Merger of Compact Stars in the Two-families Scenario

Abstract

We analyse the phenomenological implications of the two-families scenario on the merger of compact stars. That scenario is based on the coexistence of both hadronic stars and strange quark stars. After discussing the classification of the possible mergers, we turn to detailed numerical simulations of the merger of two hadronic stars, i.e., "first family" stars in which delta resonances and hyperons are present, and we show results for the threshold mass of such binaries, for the mass dynamically ejected and the mass of the disk surrounding the post-merger object. We compare these results with those obtained within the one-family scenario and we conclude that relevant signatures of the two-families scenario can be suggested, in particular: the possibility of a rapid collapse to a black hole for masses even smaller than the ones associated to GW170817; during the first milliseconds, oscillations of the postmerger remnant at frequencies higher than the ones obtained in the one-family scenario; a large value of the mass dynamically ejected and a small mass of the disk, for binaries of low total mass. Finally, based on a population synthesis analysis, we present estimates of the number of mergers for: two hadronic stars; hadronic star -strange quark star; two strange quark stars. We show that for unequal mass systems and intermediate values of the total mass, the merger of a hadronic star and a strange quark star is very likely (GW170817 has a possible interpretation into this category of mergers). On the other hand, mergers of two strange quark stars are strongly suppressed.

Constraints on Microscopic and Phenomenological Equations of State of Dense Matter from GW170817

“…Larger hyperons concentrations could be present in the post-merger compact object and show peculiar signatures in the GW signal at a few kHz [56,57], which could be detected with the third generation of GW observatories. A similar analysis can be extended also to the case of the formation of other degrees of freedom which may be produced in the high density core of neutron stars such as quark matter or meson condensates [33,58].…”

Essentially non-oscillatory and weighted essentially non-oscillatory schemes

“…Numerical simulations of neutron star/black hole binaries in the near-equal-mass regime were performed in Foucarta et al (2019). The merger of compact stars in the twofamilies scenario was studied in Pietri et al (2019). The turbulence dynamo in the stratified medium of Galaxy clusters was simulated in Roh et al (2019).…”

On the deconfinement phase transition in neutron-star mergers

“…The possibility of the merger of pure quark stars have also investigated in the past [10]. More recently, attention has been paid to the merger of twin stars in terms of equilibrium models [11; 12] or through simulations in full general relativity of the merger of a hadronic and a quark star [13] and quark stars with hadronic crusts [14]. In a holographic approach, Ref [15] has found not to be possible to reach the phase transition to the quark phase before collapsing to a black hole.…”