摘要:

According to standard wisdom, six different nuclear burning stages, from hydrogen to silicon burning, can occur during the hydrostatic evolution of stars. However, several instabilities can lead to the mixing of layers with different compositions and produce non-standard composition mixtures. Those—when at high enough temperatures—burn due to nuclear reactions which are unimportant otherwise. We provide various examples of such occurrences, for different ratios of burning over mixing time scale. ©2001 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.1372776

出版商:AIP    

年代:1901

数据来源: AIP

摘要:

With a kinetic energy of∼1051&hthinsp;ergs,supernova explosions influence the birth of stars, are the source of the energetic cosmic-rays that irradiate us on Earth, and collectively, by their prodigious energy and momentum input during the birth of galaxies in the infant universe, may have helped shape the galaxies themselves. The neutrinos produced in great numbers during the supernova event are implicated as the source of their explosive power and their study has exercised supernova modelers for forty years, some of them productive. In this contribution, I summarize various new ideas and speculations concerning supernova physics and the role of neutrinos. In particular, I review possible systematics of nickel yields and explosion energies with progenitor mass, evidence for asymmetries in the explosion itself, evidence for kicks to neutron stars in their supernova cradle, and an example of an important (but hitherto neglected) neutrino production process. I also summarize the expected and dramatic signature in underground neutrino detectors of a galactic stellar collapse and explosion. ©2001 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.1372777

出版商:AIP    

年代:1901

数据来源: AIP

摘要:

After decades of one-dimensional nucleosynthesis calculations, the growth of computational resources has meanwhile reached a level, which for the first time allows astrophysicists to consider performing routinely realistic multidimensional nucleosynthesis calculations in explosive and, to some extent, also in non-explosive environments. In the present contribution we attempt to give a short overview of the physical and numerical problems which are encountered in these simulations. In addition, we assess the accuracy that can be currently achieved in the computation of nucleosynthetic yields, using multidimensional simulations of core collapse supernovae as an example. ©2001 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.1372778

出版商:AIP    

年代:1901

数据来源: AIP

摘要:

Core of a neutron star consists of highly dense matter above normal nuclear density&rgr;0≃0.16&hthinsp;fm−3,where phase transitions are expected to take place. We review some phase transitions and recent topics of neutron stars. ©2001 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.1372779

出版商:AIP    

年代:1901

数据来源: AIP

摘要:

We present the first calculations to follow the evolution ofallstable isotopes and their abundant radioactive progenitors in a finely zoned stellar model from the onset of central hydrogen burning through explosion as a Type II supernova. An extended adaptive nuclear reaction network is implemented that contains about 700 isotopes during hydrogen and helium burning and more than 2500 isotopes during the supernova explosion. The calculations were performed for 15, 20, and25&hthinsp;M⊙Pop I stars using the most recently available set of experimental and theoretical nuclear data. We include revised opacity tables, take into account mass loss due to stellar winds, and implement revised weak interaction rates that significantly affect the properties of the presupernova core. An s-process is present, which, along with the usual nucleosynthesis from advanced burning stages and the explosion, produces nearly solar abundances for most nuclei up toA=60in the25&hthinsp;M⊙star. BetweenA=60andA=90we find that thes-process leads to an over-production of key nuclei by a factor ∼2–3. AboveA=90thes-process has makes little contribution, but we find the approximately solar production of many proton-rich isotopes above mass numberA=120due to the &ggr;-process. ©2001 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.1372780

出版商:AIP    

年代:1901

数据来源: AIP

摘要:

We have studied the &ngr;-driven winds from the nascent proto-neutron star. We have found in the general relativistic hydrodynamical simulations using the relativistic EOS table that the short expansion time scale is realized in the cases of massive and compact proto-neutron stars. Having the trajectories of ejecta, we have performed r-process calculations to find that a successful r-process up toA∼195occurs in the &ngr;-driven winds with a short expansion time scale. ©2001 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.1372781

出版商:AIP    

年代:1901

数据来源: AIP

摘要:

Although important effort has been devoted in the last decades to measure reaction cross sections and decay half-lives of interest in astrophysics, most of the nuclear astrophysics applications still require the use of theoretical predictions to estimate experimentally unknown rates. The nuclear ingredients to the reaction or weak interaction models should preferentially be estimated from microscopic or semi-microscopic global predictions based on sound and reliable nuclear models which, in turn, can compete with more phenomenological highly-parametrized models in the reproduction of experimental data. The latest developments made in deriving the nuclear inputs of relevance in astrophysics applications are reviewed. It mainly concerns nuclear structure properties (atomic masses, deformations, radii, etc&ellip;), nuclear level densities, nucleon and &agr;-optical potentials, &ggr;-ray and Gamow-Teller strength functions. ©2001 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.1372782

出版商:AIP    

年代:1901

数据来源: AIP

摘要:

This is an overview of the current efforts to clarify the age of the universe from nucleocosmochronology, globular clusters, local stars and white dwarf cooling, and the Hubble expansion rate. A particular emphasis is placed upon areas where nuclear physics continues to play a crucial role. There have been numerous recent breakthroughs in cosmology, nucleosynthesis and astrometry. These have significantly refined our understanding of cosmic ages. Although in the past these various methods seemed to imply different ages (the age problem), there is now mounting evidence that all of these methods point toward a concordant age of13±2&hthinsp;Gyr.©2001 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.1372783

出版商:AIP    

年代:1901

数据来源: AIP

摘要:

The role of neutron cross section data on the analysis and interpretation of the Re/Os clock is described in some detail. Proposals for reducing some of the remaining uncertainties on the nuclear physics aspects of the clock are discussed. ©2001 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.1372784

出版商:AIP    

年代:1901

数据来源: AIP

摘要:

©2001 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.1372785

出版商:AIP    

年代:1901

数据来源: AIP