Roche lobe overflows in mass-conservative circular binary systems: Constraints on rates of mass exchange and orbital angular momentum loss

Author(s):  
T. T. Chia
1989 ◽  
Vol 106 ◽  
pp. 234-234
Author(s):  
Joel A. Eaton

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.


2019 ◽  
Vol 626 ◽  
pp. A68 ◽  
Author(s):  
M. I. Saladino ◽  
O. R. Pols ◽  
C. Abate

Wind mass transfer in binary systems with asymptotic giant branch (AGB) donor stars plays a fundamental role in the formation of a variety of objects, including barium stars and carbon-enhanced metal-poor (CEMP) stars. In an attempt to better understand the properties of these systems, we carry out a comprehensive set of smoothed-particle hydrodynamics (SPH) simulations of wind-losing AGB stars in binaries for a variety of binary mass ratios, orbital separations, initial wind velocities, and rotation rates of the donor star. The initial parameters of the simulated systems are chosen to match the expected progenitors of CEMP stars. We find that the strength of interaction between the wind and the stars depends on the ratio of wind velocity to orbital velocity (v∞/vorb) and on the binary mass ratio. Strong interaction occurs for close systems and comparable mass ratios, and gives rise to a complex morphology of the outflow and substantial angular-momentum loss, which leads to a shrinking of the orbit. As the orbital separation increases and the mass of the companion star decreases, the morphology of the outflow and the angular-momentum loss become more similar to the spherically symmetric wind case. We also explore the effects of tidal interaction and find that for orbital separations up to 7−10 AU, depending on mass ratio, spin-orbit coupling of the donor star occurs at some point during the AGB phase. If the initial wind velocity is relatively low, we find that corotation of the donor star results in a modified outflow morphology that resembles wind Roche-lobe overflow. In this case the mass-accretion efficiency and angular-momentum loss differ from those found for a non-rotating donor. Finally, we provide relations for the mass-accretion efficiency and angular-momentum loss as a function of v∞/vorb and the binary mass ratio that can be easily implemented in a population synthesis code to study populations of barium stars, CEMP stars, and other products of interaction in AGB binaries, such as cataclysmic binaries and type Ia supernovae.


1982 ◽  
Vol 69 ◽  
pp. 187-189
Author(s):  
F. Mardirossian ◽  
G. Giuricin

AbstractWe have examined the observational data of 102 Algols in order to clarify the implications on their evolutionary scenario of various assumptions concerning mass and angular momentum loss during mass transfer. We have found that case B mass exchange is strongly favoured for Algols of relatively low total mass (~ M < 7 Mʘ), while case A predominates, though not so widely as expected in Algols of higher total mass.


1992 ◽  
Vol 151 ◽  
pp. 167-173
Author(s):  
Peter P. Eggleton

Cool stars show evidence of dynamo activity which is stronger with more rapid rotation. Tidal friction in a moderately close binary can be a cause of relatively rapid rotation, so that cool components in such binaries are presumably liable to stronger stellar winds than single cool stars. As a consequence, the binary can be subject to orbital angular momentum loss. Both the mass loss and the orbital angular momentum loss can be on a timescale comparable to nuclear evolution in a red subgiant, or even faster. RS CVn stars probably give the best possibility of measuring these processes, although some observational data are difficult to reconcile with simple theories.Barium stars, and symbiotics, may both be affected by these processes. They must be the products of evolution of moderately wide binaries, as must such objects as cataclysmic variables. I attempt to define the ranges of zero-age parameters necessary to produce such varied objects. A simplistic model of the distribution of stars brighter than 6th magnitude (a ‘Theoretical Bright Star Catalogue’) suggests that for every three Ba stars with a measurable orbit, there should be one main sequence ‘Ba star’.


2006 ◽  
Vol 2 (S240) ◽  
pp. 678-681
Author(s):  
V.V. Pustynski ◽  
I. Pustylnik

AbstractIt has been shown quite recently (Morales-Rueda et al. 2003) that dB stars, extreme horizontal branch (EHB) objects in high probability all belong to binary systems. We study in detail the mass and angular momentum loss from the giant progenitors of sdB stars in an attempt to clarify why binarity must be a crucial factor in producing EHB objects. Assuming that the progenitors of EHB objects belong to binaries with initial separations of a roughly a hundred solar radii and fill in their critical Roche lobes while close to the tip of red giant branch, we have found that considerable shrinkage of the orbit can be achieved due to a combined effect of angular momentum loss from the red giant and appreciable accretion on its low mass companion on the hydrodynamical timescale of the donor, resulting in formation of helium WD with masses roughly equal to a half solar mass and thus evading the common envelope stage. A simple approximative analytical formula for mass loss rate from Roche lobe filling giant donor has been proposed depending on mass, luminosity and radius of donor.


1980 ◽  
Vol 88 ◽  
pp. 103-107
Author(s):  
J. P. De Grève ◽  
D. Vanbeveren

From a search through the literature 174 close binaries with completely known absolute dimensions are sampled. Distinction is made between systems before and after mass exchange, giving resp. 100 and 40 systems (a third group contains the systems not definitely belonging to these two). Mass, period and mass ratio distributions and relations of the group of “unevolved” binaries (i.e. prior to mass exchange) are transformed into corresponding distributions and relations of evolved binaries. The transformations are based upon the M1 f = g (M1 i) relation derived from an extended set of published theoretical computations on the evolution of close binaries. Final masses resulting from the same initial mass are averaged. Equations are derived for the cases A (for all masses), B1 (M1 i/Mo < 2.8), B2 (2.8 < M1 i/Mo < 9) and B3 (M1 i/Mo > 9). For the changes of the period due to angular momentum loss the formalism of Vanbeveren et al. (1979) was adopted. The following characteristics of the system after mass exchange are computed: M1 f, M2 f (and qf), Pf. Three different modes were applied for the mass loss from the system:a) conservative case (mass and angular momentum of the system remain constant), called C.b) non conservative case with 50% of the transferred mass leaving the system with a small or a large angular momentum loss (resp. called NC51 and NC53).c) non conservative case with 100% of the transferred mass leaving the system with a small or a large angular momentum loss (resp. called NC101 and NC103).


1981 ◽  
Vol 59 ◽  
pp. 473-475
Author(s):  
F. Mardirossian ◽  
G. Giuricin

AbstractWe have examined the observational data of 100 Algols in order to check the validity of several simple models of non-conservative mass transfer. Strong evidence of mass and angular momentum loss has been found at least in about 20% of our Algols. Case B mass exchange is favoured for low-mass Algols, while case A predominates, though not so widely as expected, in Algols of higher total mass.


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