The initial period function of late-type binary stars and its variation

Kroupa, Pavel; Petr-Gotzens, M. G.

doi:10.1051/0004-6361/201015989

Cited by 37 publications

(56 citation statements)

References 49 publications

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“…This suggests that there are no significant variations in binary-star formation depending on the ambient condition required, but that variations in the binary populations are mainly caused by stellar and dynamical evolution. This agrees with previous work and such an assumption would be similar to the universality hypothesis of the stellar IMF (Kroupa 2011;Kroupa & Petr-Gotzens 2011).…”

Section: Discussionsupporting

confidence: 93%

“…1). This distribution agrees 1 with pre-main sequence and proto-stellar multiplicity data (Kroupa & Petr-Gotzens 2011;. The period distribution is assumed to be the universal outcome of binary formation (Kroupa 2011).…”

Section: Introductionsupporting

confidence: 84%

“…There exists a formal initial binary distribution function that is consistent with the available multiplicity data of pre-main sequence and Class I protostellar populations (Kroupa & Petr-Gotzens 2011) and that helps us to understand the binary distributions in the eight objects investigated here simultaneously, assuming dynamics only. This suggests that there are no significant variations in binary-star formation depending on the ambient condition required, but that variations in the binary populations are mainly caused by stellar and dynamical evolution.…”

Section: Discussionsupporting

confidence: 67%

“…The USco-B subgroup in the Scorpius-Centaurus association is not analysed here, as the binary fraction increases with increasing period (Brandner & Koehler 1998). This is incompatible with the dynamical evolution of its binary population and may be a contamination effect (Kroupa & Petr-Gotzens 2011). We note, however, that caution that binary disruption is a highly stochastic process that influences the appearance of observed binary distributions.…”

Section: All Dynamically Evolved Initial Binary Populations Are Likelmentioning

confidence: 97%

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Inverse dynamical population synthesis

Marks

Kroupa

2012

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Binary populations in young star clusters show multiplicity fractions both lower and up to twice as high as those observed in the Galactic field. We follow the evolution of a population of binary stars in dense and loose star clusters starting with an invariant initial binary population and a formal multiplicity fraction of unity, and demonstrate that these models can explain the observed binary properties in Taurus, ρ Ophiuchus, Chamaeleon, Orion, IC 348, Upper Scorpius A, Praesepe, and the Pleiades. The model needs to consider solely different birth densities for these regions. The evolved theoretical orbital-parameter distributions are highly probable parent distributions for the observed ones. We constrain the birth conditions (stellar mass, M ecl , and half-mass radius, r h ) for the derived progenitors of the star clusters and the overall present-day binary fractions allowed by the present model. The results compare very well with properties of molecular cloud clumps on the verge of star formation. Combining these with previously and independently obtained constraints on the birth densities of globular clusters, we identify a weak stellar mass -half-mass radius correlation for cluster-forming cloud clumps, r h /pc ∝ (M ecl /M ) 0.13 ± 0.04 . The ability of the model to reproduce the binary properties in all the investigated young objects, covering present-day densities from 1−10 stars pc −3 (Taurus) to 2 × 10 4 stars pc −3 (Orion), suggests that environment-dependent dynamical evolution plays an important role in shaping the present-day properties of binary populations in star clusters, and that the initial binary properties may not vary dramatically between different environments.

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Section: Discussionsupporting

confidence: 93%

Section: Introductionsupporting

confidence: 84%

Section: Discussionsupporting

confidence: 67%

Section: All Dynamically Evolved Initial Binary Populations Are Likelmentioning

confidence: 97%

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Inverse dynamical population synthesis

Marks

Kroupa

2012

A&A

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253

302

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“…The conclusion that the distribution for M-dwarfs in the lucky imaging results is indeed that narrow originates from the observation that the distribution starts to decline strongly far from the resolution limit of the respective surveys. This apparent continuity might however be the result of the density-dependent dynamical alteration of an environment-independent birth binary population for late-type stars in young star forming regions (Kroupa 1995(Kroupa , 2011Kroupa & Petr-Gotzens 2011;Marks & Kroupa 2012;Marks et al 2014) and the subsequent addition of many such populations originating from different environments that comprise the Galactic field (Parker et al 2009;Goodwin 2010;Marks et al 2015). In particular, the mutual proximity of BD and late-M separation distributions in Janson et al (2014) might be following from separate BD and stellar populations which underwent dynamical processing, as Marks et al (2015) have demonstrated.…”

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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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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Monte Carlo modeling of globular star clusters: many primordial binaries and IMBH formation

Giersz

Leigh

Marks³

et al. 2014

Proc. IAU

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We will discuss the evolution of star clusters with an large initial binary fraction, up to 95%. The initial binary population is chosen to follow the invariant orbital-parameter distributions suggested by Kroupa (1995). The Monte Carlo MOCCA simulations of star cluster evolution are compared to the observations of Milone et al. (2012) for photometric binaries. It is demonstrated that the observed dependence on cluster mass of both the binary fraction and the ratio of the binary fractions inside and outside of the half mass radius are well recovered by the MOCCA simulations. This is due to a rapid decrease in the initial binary fraction due to the strong density-dependent destruction of wide binaries described by Marks, Kroupa & Oh (2011). We also discuss a new scenario for the formation of intermediate mass black holes in dense star clusters. In this scenario, intermediate mass black holes are formed as a result of dynamical interactions of hard binaries containing a stellar mass black hole, with other stars and binaries. We will discuss the necessary conditions to initiate the process of intermediate mass black hole formation and the dependence of its mass accretion rate on the global cluster properties.

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The initial period function of late-type binary stars and its variation

Cited by 37 publications

References 49 publications

Inverse dynamical population synthesis

Inverse dynamical population synthesis

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

Monte Carlo modeling of globular star clusters: many primordial binaries and IMBH formation

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