Star-Disc Interactions and Binary Formation

1992 ◽  
Vol 135 ◽  
pp. 176-184
Author(s):  
Cathie Clarke
Keyword(s):  
Mass Exchange ◽  
Main Sequence ◽  
Orbital Evolution ◽  
Body System ◽  
Tidal Effects ◽  
Orbital Parameters ◽  
Binary Formation

By the time a binary arrives on the main sequence, its dynamics have essentially become those of a simple two-body system, so that its orbital parameters are constants of the motion thereafter. This statement of course needs to be modified under several circumstances, such as where tidal effects, mass exchange or interactions with field stars come into play. For the majority of binaries, however, orbital evolution is all but over by the main sequence. Therefore, in order to explain the distribution of binary orbital parameters one has to look to earlier times (prior to 107 years) when the more complicated dynamics can drive the orbital evolution that establishes these parameters.

scholarly journals The eccentric behaviour of windy binary stars

2019 ◽  
Vol 629 ◽  
pp. A103 ◽  
Author(s):  
M. I. Saladino ◽  
O. R. Pols
Keyword(s):  
Mass Transfer ◽  
Binary Stars ◽  
Numerical Models ◽  
Orbital Evolution ◽  
Small Sample ◽  
Asymptotic Giant Branch ◽  
Tidal Effects ◽  
Orbital Parameters ◽  
Orbital Periods ◽  
The Impact

Carbon-enhanced metal-poor stars, CH stars, barium stars, and extrinsic S stars, among other classes of chemically peculiar stars, are thought to be the products of the interaction of low- and intermediate-mass binaries, which occurred when the most evolved star was in the asymptotic giant branch (AGB) phase. Binary evolution models predict that because of the large sizes of AGB stars, if the initial orbital periods of such systems are shorter than a few thousand days, their orbits should have circularised due to tidal effects. However, observations of the progeny of AGB binary stars show that many of these objects have substantial eccentricities, up to e ≈ 0.9. In this work we explore the impact of wind mass transfer on the orbital parameters of AGB binary stars by performing numerical simulations in which the AGB wind is modelled using a hydrodynamical code and the dynamics of the stars is evolved using an N-body code. We find that in most models the effect of wind mass transfer contributes to the circularisation of the orbit, but on longer timescales than tidal circularisation if e ≲ 0.4. For relatively low initial wind velocities and pseudo-synchronisation of the donor star, we find a structure resembling wind Roche-lobe overflow as the stars approach periastron. In this case, the interaction between the gas and the star is stronger than when the initial wind velocity is high and the orbit shrinks while the eccentricity decreases. In one of our models wind interaction is found to pump the eccentricity of the orbit on a similar timescale as tidal circularisation. However, since the orbit of this model is shrinking tidal effects will become stronger during the evolution of the system. Although our study is based on a small sample of models, it offers some insight into the orbital evolution of eccentric binary stars interacting via winds. A larger grid of numerical models for different binary parameters is needed to test if a regime exists where hydrodynamical eccentricity pumping can effectively counteract tidal circularisation, and if this can explain the puzzling eccentricities of the descendants of AGB binaries.

scholarly journals The Short-Period Binary Frequency Among Low-Mass Pre-Main Sequence Stars

1992 ◽  
Vol 135 ◽  
pp. 30-40
Author(s):  
Robert D. Mathieu
Keyword(s):  
Star Formation ◽  
Formation Process ◽  
Main Sequence ◽  
Early Period ◽  
Dynamical Evolution ◽  
Orbital Evolution ◽  
Semi Major Axis ◽  
Single Star ◽  
Binary Formation ◽  
Short Period

The pre-main sequence (PMS) binary frequency is a fundamental datum in the study of binary formation. It reflects on numerous basic issues, such as:• The formation process. Binary stars are the primary branch of the star-formation process, and thus their frequency is an essential challenge to star-formation theories. (Indeed, the infrequency of single-star formation is likely as significant as the binary frequency.)• The epoch of binary formation. Assessing whether the binary population exists in total by the pre-main sequence phase sets an upper limit on the binary formation timescale.• Early period evolution. The frequency distribution as a function of period of PMS binaries, when compared to the distribution at the zero-age main sequence, can shed light on early orbital evolution.• The interaction of binaries with disks. The formation and consequent dynamical evolution of a binary with semi-major axis less than typical disk radii must substantially modify disk structures and accretion flows. Thus the binary frequency might differ between PMS stars with and without associated disks.

scholarly journals Barium and related stars, and their white-dwarf companions

2019 ◽  
Vol 626 ◽  
pp. A128 ◽  
Author(s):  
A. Escorza ◽  
D. Karinkuzhi ◽  
A. Jorissen ◽  
L. Siess ◽  
H. Van Winckel ◽  
...  
Keyword(s):  
Radial Velocity ◽  
White Dwarf ◽  
Main Sequence ◽  
Mass Function ◽  
Orbital Evolution ◽  
Asymptotic Giant Branch ◽  
Second Phase ◽  
Evolutionary Models ◽  
Orbital Inclination ◽  
Orbital Parameters

Barium (Ba) dwarfs and CH subgiants are the less evolved analogues of Ba and CH giants. They are F- to G-type main-sequence stars polluted with heavy elements by their binary companions when the companion was on the asymptotic giant branch (AGB). This companion is now a white dwarf that in most cases cannot be directly detected. We present a large systematic study of 60 objects classified as Ba dwarfs or CH subgiants. Combining radial-velocity measurements from HERMES and SALT high-resolution spectra with radial-velocity data from CORAVEL and CORALIE, we determine the orbital parameters of 27 systems. We also derive their masses by comparing their location in the Hertzsprung–Russell diagram with evolutionary models. We confirm that Ba dwarfs and CH subgiants are not at different evolutionary stages, and that they have similar metallicities, despite their different names. Additionally, Ba giants appear significantly more massive than their main-sequence analogues. This is likely due to observational biases against the detection of hotter main-sequence post-mass-transfer objects. Combining our spectroscopic orbits with the HIPPARCOS astrometric data, we derive the orbital inclination and the mass of the WD companion for four systems. Since this cannot be done for all systems in our sample yet (but should be possible with upcoming Gaia data releases), we also analyse the mass-function distribution of our binaries. We can model this distribution with very narrow mass distributions for the two components and random orbital orientations on the sky. Finally, based on BINSTAR evolutionary models, we suggest that the orbital evolution of low-mass Ba systems can be affected by a second phase of interactions along the red giant branch of the Ba star, which impact the eccentricities and periods of the giants.

scholarly journals Evolution of subhalo orbits in a smoothly growing host halo potential

2021 ◽  
Vol 503 (1) ◽  
pp. 1233-1247
Author(s):  
Go Ogiya ◽  
James E Taylor ◽  
Michael J Hudson
Keyword(s):  
Spatial Distribution ◽  
Essential Role ◽  
Orbital Evolution ◽  
Observational Constraints ◽  
Time Varying ◽  
Cosmological Simulations ◽  
Orbital Parameters ◽  
The Impact ◽  
Spherical Potential ◽  
Radial Action

ABSTRACT The orbital parameters of dark matter (DM) subhaloes play an essential role in determining their mass-loss rates and overall spatial distribution within a host halo. Haloes in cosmological simulations grow by a combination of relatively smooth accretion and more violent mergers, and both processes will modify subhalo orbits. To isolate the impact of the smooth growth of the host halo from other relevant mechanisms, we study subhalo orbital evolution using numerical calculations in which subhaloes are modelled as massless particles orbiting in a time-varying spherical potential. We find that the radial action of the subhalo orbit decreases over the first few orbits, indicating that the response to the growth of the host halo is not adiabatic during this phase. The subhalo orbits can shrink by a factor of ∼1.5 in this phase. Subsequently, the radial action is well conserved and orbital contraction slows down. We propose a model accurately describing the orbital evolution. Given these results, we consider the spatial distribution of the population of subhaloes identified in high-resolution cosmological simulations. We find that it is consistent with this population having been accreted at $z \lesssim 3$, indicating that any subhaloes accreted earlier are unresolved in the simulations. We also discuss tidal stripping as a formation scenario for NGC 1052-DF2, an ultra diffuse galaxy significantly lacking DM, and find that its expected DM mass could be consistent with observational constraints if its progenitor was accreted early enough, $z \gtrsim 1.5$, although it should still be a relatively rare object.

5 Ceti: A Long-Period Binary Evolving Through Mass Exchange

1989 ◽  
Vol 106 ◽  
pp. 234-234
Author(s):  
Joel A. Eaton
Keyword(s):  
Angular Momentum ◽  
Orbital Angular Momentum ◽  
Mass Exchange ◽  
Main Sequence ◽  
Roche Lobe ◽  
Common Envelope ◽  
Long Period ◽  
Loss Of Mass

Binaries with very wide spearations are thought to evolve to small separations through a catastrophic form of mass exchange/loss known as common-envelope evolution. The theory of this process is fairly well developed, but proper tests remain elusive. Simply put, the theory argues that the rapidly shrinking Roche lobe of the mass losing giant will strip away the giant's main-sequence companion. Loss of mass from the system during the process carries away orbital angular momentum, thereby strengthening the effect.

scholarly journals Classical Novae – Before and After Outburst

1988 ◽  
Vol 108 ◽  
pp. 226-231
Author(s):  
Mario Livio
Keyword(s):  
White Dwarf ◽  
Main Sequence ◽  
Orbital Parameters ◽  
Classical Novae ◽  
Classical Nova ◽  
Before And After ◽  
Low Mass ◽  
Orbital Periods ◽  
Thermonuclear Runaway ◽  
Nova Outburst

Classical nova (CN) and dwarf nova (DN) systems have the same binary components (a low-mass main sequence star and a white dwarf) and the same orbital periods. An important question that therefore arises is: are these systems really different ? (and if so, what is the fundamental difference ?) or, are these the same systems, metamorphosing from one class to the other ?The first thing to note in this respect is that the white dwarfs in DN systems are believed to accrete continuously (both at quiescence and during eruptions). At the same time, both analytic (e.g. Fujimoto 1982) and numerical calculations show, that when sufficient mass accumulates on the white dwarf, a thermonuclear runaway (TNR) is obtained and a nova outburst ensues (see e.g. reviews by Gallagher and Starrfield 1978, Truran 1982). It is thus only natural, to ask the question, is the fact that we have not seen a DN undergo a CN outburst (in about 50 years of almost complete coverage) consistent with observations of DN systems ? In an attempt to answer this question, we have calculated the probability for a nova outburst not to occur (in 50 years) in 86 DN systems (for which at least some of the orbital parameters are known).

scholarly journals Disks in the Pre-Main Sequence Binary Environment

1992 ◽  
Vol 151 ◽  
pp. 21-30
Author(s):  
Robert D. Mathieu
Keyword(s):  
Binary Stars ◽  
Main Sequence ◽  
Orbital Evolution ◽  
Disk Structure

The interaction of disks and young binary stars is discussed, with particular emphasis on disk structure, the existence of accretion at the stellar surfaces and binary orbital evolution.

scholarly journals The Quadrantid Stream, Chaos or Not?

1992 ◽  
Vol 152 ◽  
pp. 329-332
Author(s):  
Zidian Wu ◽  
Iwan P Williams
Keyword(s):  
Orbital Evolution ◽  
Orbital Elements ◽  
Orbital Parameters

The Quadrantid stream covers a region of space which contains many strong resonances and commensurabilities with the Jovian orbit. We have numerically integrated the orbital evolution of over one hundred actual meteoroids backwards to BC 5000. The evolution is quit complex, but most of the meteoroids are quite well behaved with rapid but smooth changes in the orbital elements. One meteoroid however shows sharp sudden changes in its orbital parameters and these changes are generally indicative of the presence of chaos.

scholarly journals Evolution of Compact Binary Populations in Globular Clusters: a Boltzmann Study

2007 ◽  
Vol 3 (S246) ◽  
pp. 246-250
Author(s):  
Sambaran Banerjee ◽  
Pranab Ghosh
Keyword(s):  
Globular Clusters ◽  
Orbital Evolution ◽  
Encounter Rate ◽  
X Ray ◽  
Compact Binary ◽  
Binary Formation ◽  
Cluster Properties ◽  
Star Binary ◽  
Dissociation Mechanisms ◽  
X Ray Binaries

AbstractWe explore a Boltzmann scheme for studying the evolution of compact binary populations in globular clusters. We include processes of compact binary formation by tidal capture and exchange encounters, binary destruction by exchange and dissociation mechanisms and binary hardening by encounters, gravitational radiation and magnetic braking, as also the orbital evolution during mass transfer, following Roche lobe contact. From the evolution of compact-binary population, we investigate the dependence of the model number of X-ray binaries NXB on two essential cluster properties, namely, the star-star and star-binary encounter-rate parameters Γ and γ (Verbunt parameters). We find that the values of NXB and their expected scaling with the Verbunt parameters are in good agreement with results from recent X-ray observations of Galactic globular clusters.

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