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Astron. Astrophys. 349, 135-150 (1999)

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Nuclear properties in early stages of stellar collapse

F.K. Sutaria 1, A. Ray 2,3, J.A. Sheikh 2,4 and P. Ring 4

1 Inter University Center for Astronomy and Astrophysics, Pune 411 007, India
2 Tata Institute of Fundamental Research, Mumbai 400 005, India
3 Lab for High Energy Astrophysics, NASA/Goddard Space Flight Center, Greenbelt, MD 20771, USA
4 Physik-Department, Technische Universitat München, D-85747 Garching, Germany

Received 31 July 1998 / Accepted 13 April 1999


The spectroscopy of electron capture neutrinos emitted from nearby pre-supernova collapsing stars before the neutrino trapping sets in, can yield useful information on the physical conditions and on the nuclear composition of the core. The neutrino spectrum depends on the thermodynamic conditions of the core, the nuclear abundances, the lepton fractions and relevant nuclear properties. In the pre-trapping core, the density ranges from [FORMULA] g/cm3 and the temperature from [FORMULA] MeV. The nuclear abundances can be obtained under the assumption of Nuclear Statistical Equilibrium (NSE). The nuclear abundances as well as the electron capture rates are thus determined, among other things, by the nuclear binding energies and the free nucleon chemical potentials. Because shell and pairing effects persist strongly up to temperatures of [FORMULA] MeV, any equation of state (EOS) relevant to this phase of the collapse must reproduce well the zero temperature nuclear properties and it must show a smooth transition to the known high temperature and high density limits. In this work we use the microscopic Relativistic Mean Field (RMF) theory based on a Lagrangian with non-linear self-interactions of the [FORMULA]-field for the neutron-rich nuclei of interest in the [FORMULA] shell to determine nuclear chemical potentials. We compare these results with those computed from an EOS calculated with the macroscopic liquid drop model. We also discuss extensions to finite temperature and we incorporate nuclear lattice effects into the microscopic calculations.

Key words: stars: supernovae: general – equation of state – nuclear reactions, nucleosynthesis, abundances

Send offprint requests to: A. Ray (akr@tifr.res.in)

Correspondence to: Tata Institute of Fundamental Research, Mumbai 400 005, India

© European Southern Observatory (ESO) 1999

Online publication: August 25, 1999