The two-families scenario of compact stars: signatures and implications on GRBs

In the last years the possibility of discriminating between the various theoretically possible compositions of a compact “neutron” star has become more and more convincing and it is based on the measure of a few fundamental quantities, such as the radii (NICER, LOFT), the moment of inertia (SKA) and/or the gravitational wave signal before and after the merging of two compact stars (VIRGO, LIGO).
I will outline the so-called two-families scenario in which both stars having very small radii (of the order of about 10.5 km) and stars having very large masses (of the order or larger than about 2 Ms) can exist. In that scenario very dense stars, having small radii, are made of neutron, protons, hyperons and other hadronic resonances, while the most massive stars are strange-quark stars, i.e. objects entirely made of deconfined quark matter. I will discuss the implications of the two-families scenario on short and long Gamma Ray Bursts within the proto-magnetar model of GRBs, showing that quark deconfinement can be responsible both of the rapid termination of the prompt emission in short GRBs and of late time activity in long GRBs.