Ch. J. Velchev

Properties of the outer crust of strongly magnetized neutron stars from Hartree-Fock-Bogoliubov atomic mass models

The equilibrium properties of the outer crust of cold nonaccreting magnetars (i.e. neutron stars endowed with very strong magnetic fields) are studied using the latest experimental atomic mass data complemented with a microscopic atomic mass model based on the Hartree-Fock-Bogoliubov method. The Landau quantization of electron motion caused by the strong magnetic field is found to have a significant impact on the composition and the equation of state of crustal matter. It is also shown that the outer crust of magnetars could be much more massive than that of ordinary neutron stars.

Effects induced by nuclear deformations and electron correlations on the ground-state energy of low and multiply charged helium like ions in high-temperature plasmas

The present work deals with the effects induced by nuclear deformations and electron correlations on the electron ground-state energies of low and multiply charged helium like ions. Numerical calculations of the ground state energies including mass corrections and polarization of the electronic system have been performed for such heliumoid ions with nuclear charge number from Z=2 to Z=118. A perturbation method has been developed based on a variational principle using explicitly correlated two-electron wave functions. The mass-polarization term accounting for correlation effects has been included for the first time in the minimization procedure. These effects have been found to be particularly pronounced for ions corresponding to nuclear magic numbers. The present method provides a general framework for high-precision calculations of plasma diagnostics.

Effects of Isotope Characteristics on the Electron System Ground State Energy of Helium-Like Ions

The main goal of this work is to establish a link between the energy characteristics of the ground state of helium-like ions and the isotope characteristics of the nucleus of the system. High-precision calculations of the electron ground state energies of helium-like ions require to take into account the effects associated with nuclear characteristics and electron correlations. In our previous work, we calculated ground state electron energies, mass corrections and mass polarization effects of helium-like isoelectronic ions for the main nuclides with nuclear charge from \(Z=2\) to \(Z=118\). In the present work are discussed the results for 3833 existing isotopes in the same range of nuclear charge. The results presented are without the inclusion of the mass polarization effect in the minimization procedure. The complex dependence of the ground state energy on the mass corrections and mass polarization effects as a function of charge Z and neutron number N are studied. Staggering analysis for the ground state energy dependence on Z and N helped establish the electron characteristic dependence on the nuclear magic numbers.

Nuclear induces effects and mass correlations in low and multiply charged helium-like ions

The ground-state electron energies, the mass correction and mass polarization of low and multiply charged helium-like ions are analytically and numerically calculated. Approximately 3500 different kinds of ions with charge Z = 2 ÷ 118 are considered. The two-electron Schrodinger equation was solved using a discrete variational-perturbation approach developed by the authors and based on explicitly correlated wave functions. This approach takes into account the motion of the nucleus and yields accurate values for the electron characteristics. The results are presented with and without the inclusion of the mass polarization in the minimization procedure. The relative importance of mass correlations and relativistic effects in the formation of the electron energy characteristics of the helium-like ions are studied for different values of Z. The role of the inclusion of the mass polarization in the minimization procedure as an instrument to present and take into account the effects induced by the nuclear properties, structure and characteristics has been shown.

Unified description of dense matter in neutron stars and magnetars

We have recently developed a set of equations of state based on the nuclear energy density functional theory providing a unified description of the different regions constituting the interior of neutron stars and magnetars. The nuclear functionals, which were constructed from generalized Skyrme effective nucleon-nucleon interactions, yield not only an excellent fit to essentially all experimental atomic mass data but were also constrained to reproduce the neutron-matter equation of state as obtained from realistic many-body calculations.

Electron Correlation and Nuclear Motion Corrections to the Ground-State Energy of Helium Isoelectronic Ions from Li to Kr

Nonrelativistic energies for the ground state of helium isoelectronic ions with Z = 2–54 are computed. Calculations are performed using explicitly correlated wavefunctions of a generalized Hylleraas type. The variational procedure used allows solving the two-electron Schrodinger equation with a practically unlimited number of parameters, for trial wavefunctions expanded in products of positive powers of the Hylleraas coordinates. A non-conventional optimization procedure, involving nonlinear programming, is applied. The contribution of the various terms is assessed, including nuclear finite mass and polarization corrections. Our results are compared to other theoretical results. Combined with noncorrelated relativistic energies, they yield good agreement with available experimental data.