A NEW SPHERICALLY SYMMETRIC ANISOTROPIC NEUTRON STAR MODEL USING FIELD EQUATIONS
ANISOTROPIC NEUTRON STAR MODEL
DOI:
https://doi.org/10.55766/sujst-2023-04-e01026Keywords:
Anisotropic Spherical Symmetry, Einstein’s Field Equations, Exact Solutions, Neutron StarsAbstract
In this paper, we obtain a new static spherically symmetric anisotropic fluid model of a neutron star in curvature coordinates. We consider , where , by taking the value of parameter in Durgapal solutions (Durgapal, 1982). The energy density, radial pressure, tangential pressure, and redshift are positive finite, and decreasing with respect to the increasing radius in this model. The pressure and density also decrease from the inner core to the crust of the object. We obtain this model by the specific choice of the constants and the anisotropy factor . The central value of the anisotropy factor is zero due to the perfect fluid nature at the center of the anisotropic model and it is increasing with the increasing radius. In our analysis we take and The model well behaves for the anisotropic neutron stars, which is shown analytically and graphically. The solution is free from any central singularity. We take realistic objects such as EXO 1785-248, SMC X-1, Her X-1, 4U 1538-52, LMC X-4, RX J1856-37, Cen X-3, PSR J1903-327, and Vela X-1 to represent our solutions graphically and numerically. We obtain this solution for for the first time. Therefore, the solution is quite new and derived for the first time.
References
Ali, S.S., Bharadwaj, S., and Pandey, B. (2005). What will anisotropies in the clustering pattern in redshifted 21-cm maps tell us? Monthly Notices of the Royal Astronomical Society, 363(1):251-258. https://doi.org/10.1111/j.1365-2966.2005.09444.x
Andréasson, H. (2009). Sharp bounds on the critical stability radius for relativistic charged spheres. Communications in Mathematical Physics, 288(2):715-730. https://doi.org/ 10.1007/s00220-008-0690-3
Bhar, P. (2019). Anisotropic compact star model: a brief study via embedding. The European Physical Journal C, 79(2):1-13. https://doi.org/10.1140/epjc/s10052-019-6642-6
Bhar, P. and Rej, P. (2021). Compact stellar model in the presence of pressure anisotropy in modified Finch Skea space-time. Journal of Astrophysics and Astronomy, 42(2):1-16. https://doi.org/10.1007/s12036-021-09739-x
Bhar, P., Rej, P., Takisa, P., and Zubair, M. (2021). Relativistic compact stars in Tolman spacetime via an anisotropic approach. The European Physical Journal C, 81(6):1-13. https://doi.org/10.1140/epjc/s10052-021-09340-0
Bordbar, G.H., Nourafshan, M., and Khosropour, B. (2019). Calculation of strange star structure. Iranian Journal of Physics Research, 9(3):237-248.
Borissova, J., Georgiev, L., Hanson, M.M., Clarke, J.R.A., Kurtev, R., Ivanov, V.D., Penaloza, F., Hillier, D.J., and Zsargó, J. (2012). Obscured clusters-IV. The most massive stars in [DBS2003] 179. Astronomy and Astrophysics, 546:A110. https://doi.org/10.1051/0004-6361/201118348
Bowers, R.L. and Liang, E.P.T. (1974). Anisotropic Spheres in General Relativity. Astrophysics Journal, 188:657-665. https://doi.org/10.1086/152760
Das, S., Singh, K., Baskey, L., Rahaman, F., and Aria, A.K. (2021). Modeling of compact stars: an anisotropic approach. General Relativity and Gravitation, 53(3):1-32. https://doi.org/10.1007/s10714-021-02792-5
Deb, D., Chowdhury, S.R., Ray, S., Rahaman, F., and Guha, B.K. (2017). Relativistic model for anisotropic strange stars. Annals of Physics, 387:239-252. https://doi.org/10.1016/ j.aop.2017.10.010
Deb, D., Mukhopadhyay, B., and Weber, F. (2021). Effects of anisotropy on strongly magnetized neutron and strange quark stars in general relativity. The Astrophysical Journal, 922(2):149. https://doi.org/10.3847/1538-4357/ ac222a
Delliou, M.L., Deliyergiyev, M., and Del Popolo, A. (2020). An anisotropic model for the universe. Symmetry, 12(10):1741. https://doi.org/10.3390/sym12101741
Durgapal, M.C. (1982). A class of new exact solutions in general relativity. Journal of Physics A: Mathematical and General, 15(8):2637. https://doi.org/10.1088/0305-4470/ 15/8/039
Einstein, A. (1915). Die feldgleichungen der gravitation. Sitz physik-math Klas, 25, 844-847.
Fulara, P.C. and Sah, A. (2018). A spherical relativistic anisotropic compact star model. International Journal of Astronomy and Astrophysics, 8(01):46-67. https://doi.org/ 10.4236/ijaa.2018.81004
Goswami, K.B., Saha, A., and Chattopadhyay, P.K. (2020). New class of relativistic anisotropic strange star in Vaidya-Tikekar model. Astrophysics and Space Science, 365(8):141. https://doi.org/10.1007/s10509-020-03856-9
Hansraj, S., Govender, M., Moodly, L., and Singh, K.N. (2022). Strange stars in the framework of higher curvature gravity. Physical Review D, 105(4):044030. https://doi.org/ 10.1103/PhysRevD.105.044030
Harko, T. and Cheng, K.S. (2002). Maximum mass and radius of strange stars in the linear approximation of the EOS. Astronomy and Astrophysics, 385(3):947-950. https://doi.org/10.1051/0004-6361:20020260
Herrera, L., Di Prisco, A., Fuenmayor, E., and Troconis, O. (2009). Dynamics of viscous dissipative gravitational collapse: a full causal approach. International Journal of Modern Physics D, 18(01):129-145. https://doi.org/ 10.1142/S0218271809014285
Islam, R., Molla, S., and Kalam, M. (2019). Analytical model of a strange star in Durgapal spacetime. Astrophysics and Space Science, 364(7):122. https://doi.org/10.1007/ s10509-019-3603-3
Karmakar, S., Mukherjee, S., Sharma, R., and Maharaj, S.D. (2007). The role of pressure anisotropy on the maximum mass of cold compact stars. Pramana, 68(6):881-889. https://doi.org/10.1007/s12043-007-0088-3
Kaur, S. and Shukla, S. (2022). A new class of charged spherically symmetric and static superdense star configurations. International Journal of Modern Physics D, 31(12):2250086. https://doi.org/10.1142/S0218271822 500869
Li, X.D., Bombaci, I., Dey, M., Dey, J., and Van Den Heuvel, E.P.J. (1999). Is SAX J1808. 4-3658 a strange star? Physical Review Letters, 83(19):3776. https://doi.org/ 10.1103/PhysRevLett.83.3776
Malaver, M. (2014). Strange quark star model with quadratic equation of state. Frontiers of Mathematics and Its Applications, 1(1):9-15. https://doi.org/10.12966/ fmia.03.02.2014
Maurya, S.K. and Gupta, Y.K. (2012). A family of anisotropic super-dense star models using a space-time describing charged perfect fluid distributions. Physica Scripta, 86(2):025009. https://doi.org/10.1088/0031-8949/86/02/ 025009
Maurya, S.K. and Gupta, Y.K. (2014). A new class of relativistic charged anisotropic super dense star models. Astrophysics and Space Science, 353(2):657-665. https://doi.org/ 10.1007/s10509-014-2041-5
Maurya, S.K., Gupta, Y.K., Ray, S., and Chowdhury, S.R. (2015). Spherically symmetric electromagnetic mass models of embedding class one. arXiv preprint arXiv:1506.02498.
Maurya, S.K., Singh, K.N., Govender, M., and Hansraj, S. (2022). Gravitationally decoupled strange star model beyond the standard maximum mass limit in einstein-gauss-bonnet gravity. The Astrophysical Journal, 925(2):208. https://doi.org/10.3847/1538-4357/ac4255
Messineo, M., Zhu, Q., Menten, K.M., Ivanov, V.D., Figer, D.F., Habing, H., Kudritzki, R.P., Chen, C.-H.R., Davies, B., and Churchwell, E. (2016). Hunting for massive late-type stars in the inner disk of the milky way. In: Proceeding of CoolStar19 Works, p. 120-123. https://doi.org/ 10.5281/zenodo.59139
Molla, S., Murshid, M., and Kalam, M. (2022). Analytical model on mass limits of strange stars. Astrophysics and Space Science, 367(1):1-11. https://doi.org/10.1007/s10509-021-04035-0
Mustafa, G., Errehymy, A., Maurya, S.K., Jasim, M.K., and Ditta, A. (2022). Study on anisotropic star in extended teleparallel gravity with minimal matter coupling. Chinese Journal of Physics, 77:1742-1754. https://doi.org/ 10.1016/j.cjph.2022.02.013
Özel, F., Güver, T., and Psaltis, D. (2009). The mass and radius of the neutron star in EXO 1745−248. The Astrophysical Journal, 693(2):1775. https://doi.org/10.1088/0004-637X/ 693/2/1775
Rawls, M.L., Orosz, J.A., McClintock, J.E., Torres, M.A., Bailyn, C.D., and Buxton, M.M. (2011). Refined neutron star mass determinations for six eclipsing x-ray pulsar binaries. The Astrophysical Journal, 730(1):25. https://doi.org/10.1088/0004-637X/730/1/25
Sah, A. and Chandra, P. (2016). Class of charged fluid balls in general relativity. International Journal of Astronomy and Astrophysic, 6(4):494-511. https://doi.org/10.4236/ ijaa.2016.64038
Samuroff, S., Mandelbaum, R., and Di Matteo, T. (2020). Testing the impact of satellite anisotropy on large-and small-scale intrinsic alignments using hydrodynamical simulations. Monthly Notices of the Royal Astronomical Society, 491(4):5330-5350. https://doi.org/10.1093/mnras/stz3114
Sana, H., Momany, Y., Gieles, M., Carraro, G., Beletsky, Y., Ivanov, V. D., De Silva, G., and James, G. (2010). A MAD view of Trumpler 14. Astronomy and Astrophysics, 515:A26. https://doi.org/10.1051/0004-6361/200913688
Schwarzschild, K. (1916). Über das gravitationsfeld einer kugel aus inkompressibler flüssigkeit nach der einsteinschen theorie. Sitzung kön pre Akad Wiss Ber, p. 424-434.
Singh, K.N., Bhar, P., and Pant, N. (2016). A new solution of embedding class I representing anisotropic fluid sphere in general relativity. International Journal of Modern Physics D, 25(14):1650099. https://doi.org/10.1142/S02182718 16500991
Singh, K.N., Bhar, P., Rhaman, F., and Pant, N. (2018). Effect of electric charge on anisotropic compact stars in conformally symmetric spacetime. Journal of Physics Communications, 2(1):015002. https://doi.org/10.1088/ 2399-6528/aa9c50
Szkudlarek, M., Gondek-Rosińska, D., Villain, L., and Ansorg, M. (2019). Maximum mass of differentially rotating strange quark stars. The Astrophysical Journal, 879(1):44. https://doi.org/10.3847/1538-4357/ab1752
Tamta, P. and Fuloria, P. (2022). The physically realizable anisotropic strange star models. Indian Journal of Physics, 96(5):1577-1590. https://doi.org/10.1007/s12648-021-02069-2
Tewari, B.C. and Charan, K. (2015a). Horizon free eternally collapsing anisotropic radiating star. Astrophysics and Space Science, 357(2):107. https://doi.org/10.1007/ s10509-015-2335-2
Tewari, B.C. (2013). Collapsing shear-free radiating fluid spheres. General Relativity and Gravitation, 45(8):1547-1558. https://doi.org/10.1007/s10714-013-1545-6
Tewari, B.C. and Charan, K. (2015b). Gravitational collapse, shear-free anisotropic radiating star. arXiv preprint arXiv:1503.02165.
Tewari, B.C., Charan, K., and Rani, J. (2016). Spherical gravitational collapse of anisotropic radiating fluid sphere. International Journal of Astronomy and Astrophysics, 6(2):155-165. https://doi.org/10.4236/ijaa.2016.62013
Thirukkanesh, S. and Ragel, F.C. (2013). A class of exact strange quark star models. Pramana, 81(2):275-286. https://doi.org/10.1007/s12043-013-0582-8
Tolman, R.C. (1939). Static solutions of Einstein’s field equations for spheres of fluid. Physical Review Journals Archive, 55(4):364. https://doi.org/10.1103/PhysRev. 55.364








