The<i>q</i>= 1 peak in the mass-ratios for Hipparcos visual binaries

Söderhjelm, S.

doi:10.1051/0004-6361:20066024

Cited by 19 publications

(26 citation statements)

References 26 publications

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“…However, despite the fact that the fraction of twins decreases with increasing separation, the mass ratio distributions of both the short‐ and long‐period binaries appear to have a peak at M 2 / M 1 = 1 (e.g. Tokovinin 2000b; Halbwachs et al 2003; Söderhjelm 2007). These observed relations are in qualitative agreement with the decreasing median mass ratio with increasing separation discussed above.…”

Section: Resultsmentioning

confidence: 99%

Stellar, brown dwarf and multiple star properties from hydrodynamical simulations of star cluster formation

Bate

2009

Monthly Notices of the Royal Astronomical Society

414

603

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We report the statistical properties of stars, brown dwarfs and multiple systems obtained from the largest hydrodynamical simulation of star cluster formation to date that resolves masses down to the opacity limit for fragmentation (a few Jupiter masses). The simulation is essentially identical to that of Bate, Bonnell & Bromm except that the initial molecular cloud is larger and more massive. It produces more than 1250 stars and brown dwarfs, providing unprecedented statistical information that can be compared with observational surveys. The calculation uses sink particles to model the stars and brown dwarfs. Part of the calculation is rerun with smaller sink particle accretion radii and gravitational softening to investigate the effect of these approximations on the results. We find that hydrodynamical/sink particle simulations can reproduce many of the observed stellar properties very well. Multiplicity as a function of the primary mass, the frequency of very low mass (VLM) binaries, general trends for the separation and mass ratio distributions of binaries and the relative orbital orientations of triples systems are all in reasonable agreement with observations. We also examine the radial variations of binarity, velocity dispersion and mass function in the resulting stellar cluster and the distributions of disc truncation radii due to dynamical interactions. For VLM binaries, because their separations are typically close, we find that their frequency is sensitive to the sink particle accretion radii and gravitational softening used in the calculations. Using small accretion radii and gravitational softening results in a frequency of VLM binaries similar to that expected from observational surveys (≈20 per cent). We also find that VLM binaries evolve from wide, unequal‐mass systems towards close equal‐mass systems as they form. The two main deficiencies of the calculations are that they overproduce brown dwarfs relative to stars and that there are too few unequal‐mass binaries with K‐ and G‐dwarf primaries. The former of these is likely due to the absence of radiative feedback and/or magnetic fields.

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Section: Resultsmentioning

confidence: 99%

Stellar, brown dwarf and multiple star properties from hydrodynamical simulations of star cluster formation

Bate

2009

Monthly Notices of the Royal Astronomical Society

414

603

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“…The peak at q = 1 which historically has always been a matter of debate (as it may be produced e.g. by a photometric selection bias of twins) seems to be present at small periods, and it may even decrease with mass [37]. Concerning this point, but also more generally, the simulated models should absolutely not be taken at face value as there is a considerable statistical uncertainty in the published results.…”

Section: Mass-ratiomentioning

confidence: 99%

Simulating multiple stars in preparation for Gaia

Arenou¹,

Docobo²,

Tamazian³

et al. 2011

AIP Conference Proceedings

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Abstract. The scientific preparation of the Gaia mission encompasses both the data reduction algorithms and the generation of simulated data which have to be as realistic as possible. In this respect, binaries and multiple stars are a mandatory component in the simulation of the Milky Way as they impact on the performance tests of the on-ground data processing. The ingredients for the simulation of multiple stars are described and the predictions are compared to observed data or outcomes from stellar multiplicity studies.

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“…This bias can be dramatic if the initial-mass-ratio distribution is flat, i.e. dN ∝ dq, or even worse if it favours the formation of binaries with equal masses (often referred to as the "twin peak", see e.g., Söderhjelm 2007;Lucy 2006;Simon & Obbie 2009). In this case, the intrinsic population of pre-CVs would be dominated by systems with relatively massive secondary stars.…”

Section: Mass Growth In Cvs?mentioning

confidence: 99%

Post common envelope binaries from SDSS

Zorotovic

Schreiber

Gänsicke

2011

A&A

300

336

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Context. We have known for a long time that many of the measured white dwarf (WD) masses in cataclysmic variables (CVs) significantly exceed the mean mass of single WDs. This was thought to be related to observational biases, but recent high-precision measurements of WD masses in a great number of CVs are challenging this interpretation. A crucial question in this context is whether the high WD masses seen among CVs are already imprinted in the mass distribution of their progenitors, i.e. among detached postcommon-envelope binaries (PCEBs) that consist of a WD and a main-sequence star. Aims. We review the measured WD masses of CVs, determine the WD-mass distribution of an extensive sample of PCEBs that are representative for the progenitors of the current CV population (pre-CVs) and compare both distributions. Methods. We calculate the CV formation time of the PCEBs in our sample by determining the post common-envelope (CE) and the main-sequence evolution of the binary systems and define a pre-CV to be a PCEB that evolves into a semi-detached configuration with stable mass transfer within less than the age of the Galaxy. Possible observational biases affecting the WD-mass distribution for the pre-CV and the CV samples are discussed. Results. The mean WD mass among CVs is M wd = 0.83 ± 0.23 M , much larger than that found for pre-CVs, M wd = 0.67 ± 0.21 M . Selection effects cannot explain the high WD masses observed in CVs. We also note that compared to the predictions of binary-population models, the observed fraction of He-core WDs is small both among CVs (≤10%) and pre-CVs (≤17 ± 8%). Conclusions. We suggest two possible explanations for the high WD masses among CVs, both of which imply substantial revisions to the standard model of CV evolution: either most CVs have formed above the orbital-period gap (which requires a high WD mass to initiate stable mass transfer or a previous phase of thermal-timescale mass transfer), or the mass of the WDs in CVs grows through accretion (which strongly disagrees with the predictions of classical nova models). Both options may imply that CVs contribute to the single-degenerate progenitors of type Ia supernovae. The number of He-core WDs in CVs (≤10%) is roughly consistent with the number of He-core WDs in pre-CVs (≤17 ± 8%). This indicates a low value of the CE efficiency.

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Theq= 1 peak in the mass-ratios for Hipparcos visual binaries

Cited by 19 publications

References 26 publications

Stellar, brown dwarf and multiple star properties from hydrodynamical simulations of star cluster formation

Stellar, brown dwarf and multiple star properties from hydrodynamical simulations of star cluster formation

Simulating multiple stars in preparation for Gaia

Post common envelope binaries from SDSS

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