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1.
We find that in general relativity slow down of the pulsar rotation due to the magnetodipolar radiation is more faster for
the strange star with comparison to that for the ordinary neutron star of the same mass. Comparison with astrophysical observations
on pulsars spindown data may provide an evidence for the strange star existence and, thus, serve as a test for distinguishing
it from the neutron star. 相似文献
2.
In this paper we have studied a particular class of exact solutions of Einstein’s gravitational field equations for spherically symmetric and static perfect fluid distribution in isotropic coordinates. The Schwarzschild compactness parameter, GM/c 2 R, can attain the maximum value 0.1956 up to which the solution satisfies the elementary tests of physical relevance. The solution also found to have monotonic decreasing adiabatic sound speed from the centre to the boundary of the fluid sphere. A wide range of fluid spheres of different mass and radius for a given compactness is possible. The maximum mass of the fluid distribution is calculated by using stellar surface density as parameter. The values of different physical variables obtained for some potential strange star candidates like Her X-1, 4U 1538–52, LMC X-4, SAX J1808.4?3658 given by our analytical model demonstrate the astrophysical significance of our class of relativistic stellar models in the study of internal structure of compact star such as self-bound strange quark star. 相似文献
3.
Strange stars are compact objects similar to neutron stars composed of strange matter. This paper investigates the observational effects of the strong interaction between quarks. We believe: 1) that the conversion of a neutron star to a strange star is a large “period glitch” which is determined by the strong interaction; 2) that the strong interaction results in effective damping of oscillation of hot strange stars, which could be a new mechanism of driving supernova explosions; 3) that the strong interaction increases the difference in rotation between strange and neutron stars under high temperatures, making the minimum period for strange stars lower than that for neutron stars. 相似文献
4.
5.
We study the conversion of a neutron star to a strange star as a possible energy source for gamma-ray bursts. We use different recent models for the equation of state of neutron star matter and strange quark matter. We show that the total amount of energy liberated in the conversion is in the range of &parl0;1-4&parr0;x1053 ergs (1 order of magnitude larger than previous estimates) and is in agreement with the energy required to power gamma-ray burst sources at cosmological distances. 相似文献
6.
In this work, we first obtain the hydrostatic equilibrium equation in dilaton gravity. Then, we examine some of the structural characteristics of a strange quark star in dilaton gravity in the context of Einstein gravity. We show that the variations of dilaton parameter do not affect the maximum mass, but variations in the cosmological constant lead to changes in the structural characteristics of the quark star. We investigate the stability of strange quark stars by applying the MIT bag model with dilaton gravity. We also provide limiting values for the dilaton field parameter and cosmological constant. We also study the effects of dilaton gravity on the other properties of a quark star such as the mean density and gravitational redshift.We conclude that the last reported value for the cosmological constant does not affect the maximum mass of a strange quark star. 相似文献
7.
Huan-yu Jia Bao-xi Sun Jie Meng En-guang Zhao 《Chinese Astronomy and Astrophysics》2002,26(4):901-413
Neutron stars are studied in the framework of the relativistic mean field theory of interacting nucleons, hyperons, and mesons. Within the hadronic freedom, the cores of neutron stars are found to be dominated by hyperons when the density is sufficiently high. The influence of hyperon coupling constants on the transition from a neutron star to a hyperon-dominated strange neutron star is also investigated. It is found that the transition density gets its minimum value when the ratio of hyperon coupling constant to nucleon's takes the value of 0.65, and the calculated maximum mass of the neutron star is 1.4 M which lies within the range of the observational results. 相似文献
8.
Finite temperature calculations for the bulk properties of a strange star using a many-body approach
We have considered a hot strange star matter, just after the collapse of a supernova, as a composition of strange, up and
down quarks to calculate the bulk properties of this system at finite temperature with the density dependent bag constant.
To parameterize the density dependent bag constant, we use our results for the lowest-order constrained variational (LOCV)
calculations of asymmetric nuclear matter. Our calculations for the structure properties of the strange star at different
temperatures indicate that its maximum mass decreases by increasing the temperature. We have also compared our results with
those of a fixed value of the bag constant. It can be seen that the density-dependent bag constant leads to higher values
of the maximum mass and radius for the strange star. 相似文献
9.
We investigate the influence of the following parameters on the crust properties of strange stars: the strange quark mass
(m
s), the strong coupling constant (αc) and the vacuum energy density (B). It is found that the mass density at the crust base of strange stars cannot reach the neutron drip density. For a conventional
parameter set of m
s=200 MeV, B
1/4 = 145 MeV and αc = 0.3, the maximum density at the crust base of a typical strange star is only 5.5 × 1010 gcm-3, and correspondingly the maximum crust mass is 1.4 ×10-6 M⊙. Subsequently, we present the thermal structure and the cooling behavior of strange stars with crusts of different thickness,
and under different diquark pairing gaps. Our work might provide important clues for distinguishing strange stars from neutron
stars. 相似文献
10.
《Chinese Astronomy and Astrophysics》2005,29(1):53-60
Taking into account the peculiar properties of hybrid stars, stars containing both a core of strange quark matter and the solid crust of a neutron star, and employing a fully self-consistent second-order correction technique, we study the time scale of bulk viscosity dissipation at the low temperature limit (T < 109 K) and with this time scale we calculate the critical spin frequency of the hybrid star. It is found that its minimal value is 704.42 Hz (corresponding to a pulse period of 1.42 ms). When this is compared with the periods of neutron and strange stars, a better interpretation of the observational data is obtained. 相似文献
11.
RX J1856.5-3754 has been proposed as a strange star candidate due to its very small apparent radius measured from its X-ray
thermal spectrum. However, its optical emission requires a much larger radius and thus most of the stellar surface must be
cold and undetectable in X-rays. In the case the star is a neutron star such a surface temperature distribution can be explained
by the presence of a strong toroidal field in the crust (Pérez-Azorín et al.: Astron. Astrophys. 451, 1009 (2006); Geppert
et al.: Astron. Astrophys. 457, 937 (2006)) We consider a similar scenario for a strange star with a thin baryonic crust to
determine if such a magnetic field induced effect is still possible.
This work was partially supported by PAPIIT, UNAM, grant IN119306. J.A.H. studies at UNAM and travel to London are covered
by fellowships from UNAM’s Dirección General de Estudios de Posgrado. 相似文献
12.
The “strange star - NDAF” model (NDAF: Neutrino Dominated Accretion Flow) is proposed as an alternative central engine of gamma-ray bursts for unifying the interpretation of the prompt emission and postburst activities of gamma-ray bursts. The structure of NDAF around a strange star is calculated. Different from other central compact objects, the strange star will feed back the phase transition energy of strangization on the accretion flow, with neutrinos as energy carriers. The friction between NDAF and strange star is ignored in this paper. The results indicate: firstly, the structure of NDAF around a strange star is sensitive to accretion rate; secondly, if accretion rate is larger than 0.18 M? s-1, the “strange star - NDAF” model can unify the explanation on the prompt emission and postburst activities of gamma-ray bursts, and the range of allowable accretion rates is wider than that in frictionless “neutron star - NDAF” models; thirdly, the range of annihilation energy of “strange star - NDAF” model is very wide, when the accretion rate is higher than 0.3 M? s-1, the annihilation energy is greater than 1051 erg; finally, if the accretion rate is greater than 0.3 M? s-1, the annihilation energy of “strange star - NDAF” model is larger than what of “black hole - NDAF” model at the same accretion rate by more than one order of magnitude, it is favorable to explaining some extremely energetic gamma-ray bursts. 相似文献
13.
本文利用广义相对论数值计算研究了从不同物态的中子星到不同物志的奇异星的转变过程．对于热中子星，转变可引起很大的脉冲星周期突变，其大小取决于中子物质的物态，其时标取决于奇异物质的物态．对于冷中子星，转变可产生一类γ射线爆． 相似文献
14.
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
15.
We present the results of numerical simulations of stationary, spherically outflowing, e ± pair winds, with total luminosities in the range 1034–1042 ergs s?1. In the concrete example described here, the wind injection source is a hot, bare, strange star, predicted to be a powerful source of e ± pairs created by the Coulomb barrier at the quark surface. We find that photons dominate in the emerging emission, and the emerging photon spectrum is rather hard and differs substantially from the thermal spectrum expected from a neutron star with the same luminosity. This might help distinguish the putative bare strange stars from neutron stars. 相似文献
16.
A. I. Chugunov 《Monthly notices of the Royal Astronomical Society》2006,371(1):363-368
We study acoustic oscillations (eigenfrequencies, velocity distributions, damping times) of normal crusts of strange stars. These oscillations are very specific because of huge density jump at the interface between the normal crust and the strange matter core. The oscillation problem is shown to be self-similar. For a low (but non-zero) multipolarity l , the fundamental mode (without radial nodes) has a frequency of ∼300 Hz and mostly horizontal oscillation velocity; other pressure modes have frequencies ≳20 kHz and almost radial oscillation velocities. The latter modes are similar to radial oscillations (having approximately the same frequencies and radial velocity profiles). The oscillation spectrum of strange stars with crust differs from the spectrum of neutron stars. If detected, acoustic oscillations would allow one to discriminate between strange stars with crust and neutron stars and constrain the mass and radius of the star. 相似文献
17.
Valery Suleimanov Juri Poutanen 《Monthly notices of the Royal Astronomical Society》2006,369(4):2036-2048
Spectra of the spreading layers on the neutron star surface are calculated on the basis of the Inogamov–Sunyaev model taking into account general relativity correction to the surface gravity and considering various chemical composition of the accreting matter. Local (at a given latitude) spectra are similar to the X-ray burst spectra and are described by a diluted blackbody. Total spreading layer spectra are integrated accounting for the light bending, gravitational redshift and the relativistic Doppler effect and aberration. They depend slightly on the inclination angle and on the luminosity. These spectra also can be fitted by a diluted blackbody with the colour temperature depending mainly on a neutron star compactness. Owing to the fact that the flux from the spreading layer is close to the critical Eddington, we can put constraints on a neutron star radius without the need to know precisely the emitting region area or the distance to the source. The boundary layer spectra observed in the luminous low-mass X-ray binaries, and described by a blackbody of colour temperature T c = 2.4 ± 0.1 keV , restrict the neutron star radii to R = 14.8 ± 1.5 km (for a 1.4-M⊙ star and solar composition of the accreting matter), which corresponds to the hard equation of state. 相似文献
18.
The discovery of kilohertz quasi-periodic oscillations (kHz QPOs) in low-mass X-ray binaries (LMXBs) with the Rossi X-Ray Timing Explorer has stimulated extensive studies of these sources. Recently, Osherovich & Titarchuk suggested a new model for kHz QPOs and the related correlations between kHz QPOs and low-frequency features in LMXBs. Here we use their results to study the mass-radius relation for the atoll source 4U 1728-34. We find that, if this model is correct, 4U 1728-34 is possibly a strange star rather than a neutron star. 相似文献
19.
Resonant cyclotron scattering in pulsar magnetospheres and its application to isolated neutron stars
Resonant cyclotron scattering(RCS)in pulsar magnetospheres is considered.The photon diffusion equation(Kompaneets equation)for RCS is derived.The photon system is modeled three dimensionally.Numerical calculations show that there exist not only up scattering but also down scattering of RCS,depending on the parameter space.RCS's possible applications to spectral energy distributions of magnetar candidates and radio quiet isolated neutron stars(INSs)are pointed out.The optical/UV excess of INSs may be caused by the down scattering of RCS.The calculations for RX J1856.5-3754 and RX J0720.4-3125 are presented and compared with their observational data.In our model,the INSs are proposed to be normal neutron stars,although the quark star hypothesis is still possible.The low pulsation amplitude of INSs is a natural consequence in the RCS model. 相似文献
20.
The magneto-rotational evolution of a neutron star in the massive binary system 4U 2206+54 is discussed in light of the recent
discovery of its 5555 s rotational period and its average rate of spin-down. We show that this behavior of the neutron star
means that its magnetic field exceeds the quantum mechanical critical limit and it is an accretion magnetar. The system’s
evolution is explained by wind driven mass transfer without formation of an accretion disk. The constant character of the
x-ray source indicates a steady rate of accretion and raises anew the question of the stability of the boundary of the magnetosphere
of a star undergoing spherical accretion. A solution to this problem is also a key to determining the mechanism for the slowing
down of the star’s rotation. 相似文献