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1.
A new class of charged super-dense star models is obtained by using an electric intensity, which involves a parameter, K. The metric describing the model shares its metric potential g 44 with that of Durgapal’s fourth solution (J. Phys. A, Math. Gen. 15:2637, 1982). The pressure-free surface is kept at the density ρ b =2×1014 g/cm3 and joins smoothly with the Reissner-Nordstrom solution. The charge analogues are well-behaved for a wide range, 0≤K≤59, with the optimum value of X=0.264 i.e. the pressure, density, pressure–density ratio and velocity of sound are monotonically decreasing and the electric intensity is monotonically increasing in nature for the given range of the parameter K. The maximum mass and the corresponding radius occupied by the neutral solution are 4.22M Θ and 20 km, respectively for X=0.264. For the charged solution, the maximum mass and radius are defined by the expressions M≈(0.0059K+4.22)M Θ and r b ≈−0.021464K+20 km respectively. 相似文献
2.
We obtain a new class of charged super-dense star models after prescribing particular forms of the metric potential g
44 and electric intensity. The metric describing the superdense stars joins smoothly with the Reissner-Nordstrom metric at the
pressure free boundary. The interior of the stars possess there energy density, pressure, pressure-density ratio and velocity
of sound to be monotonically decreasing towards the pressure free interface. In view of the surface density 2×1014 g/cm3, the heaviest star occupies a mass 5.6996 M
⊙ with its radius 17.0960 km. The red shift at the centre and boundary are found to be 3.5120 and 1.1268 respectively. In absence
of the charge we are left behind with the regular and well behaved fifth model of Durgapal (J. Phys. A 15:2637, 1982). 相似文献
3.
We obtain a new parametric class of exact solutions of Einstein–Maxwell field equations which are well behaved. We present a charged super-dense star model after prescribing particular forms of the metric potential and electric intensity. The metric describing the super dense stars joins smoothly with the Reissner–Nordstrom metric at the pressure free boundary. The electric density assumed is where n may take the values 0,1,2,3,4 and so on and K is a positive constant. For n=0,1 we rediscover the solutions by Gupta and Maurya (Astrophys. Space Sci. 334(1):155, 2011) and Fuloria et al. (J. Math. 2:1156, 2011) respectively. The solution for n=2 have been discussed extensively keeping in view of well behaved nature of the charged solution of Einstein–Maxwell field equations. The solution for n=3 and n=4 can be also studied likewise. In absence of the charge we are left behind with the regular and well behaved fifth model of Durgapal (J. Phys. A 15:2637, 1982). The outmarch of pressure, density, pressure-density ratio and the velocity of sound is monotonically decreasing, however, the electric intensity is monotonically increasing in nature. For this class of solutions the mass of a star is maximized with all degree of suitability, compatible with Neutron stars and Pulsars. 相似文献
4.
Naveen Bijalwan 《Astrophysics and Space Science》2011,336(2):413-418
Recently, Bijalwan (Astrophys. Space Sci., doi:, 2011a) discussed charged fluid spheres with pressure while Bijalwan and Gupta (Astrophys. Space Sci. 317, 251–260, 2008) suggested using a monotonically decreasing function f to generate all possible physically viable charged analogues of Schwarzschild interior solutions analytically. They discussed
some previously known and new solutions for Schwarzschild parameter
u( = \fracGMc2a ) ￡ 0.142u( =\frac{GM}{c^{2}a} ) \le 0.142, a being radius of star. In this paper we investigate wide range of u by generating a class of solutions that are well behaved and suitable for modeling Neutron star charge matter. We have exploited
the range u≤0.142 by considering pressure p=p(ω) and
f = ( f0(1 - \fracR2(1 - w)a2) +fa\fracR2(1 - w)a2 )f = ( f_{0}(1 - \frac{R^{2}(1 - \omega )}{a^{2}}) +f_{a}\frac{R^{2}(1 - \omega )}{a^{2}} ), where
w = 1 -\fracr2R2\omega = 1 -\frac{r^{2}}{R^{2}} to explore new class of solutions. Hence, class of charged analogues of Schwarzschild interior is found for barotropic equation
of state relating the radial pressure to the energy density. The analytical models thus found are well behaved with surface
red shift z
s
≤0.181, central red shift z
c
≤0.282, mass to radius ratio M/a≤0.149, total charge to total mass ratio e/M≤0.807 and satisfy Andreasson’s (Commun. Math. Phys. 288, 715–730, 2009) stability condition. Red-shift, velocity of sound and p/c
2
ρ are monotonically decreasing towards the surface while adiabatic index is monotonically increasing. The maximum mass found
to be 1.512 M
Θ with linear dimension 14.964 km. Class of charged analogues of Schwarzschild interior discussed in this paper doesn’t have
neutral counter part. These solutions completely describe interior of a stable Neutron star charge matter since at centre
the charge distribution is zero, e/M≤0.807 and a typical neutral Neutron star has mass between 1.35 and about 2.1 solar mass, with a corresponding radius of about
12 km (Kiziltan et al., [astro-ph.GA], 2010). 相似文献
5.
The paper presents a variety of classes of interior solutions of Einstein–Maxwell field equations of general relativity for
a static, spherically symmetric distribution of the charged fluid with well behaved nature. These classes of solutions describe
perfect fluid balls with positively finite central pressure, positively finite central density; their ratio is less than one
and causality condition is obeyed at the center. The outmarch of pressure, density, pressure–density ratio and the adiabatic
speed of sound is monotonically decreasing for these solutions. Keeping in view of well behaved nature of these solutions,
two new classes of solutions are being studied extensively. Moreover, these classes of solutions give us wide range of constant
K for which the solutions are well behaved hence, suitable for modeling of super dense star. For solution (I1) the mass of a star is maximized with all degree of suitability and by assuming the surface density ρ
b
=2×1014 g/cm3 corresponding to K=1.19 and X=0.20, the maximum mass of the star comes out to be 2.5M
Θ with linear dimension 25.29 Km and central redshift 0.2802. It has been observed that with the increase of charge parameter K,
the mass of the star also increases. For n=4,5,6,7, the charged solutions are well behaved with their neutral counterparts however, for n=1,2,3, the charged solution are well behaved but their neutral counterparts are not well behaved. 相似文献
6.
We present a variety of well behaved classes of Charge Analogues of Tolman’s iv (1939). These solutions describe charged fluid
balls with positively finite central pressure, positively finite central density; their ratio is less than one and causality
condition is obeyed at the centre. The outmarch of pressure, density, pressure-density ratio and the adiabatic speed of sound
is monotonically decreasing, however, the electric intensity is monotonically increasing in nature. These solutions give us
wide range of parameter for every positive value of n for which the solution is well behaved hence, suitable for modeling
of super dense stars. keeping in view of well behaved nature of these solutions, one new class of solutions is being studied
extensively. Moreover, this class of solutions gives us wide range of constant K (0.3≤K≤0.91) for which the solution is well behaved hence, suitable for modeling of super dense stars like Strange Quark stars,
Neutron stars and Pulsars. For this class of solutions the mass of a star is maximized with all degree of suitability, compatible
with Quark stars, Neutron stars and Pulsars. By assuming the surface density ρ
b
=2×1014 g/cm3 (like, Brecher and Caporaso in Nature 259:377, 1976), corresponding to K=0.30 with X=0.39, the resulting well behaved model has the mass M=2.12M
Θ, radius r
b
≈15.27 km and moment of inertia I=4.482×1045 g cm2; for K=0.4 with X=0.31, the resulting well behaved model has the mass M=1.80M
Θ, radius r
b
≈14.65 km and moment of inertia I=3.454×1045 g cm2; and corresponding to K=0.91 with X=0.135, the resulting well behaved model has the mass M=0.83M
Θ, radius r
b
≈11.84 km and moment of inertia I=0.991×1045 g cm2. For n=0 we rediscovered Pant et al. (in Astrophys. Space Sci. 333:161, 2011b) well behaved solution. These values of masses and moment of inertia are found to be consistent with other models of Neutron
stars and Pulsars available in the literature and are applicable for the Crab and the Vela Pulsars. 相似文献
7.
Recently, Bijalwan (Astrophys. Space Sci. doi:, 2011) discussed all important solutions of charged fluid spheres with pressure and Gupta et al. (Astrophys. Space Sci. doi:, 2010) found first closed form solutions of charged Vaidya-Tikekar (V-T) type super-dense star. We extend here the approach evolved
by Bijalwan (Astrophys. Space Sci. doi:, 2011) to find all possible closed form solutions of V-T type super-dense stars. The existing solutions of Vaidya-Tikekar type
charged fluid spheres considering particular form of electric field intensity are being used to model massive stars. Infact
at present maximum masses of the star models are found to be 8.223931M
Θ and 8.460857M
Θ subject to ultra-relativistic and non-relativistic conditions respectively. But these stars with such are large masses are
not well behaved due to decreasing velocity of sound in the interior of star. We present new results concerning the existence
of static, electrically charged perfect fluid spheres that have a regular interior. It is observed that electric intensity
used in this article can be used to model superdense stars with ultrahigh surface density of the order 2×1014 gm/cm3 which may have maximum mass 7.26368240M
Θ for ultra-relativistic condition and velocity of sound found to be decreasing towards pressure free interface. We solve the
Einstein-Maxwell equations considering a general barotropic equation of state with pressure. For brevity we don’t present
a detailed analysis of the derived solutions in this paper. 相似文献
8.
A new class of well behaved anisotropic super-dense stars has been derived with the help of a given class of charged fluid distributions. The anisotropy parameter (or the electric intensity) is zero at the centre and monotonically increasing towards the pressure free interface. All the physical parameter such as energy density, radial pressure, tangential pressure and velocity of sound are monotonically decreasing towards the surface. The maximum mass measures 3.8593 solar mass and the corresponding radius is 21.2573 km for n=1 i.e. N tends to infinity. 相似文献
9.
A class of well behaved charged superdense star models of embedding class one is obtained by taking perfect fluid to be interior
matter. In the process we come across the models for white dwarf, quark and neutron stars. Maximum mass of the star of this
class is found to be 6.716998M
Θ with its radius is 18.92112 Km. In the absence of charge the models reduce to Schwarzchild’s interior model with constant
density. 相似文献
10.
In the present paper, we have obtained a class of charged super dense star models, starting with a static spherically symmetric metric in isotropic coordinates for perfect fluid by considering Hajj-Boutros (in J. Math. Phys. 27:1363, 1986) type metric potential and a specific choice of electrical intensity which involves a parameter K. The resulting solutions represent charged fluid spheres joining smoothly with the Reissner-Nordstrom metric at the pressure free interface. The solutions so obtained are utilized to construct the models for super-dense star like neutron stars (ρ b =2 and 2.7×1014 g/cm3) and Quark stars (ρ b =4.6888×1014 g/cm3). Our solution is well behaved for all values of n satisfying the inequalities \(4 < n \le4(4 + \sqrt{2} )\) and K satisfying the inequalities 0≤K≤0.24988, depending upon the value of n. Corresponding to n=4.001 and K=0.24988, we observe that the maximum mass of quark star M=2.335M ⊙ and radius R=10.04 km. Further, this maximum mass limit of quark star is in the order of maximum mass of stable Strange Quark Star established by Dong et al. (in arXiv:1207.0429v3, 2013). The robustness of our results is that the models are alike with the recent discoveries. 相似文献
11.
We present a well behaved class of Charge Analogue of Heintzmann (Z. Phys. 228:489, 1969) solution. This solution describes charge fluid balls with positively finite central pressure and positively finite central
density ; their ratio is less than one and causality condition is obeyed at the centre. The outmarch of pressure, density,
pressure-density ratio and the adiabatic speed of sound is monotonically decreasing, however, the electric intensity is monotonically
increasing in nature. The solution gives us wide range of constant K (1.25≤K≤15) for which the solution is well behaved and therefore, suitable for modeling of super dense star. For this solution the
mass of a star is maximized with all degrees of suitability and by assuming the surface density ρ
b
=2×1014 g/cm3. Corresponding to K=1.25 and X=0.42, the maximum mass of the star comes out to be 3.64M
Θ with linear dimension 24.31 km and central redshift 1.5316. 相似文献
12.
Neeraj Pant 《Astrophysics and Space Science》2011,332(2):403-408
The paper presents a class of interior solutions of Einstein–Maxwell field equations of general relativity for a static, spherically
symmetric distribution of the charged fluid. This class of solutions describes well behaved charged fluid balls. The class
of solutions gives us wide range of parameter K (0≤K≤42) for which the solution is well behaved hence, suitable for modeling of super dense star. For this solution the mass of
a star is maximized with all degree of suitability and by assuming the surface density ρ
b
=2×1014 g/cm3. Corresponding to K=2 and X=0.30, the maximum mass of the star comes out to be 4.96 M
Θ with linear dimension 34.16 km and central redshift and surface redshift 2.1033 and 0.683 respectively. In absence of the
charge we are left behind with the well behaved fourth model of Durgapal (J. Phys., A, Math. Gen. 15:2637, 1982). 相似文献
13.
Naveen Bijalwan 《Astrophysics and Space Science》2012,337(1):161-167
We show in this article that charged fluid with pressure derived by Bijalwan (Astrophys. Space. Sci. doi:, 2011a) can be used to model classical electron, quark, neutron stars and pulsar with charge matter, quasi black hole, white dwarf,
super-dense star etc. Recent analysis by Bijalwan (Astrophys. Space. Sci., 2011d) that all charged fluid solutions in terms of pressure mimic the classical electron model are partially correct because solutions
by Bijalwan (Astrophys. Space. Sci. doi:, 2011a) may possess a neutral counterpart. In this paper we characterized solutions in terms of pressure for charged fluids that
have and do not have a well behaved neutral counter part considering same spatial component of metric e
λ
for neutral and charged fluids. We discussed solution by Gupta and Maurya (Astrophys. Space Sci. 331(1):135–144, 2010a) and solutions by Bijalwan (Astrophys. Space Sci. doi:, 2011b; Astrophys. Space Sci. doi:, 2011c; Astrophys. Space Sci., 2011d) such that charged fluids possess and do not possess a neutral counterpart as special cases, respectively. For brevity, we
only present some analytical results in this paper. 相似文献
14.
In the present article models of well behaved charged superdense stars with surface density 2×1014 gm/cm3 are constructed by considering a static spherically symmetric metric with t = const hypersurfaces as spheroids and hyperboloids. Maximum mass of the star is found to be 7.66300M
Θ with radius 19.35409 km for spheroids case while 1.51360M
Θ with radius 13.72109 km for hyperboloid case satisfying ultra-relativistic conditions. The solutions thus found satisfy all
the reality and causality conditions. For brevity we don’t present a detailed analysis of the derived solutions in this paper. 相似文献
15.
Naveen Bijalwan 《Astrophysics and Space Science》2011,336(2):485-489
Rahaman et al. (Astrophys. Space. Sci. 331:191–197, 2010) discussed some classical electron models (CEM) in general relativity. Bijalwan (Astrophys. Space. Sci. 334:139–143, 2011) present a general exact solution of the Einstein-Maxwell equations in terms of pressure. We showed that charged fluid solutions
in terms of pressure are not reducible to a well behaved neutral counter part for a spatial component of metrice
λ
. Hence, these solutions represent an electron model in general relativity. We illustrated solutions in terms of pressure
briefly with de-Sitter equation of state and charged analogues of Kohler Chao interior solution as a special cases. 相似文献
16.
A family of charge analogues of a neutral solution with g
44=(1+Cr
2)6 has been obtained by using a specific electric intensity, which involves a parameter K. Both neutral and charged solutions are analysed physically subject to the surface density 2×1014 gm/cm3 (neutron star). The neutral solution is well behaved for 0.0<Ca
2≤0.10477 while its charge analogues are well behaved for a wide range of a parameter K (0≤K≤72) i.e. pressure, density, pressure-density ratio, velocity of sound is monotonically decreasing and the electric intensity
is monotonically increasing in nature for the given range of the parameter K. The maximum mass and radius occupied by the neutral solution are 3.4126M
Θ and 18.9227 km for Ca
2=0.10447 respectively. While the red shift at centre Z
0=0.9686 and red shift at the surface Z
a
=0.4612. For the charged solution, the maximum mass and radius are 5.6111M
Θ and 17.2992 km respectively for K=3.0130 and Ca
2=0.2500, with the red shift Z
0=3.0113 and Z
a
=1.0538. 相似文献
17.
In this article we have derived a set of three static spherical symmetric well behaved solutions of Einstein-Maxwell field
equations is obtained for a specific choice of electric field involving a parameter K. The solutions so obtained can be seen as a charge analogue of the neutral solution due to Vlasenko and Pronin. The physical
features of solutions so obtained and that of Vlasenko and Pronin are investigated subject to the reality and the causality
conditions i.e. Pressure, density (greater than pressure), pressure-density ratio and velocity of sound (less than the velocity
of light) are positive and monotonically decreasing and the electric intensity is monotonically increasing in nature away
from the centre. The maximum mass and radius occupied by the neutral solution are 2.1434 M
Θ and 16.7300 km respectively. For the charged solution, overall maximum mass and corresponding radius are found to be 6.8714
M
Θ and 20.6166 km respectively (for K=1.343). 相似文献
18.
First ever closed form solution for charged fluid sphere expressed by a space time with its hypersurfaces t= constant as spheroid is obtained for the case 0<K<1. The same is utilized to construct a superdense star with surface density 2×1014 gm/cm3. The star is seen to satisfy the reality and causality conditions for 0<K≤0.045 and possesses maximum mass and radius to be 0.065216M
Θ and 1.137496 km respectively. Moreover the interior of the star satisfy strong energy condition. However in the absence of
the causality condition, the reality conditions are valid for a wider range 0<K≤0.13. The maximum mass and radius for the later case are 1.296798M
Θ and 2.6107 km respectively for the strong energy condition, while the said parameters for the weak energy condition read
as 1.546269M
Θ and 2.590062 km respectively. 相似文献
19.
In the present article a model of well behaved charged superdense star with surface density 2×1014 gm/cm3 is constructed by considering a static spherically symmetric metric with t=const hypersurfaces as hyperboloid. So far well behaved model described by such metric could not be obtained. Maximum mass
of the star is found to be 0.343457M
⊙ and the corresponding radius is 9.57459 km. The red shift at the centre and on the surface are given as 0.068887 and 0.031726
respectively. 相似文献
20.
Neeraj Pant 《Astrophysics and Space Science》2011,334(2):267-271
The paper presents a class of interior solutions of Einstein-Maxwell field equations of general relativity for a static, spherically
symmetric distribution of the charged fluid. This class of solutions describes well behaved charged fluid balls. The class
of solutions gives us wide range of parameter K (0.3277≤K≤0.49), for which the solution is well behaved hence, suitable for modeling of super dense star. For this solution the mass
of a star is maximized with all degree of suitability and by assuming the surface density ρ
b
=2×1014 g/cm3. Corresponding to K=0.3277 with X=−0.15, the maximum mass of the star comes out to be M=0.92M
Θ with radius r
b
≈17.15 km and the surface red shift Z
b
≈0.087187. It has been observed that under well behaved conditions this class of solutions gives us the mass of super dense
object within the range of white-dwarf. 相似文献