Mass Loss of B1Ia-O Supergiants and Evolutionary Consequences

1979 ◽  
pp. 35-38
Author(s):  
B. Wolf ◽  
C. Sterken
Keyword(s):  
Mass Loss ◽  
Evolutionary Consequences

scholarly journals Model Atmospheres with Periodic Shocks

1989 ◽  
Vol 106 ◽  
pp. 269-283
Author(s):  
G. H. Bowen
Keyword(s):  
Mass Loss ◽  
Variable Star ◽  
Outer Region ◽  
Thermal Relaxation ◽  
Relaxation Processes ◽  
Long Period ◽  
Period Variable ◽  
Evolutionary Consequences ◽  
Dependent Processes ◽  
Rapid Mass

AbstractThe pulsation of a long-period variable star generates shock waves which dramatically affect the structure of the star's atmosphere and produce conditions that lead to rapid mass loss. Numerical modeling of atmospheres with periodic shocks is being pursued to increase our understanding of the processes involved and of the evolutionary consequences for the stars. It is characteristic of these complex dynamical systems that most effects result from the interaction of various time-dependent processes. For example, rapid mass loss in the models is a joint consequence of the enormous extension of the atmosphere caused by shocks, and of radiation pressure on grains formed in the cool outer region; it is also affected by thermal relaxation processes, which determine the temperature distribution. The progress and significance of these modeling calculations will be reviewed.

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 Mass loss of B1Ia-O supergiants and evolutionary consequences

1979 ◽  
Vol 83 ◽  
pp. 35-38 ◽  
Author(s):  
B. Wolf ◽  
C. Sterken
Keyword(s):  
Mass Loss ◽  
Southern Hemisphere ◽  
High Dispersion ◽  
Spectroscopic Observations ◽  
Characteristic Data ◽  
Evolutionary Consequences

The superluminous B supergiants are loosing mass and their progenitors are supposed to be O stars between 03 and 06 and hence it is justified to talk about B1Ia-O supergiants in this Symposium. Extensive high dispersion spectroscopic observations of four luminous B1 supergiants of the southern hemisphere have been carried out during 1972 and 1975 at ESO, La Silla. Some characteristic data of the program stars are summarized in Table 1.

scholarly journals Massive Star Evolution: Mass Loss and Mixing

1986 ◽  
Vol 116 ◽  
pp. 287-300
Author(s):  
André Maeder
Keyword(s):  
Mass Loss ◽  
Massive Star ◽  
Main Sequence ◽  
Relative Mass ◽  
Physical Processes ◽  
Mixing Processes ◽  
Physical Reason ◽  
Star Evolution ◽  
Massive Star Evolution ◽  
Evolutionary Consequences

At first it may be surprising that mass loss, overshooting and mixing, which are indeed very different physical processes, have similar consequences on stellar evolution. These various processes may increase the Main-Sequence (MS) lifetime, extend the width of the MS, bring CNO-processed materials to stellar surfaces and, in extreme cases, lead to quasi-homogeneous evolution. The physical reason of this similarity is that these processes increase the relative mass fraction of the stellar cores. Thus we understand that, on the basis of their evolutionary consequences, it may not be easy to disentangle the contributions of mass loss, overshooting and mixing processes. The present status of our knowledge on these effects, which appear to have major consequences on the evolution of massive stars, is now examined in detail.

scholarly journals The evolution of magnetic hot massive stars: Implementation of the quantitative influence of surface magnetic fields in modern models of stellar evolution

2016 ◽  
Vol 12 (S329) ◽  
pp. 250-254 ◽  
Author(s):  
Zsolt Keszthelyi ◽  
Gregg A. Wade ◽  
Véronique Petit
Keyword(s):  
Magnetic Fields ◽  
Mass Loss ◽  
Stellar Evolution ◽  
Large Scale ◽  
Massive Stars ◽  
Model Calculations ◽  
Magnetic Mass ◽  
Evolutionary Consequences ◽  
The Impact ◽  
Quantitative Influence

AbstractLarge-scale dipolar surface magnetic fields have been detected in a fraction of OB stars, however only few stellar evolution models of massive stars have considered the impact of these fossil fields. We are performing 1D hydrodynamical model calculations taking into account evolutionary consequences of the magnetospheric-wind interactions in a simplified parametric way. Two effects are considered: i) the global mass-loss rates are reduced due to mass-loss quenching, and ii) the surface angular momentum loss is enhanced due to magnetic braking. As a result of the magnetic mass-loss quenching, the mass of magnetic massive stars remains close to their initial masses. Thus magnetic massive stars - even at Galactic metallicity - have the potential to be progenitors of ‘heavy’ stellar mass black holes. Similarly, at Galactic metallicity, the formation of pair instability supernovae is plausible with a magnetic progenitor.

Water accumulation as a function of temperature on specimens in an electron microscope cold stage

1986 ◽  
Vol 44 ◽  
pp. 114-115 ◽  
Author(s):  
M.K. Lamvik ◽  
D.A. Kopf ◽  
S.D. Davilla ◽  
J.D. Robertson
Keyword(s):  
Electron Microscope ◽  
Mass Loss ◽  
Liquid Helium ◽  
Liquid Nitrogen ◽  
Liquid Nitrogen Temperature ◽  
Liquid Helium Temperature ◽  
Helium Temperature ◽  
Cold Stage ◽  
Water Accumulation ◽  
Better Than

Last year we reported1 that there is a striking reduction in the rate of mass loss when a specimen is observed at liquid helium temperature. It is important to determine whether liquid helium temperature is significantly better than liquid nitrogen temperature. This requires a good understanding of mass loss effects in cold stages around 100K.

Electron Beam-Induced Mass Loss in Freeze-Dried Tissue and Protein Samples

1985 ◽  
Vol 43 ◽  
pp. 470-471
Author(s):  
M.E. Cantino ◽  
M.K. Goddard ◽  
L.E. Wilkinson ◽  
D.E. Johnson
Keyword(s):  
Electron Beam ◽  
Salivary Gland ◽  
Mass Loss ◽  
Counting Rate ◽  
Dose Dependence ◽  
X Ray ◽  
Large Samples ◽  
Freeze Dried ◽  
Muscle Homogenate ◽  
Large Muscle

Quantification in biological x-ray microanalysis depends on accurate evaluation of mass loss. Although several studies have addressed the problem of electron beam induced mass loss from organic samples (eg., 1,2). uncertainty persists as to the dose dependence, the extent of loss, the elemental constituents affected, and the variation in loss for different materials and tissues. in the work described here, we used x-ray counting rate changes to measure mass loss in albumin (used as a quantification standard), salivary gland, and muscle.In order to measure mass loss at low doses (10-4 coul/cm2 ) large samples were needed. While freeze-dried salivary gland sections of the required dimensions were available, muscle sections of this size were difficult to obtain. To simulate large muscle sections, frog or rat muscle homogenate was injected between formvar films which were then stretched over slot grids and freeze-dried. Albumin samples were prepared by a similar procedure. using a solution of bovine serum albumin in water. Samples were irradiated in the STEM mode of a JEOL 100C.

Elemental mass loss in silicate minerals during x-ray analysis

1990 ◽  
Vol 48 (4) ◽  
pp. 804-805
Author(s):  
P.E. Champness ◽  
R.W. Devenish
Keyword(s):  
Mass Loss ◽  
Current Density ◽  
Damage Mechanism ◽  
Beam Current ◽  
Single Chain ◽  
Plagioclase Feldspar ◽  
X Ray ◽  
Alkali Ions ◽  
Structural Order ◽  
Sheet Silicate

It has long been recognised that silicates can suffer extensive beam damage in electron-beam instruments. The predominant damage mechanism is radiolysis. For instance, damage in quartz, SiO2, results in loss of structural order without mass loss whereas feldspars (framework silicates containing Ca, Na, K) suffer loss of structural order with accompanying mass loss. In the latter case, the alkali ions, particularly Na, are found to migrate away from the area of the beam. The aim of the present study was to investigate the loss of various elements from the common silicate structures during electron irradiation at 100 kV over a range of current densities of 104 - 109 A m−2. (The current density is defined in terms of 50% of total current in the FWHM probe). The silicates so far ivestigated are:- olivine [(Mg, Fe)SiO4], a structure that has isolated Si-O tetrahedra, garnet [(Mg, Ca, Fe)3Al2Si3AO12 another silicate with isolated tetrahedra, pyroxene [-Ca(Mg, Fe)Si2O6 a single-chain silicate; mica [margarite, -Ca2Al4Si4Al4O2O(OH)4], a sheet silicate, and plagioclase feldspar [-NaCaAl3Si5O16]. Ion- thinned samples of each mineral were examined in a VG Microscopes UHV HB501 field- emission STEM. The beam current used was typically - 0.5 nA and the current density was varied by defocussing the electron probe. Energy-dispersive X-ray spectra were collected every 10 seconds for a total of 200 seconds using a Link Systems windowless detector. The thickness of the samples in the area of analysis was normally 50-150 nm.

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