TY  - JOUR
A1  - Yoon, S.-C.
A1  - Langer, Norbert
A1  - Scheithauer, S.
T1  - Effects of rotation on the helium burning shell source in accreting white dwarfs
N2  - We investigate the effects of rotation on the behavior of the helium-burning shell source in accreting carbon- oxygen white dwarfs, in the context of the single degenerate Chandrasekhar mass progenitor scenario for type la supernovae (SNe Ia). We model the evolution of helium-accreting white dwarfs of initially 1 M-circle dot, assuming four different constant accretion rates (2, 3, 5 and 10 x 10(-7) M-circle dot/yr). In a one-dimensional approximation, we compute the mass accretion and subsequent nuclear fusion of helium into carbon and oxygen, as well as angular momentum accretion, angular momentum transport inside the white dwarf, and rotationally induced chemical mixing. Our models show two major effects of rotation: a) The helium-burning nuclear shell source in the rotating models is much more stable than in corresponding non-rotating models - which increases the likelihood that accreting white dwarfs reach the stage of central carbon ignition. This effect is mainly due to rotationally induced mixing at the CO/He interface which widens the shell source, and due to the centrifugal force lowering the density and degeneracy at the shell source location. b) The C/O-ratio in the layers which experience helium shell burning - which may affect the energy of an SN Ia explosion - is strongly decreased by the rotationally induced mixing of a-particles into the carbon-rich layers. We discuss implications of our results for the evolution of SNe la progenitors
Y1  - 2004
SN  - 0004-6361
ER  - 
TY  - GEN
A1  - Morel, T.
A1  - Castro, Norberto
A1  - Fossati, Luca
A1  - Hubrig, Swetlana
A1  - Langer, N.
A1  - Przybilla, Norbert
A1  - Schöller, Markus
A1  - Carroll, Thorsten Anthony
A1  - Ilyin, Ilya
A1  - Irrgang, Andreas
A1  - Oskinova, Lida
A1  - Schneider, Fabian R. N.
A1  - Simon Díaz, Sergio
A1  - Briquet, Maryline
A1  - González, Jean-Francois
A1  - Kharchenko, Nina
A1  - Nieva, M.-F.
A1  - Scholz, Ralf-Dieter
A1  - de Koter, Alexander
A1  - Hamann, Wolf-Rainer
A1  - Herrero, Artemio
A1  - Maíz Apellániz, Jesus
A1  - Sana, Hugues
A1  - Arlt, Rainer
A1  - Barbá, Rodolfo H.
A1  - Dufton, Polly
A1  - Kholtygin, Alexander
A1  - Mathys, Gautier
A1  - Piskunov, Anatoly E.
A1  - Reisenegger, Andreas
A1  - Spruit, H.
A1  - Yoon, S.-C.
T1  - The B fields in OB stars (BOB) survey
T2  - Postprints der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe
N2  - The B fields in OB stars (BOB) survey is an ESO large programme collecting spectropolarimetric observations for a large number of early-type stars in order to study the occurrence rate, properties, and ultimately the origin of magnetic fields in massive stars. As of July 2014, a total of 98 objects were observed over 20 nights with FORS2 and HARPSpol. Our preliminary results indicate that the fraction of magnetic OB stars with an organised, detectable field is low. This conclusion, now independently reached by two different surveys, has profound implications for any theoretical model attempting to explain the field formation in these objects. We discuss in this contribution some important issues addressed by our observations (e.g., the lower bound of the field strength) and the discovery of some remarkable objects.
T3  - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - 821 
KW  - magnetic fields
KW  - stars: early-type
KW  - stars: magnetic fields
KW  - stars: individual (HD 164492C, CPD –57 ◦ 3509, HD 54879, β CMa, ε CMa)
Y1  - 2020
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-415238
SN  - 1866-8372
IS  - 821
ER  - 
TY  - JOUR
A1  - Langer, Norbert
A1  - Yoon, S.-C
A1  - Wellstein, Stephan
A1  - Scheithauer, S.
T1  - On the evolution of interacting binaries which contain a white dwarf
N2  - We discuss the evolution of white dwarf containing binaries, in particular such systems consisting of a white dwarf and a main sequence star which have the potential to produce a Type Ia supernova. After investigating current problems in connecting observations of supersoft X-ray sources with such systems, we consider two major problems which theoretical models encounter to produce Chandrasekhar-mass white dwarfs: the helium shell burning instability and the white dwarf spin-up. We conclude by suggesting that the formation of Chandrasekhar-mass white dwarfs may be easier when these two problem are considered simultaneously.
Y1  - 2002
SN  - 1-58381-101-X
ER  -