On the generation of mass loss in cool giant stars due to propagating shock waves

1990 ◽  
Vol 353 ◽  
pp. 255 ◽  
Author(s):  
Manfred Cuntz
Keyword(s):  
Shock Waves ◽  
Mass Loss ◽  
Giant Stars

scholarly journals Molecular Spectroscopy as Diagnostics of Outer Atmosphere of Cool Luminous Stars: Quasi-Static Turbulent Molecular Formation Zone and Stellar Mass-Loss

1988 ◽  
Vol 108 ◽  
pp. 158-166
Author(s):  
Takashi Tsuji
Keyword(s):  
Mass Loss ◽  
Molecular Spectroscopy ◽  
Recent Theory ◽  
Cool Component ◽  
Giant Stars ◽  
Molecular Formation ◽  
Formation Zone ◽  
Thermally Driven ◽  
Molecular Cooling ◽  
Outer Atmosphere

AbstractThe origin of mass-loss in cool luminous stars is still obscure; several known mechanisms such as thermally driven wind, radiation-driven wind(via dust), wave-driven wind etc all have serious difficulties, if examined in the light of recent observations. At the same time, recent observations in the infrared and radio spectral domains revealed that outer envelope of red (super)giant stars has highly complicated spatial and velocity structures, while inner envelope may have new component that had not been recognized before. For example, recent high resolution infrared spectroscopy revealed a possible presence of a quasi-static turbulent molecular dissociation zone somewhere in the outer atmosphere. This new component may represent a transition zone between the warm chromosphere and the huge expanding molecular envelope, and may be a cool component of chromospheric inhomogeneity or a moleclar condensation in a cool corona extended by turbulent pressure. Such a result can be regarded as observational evidence in support of a recent theory of autocatalytic molecular formation by thermal instability due to molecular cooling. Thus, observation and theory consistently show the presence of a new component - quasi-static turbulent molecular formation zone - in outer atmosphere of cool luminous stars, and a possibility of a unified understanding of outer atmospheric structure and mass-loss, in which turbulence may play important role, can be proposed.

scholarly journals Red Giant Stars: Comparison of Observations and Theory

1984 ◽  
Vol 108 ◽  
pp. 195-206
Author(s):  
Jeremy Mould
Keyword(s):  
Mass Loss ◽  
Parameter Space ◽  
Loss Rate ◽  
Mass Loss Rate ◽  
Magellanic Clouds ◽  
Asymptotic Giant Branch ◽  
Carbon Stars ◽  
Giant Stars ◽  
Theoretical Investigations ◽  
Red Giant

Recent observations in both the field and the clusters of the Magellanic Clouds suggest a higher mass loss rate during or at the end of the asymptotic giant branch phase than previously supposed. Recent theoretical investigations offer an explanation for the frequency of carbon stars in the Clouds, but a rich parameter space remains to be explored, before detailed agreement can be expected.

Evolution and Problems of Red Long Period Variables

1979 ◽  
Vol 46 ◽  
pp. 163-176
Author(s):  
P. R. Wood
Keyword(s):  
Mass Loss ◽  
Atomic Mass ◽  
Surface Enrichment ◽  
Giant Stars ◽  
Long Period ◽  
Wide Range ◽  
Comprehensive Picture ◽  
Period Variable ◽  
Red Giant ◽  
Process Elements

Variability on the red giant branch (RGB) occurs at an interesting and important stage in the life of a star. This phase of evolution is characterized by a substantial amount of mass loss (as a continuous stellar wind or as an abrupt planetary nebula ejection), by flashing of the helium burning shell (at least in stars less massive than ~ 8 M) and by surface enrichment of elements heavier than hydrogen. The galactic importance of these processes is illustrated by the calculations of Cahn and Wyatt (1978) who estimate that material is presently being lost by stars on the RGB at a rate which is roughly equal to the rate at which material is being locked up in stars by star formation. A complementary calculation by Iben and Truran (1978) shows that shell flashing in red giant stars, coupled with mass loss, is a major source of enrichment of the interstellar medium over a wide range of atomic mass from C to heavy s-process elements. Hopefully, studies of the red long period variable (RLPV) stars can assist in the investigation of some of the above processes so that a comprehensive picture of the later phases of stellar evolution can be obtained.

Chromospheres and mass loss in metal-deficient giant stars

1984 ◽  
Vol 281 ◽  
pp. L37 ◽  
Author(s):  
A. K. Dupree ◽  
L. Hartmann ◽  
E. H. Avrett
Keyword(s):  
Mass Loss ◽  
Giant Stars

scholarly journals Dust Driven Mass Loss from Pulsating AGB-Stars

1993 ◽  
Vol 155 ◽  
pp. 364-364
Author(s):  
E.A. Dorfi ◽  
M.U. Feuchtinger ◽  
S. Höfner
Keyword(s):  
Shock Waves ◽  
Mass Loss ◽  
Mass Loss Rate ◽  
Numerical Procedure ◽  
Stellar Atmospheres ◽  
Stellar Winds ◽  
Temperature Structure ◽  
Cooling Zone ◽  
Grid Points ◽  
Slow Wind

A new numerical method allows an acurate calculation of the radiation hydrodynamics of time dependent stellar winds including also the radiation pressure on newly formed dust grains. The numerical procedure is based on an adaptive grid which distributes the grid points at locations of large gradients. All equations are written in conservation form and a monotonic 2. order transport scheme is used to advect the physical variables through the cell boundaries. We are able to resolve the shock waves running through the stellar atmospheres. These waves are generated by a pulsating star which is simulated by a moving piston. The following plots show the radial velocity and temperature structure of an extended atmosphere and several shock waves are clearly seen. Note that the innermost shock waves is a so-called supercritical shock where the radiative cooling zone behind the wave is clearly visible. The outer waves are almost isothermal because the material is optically thin in this region. The stellar parameters of this example are given by M = 1.2 M⊙, L = 5315L⊙ and R = 270R⊙ and the period of the moving piston is fixed at 350 days yielding a massive and slow wind with a mass loss rate of · = 1.24 10−6M⊙ yr−1 and a final velocity of v = 7.7 km s−1.

scholarly journals The N/O-Core Mass Relation in Planetary Nebulae

1989 ◽  
Vol 106 ◽  
pp. 235-235
Author(s):  
J.B. Kaler ◽  
R.A. Shaw ◽  
K.B. Kwitter
Keyword(s):  
Mass Loss ◽  
Planetary Nebulae ◽  
Nitrogen Enrichment ◽  
Mass Relation ◽  
Core Mass ◽  
Giant Stars ◽  
Rate Of Increase ◽  
The Relationship

We define the relationship between nitrogen enrichment in planetary nebulae and the mass of the nucleus. N/O remains flat at about 0.3 (double solar) from a core mass of 0.55 M(sun) to 0.8 M(sun), whereupon it rises quickly to values that approach and may exceed 2. The rate of increase of N/O with core mass exceeds that predicted for giant stars by standard dredge-up and mass-loss theories.

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