scholarly journals Interaction of Close‐in Planets with the Magnetosphere of Their Host Stars. I. Diffusion, Ohmic Dissipation of Time‐dependent Field, Planetary Inflation, and Mass Loss

2008 ◽  
Vol 685 (1) ◽  
pp. 521-542 ◽  
Author(s):  
Randy O. Laine ◽  
Douglas N. C. Lin ◽  
Shawfeng Dong
Keyword(s):  
Mass Loss ◽  
Time Dependent ◽  
Ohmic Dissipation ◽  
Host Stars ◽  
Dependent Field

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 Time-Dependent Field Effect in Three-Dimensional Lead-Halide Perovskite Semiconductor Thin Films

2021 ◽  
Author(s):  
Anil Reddy Pininti ◽  
James M. Ball ◽  
Munirah D. Albaqami ◽  
Annamaria Petrozza ◽  
Mario Caironi
Keyword(s):  
Thin Films ◽  
Field Effect ◽  
Three Dimensional ◽  
Time Dependent ◽  
Semiconductor Thin Films ◽  
Halide Perovskite ◽  
Lead Halide ◽  
Dependent Field

scholarly journals Modelling Time-Dependent Diffusion in Am Star Envelopes

1993 ◽  
Vol 137 ◽  
pp. 272-274 ◽  
Author(s):  
G. Alecian
Keyword(s):  
Diffusion Process ◽  
Mass Loss ◽  
Main Sequence ◽  
Convection Zone ◽  
Time Dependent ◽  
Radiative Zone

AbstractWe study the diffusion process occurring just below the superficial convection zone of Am stars, improving the methods used sofar. We are now able to compute, in a more realistic way, the evolution of the concentrations during the stay of the stars on the main sequence for a large number of elements. This allows to better constrain the different properties (mass loss, depth of the superficial convection zone, transition between convection and radiative zone) entering the modelling of Am stars in the framework of a diffusion-dominant description.

scholarly journals Mass loss from the exoplanet WASP-12b inferred from Spitzer phase curves

2019 ◽  
Vol 489 (2) ◽  
pp. 1995-2013 ◽  
Author(s):  
Taylor J Bell ◽  
Michael Zhang ◽  
Patricio E Cubillos ◽  
Lisa Dang ◽  
Luca Fossati ◽  
...  
Keyword(s):  
Mass Loss ◽  
Infrared Radiation ◽  
High Energy ◽  
The Other ◽  
Phase Curve ◽  
Near Ultraviolet ◽  
Energy Irradiation ◽  
Ultraviolet Observations ◽  
Host Stars ◽  
Co Emission

ABSTRACT The exoplanet WASP-12b is the prototype for the emerging class of ultrahot, Jupiter-mass exoplanets. Past models have predicted – and near-ultraviolet observations have shown – that this planet is losing mass. We present an analysis of two sets of 3.6 and 4.5 $\mu \rm{m}$Spitzer phase curve observations of the system which show clear evidence of infrared radiation from gas stripped from the planet, and the gas appears to be flowing directly toward or away from the host star. This accretion signature is only seen at 4.5 $\mu \rm{m}$, not at 3.6 $\mu \rm{m}$, which is indicative either of CO emission at the longer wavelength or blackbody emission from cool, ≲600 K gas. It is unclear why WASP-12b is the only ultrahot Jupiter to exhibit this mass-loss signature, but perhaps WASP-12b’s orbit is decaying as some have claimed, while the orbits of other exoplanets may be more stable; alternatively, the high-energy irradiation from WASP-12A may be stronger than the other host stars. We also find evidence for phase offset variability at the level of 6.4σ (46.2°) at 3.6 $\mu \rm{m}$.

scholarly journals Growth Rate of White Dwarf Mass in Binaries

1989 ◽  
Vol 114 ◽  
pp. 507-510
Author(s):  
Mariko Kato ◽  
Hideyuki Saio ◽  
Izumi Hachisu
Keyword(s):  
Growth Rate ◽  
Steady State ◽  
Star Formation ◽  
Neutron Star ◽  
Mass Loss ◽  
White Dwarf ◽  
Accretion Rate ◽  
Time Dependent ◽  
Type I ◽  
Wide Range

AbstractThe growth rate of a white dwarf which accretes hydrogen-rich or helium matter is studied. If the accretion rate is relatively small, unstable shell flash occurs and during which the envelope mass is lost. We have followed the evolutions of shell flashes by steady state approach with wind mass loss solutions to determined the mass lost from the system for wide range of binary parameters. The time-dependent models are also calculated in some cases. The mass loss due to the Roche lobe overflow are taken into account. This results seriously affects the existing scenarios on the origin of the type I supernova or on the neutron star formation induced by accretion.

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