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HK: Fachverband Physik der Hadronen und Kerne
HK 47: Nuclear Astrophysics I
HK 47.1: Gruppenbericht
Donnerstag, 2. April 2020, 14:00–14:30, J-HS B
Electron capture processes in intermediate-mass stars — •Dag F. Strömberg1,2, Gabriel Martínez-Pinedo2,1, and Karlheinz Langanke2,1 — 1Institut für Kernphysik (Theoriezentrum), Technische Universität Darmstadt, Schlossgartenstr. 2, 64289 Darmstadt, Germany — 2Gesellschaft für Schwerionenforschung, Planckstr. 1, 64259 Darmstadt, Germany
Following carbon burning, intermediate-mass stars (initial mass ∼7−11 solar masses) form degenerate cores composed primarily of 16O and 20Ne, with smaller amounts of 23Na, 24Mg and 25Mg. When such cores grow massive enough electron capture reactions are triggered due to the high chemical potential of the electrons. Most notably, the double electron capture 20Ne→20F→20O releases enough heat to ignite runaway oxygen burning resulting in either a collapse to a neutron star or a thermonuclear explosion.
In this contribution we will discuss how details of the electron capture reactions can affect the conditions at oxygen ignition and thus the outcome of the runaway reaction. Due to the comparatively low temperatures (T<1 GK) prior to oxygen ignition the electron capture rates are fully determined by a small number of transitions. Some of these are forbidden, such as the recently measured 0+→2+ transition between the ground states of 20Ne and 20F. We will examine the impact of such transitions and how this depends on the growth rate and composition of the core.
This work is supported by the Deutsche Forschungsgemeinschaft via contract SFB 1245 and the EU COST Action CA1611 (ChETEC).