CHARGED-PARTICLE AND NEUTRON-CAPTURE PROCESSES IN THE HIGH-ENTROPY WIND OF CORE-COLLAPSE SUPERNOVAE

Journal Article · Thu Apr 01 00:00:00 EDT 2010 · Astrophysical Journal

DOI:https://doi.org/10.1088/0004-637X/712/2/1359· OSTI ID:21394170

Farouqi, K; Truran, J W ^[1]; Kratz, K -L ^[2]; Pfeiffer, B ^[3]; Rauscher, T

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1. Department of Astrophysics and Astronomy, University of Chicago, Chicago, IL 60637 (United States)
2. HGF Virtuelles Institut fuer Kernstruktur und Nukleare Astrophysik, Universitaet Mainz, D-55128 Mainz (Germany)
3. Institut fuer Kernchemie, Universitaet Mainz, D-55128 Mainz (Germany)

The astrophysical site of the r-process is still uncertain, and a full exploration of the systematics of this process in terms of its dependence on nuclear properties from stability to the neutron drip-line within realistic stellar environments has still to be undertaken. Sufficiently high neutron-to-seed ratios can only be obtained either in very neutron-rich low-entropy environments or moderately neutron-rich high-entropy environments, related to neutron star mergers (or jets of neutron star matter) and the high-entropy wind of core-collapse supernova explosions. As chemical evolution models seem to disfavor neutron star mergers, we focus here on high-entropy environments characterized by entropy S, electron abundance Y{sub e} , and expansion velocity V{sub exp}. We investigate the termination point of charged-particle reactions, and we define a maximum entropy S{sub final} for a given V{sub exp} and Y{sub e} , beyond which the seed production of heavy elements fails due to the very small matter density. We then investigate whether an r-process subsequent to the charged-particle freeze-out can in principle be understood on the basis of the classical approach, which assumes a chemical equilibrium between neutron captures and photodisintegrations, possibly followed by a beta-flow equilibrium. In particular, we illustrate how long such a chemical equilibrium approximation holds, how the freeze-out from such conditions affects the abundance pattern, and which role the late capture of neutrons originating from beta-delayed neutron emission can play. Furthermore, we analyze the impact of nuclear properties from different theoretical mass models on the final abundances after these late freeze-out phases and beta-decays back to stability. As only a superposition of astrophysical conditions can provide a good fit to the solar r-abundances, the question remains how such superpositions are attained, resulting in the apparently robust r-process pattern observed in low metallicity stars.

• OSTI ID: 21394170
• Journal Information: Astrophysical Journal, Vol. 712, Issue 2; Other Information: DOI: 10.1088/0004-637X/712/2/1359; ISSN 0004-637X
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTROPHYSICS
COSMOLOGY AND ASTRONOMY
ABUNDANCE
ASTROPHYSICS
BETA DECAY
CAPTURE
CHARGED PARTICLES
CHARGED-PARTICLE REACTIONS
DELAYED NEUTRONS
ELECTRONS
ENTROPY
FREEZING OUT
NEUTRON REACTIONS
NEUTRON STARS
NUCLEAR PROPERTIES
NUCLEOSYNTHESIS
PHOTONUCLEAR REACTIONS
R PROCESS
SUN
SUPERNOVAE
BARYON REACTIONS
BARYONS
BINARY STARS
DECAY
ELEMENTARY PARTICLES
ERUPTIVE VARIABLE STARS
EVOLUTION
FERMIONS
FISSION NEUTRONS
HADRON REACTIONS
HADRONS
LEPTONS
MAIN SEQUENCE STARS
NEUTRONS
NUCLEAR DECAY
NUCLEAR REACTIONS
NUCLEON REACTIONS
NUCLEONS
PHYSICAL PROPERTIES
PHYSICS
SEPARATION PROCESSES
STAR EVOLUTION
STARS
SYNTHESIS
THERMODYNAMIC PROPERTIES
VARIABLE STARS