TY  - JOUR
A1  - Thomas, Timon
A1  - Feldmeier, Achim
T1  - Radiative waves in stellar winds with line scattering
JF  - Monthly notices of the Royal Astronomical Society
N2  - Photospheric radiation can drive winds from hot, massive stars by direct momentum transfer through scattering in bound-bound transitions of atmospheric ions. The line radiation force should cause a new radiative wave mode. The dispersion relation from perturbations of the line force was analysed so far either in Sobolev approximation or for pure line absorption. The former does not include the line-driven instability, and the latter cannot account for upstream propagating, radiative waves. We consider a non-Sobolev line force that includes scattering in a simplified way, accounting however for the important line-drag effect. We derive a new dispersion relation for radiative waves, and analyse wave propagation using Fourier methods, and by numerical solution of an integro-differential equation. The existence of an upstream propagating, dispersive radiative wave mode is demonstrated.
KW  - hydrodynamics
KW  - radiative transfer
KW  - waves
KW  - stars: winds
KW  - outflows
Y1  - 2016
U6  - https://doi.org/10.1093/mnras/stw1008
SN  - 0035-8711
SN  - 1365-2966
VL  - 460
SP  - 1923
EP  - 1933
PB  - Oxford Univ. Press
CY  - Oxford
ER  - 
TY  - JOUR
A1  - Sandin, C.
A1  - Steffen, M.
A1  - Schoenberner, D.
A1  - Rühling, Ute
T1  - Hot bubbles of planetary nebulae with hydrogen-deficient winds I. Heat conduction in a chemically stratified plasma
JF  - Frontiers in psychology
N2  - Heat conduction has been found a plausible solution to explain discrepancies between expected and measured temperatures in hot bubbles of planetary nebulae (PNe). While the heat conduction process depends on the chemical composition, to date it has been exclusively studied for pure hydrogen plasmas in PNe. A smaller population of PNe show hydrogen-deficient and helium-and carbon-enriched surfaces surrounded by bubbles of the same composition; considerable differences are expected in physical properties of these objects in comparison to the pure hydrogen case. The aim of this study is to explore how a chemistry-dependent formulation of the heat conduction affects physical properties and how it affects the X-ray emission from PN bubbles of hydrogen-deficient stars. We extend the description of heat conduction in our radiation hydrodynamics code to work with any chemical composition. We then compare the bubble-formation process with a representative PN model using both the new and the old descriptions. We also compare differences in the resulting X-ray temperature and luminosity observables of the two descriptions. The improved equations show that the heat conduction in our representative model of a hydrogen-deficient PN is nearly as efficient with the chemistry-dependent description; a lower value on the diffusion coefficient is compensated by a slightly steeper temperature gradient. The bubble becomes somewhat hotter with the improved equations, but differences are otherwise minute. The observable properties of the bubble in terms of the X-ray temperature and luminosity are seemingly unaffected.
KW  - conduction
KW  - hydrodynamics
KW  - planetary nebulae: general
KW  - stars: AGB and post-AGB
KW  - stars: Wolf-Rayet
KW  - X-rays: stars
Y1  - 2016
U6  - https://doi.org/10.1051/0004-6361/201527357
SN  - 1432-0746
VL  - 586
PB  - EDP Sciences
CY  - Les Ulis
ER  -