TY  - JOUR
A1  - Sander, A.
A1  - Hamann, Wolf-Rainer
A1  - Hainich, Rainer
A1  - Shenar, Tomer
A1  - Todt, Helge Tobias
T1  - Hydrodynamic modeling of massive star atmospheres
JF  - Wolf-Rayet Stars : Proceedings of an International Workshop held in Potsdam, Germany, 1.–5. June 2015
N2  - In the last decades, stellar atmosphere codes have become a key tool in understanding massive stars, including precise calculations of stellar and wind parameters, such as temperature, massloss rate, and terminal wind velocity. Nevertheless, for these models the hydrodynamic equation is not solved in the wind. Motivated by the results of the CAK theory, the models typically use a beta velocity law, which however turns out not to be adequate for stars with very strong winds, and treat the mass-loss rate as a free parameter. In a new branch of the Potsdam Wolf-Rayet model atmosphere (PoWR) code, we solve the hydrodynamic equation consistently throughout the stellar atmosphere. The PoWR code performs the calculation of the radiative force without approximations (e.g. Sobolev). We show the impact of hydrodynamically consistent modelling on OB and WR stars in comparison to conventional models and discuss the obtained velocity fields and their impact on the observed spectral lines.
Y1  - 2015
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-87857
SP  - 139
EP  - 142
ER  - 
TY  - JOUR
A1  - Kubátová, Brankica
A1  - Hamann, Wolf-Rainer
A1  - Todt, Helge Tobias
A1  - Sander, A.
A1  - Steinke, M.
A1  - Hainich, Rainer
A1  - Shenar, Tomer
T1  - Macroclumping in WR 136
JF  - Wolf-Rayet Stars : Proceedings of an International Workshop held in Potsdam, Germany, 1.–5. June 2015
N2  - Macroclumping proved to resolve the discordance between different mass-loss rate diagnostics for O-type stars, in particular between Hα and the P v resonance lines. In this paper, we report first results from a corresponding investigation for WR stars. We apply our detailed 3-D Monte Carlo (MC) line formation code to the P v resonance doublet and show, for the Galactic WNL star WR136, that macroclumping is require to bring this line in accordance with the mass-loss rate derived from the emission-line spectrum.
Y1  - 2015
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-87823
SP  - 125
EP  - 128
ER  - 
TY  - JOUR
A1  - Steinke, M.
A1  - Oskinova, Lida
A1  - Hamann, Wolf-Rainer
A1  - Sander, A.
T1  - The Wolf-Rayet stars WR102c and 102ka and their isolation
JF  - Wolf-Rayet Stars : Proceedings of an International Workshop held in Potsdam, Germany, 1.–5. June 2015
N2  - While the majority of very massive stars is clearly found in clusters, there are also very massive objects not associated with any cluster, suggesting they may have been born in isolation. In order to gain more insights, we studied the regions around two WR stars in the Galactic Center region. To understand the nature of the potential cluster around massive stars, photometry alone is not sufficient. We therefore used the ESO VLT/SINFONI integral field spectrograph to obtain photometry and spectra for the whole region around our two candidate stars. In total, more than 60 stars have been found and assigned a spectral type.
Y1  - 2015
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-88503
SP  - 365
ER  - 
TY  - GEN
A1  - Vink, Jorick Sandor
A1  - Heger, Alexander
A1  - Krumholz, Mark R.
A1  - Puls, Joachim
A1  - Banerjee, Shiladitya
A1  - Castro, Norberto
A1  - Chen, K.-J.
A1  - Chenè, A.-N.
A1  - Crowther, P. A.
A1  - Daminelli, A.
A1  - Gräfener, G.
A1  - Groh, J. H.
A1  - Hamann, Wolf-Rainer
A1  - Heap, S.
A1  - Herrero, A.
A1  - Kaper, L.
A1  - Najarro, F.
A1  - Oskinova, Lida
A1  - Roman-Lopes, A.
A1  - Rosen, A.
A1  - Sander, A.
A1  - Shirazi, M.
A1  - Sugawara, Y.
A1  - Tramper, F.
A1  - Vanbeveren, D.
A1  - Voss, R.
A1  - Wofford, A.
A1  - Zhang, Y.
T1  - Very massive stars in the local universe
T2  - Postprints der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe
N2  - Recent studies have claimed the existence of very massive stars (VMS) up to 300 M⊙ in the local Universe. As this finding may represent a paradigm shift for the canonical stellar upper-mass limit of 150 M⊙, it is timely to discuss the status of the data, as well as the far-reaching implications of such objects. We held a Joint Discussion at the General Assembly in Beijing to discuss (i) the determination of the current masses of the most massive stars, (ii) the formation of VMS, (iii) their mass loss, and (iv) their evolution and final fate. The prime aim was to reach broad consensus between observers and theorists on how to identify and quantify the dominant physical processes.
T3  - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - 601 
KW  - stars: massive stars
KW  - stars: mass-loss
KW  - stars: stellar evolution
Y1  - 2019
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-415220
SN  - 1866-8372
IS  - 601
ER  -