Has deconfined quark matter been detected during GW170817/AT2017gfo?

Abstract

The detection of GW170817 and its electromagnetic counterparts allows to constrain the equation of state of dense matter in new and complementary ways. Very stiff equations of state are ruled out by the upper limit on the tidal deformability requested by the detected gravitational wave signal. Very soft equations of state are also disfavored by considering the large amount of ejected matter which powers the kilonova AT2017gfo. This translates into an allowed window for the radius of the \(1.4 M_{\odot}\) stellar configuration between \(\sim 11.5\) and \(13.5\,\)km. On the other hand, several analyses of X-ray observations suggest radii significantly smaller than \(11.5\,\)km. Here we show that by interpreting the event of August 2017 as due to the merger of a hadronic star and of a quark (or hybrid) star it is possible to satisfy all the observational constraints derived from GW170817/AT2017gfo as well as the constraints obtained by the modeling of the X-ray spectra of compact stars.