14071447
HAVE WE OBSERVED THE SKIN VIBRATION OF REALISTIC STRANGE STARS (ReSS)
Skin vibration of ReSS and consequent resonance absorption can account for the absorption lines in the spectrum of X-ray emission from many compact stellar objects and in particular, the stars J1210-5226 and RXJ1856-3754. Observations of the X-ray spectrum of these stars is difficult to explain, if they are neutron stars.
10219702
Stability of strange stars (SS) derived from a realistic equation of state.
A realistic EOS (equation of state) leads to strange stars (ReSS) which are compact in the mass–radius (M–R) plot, close to the Schwarzschild limiting line.1 Many of the observed stars fit in with this kind of compactness, irrespective of whether they are X-ray pulsars, bursters or soft γ repeaters or even radio pulsars. We point out that a change in the radius of a star can be small or large, when its mass is increasing and this depends on the position of a particular star on the M–R curve. We carry out a stability analysis against radial oscillations and compare with the EOS of other SS models. We find that the ReSS is stable and an M–R region can be identified to that effect.
197508300
CMB power spectrum estimation with non-circular beam and incomplete sky coverage
15400142
Strange Stars : An interesting member of the compact object family
We have studied strange star properties both at zero temperature and at finite temperatures and searched signatures of strange stars in gamma‐ray, x‐ray and radio astronomy. We have a set of Equations of State (EoS) for strange quark matter (SQM) and solving the TOV equations, we get the structure of strange stars. The maximum mass for a strange star decreases with the increase of temperature, because at high temperatures, the EoS become softer. One important aspect of strange star is that, surface tension depends on the size and structure of the star and is significantly larger than the conventional values. Moment of inertia is another important parameter for compact stars as by comparing theoretical values with observed estimate, it is possible to constrain the dense matter Equation of State. We hope that this approach will help us to decide whether the members of the double pulsar system PSR J0737‐3039 are neutron stars or strange stars.
8136121
Chromo-thermal instabilities and collapse of quark stars to black holes Astrophysical Implications
We have studied the effects of temperature on the properties of strange stars. We find that the maximum mass of the strange star decreases with the increase of temperature, because at high temperatures the equation of states become softer. Moreover, if the temperature of a strange star increases keeping its baryon number fixed, its gravitational mass increases and radius decreases which leads to a limiting temperature where it turns into a black hole. These features of strange stars is a combined effect of change of gluon mass and the quark distribution function with temperature. We have discovered a new kind of radial oscillations of strange stars driven by what we named chromo-thermal instability. This instability and the related radial oscillations of the star is inherent to strange quark matter making strange stars even more exotic than neutron stars within astrophysical context. In particular, we discuss the relevance of our findings in the astrophysics of core collapse supernovae and gamma ray bursts. Subject headings: compact object – neutron star – strange star – black hole – GRB – afterglow
15882822
Entropy & viscosity bound of strange stars
At finite temperature (T) there is a link with general relativity and hydrodynamics that leads to a lower bound for the ratio of shear viscosity and entropy density (\eta/s). We find that the bound is saturated in the simple model for quark matter that we use for strange stars at T = 80 MeV, at the surface of a strange star. At this T we have the possibility of cosmic separation of phases. We find that, although strongly correlated, the quark matter at the surface of strange stars constitute the most perfect interacting fluid permitted by nature. At the centre of the star, however, the density is higher and conditions are more like the results found for perturbative QCD.
119278726
ANISOTROPIC COMPACT STARS WITH VARIABLE COSMOLOGICAL CONSTANT
Recently, the small value of the cosmological constant and its ability to accelerate the expansion of the universe is of great interest. We discuss the possibility of forming of anisotropic compact stars from this cosmological constant as one of the competent candidates of dark energy. For this purpose, we consider the analytical solution of Krori and Barua metric. We take the radial dependence of cosmological constant and check all the regularity conditions, TOV equations, stability and surface redshift of the compact stars. It has been shown as conclusion that this model is valid for any compact star and we have cited 4U 1820-30 as a specific example of that kind of star.
118446785
Wormholes supported by two non-interacting fluids
We provide a new matter source that supplies fuel to construct wormhole spacetime. The exact wormhole solutions are found in the model having, besides real matter, an anisotropic dark energy. We have shown that the exotic matters that are the necessary ingredients for wormhole physics violate null and weak energy conditions but obey strong energy condition marginally. Though the wormhole comprises of exotic matters yet the effective mass remains positive. We have calculated the effective mass of the wormhole up to 8 km from the throat (assuming throat radius as 4 km) as 1.3559M⊙. Some physical features are briefly discussed.
117617513
A class of solutions for Einstein field equations with spatially varying cosmological constant in spherically symmetric anisotropic source
In this work a class of interior solution for Einstein field equations corresponding to a spherically symmetric anisotropic fluid sphere has been obtained under the assumption that the cosmological constant is spatially variable. The solution obtained has the characteristics that the pressure and the cosmological parameter vanish at the centre and at the boundary with a maximum value somewhere inside the body. It has been argued that a variable $ \Lambda $ is as much important physically in Astrophysics as in Cosmology.
119307073
Anisotropic strange star with de Sitter spacetime
Stars can be treated as self-gravitating fluid. Krori and Barua (J. Phys. A., Math. Gen. 8:508, 1975) gave an analytical solution to that kind of fluids. In this connection, we propose a de Sitter model for an anisotropic strange star with the Krori–Barua spacetime. We incorporate the existence of the cosmological constant on a small scale to study the structure of anisotropic strange stars and come to the conclusion that this doping is very well compatible with the well-known physical features of strange stars.
117757665
Equation of state for asymmetric nuclear matter with infinite-order summation of ring diagrams
The particle-particle hole-hole ring-diagram summation method is employed to obtain the equation of state of asymmetric nuclear matter over a wide range of asymmetry fraction. Compared with Brueckner Hartree-Fock and model-space Brueckner Hartree-Fock calculations, this approach gives a softer equation of state, increased symmetry energy and a lower value for the incompressibility modulus which agrees quite well with the values used in the hydrodynamical model for the supernovae explosion.