Neutron stars in a perturbative<i>f</i>(<i>R</i>) gravity model with strong magnetic fields

Cheoun, Myung-Ki; Deliduman, Cemsinan; Güngör, Can; Keleş, Vildan; Ryu, C. Y.; Kajino, Toshitaka; Mathews, Grant J.

doi:10.1088/1475-7516/2013/10/021

Cited by 43 publications

(26 citation statements)

References 46 publications

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“…Some other authors, nevertheless, supported our work in their computations [17][18][19], In fact, Federbush et al [19], by an extensive mathematical analysis, have shown the existence of stable magnetic star solutions, which include our super-Chandrasekhar white dwarfs [10]. Nityananda and Konar [20] have raised exactly the same question as the earlier critics [15,16], but have only stated it more circuitously, contributing nothing new in our view.…”

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confidence: 72%

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Reply to “Comment on ‘Strongly magnetized cold degenerate electron gas: Mass-radius relation of the magnetized white dwarf’”

Das

Mukhopadhyay

2015

Phys. Rev. D

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We show that the upper bound for the central magnetic field of a super-Chandrasekhar white dwarf calculated by Nityananda and Konar [Phys. Rev. D 89, 103017 (2014)] and in the concerned comment, by the same authors, against our work [U. Das and B. Mukhopadhyay, Phys. Rev. D 86, 042001 (2012)] is erroneous. This in turn strengthens the argument in favor of the stability of the recently proposed magnetized super-Chandrasekhar white dwarfs. We also point out several other numerical errors in their work. Overall we conclude that the arguments put forth by Nityananda and Konar are misleading.Super-Chandrasekhar white dwarfs are currently in the limelight. This is, on one hand, due to the discovery of several peculiar, overluminous type la supemovae, e.g. SN 2006gz, SN 2007if, SN 2009dc, SN 2003fg [1-6], which seem to invoke the explosion of super-Chandrasekhar white dwarfs having mass 2.1-2.8MQ. This is all the more so, since Mukhopadhyay and his collaborators [7][8][9][10][11][12][13][14] initiated the explanation of such overluminous type la supemovae by proposing the existence of highly magnetized superChandrasekhar white dwarfs.Some authors [15,16] raised doubts regarding the stability of these super-Chandrasekhar white dwarfs, which, however, we have addressed and answered in detail in our latest works [13,14]. Some other authors, nevertheless, supported our work in their computations [17][18][19], In fact, Federbush et al. [19], by an extensive mathematical analysis, have shown the existence of stable magnetic star solutions, which include our super-Chandrasekhar white dwarfs [10]. Nityananda and Konar [20] have raised exactly the same question as the earlier critics [15,16], but have only stated it more circuitously, contributing nothing new in our view. A more serious concern, however, is that they [20] have presented erroneous results, which we correct in this article. Note that we use exactly the same symbols as in [20] for ease of comparison. Additionally, note that Nityananda and Konar [20] have used both Rt and R alternately to denote the stellar radius; however, in the present work we use only R to avoid confusion. We begin by stating that we have already solved the problem posed in Sec. IIA of [20] in our latest work [14]. In this work [14], by considering various magnetic field profdes, we have obtained stable magnetostatic equilibrium solutions of super-Chandrasekhar white dwarfs having mass as high as 3M0 in a general relativistic framework. Corresponding author. bm@physics.iisc.emet.in tupasana@physics.iisc.emet.in Next coming to Sec. IIB of [20], we note that although the formulas used in this section are correct, all the numerical estimates are incorrect. We point out that Table I of [20] lists incorrect values of Q(R9 m/R ) 4 corre sponding to different n. However, before we correct their table and comment accordingly, first we point out that even if one uses the incorrect values given in Table I of [20], then also one does not arrive at the maximum allowed central field SU pper-bound -1016 G, ...

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confidence: 72%

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confidence: 67%

Reply to “Comment on ‘Strongly magnetized cold degenerate electron gas: Mass-radius relation of the magnetized white dwarf’”

Das

Mukhopadhyay

2015

Phys. Rev. D

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“…Whittenbury et al (2012), based on quark-meson coupling model, showed that the maximum mass of neutron stars could be ≈ 2M⊙, when nuclear matter is in β-equilibrium and hyperons must appear. Apart from the exploration based on the equation of state (EoS), as mentioned above, neutron stars with ⋆ sathynius2@gmail.com † bm@physics.iisc.ernet.in mass 2M⊙ were shown to be possible by exploring effects of magnetic fields, with central field Bc ∼ 10 16 G (Pili et al 2014;Sinha et al 2013), and modification to Einstein's gravity (Arapoglu et al 2014;Astashenok et al 2012;Cheoun et al 2013). …”

Section: Introductionmentioning

confidence: 99%

GRMHD formulation of highly super-Chandrasekhar rotating magnetized white dwarfs: stable configurations of non-spherical white dwarfs

Subramanian

Mukhopadhyay

2015

Mon. Not. R. Astron. Soc.

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Here we extend the exploration of significantly super-Chandrasekhar magnetised white dwarfs by numerically computing axisymmetric stationary equilibria of differentially rotating magnetised polytropic compact stars in general relativity (GR), within the ideal magnetohydrodynamic regime. We use a general relativistic magnetohydrodynamic (GRMHD) framework that describes rotating and magnetised axisymmetric white dwarfs, choosing appropriate rotation laws and magnetic field profiles (toroidal and poloidal). The numerical procedure for finding solutions in this framework uses the 3 + 1 formalism of numerical relativity, implemented in the open source XNS code. We construct equilibrium sequences by varying different physical quantities in turn, and highlight the plausible existence of super-Chandrasekhar white dwarfs, with masses in the range of 2 − 3 solar mass, with central (deep interior) magnetic fields of the order of 10 14 G and differential rotation with surface time periods of about 1 − 10 seconds. We note that such white dwarfs are candidates for the progenitors of peculiar, overluminous type Ia supernovae, to which observational evidence ascribes mass in the range 2.1 − 2.8 solar mass. We also present some interesting results related to the structure of such white dwarfs, especially the existence of polar hollows in special cases.

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“…Modification of gravity can affect a number of important physical characteristics of NSs which can, in principle, be directly verified observationally. Among them are the mass-radius (M − R) relation [16][17][18], the properties of electromagnetic radiation from the surface of accretion disks [19], and the structure of internal and external magnetic fields [20][21][22][23]. Considering such objects within the framework of different types of f (R) gravities and using various equations of state (EoSs) for neutron matter, one can reveal the allowed forms of f (R) and EoSs satisfying the observational constraints.…”

Section: Introductionmentioning

confidence: 99%

Anisotropic neutron stars in R2 gravity

Folomeev

2018

Phys. Rev. D

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We consider static neutron stars within the framework of R 2 gravity. The neutron fluid is described by three different types of realistic equations of state (soft, moderately stiff, and stiff). Using the observational data on the neutron star mass-radius relation, it is demonstrated that the characteristics of the objects supported by the isotropic fluid agree with the observations only if one uses the soft equation of state. We show that the inclusion of the fluid anisotropy enables one also to employ more stiff equations of state to model configurations that will satisfy the observational constraints sufficiently. Also, using the standard thin accretion disk model, we demonstrate potentially observable differences, which allow us to distinguish the neutron stars constructed within the modified gravity framework from those described in Einstein's general relativity.

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Neutron stars in a perturbativef(R) gravity model with strong magnetic fields

Cited by 43 publications

References 46 publications

Reply to “Comment on ‘Strongly magnetized cold degenerate electron gas: Mass-radius relation of the magnetized white dwarf’”

Reply to “Comment on ‘Strongly magnetized cold degenerate electron gas: Mass-radius relation of the magnetized white dwarf’”

GRMHD formulation of highly super-Chandrasekhar rotating magnetized white dwarfs: stable configurations of non-spherical white dwarfs

Anisotropic neutron stars in R2 gravity

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