The evolution of binary neutron star post-merger remnants: a review

• Published in: General relativity and gravitation Vol. 53; no. 6
• Main Authors: Sarin, Nikhil, Lasky, Paul D.
• Format: Journal Article
• Language: English
• Published: New York Springer US 01.06.2021; Springer Nature B.V
• Subjects: Astronomy; Astrophysics and Cosmology; Binary Neutron Star mergers; Binary stars; Black holes; Bulk density; Classical and Quantum Gravitation; Differential Geometry; Equations of state; Explosions; Gamma ray astronomy; Gamma ray bursts; Gamma rays; Gravitational waves; Gravity; Invited Review: State of the Field; Mathematical and Computational Physics; Neutron stars; Neutrons; Nuclear matter; Physics; Physics and Astronomy; Quantum Physics; Relativity Theory; Star mergers; Stellar evolution; Terrestrial environments; Theoretical; Universe; Remnants; Gamma-ray bursts; Kilonovae; Gravitational waves; Binary neutron star mergers
• ISSN: 0001-7701; 1572-9532
• DOI: 10.1007/s10714-021-02831-1

Two neutron stars merge somewhere in the Universe approximately every 10 to 100 s, creating violent explosions potentially observable in gravitational waves and across the electromagnetic spectrum. The transformative coincident gravitational-wave and electromagnetic observations of the binary neutron star merger GW170817 gave invaluable insights into these cataclysmic collisions, probing bulk nuclear matter at supranuclear densities, the jet structure of gamma-ray bursts, the speed of gravity, and the cosmological evolution of the local Universe, among other things. Despite the wealth of information, it is still unclear when the remnant of GW170817 collapsed to form a black hole. Evidence from other short gamma-ray bursts indicates a large fraction of mergers may form long-lived neutron stars. We review what is known observationally and theoretically about binary neutron star post-merger remnants. From a theoretical perspective, we review our understanding of the evolution of short- and long-lived merger remnants, including fluid, magnetic-field, and temperature evolution. These considerations impact prospects of detection of gravitational waves from either short- or long-lived neutron star remnants which potentially allows for new probes into the hot nuclear equation of state in conditions inaccessible in terrestrial experiments. We also review prospects for determining post-merger physics from current and future electromagnetic observations, including kilonovae and late-time X-ray and radio afterglow observations.