Quark stars with 2.6 $$M_\odot $$ in a non-minimal geometry-matter coupling theory of gravity

Abstract This work analyses the hydrostatic equilibrium configurations of strange stars in a non-minimal geometry-matter coupling (GMC) theory of gravity. Those stars are made of strange quark matter, whose distribution is governed by the MIT equation of state. The non-minimal GMC theory is described by the following gravitational action: $$f(R,L)=R/2+L+\sigma RL$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow> <mml:mi>f</mml:mi> <mml:mo>(</mml:mo> <mml:mi>R</mml:mi> <mml:mo>,</mml:mo> <mml:mi>L</mml:mi> <mml:mo>)</mml:mo> <mml:mo>=</mml:mo> <mml:mi>R</mml:mi> <mml:mo>/</mml:mo> <mml:mn>2</mml:mn> <mml:mo>+</mml:mo> <mml:mi>L</mml:mi> <mml:mo>+</mml:mo> <mml:mi>σ</mml:mi> <mml:mi>R</mml:mi> <mml:mi>L</mml:mi> </mml:mrow> </mml:math> , where R represents the curvature scalar, L is the matter Lagrangian density, and $$\sigma $$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mi>σ</mml:mi> </mml:math> is the coupling parameter. When considering this theory, the strange stars become larger and more massive. In particular, when $$\sigma =50$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow> <mml:mi>σ</mml:mi> <mml:mo>=</mml:mo> <mml:mn>50</mml:mn> </mml:mrow> </mml:math> km $$^2$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:msup> <mml:mrow/> <mml:mn>2</mml:mn> </mml:msup> </mml:math> , the theory can achieve the 2.6 $$M_\odot $$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:msub> <mml:mi>M</mml:mi> <mml:mo>⊙</mml:mo> </mml:msub> </mml:math> , which is suitable for describing the pulsars PSR J2215+5135 and PSR J1614-2230, and the mass of the secondary object in the GW190814 event. The 2.6 $$M_\odot $$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:msub> <mml:mi>M</mml:mi> <mml:mo>⊙</mml:mo> </mml:msub> </mml:math> is a value hardly achievable in General Relativity, even considering fast rotation effects, and is also compatible with the mass of PSR J0952-0607 ( $$M = 2.35 \pm 0.17 ~M_\odot $$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow> <mml:mi>M</mml:mi> <mml:mo>=</mml:mo> <mml:mn>2.35</mml:mn> <mml:mo>±</mml:mo> <mml:mn>0.17</mml:mn> <mml:mspace/> <mml:msub> <mml:mi>M</mml:mi> <mml:mo>⊙</mml:mo> </mml:msub> </mml:mrow> </mml:math> ), the heaviest and fastest pulsar in the disk of the Milky Way, recently measured, supporting the possible existence of strange quark matter in its composition. The non-minimal GMC theory can also give feasible results to describe the macroscopical features of strange star candidates.

Hali tarjima qilinmagan