Mass-luminosity relation for massive stars

A catalog of massive (⩾10 M _⊙) stars in binary and multiple systems with well-known masses and luminosities has been compiled. The catalog is analyzed using a theoretical mass-luminosity relation. This relation allows both normal main-sequence stars and stars with peculiarities: with clear manifestations of mass transfer, mass accretion, and axial rotation, to be identified. Least-squares fitting of the observational data in the range of stellar masses 10M _⊙ ⩽ M ≲ 50 M _⊙ yields the relation L ∼ M ^2.76. An erratum to this article is available at .     

Similarity theory of stellar models and the structure of very massive stars

The similarity theory of stellar models is used to study the properties of very massive stars when all the opacity sources, except the Thomson scattering, can be disregarded. The dimensionless internal structure of such stars is essentially independent of the energy generation law. It is shown that the mass-luminosity relation can be fitted by an analytical expression that is virtually universal with regard to the chemical composition and the energy generation law. A detailed comparison with the Eddington standard model is made. The application of the results obtained to the observations of massive stars is briefly discussed.     

Model equation of state to investigate the structure and evolution of superdense stars with a phase transition

A model equation of state that describes the phase transition to quark matter is proposed. This equation of state is used to construct hydrostatically equilibrium stellar models for various values of the entropy and the negative bag constant B added to the pressure of quarkmatter. Parameters of the calculated models and conditions for their stability are discussed.     

Variational principle for stars with a phase transition

The variational principle for stars with a phase transition has been investigated. The term outside the integral in the expression for the second variation of the total energy of a star is shown to be obtained by passage to the limit from the integration over the region of mixed states in the star. The form of the trial functions ensuring this passage has been found. All of the results have been generalized to the case where general relativity is applicable. The known criteria for the dynamical stability of a star when a new phase appears at its center are shown to follow automatically from the variational principle. Numerical calculations of hydrostatically equilibrium models for hybrid stars with a phase transition have been performed. The form of the trial functions for the second variation of the total energy of a star that describes almost exactly the stability boundaries of such stellar models is proposed.     

Low-Mass Neutron Stars with Rotation

Astronomy Letters - The properties of low-mass neutron stars with rigid rotation are considered. The possible evolution paths of such stars in a close binary system with mass transfer are...     

Special point on the mass-radius diagram of hybrid stars

An analytical study that explains the existence of a very small region on the mass-radius (M-R) diagram of hybrid stars where all of the lines representing the sequences of models with different constant values of the bag constant B intersect is presented. This circumstance is shown to be a consequence of the linear dependence of pressure on energy density in the quark cores of hybrid stars.