Research in Astronomy and Astrophysics A note on the discovery of a 2M pulsar ∗

Abstract It is conventionally thought that the state equation of dense matter softens and thus cannot result in high maximum mass if pulsars are quark stars and that a recently discovered 2M pulsar (PSR J1614–2230) may make pulsars unlikely to be quark stars. However, this standard point of view would be revisited and updated if quark clustering could occur in cold quark matter because of the strong coupling be-tween quarks at realistic baryon densities in compact stars. It can be argued that the state equation of clustered quark matter stiffens to support compact stars with maxi-mum mass Mmax> 2M. In this brief note, it is demonstrated that large parameter space ranges are allowed for Mmax> 2M in a Lennard-Jones model of clustered quark matter and the newly measured highest mass of PSR J1614–2230 would be meaningful for constraining the number of quarks inside a single quark-cluster to be Nq <∼103. Key words: dense matter — elementary particles — pulsars: general — stars: neutro