The effect of star-disc interactions on the binary mass-ratio distribution

McDonald, J. M.; Clarke, C. J.

doi:10.1093/mnras/275.3.671

Cited by 69 publications

(46 citation statements)

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“…McDonald & Clarke (1995) included star-disk interactions in order to model the effects of gas dynamics on cluster decay and found that the selection of secondary masses in binaries is essentially randomized when including strong dissipation. This also increases the fraction of lower-mass primaries significantly.…”

Section: -mentioning

confidence: 99%

“…This two-step process does a better job of matching the observed gradual increase in binary fraction with stellar mass than the steep increase found in earlier dynamical decay studies of few-body clusters by McDonald & Clarke (1993), where cluster members were chosen randomly from an IMF without a total cluster mass spectrum constraint. Dissipation due to gas dynamic effects, as in McDonald & Clarke (1995), is not required by DSP to match the observational data.…”

Section: Introductionmentioning

confidence: 99%

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Imprints of dynamical interactions on brown dwarf pairing statistics and kinematics

Sterzik

Durisen

2003

A&A

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Abstract. We present statistically robust predictions of brown dwarf properties arising from dynamical interactions during their early evolution in small clusters. Our conclusions are based on numerical calculations of the internal cluster dynamics as well as on Monte-Carlo models. Accounting for recent observational constraints on the sub-stellar mass function and initial properties in fragmenting star forming clumps, we derive multiplicity fractions, mass ratios, separation distributions, and velocity dispersions. We compare them with observations of brown dwarfs in the field and in young clusters. Observed brown dwarf companion fractions around 15 ± 7% for very low-mass stars as reported recently by Close et al. (2003) are consistent with certain dynamical decay models. A significantly smaller mean separation distribution for brown dwarf binaries than for binaries of late-type stars can be explained by similar specific energy at the time of cluster formation for all cluster masses. Due to their higher velocity dispersions, brown-dwarfs and low-mass single stars will undergo time-dependent spatial segregation from higher-mass stars and multiple systems. This will cause mass functions and binary statistics in star forming regions to vary with the age of the region and the volume sampled.

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Section: -mentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Imprints of dynamical interactions on brown dwarf pairing statistics and kinematics

Sterzik

Durisen

2003

A&A

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“…For example, a mass-ratio distribution that is consistent with random pairings drawn from the initial mass function (IMF) would suggest that the companions formed relatively independently from the primaries (Abt et al 1990;Tout 1991;McDonald & Clarke 1995). Alternatively, correlated component masses, which are expected and generally observed for close binaries (Tokovinin 2000;Raghavan et al 2010;Sana et al 2012), indicate coevolution during the pre-MS phase via physical processes such as fragmentation, fission, competitive accretion, and/or mass transfer (MT) through Roche lobe overflow (RLOF; Bonnell & Bastien 1992;Kroupa 1995aKroupa , 1995bClarke 1996;Bate & Bonnell 1997;Kratter & Matzner 2006;Kouwenhoven et al 2009;Marks & Kroupa 2011;Bate 2012).…”

Section: Introductionmentioning

confidence: 99%

Mind Your Ps and Qs: The Interrelation between Period (P) and Mass-ratio (Q) Distributions of Binary Stars

Moe

Stefano

2017

ApJS

1,060

1,200

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We compile observations of early-type binaries identified via spectroscopy, eclipses, long-baseline interferometry, adaptive optics, common proper motion, etc. Each observational technique is sensitive to companions across a narrow parameter space of orbital periods P and mass ratios q=M comp /M 1 . After combining the samples from the various surveys and correcting for their respective selection effects, we find that the properties of companions to O-type and B-type main-sequence (MS) stars differ among three regimes. First, at short orbital periods P20days (separations a0.4 au), the binaries have small eccentricities e0.4, favor modest mass ratios á ñ » q 0.5, and exhibit a small excess of twins q>0.95. Second, the companion frequency peaks at intermediate periods log P (days)≈3.5 (a ≈ 10 au), where the binaries have mass ratios weighted toward small values q≈0.2-0.3 and follow a Maxwellian "thermal" eccentricity distribution. Finally, companions with long orbital periods log P (days)≈5.5-7.5 (a ≈ 200-5000 au) are outer tertiary components in hierarchical triples and have a mass ratio distribution across q≈0.1-1.0 that is nearly consistent with random pairings drawn from the initial mass function. We discuss these companion distributions and properties in the context of binary-star formation and evolution. We also reanalyze the binary statistics of solar-type MS primaries, taking into account that 30% ±10% of single-lined spectroscopic binaries likely contain white dwarf companions instead of low-mass stellar secondaries. The mean frequency of stellar companions with q>0.1 and log P (days)<8.0 per primary increases from 0.50±0.04 for solar-type MS primaries to 2.1±0.3 for O-type MS primaries. We fit joint probability density functions ¹ ( ) ( ) ( ) ( ) ( ) f M q P e f M f q f P f e , , , 1 1 to the corrected distributions, which can be incorporated into binary population synthesis studies.

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“…For each primary star the mass of the secondary is chosen randomly from the single star mass function and the secondary mass distribution would reflect the IMF. While tidal capture appears to be too inefficient in reproducing high binary fractions, it has been noticed that, particularly in small groups of stars, star-disk encounters may form binaries (McDonald & Clarke 1995). In any case even this disk-assisted capture, whereby a star passing through the disk of another which dissipates enough kinetic energy to form a bound system, is unlikely to be the most relevant binary formation mechanism (Boffin et al 1998).…”

Section: Introductionmentioning

confidence: 99%

Binary Formation Mechanisms: Constraints From the Companion Mass Ratio Distribution

Reggiani

Meyer

2011

ApJ

103

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We present a statistical comparison of the mass ratio distribution of companions, as observed in different multiplicity surveys, to the most recent estimate of the single-object mass function. The main goal of our analysis is to test whether or not the observed companion mass ratio distribution (CMRD) as a function of primary star mass and star formation environment is consistent with having been drawn from the field star initial mass function (IMF). We consider samples of companions for M dwarfs, solar-type stars, and intermediate-mass stars, both in the field as well as clusters or associations, and compare them with populations of binaries generated by random pairing from the assumed IMF for a fixed primary mass. With regard to the field we can reject the hypothesis that the CMRD was drawn from the IMF for different primary mass ranges: the observed CMRDs show a larger number of equal-mass systems than predicted by the IMF. This is in agreement with fragmentation theories of binary formation. For the open clusters α Persei and the Pleiades we also reject the IMF random-pairing hypothesis. Concerning young star-forming regions, currently we can rule out a connection between the CMRD and the field IMF in Taurus but not in Chamaeleon I. Larger and different samples are needed to better constrain the result as a function of the environment. We also consider other companion mass functions and we compare them with observations. Moreover the CMRD both in the field and clusters or associations appears to be independent of separation in the range covered by the observations. Combining therefore the CMRDs of M (1-2400 AU) and G (28-1590 AU) primaries in the field and intermediate-mass primary binaries in Sco OB2 (29-1612 AU) for mass ratios, q = M 2 /M 1 , from 0.2 to 1, we find that the best chi-square fit follows a power law dN/dq ∝ q β , with β = −0.50 ± 0.29, consistent with previous results. Finally, we note that the Kolmogorov-Smirnov test gives a ∼1% probability of the observed CMRD in the Pleiades and Taurus being consistent with that observed for solar-type primaries in the field over comparable primary mass range. This highlights the value of using CMRDs to understand which star formation events contribute most to the field.

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The effect of star-disc interactions on the binary mass-ratio distribution

Cited by 69 publications

References 0 publications

Imprints of dynamical interactions on brown dwarf pairing statistics and kinematics

Imprints of dynamical interactions on brown dwarf pairing statistics and kinematics

Mind Your Ps and Qs: The Interrelation between Period (P) and Mass-ratio (Q) Distributions of Binary Stars

Binary Formation Mechanisms: Constraints From the Companion Mass Ratio Distribution

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