scholarly journals Time-dependent atomic diffusion in the atmospheres of CP stars. A big step forward: introducing numerical models including a stellar mass-loss

2018 ◽  
Vol 482 (4) ◽  
pp. 4519-4527 ◽  
Author(s):  
G Alecian ◽  
M J Stift
Keyword(s):  
Mass Loss ◽  
Numerical Models ◽  
Stellar Mass ◽  
Time Dependent ◽  
Atomic Diffusion

scholarly journals Evolution of planetary systems with time-dependent stellar mass-loss

2013 ◽  
Vol 432 (1) ◽  
pp. 438-454 ◽  
Author(s):  
Fred C. Adams ◽  
Kassandra R. Anderson ◽  
Anthony M. Bloch
Keyword(s):  
Mass Loss ◽  
Planetary Systems ◽  
Stellar Mass ◽  
Time Dependent

scholarly journals Radial density profiles of PNe halos from numerical models of mass-loss history

2011 ◽  
Vol 7 (S283) ◽  
pp. 518-519
Author(s):  
Juan-Luis Verbena ◽  
Klaus-Peter Schröder ◽  
Astrid Wachter
Keyword(s):  
Mass Loss ◽  
Observational Data ◽  
Numerical Models ◽  
Stellar Mass ◽  
Line Of Sight ◽  
Red Giants ◽  
Agb Stars ◽  
Radial Density ◽  
Density Profiles ◽  
Outflow Velocity

AbstractWe review the stellar mass loss of red giants and tip-AGB objects analizing the variation in the outflow velocity for different mass models (Wachter et al. 2002). We approach the superwind problem and see the evolution of tip-AGB stars via previously made mass-loss histories that are consistent with the Weidemann initial-final mass relationship (for carbon-rich stars). Finally density profiles are produced from these mass-loss histories, and the corresponding line-of-sight integration is compared with observational data (Phillips et al. 2009). We note the resemblance between the results obtained with our models and the observational data. We are thus able to reproduce the general trends of the emission from simple models (see Verbena et al. 2011).

Density evolution of radio sources fuelled by stellar mass loss

Nature ◽  
1981 ◽  
Vol 289 (5799) ◽  
pp. 659-661 ◽  
Author(s):  
M. E. Bailey ◽  
J. MacDonald
Keyword(s):  
Mass Loss ◽  
Stellar Mass ◽  
Radio Sources ◽  
Density Evolution

scholarly journals Stellar mass-loss near the Eddington limit

2013 ◽  
Vol 560 ◽  
pp. A6 ◽  
Author(s):  
G. Gräfener ◽  
J. S. Vink
Keyword(s):  
Mass Loss ◽  
Stellar Mass ◽  
Eddington Limit

scholarly journals Two-dimensional modeling of density and thermal structure of dense circumstellar outflowing disks

2018 ◽  
Vol 613 ◽  
pp. A75 ◽  
Author(s):  
P. Kurfürst ◽  
A. Feldmeier ◽  
J. Krtička
Keyword(s):  
Mass Loss ◽  
Optical Depth ◽  
Massive Stars ◽  
Thermal Structure ◽  
Time Dependent ◽  
Navier Stokes ◽  
Viscous Heating ◽  
Two Dimensional ◽  
Dense Region ◽  
Loss Rates

Context. Evolution of massive stars is affected by a significant loss of mass either via (nearly) spherically symmetric stellar winds or by aspherical mass-loss mechanisms, namely the outflowing equatorial disks. However, the scenario that leads to the formation of a disk or rings of gas and dust around massive stars is still under debate. It is also unclear how various forming physical mechanisms of the circumstellar environment affect its shape and density, as well as its kinematic and thermal structure. Aims. We study the hydrodynamic and thermal structure of optically thick, dense parts of outflowing circumstellar disks that may be formed around various types of critically rotating massive stars, for example, Be stars, B[e] supergiant (sgB[e]) stars or Pop III stars. We calculate self-consistent time-dependent models of temperature and density structure in the disk’s inner dense region that is strongly affected by irradiation from a rotationally oblate central star and by viscous heating. Methods. Using the method of short characteristics, we specify the optical depth of the disk along the line-of-sight from stellar poles. Within the optically thick dense region with an optical depth of τ > 2∕3 we calculate the vertical disk thermal structure using the diffusion approximation while for the optically thin outer layers we assume a local thermodynamic equilibrium with the impinging stellar irradiation. For time-dependent hydrodynamic modeling, we use two of our own types of hydrodynamic codes: two-dimensional operator-split numerical code based on an explicit Eulerian finite volume scheme on a staggered grid, and unsplit code based on the Roe’s method, both including full second-order Navier-Stokes shear viscosity. Results. Our models show the geometric distribution and contribution of viscous heating that begins to dominate in the central part of the disk for mass-loss rates higher than Ṁ ≳ 10−10 M⊙ yr−1. In the models of dense viscous disks with Ṁ > 10−8 M⊙ yr−1, the viscosity increases the central temperature up to several tens of thousands of Kelvins, however the temperature rapidly drops with radius and with distance from the disk midplane. The high mass-loss rates and high viscosity lead to instabilities with significant waves or bumps in density and temperature in the very inner disk region. Conclusions. The two-dimensional radial-vertical models of dense outflowing disks including the full Navier-Stokes viscosity terms show very high temperatures that are however limited to only the central disk cores inside the optically thick area, while near the edge of the optically thick region the temperature may be low enough for the existence of neutral hydrogen, for example.

scholarly journals An exoplanet's response to anisotropic stellar mass loss during birth and death

2013 ◽  
Vol 435 (3) ◽  
pp. 2416-2430 ◽  
Author(s):  
Dimitri Veras ◽  
John D. Hadjidemetriou ◽  
Christopher A. Tout
Keyword(s):  
Mass Loss ◽  
Stellar Mass

Critical Rates of Stellar Mass Loss

1979 ◽  
pp. 349-356
Author(s):  
D. S. P. Dearborn ◽  
J. B. Blake
Keyword(s):  
Mass Loss ◽  
Stellar Mass

scholarly journals Approach for Optimisation of Tunnel Lining Design

2020 ◽  
Vol 10 (19) ◽  
pp. 6705
Author(s):  
Marek Mohyla ◽  
Karel Vojtasik ◽  
Eva Hrubesova ◽  
Martin Stolarik ◽  
Jan Nedoma ◽  
...  
Keyword(s):  
Rock Mass ◽  
Numerical Models ◽  
Tunnel Lining ◽  
Time Dependent ◽  
Design Element ◽  
Heterogeneous Structure ◽  
Underground Engineering ◽  
Software Application ◽  
Tunnel Lining Design ◽  
Dependent Property

This paper presents an approach that enables the specific characteristics of a primary tunnel lining implemented using numerical modelling to be taken into account during its design. According to the fundamental principles of the New Austrian Tunnelling Method, the primary lining undergoes time-dependent deformation, which is determined by its design. The main design element is shotcrete, which, shortly after its application, interacts with the surrounding rock mass and steel arch frame. The primary lining ensures the equilibrium stress–strain state of “rock mass–tunnel lining” during excavation. The structural interaction varies depending on the hardening of the shotcrete, the rheological properties of the rock mass, and other factors. The proposed approach uses the Homogenisation software application, which was developed by the Faculty of Civil Engineering at the Department of Geotechnics and Underground Engineering of the VSB—Technical University of Ostrava. This software allows the heterogeneous structure of the lining to be considered by replacing it with a homogenous structure. The parameters of the homogeneous primary lining, which take into account the steel reinforcement elements and the time-dependent property of the shotcrete, are included in numerical models.

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