scholarly journals Formation and Evolution of Low-Mass Algols

1989 ◽  
Vol 107 ◽  
pp. 141-153
Author(s):  
L.R. Yungelson ◽  
A.V. Tutukov ◽  
A.V. Fedorova
Keyword(s):  
Angular Momentum ◽  
Gravitational Waves ◽  
Stellar Winds ◽  
Momentum Loss ◽  
Angular Momentum Loss ◽  
Low Mass ◽  
Formation And Evolution

AbstractWe discuss the origin, evolution and fate of low-mass Algols (LMA) that have components with initial masses less than 2.5 M0. The semi-major axes of orbits of pre-LMA do not exceed 20-25 R0. The rate of formation of Algol-type stars is ~ 0.01/year. Magnetic stellar winds may be the factor that determines the evolution of LMA. Most LMA end their lives as double helium degenerate dwarfs with M1/M2 ~ 0.88 (like L870-2). Some of them even merge through angular momentum loss caused by gravitational waves.

scholarly journals The rotation of very low-mass stars and brown dwarfs

2007 ◽  
Vol 3 (S243) ◽  
pp. 241-248
Author(s):  
Jochen Eislöffel ◽  
Alexander Scholz
Keyword(s):  
Angular Momentum ◽  
Brown Dwarfs ◽  
Magnetic Interaction ◽  
Stellar Winds ◽  
Solar Mass ◽  
Low Mass Stars ◽  
Angular Momentum Loss ◽  
Rotational Evolution ◽  
Solar Type ◽  
Low Mass

AbstractThe evolution of angular momentum is a key to our understanding of star formation and stellar evolution. The rotational evolution of solar-mass stars is mostly controlled by magnetic interaction with the circumstellar disc and angular momentum loss through stellar winds. Major differences in the internal structure of very low-mass stars and brown dwarfs – they are believed to be fully convective throughout their lives, and thus should not operate a solar-type dynamo – may lead to major differences in the rotation and activity of these objects. Here, we report on observational studies to understand the rotational evolution of the very low-mass stars and brown dwarfs.

scholarly journals Stellar Winds and Spindown in Solar Type Stars

1983 ◽  
Vol 102 ◽  
pp. 449-460 ◽  
Author(s):  
I.W. Roxburgh
Keyword(s):  
Angular Momentum ◽  
Loss Rate ◽  
Neutrino Flux ◽  
Flow Speed ◽  
Stellar Winds ◽  
Sudden Increase ◽  
Momentum Loss ◽  
Rotational Discontinuity ◽  
Angular Momentum Loss ◽  
Solar Type

The angular momentum loss produced by stellar winds is reviewed and a simple model of angular momentum loss with multipole fields is presented in which the field is potential when the flow speed is less than the Alfvén speed, and radial when greater than the Alfvén speed. The simpler the magnetic geometry, the larger is the angular momentum loss rate. This result is used to explain the rotational discontinuity across the Vaughan-Preston gap as being due to a sudden increase in angular momentum loss when the dynamo field switches from a quadropole to a dipole geometry.The evolution of the internal rotation of stars as a result of surface angular momentum loss is considered. In the absence of a magnetic field, differential rotation can drive instabilities which then transport angular momentum out from the interior down the angular velocity gradient. Other instabilities such as that caused by the build up of 3He can also transport angular momentum outwards. If angular momentum is transported by such weak turbulence, it also makes the star more homogeneous than standard evolutionary models and lowers the predicted value of the solar neutrino flux.The recent results on rotational splitting of solar oscillations are considered: these suggest that the inside of the sun is spinning faster than the surface and are compatible with models in which angular momentum is transported by mild turbulence. But data is scarce — and in such circumstances the speculations of the theorist must be viewed with caution!

scholarly journals On the Evolutionary History of Progenitors of EHBs and Related Binary Systems from their Observed Properties

2006 ◽  
Vol 2 (S240) ◽  
pp. 678-681
Author(s):  
V.V. Pustynski ◽  
I. Pustylnik
Keyword(s):  
Angular Momentum ◽  
Binary Systems ◽  
Mass Loss Rate ◽  
Analytical Formula ◽  
Solar Mass ◽  
Momentum Loss ◽  
Angular Momentum Loss ◽  
History Of ◽  
Low Mass ◽  
Red Giant

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.

scholarly journals Non conservative evolutionary scenario for 100 Algols

1981 ◽  
Vol 59 ◽  
pp. 473-475
Author(s):  
F. Mardirossian ◽  
G. Giuricin
Keyword(s):  
Mass Transfer ◽  
Angular Momentum ◽  
Observational Data ◽  
Mass Exchange ◽  
Strong Evidence ◽  
Total Mass ◽  
Momentum Loss ◽  
Evolutionary Scenario ◽  
Angular Momentum Loss ◽  
Low Mass

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.

scholarly journals Mass-Loss From Spinning Stars

1980 ◽  
Vol 5 ◽  
pp. 601-613
Author(s):  
S. R. Sreenivasan
Keyword(s):  
Angular Momentum ◽  
Mass Loss ◽  
Massive Stars ◽  
Stellar Winds ◽  
Late Type ◽  
Momentum Loss ◽  
Adequate Understanding ◽  
Angular Momentum Loss ◽  
Evolutionary Consequences ◽  
Acceptable Theory

AbstractThe effects of mass-loss and angular momentum loss on the evolution of massive stars are discussed bringing out the main results as well as the limitations of recent studies. It is pointed out that an acceptable theory of stellar winds in early as well as late type stars is needed as well as a satisfactory assessment of a number of instabilities in these contexts for an adequate understanding of the evolutionary consequences for a wide variety of population I and polulation II stars, which are affected by mass-loss.

scholarly journals A nonextensive approach for the angular momentum loss rate in low-mass stars

2012 ◽  
Vol 8 (S294) ◽  
pp. 197-198
Author(s):  
Daniel B. de Freitas ◽  
J. R. De Medeiros
Keyword(s):  
Angular Momentum ◽  
Loss Rate ◽  
Rotational Velocity ◽  
Low Mass Stars ◽  
New Approach ◽  
Momentum Loss ◽  
Angular Momentum Loss ◽  
Low Mass

AbstractThe present study demonstrates that behavior of rotational velocity as a function of stellar age is consistent using Tsallis' nonextensive formalism, resulting in a new approach to understanding the stellar rotational scenario.

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