TY  - CHAP
A1  - Bouret, J.-C.
A1  - Lanz, T.
A1  - Hillier, D. J.
A1  - Foellmi, C.
T1  - Clumping in O-type Supergiants
N2  - We have analyzed the spectra of seven Galactic O4 supergiants, with the NLTE wind code CMFGEN. For all stars, we have found that clumped wind models match well lines from different species spanning a wavelength range from FUV to optical, and remain consistent with Hα data. We have achieved an excellent match of the P V λλ1118, 1128 resonance doublet and N IV λ1718, as well as He II λ4686 suggesting that our physical description of clumping is adequate. We find very small volume filling factors and that clumping starts deep in the wind, near the sonic point. The most crucial consequence of our analysis is that the mass loss rates of O stars need to be revised downward significantly, by a factor of 3 and more compared to those obtained from smooth-wind models.
Y1  - 2007
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus-17662
ER  - 
TY  - CHAP
A1  - Moffat, Anthony F. J.
A1  - Hillier, D. J.
A1  - Hamann, Wolf-Rainer
A1  - Owocki, S. P.
T1  - General Discussion
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-17953
ER  - 
TY  - CHAP
A1  - Groh, J. H.
A1  - Hillier, D. J.
A1  - Damineli, A.
T1  - Mass-loss rate and clumping in LBV stars : the impact of time-dependent effects
N2  - This paper outlines a newly-developed method to include the effects of time variability in the radiative transfer code CMFGEN. It is shown that the flow timescale is often large compared to the variability timescale of LBVs. Thus, time-dependent effects significantly change the velocity law and density structure of the wind, affecting the derivation of the mass-loss rate, volume filling factor, wind terminal velocity, and luminosity. The results of this work are directly applicable to all active LBVs in the Galaxy and in the LMC, such as AG Car, HR Car, S Dor and R 127, and could result in a revision of stellar and wind parameters. The massloss rate evolution of AG Car during the last 20 years is presented, highlighting the need for time-dependent models to correctly interpret the evolution of LBVs.
Y1  - 2007
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus-17773
ER  - 
TY  - CHAP
A1  - Najarro, F.
A1  - Puls, Joachim
A1  - Herrero, A.
A1  - Hanson, M. M.
A1  - Martín-Pintado, J.
A1  - Hillier, D. J.
T1  - Tracking the Clumping in OB Stars from UV to radio
N2  - We review different line and continua diagnostics from the UV to radio, which can be utilized to simultaneously constrain the clumping structure throughout the stellar wind of massive OB stars.
Y1  - 2007
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus-17701
ER  - 
TY  - CHAP
A1  - Hillier, D. J.
T1  - On the influence of clumping on O and Wolf-Rayet spectra
N2  - Overwhelming observational and theoretical evidence suggests that the winds of massive stars are highly clumped. We briefly discuss the influence of clumping on model diagnostics and the difficulties of allowing for the influence of clumping on model spectra. Because of its simplicity, and because of computational ease, most spectroscopic analyses incorporate clumping using the volume filling factor. The biases introduced by this approach are uncertain. To investigate alternative clumping models, and to help determine the validity of parameters derived using the volume filling factor method, we discuss results derived using an alternative model in which we assume that the wind is composed of optically thick shells.
Y1  - 2007
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus-17903
ER  -