Gravitational Waves from the Phase Transition of NS to QS

• Published in: The Astrophysical journal Vol. 893; no. 2; pp. 151 - 162
• Main Authors: Prasad, R, Mallick, Ritam
• Format: Journal Article
• Language: English
• Published: Philadelphia The American Astronomical Society 01-04-2020; IOP Publishing
• Subjects: Astrophysics; Combustion; Density; Flavors; Frequency ranges; Gravitation; Gravitational waves; Neutron star cores; Neutron stars; Neutrons; Nuclear matter; Phase transitions; Quarks; Shock discontinuity; Shock waves; Shocks
• ISSN: 0004-637X; 1538-4357
• DOI: 10.3847/1538-4357/ab7f2b

In this article, we study the combustion of a neutron star to a hybrid star. We assume that a sudden density fluctuation at the center of the neutron star initiates a shock discontinuity near the center of the star. This shock discontinuity deconfines nuclear matter to two-flavor quark matter, initiating the combustion of the star. This combustion front propagates from the center to the surface, converting nuclear matter to two-flavor quark matter. This combustion stops at some radial point inside the star, as at this density the shock wave becomes rather weak. Although the combustion stops, a simple shock wave propagates to the surface. We study the gravitational-wave signal for such a phase transition of a neutron star to a hybrid star. We find that such a phase transition has a unique gravitational-wave strain of amplitude 10−21. These signals last for few tens of s and show small oscillating behavior where the phase transition stops. The power spectrum consists of peaks at the fairly high-frequency range. The conversion from neutron star to hybrid star has a unique signature in the gravitational-wave signal, which could help with defining the phase transition and the fate of the neutron star.