scholarly journals Charged anisotropic compact star core-envelope model with polytropic core and linear envelope

2021 ◽  
Vol 81 (10) ◽  
Author(s):  
S. A. Mardan ◽  
I. Noureen ◽  
A. Khalid
Keyword(s):  
Graphical Representation ◽  
Compact Star ◽  
Compact Object ◽  
Compact Objects ◽  
Compact Stars ◽  
Physical Parameters ◽  
Polytropic Equation ◽  
Envelope Model ◽  
Linear Envelope ◽  
The Stability

AbstractThis manuscript is related to the construction of relativistic core-envelope model for spherically symmetric charged anisotropic compact objects. The polytropic equation of state is considered for core, while it is linear in the case of envelope. We present that core, envelope and the Reissner Nordstr$$\ddot{o}$$ o ¨ m exterior regions of stars match smoothly. It has been verified that all physical parameters are well behaved in the core and envelope region for the compact stars SAX J1808.4-3658 and 4U1608-52. Various physical parameters inside star are discussed herein, non-singularity and continuity at the junction has been catered as well. Impact of charged compact object together with core-envelope model on the mass, radius and compactification factor is described by graphical representation in both core and envelop regions. The stability of the model is worked out with the help of Tolman–Oppenheimer–Volkoff equations and radial sound speed.

scholarly journals A new solution of embedding class I representing anisotropic fluid sphere in general relativity

2016 ◽  
Vol 25 (14) ◽  
pp. 1650099 ◽  
Author(s):  
Ksh. Newton Singh ◽  
Piyali Bhar ◽  
Neeraj Pant
Keyword(s):  
Graphical Representation ◽  
Compact Objects ◽  
Compact Stars ◽  
Anisotropic Fluid ◽  
Physical Parameters ◽  
Satisfactory Description ◽  
Anisotropic Fluid Sphere ◽  
Acceptable Model ◽  
Anisotropic Star ◽  
New Formula

In this paper, we are willing to develop a model of an anisotropic star by choosing a new [Formula: see text] metric potential. All the physical parameters like the matter density, radial and transverse pressure are regular inside the anisotropic star, with the speed of sound less than the speed of light. So the new solution obtained by us gives satisfactory description of realistic astrophysical compact stars. The model of this paper is compatible with observational data of compact objects like RX J1856-37, Her X-1, Vela X-12 and Cen X-3. A particular model of Her X-1 (Mass 0.98 [Formula: see text] and radius[Formula: see text]=[Formula: see text]6.7 km.) is studied in detail and found that it satisfies all the condition needed for physically acceptable model. Our model is described analytically as well as with the help of graphical representation.

Color-flavor locked compact stars: An exact solution approach

2021 ◽  
Author(s):  
Ksh. Newton Singh ◽  
Shyam Das ◽  
Piyali Bhar ◽  
Monsur Rahaman ◽  
Farook Rahaman
Keyword(s):  
Exact Solution ◽  
Compact Star ◽  
Density Perturbation ◽  
Compact Stars ◽  
Stable Configuration ◽  
Physical Parameters ◽  
Superconducting Gap ◽  
Field Equations ◽  
Critical Limit ◽  
Solution Approach

We present an exact solution that could describe compact star composed of color-flavor locked (CFL) phase. Einstein’s field equations were solved through CFL equation of state (EoS) along with a specific form of [Formula: see text] metric potential. Further, to explore a generalized solution we have also included pressure anisotropy. The solution is then analyzed by varying the color superconducting gap [Formula: see text] and its effects on the physical parameters. The stability of the solution through various criteria is also analyzed. To show the physical validity of the obtained solution we have generated the [Formula: see text] curve and fitted three well-known compact stars. This work shows that the anisotropy of the pressure at the interior increases with the color superconducting gap leading to decrease in adiabatic index closer to the critical limit. Further, the fluctuating range of mass due to the density perturbation is larger for lower color superconducting gap leading to more stable configuration.

Stability of generalized polytropic models

2019 ◽  
Vol 16 (04) ◽  
pp. 1950056
Author(s):  
I. Nazir ◽  
M. Azam
Keyword(s):  
Equation Of State ◽  
Local Density ◽  
Hydrostatic Equilibrium ◽  
Physical Parameters ◽  
Spherically Symmetric ◽  
Anisotropic Matter ◽  
Polytropic Equation ◽  
Density Perturbations ◽  
Radial Forces ◽  
The Stability

In this paper, we have investigated the stability of a spherically symmetric object with charged anisotropic matter by using the concept of cracking. The cracking is a very intuitive technique to check the stability which is based on the analysis of the radial forces that appear on the system due to perturbations taking it out of its equilibrium state. For this, we have applied and studied the effect of local density perturbations to the hydrostatic equilibrium equation and on all the physical parameters with generalized polytropic equation of state. It is found that some of the generalized polytropic models exhibit cracking.

scholarly journals Wind Accretion by Compact Objects: The “Flip-Flop” Instability

1992 ◽  
Vol 151 ◽  
pp. 185-194
Author(s):  
Mario Livio
Keyword(s):  
Random Walk ◽  
Accretion Rate ◽  
Compact Object ◽  
Two Dimensions ◽  
Compact Objects ◽  
Numerical Calculations ◽  
Three Dimensions ◽  
Flip Flop ◽  
Accretion Flows ◽  
The Stability

The problem of the stability of wind accretion onto compact objects is examined. Recent analytical and numerical calculations show that in two dimensions, Bondi-Hoyle accretion flows are unstable to a “flip-flop” instability. The instability can manifest itself as bursts in the accretion rate and as a random walk-type spin-up, spin-down behaviour of the accreting compact object. The nature of the flow in three dimensions needs further clarification. Possible observational implications are reviewed.

scholarly journals Analysis of charged compact stars in modified gravity

2018 ◽  
Vol 27 (08) ◽  
pp. 1850082 ◽  
Author(s):  
M. Farasat Shamir ◽  
Saeeda Zia
Keyword(s):  
Modified Gravity ◽  
Compact Star ◽  
Compact Object ◽  
Relative Difference ◽  
Comprehensive Analysis ◽  
Compact Stars ◽  
Energy Conditions ◽  
Anisotropic Pressure ◽  
Field Equations ◽  
Stability Energy

Current study highlights the physical characteristics of charged anisotropic compact stars by exploring some exact solutions of modified field equations in [Formula: see text] gravity. A comprehensive analysis is performed from the obtained solutions regarding stability, energy conditions, regularity, sound velocity and compactness. These solutions can be referred to model the compact celestial entities. In particular, a compact star named, [Formula: see text] has been modeled which indicates that current solution fits and is in conformity to the observational data as well. A useful and interesting fact from this model arises that relative difference between two forces of anisotropic pressure and electromagnetic force may occur inside the aforementioned compact star. This is another mechanism which is essential for stability of the compact object and prevent stellar object to annihilate.

scholarly journals Constraint on Hybrid Stars with Gravitational Wave Events

Universe ◽  
2020 ◽  
Vol 6 (12) ◽  
pp. 231
Author(s):  
Kilar Zhang ◽  
Feng-Li Lin
Keyword(s):  
Black Hole ◽  
Dark Matter ◽  
Neutron Star ◽  
Gravitational Wave ◽  
Compact Object ◽  
Compact Objects ◽  
Compact Stars ◽  
Hybrid Star ◽  
Hybrid Stars

Motivated by the recent discoveries of compact objects from LIGO/Virgo observations, we study the possibility of identifying some of these objects as compact stars made of dark matter called dark stars, or the mix of dark and nuclear matters called hybrid stars. In particular, in GW190814, a new compact object with 2.6 M⊙ is reported. This could be the lightest black hole, the heaviest neutron star, and a dark or hybrid star. In this work, we extend the discussion on the interpretations of the recent LIGO/Virgo events as hybrid stars made of various self-interacting dark matter (SIDM) in the isotropic limit. We pay particular attention to the saddle instability of the hybrid stars which will constrain the possible SIDM models.

scholarly journals Generalized compact star models with conformal symmetry

2021 ◽  
Vol 81 (12) ◽  
Author(s):  
J. W. Jape ◽  
S. D. Maharaj ◽  
J. M. Sunzu ◽  
J. M. Mkenyeleye
Keyword(s):  
Compact Star ◽  
Conformal Symmetry ◽  
Compact Objects ◽  
Energy Conditions ◽  
Geometric Framework ◽  
Exact Model ◽  
Star Models ◽  
Special Cases ◽  
Physical Forces ◽  
The Stability

AbstractWe generate a new generalized regular charged anisotropic exact model that admits conformal symmetry in static spherically symmetric spacetime. Our model was examined for physical acceptability as realistic stellar models. The regularity is not violated, the energy conditions are satisfied, the physical forces balanced at equilibrium, the stability is satisfied via adiabatic index, and the surface red shift and mass–radius ratio are within the required bounds. Our conformal charged anisotropic exact solution contains models generated by Finch–Skea, Vaidya–Tikekar and Schwarzschild. Also, some recent charged or neutral and anisotropic or isotropic conformally symmetric models are found as special cases of our exact model. Our approach using a conformal symmetry provides a generalized geometric framework for studying compact objects.

scholarly journals Distinct classes of compact stars based on geometrically deduced equations of state

2021 ◽  
pp. 2150029
Author(s):  
A. C. Khunt ◽  
V. O. Thomas ◽  
P. C. Vinodkumar
Keyword(s):  
Neutron Stars ◽  
Soft Matter ◽  
Equations Of State ◽  
Compact Objects ◽  
Exotic Matter ◽  
Compact Stars ◽  
Spacetime Geometry ◽  
Superdense Stars ◽  
Einstein's Equation ◽  
Envelope Model

We have computed the properties of compact objects like neutron stars based on equation of state (EOS) deduced from a core–envelope model of superdense stars. Such superdense stars have been studied by solving Einstein’s equation based on pseudo-spheroidal and spherically symmetric spacetime geometry. The computed star properties are compared with those obtained based on nuclear matter EOSs. From the mass–radius ([Formula: see text]–[Formula: see text]) relationship obtained here, we are able to classify compact stars in three categories: (i) highly compact self-bound stars that represents exotic matter compositions with radius lying below 9[Formula: see text]km; (ii) normal neutron stars with radius between 9 to 12[Formula: see text]km and (iii) soft matter neutron stars having radius lying between 12 to 20[Formula: see text]km. Other properties such as Keplerian frequency, surface gravity and surface gravitational redshift are also computed for all the three types. This work would be useful for the study of highly compact neutron like stars having exotic matter compositions.

A relativistic two-fluid model of compact stars

2017 ◽  
Vol 32 (10) ◽  
pp. 1750055 ◽  
Author(s):  
Koushik Chakraborty ◽  
Farook Rahaman ◽  
Arkopriya Mallick
Keyword(s):  
Quark Matter ◽  
Fluid Model ◽  
Compact Star ◽  
Conformal Symmetry ◽  
Compact Objects ◽  
Compact Stars ◽  
Baryonic Matter ◽  
Spacetime Geometry ◽  
Two Fluid Model ◽  
The Masses

We propose a relativistic model of compact star admitting conformal symmetry. Quark matter and baryonic matter which are considered as two different fluids, constitute the star. We define interaction equations between the normal baryonic matter and the quark matter and study the physical situations for repulsive, attractive and zero interaction between the constituent matters. The measured value of the Bag constant is used to explore the spacetime geometry inside the star. From the observed values of the masses of some compact objects, we have obtained theoretical values of the radii. Theoretical values of the radii match well with the previous predictions for such compact objects.

scholarly journals Relativistic compact stars in Tolman spacetime via an anisotropic approach

2021 ◽  
Vol 81 (6) ◽  
Author(s):  
Piyali Bhar ◽  
Pramit Rej ◽  
P. Mafa Takisa ◽  
M. Zubair
Keyword(s):  
Graphical Representation ◽  
Dimensional Space ◽  
Compact Star ◽  
Compact Stars ◽  
Stellar Structure ◽  
Energy Conditions ◽  
Anisotropic Pressure ◽  
Model Parameters ◽  
Theory Of Relativity ◽  
Field Equations

AbstractIn this present work, we have obtained a singularity-free spherically symmetric stellar model with anisotropic pressure in the background of Einstein’s general theory of relativity. The Einstein’s field equations have been solved by exploiting Tolman ansatz [Richard C Tolman, Phys. Rev. 55:364, 1939] in $$(3+1)$$ ( 3 + 1 ) -dimensional space-time. Using observed values of mass and radius of the compact star PSR J1903+327, we have calculated the numerical values of all the constants from the boundary conditions. All the physical characteristics of the proposed model have been discussed both analytically and graphically. The new exact solution satisfies all the physical criteria for a realistic compact star. The matter variables are regular and well behaved throughout the stellar structure. Constraints on model parameters have been obtained. All the energy conditions are verified with the help of graphical representation. The stability condition of the present model has been described through different testings.

Sign in / Sign up

Export Citation Format

Share Document