Structure and stability of strange and charm stars at finite temperatures

Abstract

This paper consists of four parts. Part one deals with an investigation of the properties of P-equilibrated, electrically charged neutral quark-star matter at zero and finite temperatures, and the determination of its equation of state. In part two, the properties of sequences of quark stars, divided into strange-and charm-quark stars, depending on quark-flavor content, are investigated. The strange stars are constructed for absolutely stable strange-quark matter, whose energy per baryon number lies below the one in 56Fe. In part three, the electrostatic potential of electrons inside and in the close vicinity outside of strange stars, which is of decisive importance for the possible existence of nuclear crusts on the surfaces of such stars, is computed. It is found that finite temperatures lead to a considerable reduction of the electrostatic electron potential at the surface of a strange star, which is accompanied by a strong reduction of the Coulomb barrier associated with the difference of the electrostatic potential at the surface of the star's strange-matter core and the base of the crust. This finding is of great importance for the stable existence of crusts on strange stars, since the Coulomb barrier plays the important role of preventing atomic nuclei bound in the nuclear crust from coming into contact with the star's strange-matter core, where atomic matter by hypothesis would be converted into strange matter. The structure and stability of quark stars against radial oscillations is discussed in part four, where it is found that charm-quark stars are unstable against radial oscillations. Thus no charm-quark stars (and, as is demonstrated too, no quark-matter stars possessing still higher central mass densities) can exist in nature.PACS number(s):

Third family of superdense stars in the presence of antikaon condensates

“…dM/dε c > 0. Though the positive slope of a steller sequence is a necessary condition for stability, dynamical stability requires the analysis of the fundamental mode of radial vibration [5,6,[39][40][41]. In the third family branches in Fig.…”

Quark-nuclear hybrid star equation of state with excluded volume effects

“…For our further discussion, we shall be operating in the zero-temperature regime, further reducing the parameters to just the baryon number. For quark matter in compact star systems, due to the large threshold chemical potential for strange quarks ∼ 1500 MeV (and larger for the heavier flavors of quarks), contributions from heavy quarks are negligible [35] and therefore not considered in this approach. Utilizing the above mentioned assumptions, both the hadronic and quark-matter phase in compact stars obey the following conditions.…”

Consistency between deep crustal heating of strange stars in superbursters and soft X-ray transients

“…Because strange quark matter is self bound the density is largely constant in the core dropping by only a factor of a few from the center to the surface, where it goes from above nuclear density to zero within a few fm -see e.g. Alcock et al (1986);Haensel et al (1986); Glendenning & Weber (1992); Kettner et al (1995); Weber (1999);Glendenning (2000); Zdunik et al (2001);Zdunik (2002) for details on the global properties of strange stars. Since the electrostatic force is much weaker than the strong force confining the quarks, some of the electrons necessary to create an overall charge neutral object will form a thin atmosphere outside the quark phase held in place by a huge electric field.…”