http://arxiv.org/abs/2009.12353
We show the existence and investigate the location of the special point (SP) in which hybrid neutron star mass-radius (M-R) curves have to cross each other when they belong to a class of hybrid equation of state (EoS) constructed with generic constant–speed–of–sound (CSS) quark matter models for which the onset deconfinement is varied. We demonstrate that for a three-parameter CSS model the position of the SP in the M-R diagram is largely independent of the choice of the hadronic EoS, but in dependence on the stiffness of the quark matter EoS it spans a region that we identify. We find that the difference between the maximum mass and the SP mass depends on the mass at the onset of deconfinement so that an upper limit of $0.19~M_\odot$ for this difference is obtained from which a lower limit on the radius of hybrid stars is deduced.For neutron stars with $M<2.4~M_\odot$ this lies within a more constraining lower limit of the neutron star radius from multi-messenger observations. Together with a lower limit on the radius of hadronic stars we identify a region in the M-R diagram which can be occupied only by hybrid stars. Accordingly, we suggest that a NICER radius measurement on the massive pulsar PSR J0740+6620 in the range of 10.7-11.8 km would indicate that this pulsar is a hybrid neutron star with deconfined quark matter in the inner core.
M. Cierniak and D. Blaschke
Mon, 28 Sep 20
5/52
Comments: 9 pages, 4 figures
You must be logged in to post a comment.