Darmstadt 2016 – wissenschaftliches Programm
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HK: Fachverband Physik der Hadronen und Kerne
HK 4: Nuclear Astrophysics I
HK 4.4: Vortrag
Montag, 14. März 2016, 15:00–15:15, S1/01 A02
Role of Nuclear Reactions for the Evolution of Degenerate ONeMg Cores — •Heiko Möller1, Samuel Jones2, and Gabriel Martínez-Pinedo1 — 1TU Darmstadt — 2HITS Heidelberg
Degenerate electron cores composed of oxygen, neon & magnesium (ONeMg cores) appear primarily in the context of the late stellar evolution stages of super asymptotic giant branch (SAGB) stars with masses between 8 - 10 M⊙. They can become white dwarfs, they can undergo gravitational collapse or they might even proceed towards explosive oxygen-burning and a subsequent thermonuclear explosion.
We show that an accurate description of nuclear reactions is crucial for the determination of the pre-supernova structure of these stars and point out that weak rates involving sd-shell nuclei are especially important. This concerns in particular the 20Ne electron capture, taking into account the 2nd forbidden transition to the 20F ground state, where experimental and theoretical advances in the rate determination are currently being made. We perform stellar evolution calculations of accreting ONeMg cores to study the behavior of the core prior to the ignition of oxygen and show that the development of convection is highly sensitive to the nuclear reactions being considered. Some of our models develop an oxygen-deflagration requiring a hydrodynamic description coupled with a nuclear reaction network with ∼ 200 nuclear species including all relevant electron captures and beta-decays. We present results of hydrodynamic simulations that capture the onset of the oxygen-flame ignition based on recent SAGB star models.
H.M. is supported by the Helmholtz Association through NAVI.