The merger of two compact stars: a tool for dense matter nuclear physics

TL;DR

This paper reviews how gravitational and electromagnetic signals from compact star mergers can constrain dense matter physics, highlighting insights from GW170817 and proposing interpretations within a two-families scenario.

Contribution

It analyzes multi-messenger signals from star mergers to extract information about the dense matter equation of state, including a novel interpretation of GW170817.

Findings

Constraints on the equation of state from merger signals

Impact of particle composition on post-merger remnants

Interpretation of GW170817 as a hadronic-quark star merger

Abstract

We discuss the different signals, in gravitational and electromagnetic waves, emitted during the merger of two compact stars. We will focus in particular on the possible contraints that those signals can provide on the equation of state of dense matter. Indeed, the stiffness of the equation of state and the particle composition of the merging compact stars, strongly affect e.g. the life time of the post-merger remnant and its gravitational wave signal, the emission of the short gamma-ray-burst, the amount of ejected mass and the related kilonova. The first detection of gravitational waves from the merger of two compact stars in August 2017, GW170817, and the subsequent detections of its electromagnetic counterparts, GRB170817A and AT2017gfo, is the first example of the era of "multi-messenger astronomy": we discuss what we have learned from this detection on the equation of state of compact stars and we provide a tentative interpretation of this event, within the two families scenario, as due to the merger of a hadronic star with a quark star.