Constraining quark star properties with density-dependent interactions within the MIT bag model

Abstract The nature of ultra-dense matter in compact stars remains a fundamental question in astrophysics, and quark stars representing a plausible alternative to neutron stars. The potential existence of quark stars depends on strange quark matter stability, which requires a realistic equation of state (EOS) that physically describes both deconfinement and the interactions in the deconfined phase. We therefore develop a self-consistent framework featuring two density-dependent components: a Gaussian bag pressure, modeling the approach to asymptotic freedom, and an exponentially decaying vector coupling strength, accounting for the short-range interactions due to color-charge screening in dense deconfined quark matter. Our results demonstrate that this formulation significantly enhances the stability of strange quark matter, achieving an energy per baryon below the 930 MeV threshold and effectively suppressing the speed of sound at high densities. The resulting mass–radius relations give maximum masses in the range of 2.1−2.6 $$M_{\odot }$$ <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> for $$G_{V0}$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:msub> <mml:mi>G</mml:mi> <mml:mrow> <mml:mi>V</mml:mi> <mml:mn>0</mml:mn> </mml:mrow> </mml:msub> </mml:math> = 0.1–0.3 $$\text {fm}^2$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:msup> <mml:mtext>fm</mml:mtext> <mml:mn>2</mml:mn> </mml:msup> </mml:math> . Stronger quark–quark interactions can support more massive quark stars, whereas configurations with masses below 1.8 $$M_{\odot }$$ <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> remain largely unaffected. Furthermore, the results appear compatible with many constraints from NICER, LIGO/Virgo, and other observatories.