TY  - GEN
A1  - Todt, Helge Tobias
A1  - Peña, Miriam
A1  - Zühlke, Julia
A1  - Oskinova, Lida
A1  - Hamann, Wolf-Rainer
A1  - Gräfener, Götz
T1  - Weak emission line central stars of planetary nebulae
T2  - Planetary Nebulae: an Eye to the Future
N2  - To understand the evolution and morphology of planetary nebulae, a detailed knowledge of their central stars is required. Central stars that exhibit emission lines in their spectra, indicating stellar mass-loss allow to study the evolution of planetary nebulae in action. Emission line central stars constitute about 10 % of all central stars. Half of them are practically hydrogen-free Wolf-Rayet type central stars of the carbon sequence, [WC], that show strong emission lines of carbon and oxygen in their spectra. In this contribution we address the weak emission-lines central stars (wels). These stars are poorly analyzed and their hydrogen content is mostly unknown. We obtained optical spectra, that include the important Balmer lines of hydrogen, for four weak emission line central stars. We present the results of our analysis, provide spectral classification and discuss possible explanations for their formation and evolution.
T3  - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - 462 
KW  - stars: AGB and post-AGB
KW  - stars: Wolf-Rayet
KW  - stars: abundances
Y1  - 2018
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-413775
ER  - 
TY  - GEN
A1  - Reindl, Nicole
A1  - Finch, Nicolle L.
A1  - Schaffenroth, Veronika
A1  - Barstow, Martin A.
A1  - Casewell, Sarah L.
A1  - Geier, Stephan Alfred
A1  - Bertolami Miller, Marcelo Miguel
A1  - Taubenberger, Stefan
T1  - Revealing the true nature of Hen2-428
T2  - Postprints der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe
N2  - The nucleus of Hen 2-428 is a short orbital period (4.2 h) spectroscopic binary, whose status as potential supernovae type Ia progenitor has raised some controversy in the literature. We present preliminary results of a thorough analysis of this interesting system, which combines quantitative non-local thermodynamic (non-LTE) equilibrium spectral modelling, radial velocity analysis, multi-band light curve fitting, and state-of-the art stellar evolutionary calculations. Importantly, we find that the dynamical system mass that is derived by using all available He II lines does not exceed the Chandrasekhar mass limit. Furthermore, the individual masses of the two central stars are too small to lead to an SN Ia in case of a dynamical explosion during the merger process.
T3  - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - 1129 
KW  - binaries: spectroscopic
KW  - stars: atmospheres
KW  - stars: abundances
KW  - Supernovae
Y1  - 2021
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-459703
SN  - 1866-8372
IS  - 1129
ER  - 
TY  - GEN
A1  - Martins, Fabrice
A1  - Bergemann, Maria
A1  - Bestenlehner, Joachim M.
A1  - Crowther, Paul A.
A1  - Hamann, Wolf-Rainer
A1  - Najarro, Francisco
A1  - Nieva, Maria Fernanda
A1  - Przybilla, Norbert
A1  - Freimanis, Juris
A1  - Hou, Weizhen
A1  - Kaper, Lex
T1  - SpS5 - II. Stellar and wind parameters
T2  - Postprints der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe
N2  - The development of infrared observational facilities has revealed a number of massive stars in obscured environments throughout the Milky Way and beyond. The determination of their stellar and wind properties from infrared diagnostics is thus required to take full advantage of the wealth of observations available in the near and mid infrared. However, the task is challenging. This session addressed some of the problems encountered and showed the limitations and successes of infrared studies of massive stars.
T3  - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - 688 
KW  - infrared: stars
KW  - stars: early-type
KW  - stars: late-type
KW  - stars: fundamental parameters
KW  - stars: mass loss
KW  - stars: abundances
Y1  - 2019
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-414956
SN  - 1866-8372
IS  - 688
ER  -