Mapping the Shores of the Brown Dwarf Desert. Ii. Multiple Star Formation in Taurus-Auriga

Kraus, Adam L.; Ireland, Michael; Martinache, Frantz; Hillenbrand, Lynne A.

doi:10.1088/0004-637x/731/1/8

Cited by 324 publications

(449 citation statements)

References 140 publications

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“…Within their 90% completeness limit they find a raw multiplicity fraction of 26.3 +6.6 −4.9 % in the separation range 10 − 1500 AU. After completeness correction for the full separation range they find 62 ± 14% of all Taurus companions in the range 0.7 − 1.4M ⊙ to be multiple, comparable to Kraus et al (2011) results. This corresponds to a ≈ 1σ detection for a 1.4× larger binary fraction of solar-type stars in Taurus compared to the Galactic field (Raghavan et al 2010).…”

Section: The Stellar and Substellar Population Insupporting

confidence: 75%

“…The latter consistency might be due to the inclusion of a 10× older sub-population identified by Daemgen et al (2015) which might have undergone more dynamical modification than the 1 − 2 Myr old population which likely resembles more closely the one at birth. But also Kraus et al (2011) found that lower mass Taurus members (0.25 − 0.7M ⊙ ) show a paucity of binary companions with separation 200 AU, while solar-type stars and above do not. But this may as well be due to the lack of sensitivity to lower mass companions.…”

Section: The Separation Distributionmentioning

confidence: 95%

“…The binary fraction of 42.5 ± 4.9 percent is larger by a factor of 1.93 ± 0.26 than that of solar-type main sequence stars over the accessible separation range. In a high resolution imaging study Kraus et al (2011) find that 2/3−3/4 of all Taurus stars are multiple. In the most recent near-infrared imaging search for stellar and substellar companions Daemgen et al (2015) target 64 Taurus members with masses between 0.2 and 3M ⊙ , identifying secondaries down to 2M Jup .…”

Section: The Stellar and Substellar Population Inmentioning

confidence: 98%

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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: The Stellar and Substellar Population Insupporting

confidence: 75%

Section: The Separation Distributionmentioning

confidence: 95%

Section: The Stellar and Substellar Population Inmentioning

confidence: 98%

See 1 more Smart Citation

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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“…′′ 95-17. ′′ 0 in the star-forming regions of Taurus (distance 140 pc; Torres et al 2007, age 1-2 Myr; Kraus & Hillenbrand 2009a) and Ophiuchus (distance 140 pc; Loinard et al 2008, age 1 Myr; Allers et al 2006;Luhman & Rieke 1999;Prato et al 2003) were extracted from the literature (Kraus et al 2011;Kraus & Hillenbrand 2009b;Duchêne et al 2007;Ratzka et al 2005;Haisch et al 2004;Haisch et al 2002;White & Ghez 2001;Köhler & Leinert 1998;Reipurth & Zinnecker 1993;Leinert et al 1993) (see also Table 1 for references on each object).…”

Section: Sample and Archival Datamentioning

confidence: 99%

“…The binary separation is small (2. ′′ 07; Kraus et al 2011), and the spectral types of its primary and secondary are estimated as M2 and M6.5, respectively (Kraus et al 2007). …”

Section: A13 Jh 223 Amentioning

confidence: 99%

Study of infrared excess from circumstellar disks in binaries with Spitzer/IRAC

Itoh

Fukagawa

Shibai

et al. 2015

Publications of the Astronomical Society of Japan

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The presence of excess emission at 3.6-8.0 µm was investigated in a sample of 27 binary systems located in two nearby star-forming regions, Taurus and Ophiuchus, by using Spitzer/Infrared Array Camera (IRAC) archival data. Angular (Projected) separations for the binaries are greater than 2 ′′ (∼280 AU), which allowed us to perform spatially resolved photometry of individual primary and secondary sources. The measured occurrence of infrared excess suggests that binarity plays a role in the evolution of circumstellar disks, even at such wide binary separations. Most of the binaries have excess emission from both the circumprimary and circumsecondary disks, or show photospheric levels for both components at all four wavelengths of IRAC. On the other hand, four systems (17 +11 −8 %, designated by "mixed" systems) exhibit excess emission from a single binary component. This ratio is significantly smaller than that predicted by the random pairing of single stars, suggesting that circumprimary and circumsecondary disks are synchronously dispersed. In addition, the excess frequencies (EFs) of primary and secondary sources with a projected distance of a p ≃ 280-450 AU are 100 +0 −17 % and 91 +8 −18 %, respectively, and significantly higher than that of single stars (70 ± 5%). We made a simple model describing the EF distribution as a function of the disk outer radius, R out . Comparisons with observations using the Kolmogorov-Smirnov test show that the observational data are consistent with the model when the EF ≃ 1 region is found at R out ∼ 30-100 AU. This disk radius is smaller than that typically estimated for single stars. The high EF of circumstellar disks with these radii may indicate a prolonged lifetime of dust in binary systems possibly because smaller disks counteract mass loss by photoevaporation.

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Wide σ Orionis binaries resolved by UKIDSS

Caballero

Novalbos²,

Tobal³

et al. 2017

Astron Nachr

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In spite of its importance for the study of star formation at all mass domains, the nearby young Orionis cluster still lacks a comprehensive survey for multiplicity. We try to fill that observational gap by looking for wide resolved binaries with angular separations between 0.4 and 4.0 arcsec. We search for companions to 331 cataloged cluster stellar members and candidates in public K-band UKIDSS images outside the innermost 1 arcmin, which is affected by the glare of the bright, eponymous Ori multiple system, and investigate their cluster membership with color-magnitude diagrams and previous knowledge of youth features. Of the 18 identified pairs, 10 have very low individual probabilities of chance alignment (< 1%) and are considered here as physical pairs. Four of them are new, while the other six had been discovered previously but never investigated homogeneously and in detail. Projected physical separations and magnitude differences of the 10 probably bound pairs range from 180 to 1220 au, and from 0.0 to 3.4 mag in K, respectively. Besides, we identify two cluster stars with elongated point spread functions. We determine the minimum frequency of wide multiplicity in the interval of projected physical separations s = 160-1600 au in Orionis at 3.0 +1.2 −1.1 %. We discover a new Lindroos system, find that massive and X-ray stars tend to be in pairs or trios, conclude that multiplicity truncates circumstellar disks and enhances X-ray emission, and ascribe a reported lithium depletion in a young star to unresolved binarity in spectra of moderate resolution. When accounting for all known multiples, including spectroscopic binaries, the minimum frequency of multiplicity increases to about 10%, which implies that of the order of 80-100 unknown multiple systems still await discovery in Orionis.

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Mapping the Shores of the Brown Dwarf Desert. Ii. Multiple Star Formation in Taurus-Auriga

Cited by 324 publications

References 140 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

Study of infrared excess from circumstellar disks in binaries with Spitzer/IRAC

Wide σ Orionis binaries resolved by UKIDSS

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