R. Ignace, W. L. Waldron, J. P. Cassinelli
The consequences of structured flows continue to be a pressing topic in
relating spectral data to physical processes occurring in massive star winds.
In a preceding paper, our group reported on hydrodynamic simulations of
hypersonic flow past a rigid spherical clump to explore the structure of bow
shocks that can form around wind clumps. Here we report on profiles of emission
lines that arise from such bow shock morphologies. To compute emission line
profiles, we adopt a two component flow structure of wind and clumps using two
"beta" velocity laws. While individual bow shocks tend to generate double
horned emission line profiles, a group of bow shocks can lead to line profiles
with a range of shapes with blueshifted peak emission that depends on the
degree of X-ray photoabsorption by the interclump wind medium, the number of
clump structures in the flow, and the radial distribution of the clumps. Using
the two beta law prescription, the theoretical emission measure and temperature
distribution throughout the wind can be derived. The emission measure tends to
be power law, and the temperature distribution broad in terms of wind velocity.
Although restricted to the case of adiabatic cooling, our models highlight the
influence of bow shock effects for hot plasma temperature and emission measure
distributions in stellar winds and their impact on X-ray line profile shapes.
Previous models have focused on geometrical considerations of the clumps and
their distribution in the wind. Our results represent the first time that the
temperature distribution of wind clump structures are explicitly and
self-consistently accounted in modeling X-ray line profile shapes for massive
stars.
View original:
http://arxiv.org/abs/1202.5492
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