 2010;Janson et al 2012) and in star-forming regions (e.g., Patience et al 2002). Reggiani & Meyer (2013), in an update of Reggiani & Meyer (2011), have shown that in the field the CMRD is consistent with being universal, independent of primary mass and separation in the range covered by the observations, and can be fit by a single power-law slope dN/dq ∝ q β , with β = 0.25 ± 0.29.…”

Section: Introductionmentioning

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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The Astralux Large M-Dwarf Multiplicity Survey

Cited by 245 publications

References 108 publications

Using binary statistics in Taurus-Auriga to distinguish between brown dwarf formation processes

Using binary statistics in Taurus-Auriga to distinguish between brown dwarf formation processes

CARMENES input catalogue of M dwarfs

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

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