Strange quark matter and models of strange stars     

Yu. L. Vartanyan  A. R. Arutyunyan  A. K. Grigoryan 《Astrophysics》1994,37(3):271-280

In the framework of the MIT bag model we consider absolutely stable strange quark matter consisting of u, d, and s quarks and electrons. For a realistic range of parameters of the quark bag we compute the threshold density for the appearance of strange quark matter that is realized on the surface of self-sustaining strange stars. On the basis of twelve calculated equations of state we give a detailed study of the series of configurations of strange stars consistent with the best known observational data. We show that the binding energy of the models depends essentially on the quark-gluon interaction constant _c.Translated fromAstrofizika, Vol. 37, No. 3, 1994.The authors are grateful to E. V. Chubaryan and A. M. Atoyan for assistance in overcoming the information blockade. The present paper was written in the framework of area 46/101 93-353, supported by the Ministry of Higher Education and Science of the Republic of Armenia.  相似文献   

Composition and Formation Conditions of Lower Eocene Shallow-Marine Carbonates in Southern Armenia     

Fokin  P. A.  Zakrevskaya  E. Yu.  Sahakyan  L. G.  Grigoryan  T. E. 《Lithology and Mineral Resources》2021,56(5):438-459

Lithology and Mineral Resources - Nummulite facies are known to be a good indicator of Eocene shallow-water paleoenvironments. Nummulitic limestones are widespread in the Lower Eocene of...  相似文献   

Theory of accreting neutron stars. I     

G. P. Alodzhants  L. Sh. Grigoryan  G. S. Saakyan  A. V. Sarkisyan 《Astrophysics》1988,29(3):763-768

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A red giant with a strange star as its core. Principal similarities to and differences from Thorne-Zytkow objects     

G. S. Hajyan  Yu. L. Vartanyan  A. K. Grigoryan 《Astrophysics》1998,41(4):349-355

A model red giant with a mass of 5 M_⊙ a luminosity of 41,740 L_⊙, and a radius of 960 R_⊙ and with a strange quark star as its core is constructed, and it is compared with a Thorne-Zytkow object having similar integrated parameters. The difference in internal structure is manifested right at the dense core: matter above the core is held off only by γ rays from the strange star, and convection is maintained down to the strange star. The lifetime of a red giant containing a strange star turns out to be almost 500 times shorter than that of a Thorne-Zytkow object — on the order of 10⁵ years. Translated from Astrofizika, Vol. 41. No. 4, pp. 533–544, October–December, 1998.  相似文献   

Theory of gravitation taking into account the part played by the vacuum. II     

L. Sh. Grigoryan  G. S. Saakyan 《Astrophysics》1986,24(3):338-344

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A numerical method of studying the evolution of spherically symmetric superdense celestial bodies     

O. A. Grigoryan  A. A. Sadoyan 《Astrophysics》1994,37(4):372-378

For fully relativistic strong gravitational fields we obtain a consistent set of hydrodynamic and field equations that describe the propagation of all types of waves in matter (from small perturbations to shock waves). We obtain an algorithm for numerical solution of these equations for certain equations of state of degenerate matter.Translated fromAstrofizika, Vol. 37, No. 4, 1994.We are very grateful to Prof. Chubarian for valuable instructions and discussions. The work of A. Sadoyan was sponsored in part by ISF grant RYG000.  相似文献   

Phenomenological approach to the theory of the gravitational vacuum     

L. Sh. Grigoryan  G. S. Saakyan 《Astrophysics》1984,20(3):344-353

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Presence of π−1 mesons in heavy atomic nuclei     

L. Sh. Grigoryan  G. S. Saakyan 《Astrophysics》1977,13(3):260-265

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Generalized bimetric theory of gravitation     

L. Sh. Grigoryan  A. A. Saaryan 《Astrophysics》1989,31(2):625-632

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Strange stars and their cooling with positron electrical neutralization of quark matter     

G. S. Hajyan  Yu. L. Vartanyan  A. K. Grigoryan 《Astrophysics》1999,42(4):467-476

Questions of the equilibrium, stability, and observational manifestations of strange stars are considered, in which electrical neutralization of the quark matter is provided by positrons, as occurs for some sets of bag parameters resulting in a stiffer equation of state. Such models consist entirely of self-contained, strange quark matter and their maximum mass reaches 2.4–2.5 M_⊙ with a radius of 13–14 km. The cooling of such strange quark stars both in the absence and in the presence of mass accretion is investigated. It is shown that in the absence of mass accretion onto the strange star, the dependence of temperature (T, K) on age (t, yr) depends very little on the mass of the configuration and has the form T ≈ 2.3·10⁸r^−1/5. If the star’s initial temperature is sufficiently high (T₀≥2·10¹⁰K), then the total number of electron-positron pairs emitted does not depend on it and is determined only by the total mass of the configuration. In the case of accretion, the annihilation of electrons of the infalling fatter with positrons of the strange quark matter results in the emission of γ-rays with an energy of∼0.5 MeV, by observing which one can distinguish candidates for strange stars. The maximum temperature of strange stars with mass accretion is calculated. Translated from Astrofizika, Vol. 42, No. 4, pp. 617–630, October–December, 1999.  相似文献