TY  - CHAP
A1  - Leutenegger, M. A.
A1  - Cohen, David H.
A1  - Kahn, S. M.
A1  - Owocki, S. P.
A1  - Paerels, F. B. S.
T1  - Resonance scattering in the X-ray emission lines profiles of ζ Puppis
N2  - We present XMM-Newton Reflection Grating Spectrometer observations of pairs of X-ray emission line profiles from the O star ζ Pup that originate from the same He-like ion. The two profiles in each pair have different shapes and cannot both be consistently fit by models assuming the same wind parameters. We show that the differences in profile shape can be accounted for in a model including the effects of resonance scattering, which affects the resonance line in the pair but not the intercombination line. This implies that resonance scattering is also important in single resonance lines, where its effect is difficult to distinguish from a low effective continuum optical depth in the wind. Thus, resonance scattering may help reconcile X-ray line profile shapes with literature mass-loss rates.
Y1  - 2007
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus-18085
ER  - 
TY  - CHAP
A1  - Schnerr, R. S.
A1  - Henrichs, H. F.
T1  - Magnetic fields and wind variability in massive stars
N2  - This paper describes the thesis work of Schnerr (2007) entitled ”Magnetic fields and mass loss in massive stars“, which aimed at a better understanding of the impact of magnetic fields on the winds of massive stars.
Y1  - 2007
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus-18075
ER  - 
TY  - CHAP
A1  - Ignace, R.
A1  - Gayley, K. G.
T1  - Circumstellar Magnetic Field Diagnostics from Line Polarization
Y1  - 2007
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus-18066
ER  - 
TY  - CHAP
A1  - Cassinelli, Joseph P.
A1  - Ignace, R.
A1  - Waldron, W.
A1  - Cho, J.
A1  - Murphy, N.
A1  - Lazarian, A.
T1  - X-ray line emission produced in clump bow shocks
N2  - We summarize Chandra observations of the emission line profiles from 17 OB stars. The lines tend to be broad and unshifted. The forbidden/intercombination line ratios arising from Helium-like ions provide radial distance information for the X-ray emission sources, while the H-like to He-like line ratios provide X-ray temperatures, and thus also source temperature versus radius distributions. OB stars usually show power law differential emission measure distributions versus temperature. In models of bow shocks, we find a power law differential emission measure, a wide range of ion stages, and the bow shock flow around the clumps provides transverse velocities comparable to HWHM values. We find that the bow shock results for the line profile properties, consistent with the observations of X-ray line emission for a broad range of OB star properties.
Y1  - 2007
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus-18057
ER  - 
TY  - CHAP
A1  - Vink, J. S.
T1  - Discussion: Hydrodynamic modeling
Y1  - 2007
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus-18046
ER  - 
TY  - CHAP
A1  - Runacres, M. C.
T1  - Hydrodynamical models of clumping beyond 50 R∗
N2  - We present one-dimensional, time-dependent models of the clumps generated by the linedeshadowing instability. In order to follow the clumps out to distances of more than 1000 R∗, we use an efficient moving-box technique. We show that, within the approximations, the wind can remain clumped well into the formation region of the radio continuum.
Y1  - 2007
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus-18030
ER  - 
TY  - CHAP
A1  - Walter, R.
A1  - Zurita-Heras, J.
A1  - Leyder, J.-C.
T1  - Probing clumpy stellar winds with a neutron star
N2  - INTEGRAL tripled the number of super-giant high-mass X-ray binaries (sgHMXB) known in the Galaxy by revealing absorbed and fast transient (SFXT) systems. Quantitative constraints on the wind clumping of massive stars can be obtained from the study of the hard X-ray variability of SFXT. A large fraction of the hard X-ray emission is emitted in the form of flares with a typical duration of 3 ksec, frequency of 7 days and luminosity of $10^{36}$ erg/s. Such flares are most probably emitted by the interaction of a compact object orbiting at $\sim10~R_*$ with wind clumps ($10^{22 ... 23}$ g) representing a large fraction of the stellar mass-loss rate. The density ratio between the clumps and the inter-clump medium is $10^{2 ... 4}$. The parameters of the clumps and of the inter-clump medium, derived from the SFXT flaring behavior, are in good agreement with macro-clumping scenario and line-driven instability simulations. SFXT are likely to have larger orbital radius than classical sgHMXB.
Y1  - 2007
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus-18024
ER  - 
TY  - CHAP
A1  - ud-Doula, A.
T1  - Large-scale wind structure due to magnetic fields
N2  - Magnetic fields influence the dynamics of hot-star winds and create large scale structure. Based on numerical magnetohydrodynamic (MHD) simulations, we model the wind of θ¹ Ori C, and then use the SEI method to compute synthetic line profiles for a range of viewing angles as function of rotational phase. The resulting dynamic spectrum for a moderately strong line shows a distinct modulation, but with a phase that seems at odds with available observations.
Y1  - 2007
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus-18010
ER  - 
TY  - CHAP
A1  - Puls, Joachim
T1  - Discussion : X-rays
N2  - Clumping in hot-star winds : proceedings of an international workshop held in Potsdam, Germany, 18. - 22. June 2007
Y1  - 2007
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus-18000
ER  - 
TY  - CHAP
A1  - Owocki, S. P.
T1  - Dynamical simulation of the “velocity-porosity” reduction in observed strength of stellar wind lines
N2  - I use dynamical simulations of the line-driven instability to examine the potential role of the resulting flow structure in reducing the observed strength of wind absorption lines. Instead of the porosity length formalism used to model effects on continuum absorption, I suggest reductions in line strength can be better characterized in terms of a velocity clumping factor that is insensitive to spatial scales. Examples of dynamic spectra computed directly from instability simulations do exhibit a net reduction in absorption, but only at a modest 10-20% level that is well short of the ca. factor 10 required by recent analyses of PV lines.
Y1  - 2007
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus-17992
ER  -