Probing Extreme-density Matter with Gravitational-wave Observations of Binary Neutron Star Merger Remnants

• Published in: Astrophysical journal. Letters Vol. 842; no. 2; p. L10
• Main Authors: Radice, David, Bernuzzi, Sebastiano, Pozzo, Walter Del, Roberts, Luke F., Ott, Christian D.
• Format: Journal Article
• Language: English
• Published: Austin The American Astronomical Society 20.06.2017; IOP Publishing
• Subjects: ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; BINARY STARS; BLACK HOLES; Computer simulation; DEGREES OF FREEDOM; DENSITY; Detectors; EQUATIONS OF STATE; EXCEPTIONS; GRAVITATIONAL WAVES; LUMINOSITY; NEUTRON STARS; PHASE TRANSFORMATIONS; Phase transitions; Relativity; SIMULATION; Softening; Star mergers; stars: neutron; Stellar evolution; SUPERNOVA REMNANTS
• ISSN: 2041-8205; 2041-8213
• DOI: 10.3847/2041-8213/aa775f

We present a proof-of-concept study, based on numerical-relativity simulations, of how gravitational waves (GWs) from neutron star merger remnants can probe the nature of matter at extreme densities. Phase transitions and extra degrees of freedom can emerge at densities beyond those reached during the inspiral, and typically result in a softening of the equation of state (EOS). We show that such physical effects change the qualitative dynamics of the remnant evolution, but they are not identifiable as a signature in the GW frequency, with the exception of possible black hole formation effects. The EOS softening is, instead, encoded in the GW luminosity and phase and is in principle detectable up to distances of the order of several megaparsecs with advanced detectors and up to hundreds of megaparsecs with third-generation detectors. Probing extreme-density matter will require going beyond the current paradigm and developing a more holistic strategy for modeling and analyzing postmerger GW signals.