Maximal mass strange quark stars based on the modified MIT model with variable vacuum pressure

Strange stars (SS), composed predominantly of strange quark matter (SQM) with a small fraction of electrons to maintain charge neutrality, form a continuous family with neutron stars along the mass-density curve. This study employs a modified version of the Massachusetts Institute of Technology (MIT) bag model to describe SQM, incorporating a variable vacuum pressure B that depends on the baryon number density, n B : B ( n B ) . A Gaussian approximation is used for this dependence, ensuring a finite asymptotic limit. The equations of state for SQM are calculated for various bag model parameters ( m s , α c ) and Gaussian approximation parameters. Through numerical integration of the Tolman-Oppenheimer-Volkov (TOV) equations, the integral properties of strange quark stars are derived. The model predicts maximum SS masses exceeding those of observed massive pulsars, including P S R J 0740 + 6620 ( 2.14 M ⊙ ) and P S R J 2215 + 5135 ( 2.27 M ⊙ ) , as well as the secondary component of the G W 190814 system with ( 2.50 − 2.67 ) M ⊙ . Additionally, the results align with the mass range ( 2.09 − 2.27 ) M ⊙ of the compact companion of the recently observed millisecond binary pulsar P S R J 0514 − 4003 E , detected by the Karoo Array Telescope. These findings suggest that the considered pulsars are viable candidates for SS and support the MIT bag model as a suitable framework for describing SQM.