Lifting the Veil on Quark Matter in Compact Stars with Core g-mode Oscillations

Abstract

Compact stars containing quark matter may masquerade as neutron stars in the range of measured mass and radius, making it difficult to draw firm conclusions on the phase of matter inside the star. The sensitivity of core $g$-mode oscillations to the presence of a mixed phase may alleviate this difficulty. In hybrid stars that admit quark matter in a mixed phase, the $g$-mode frequency rises sharply due to a marked decrease in the equilibrium sound speed. Resonant excitation of $g$-modes can leave an imprint on the waveform of coalescing binary compact stars. We present some analytic and numeric results to assess the sensitivity displayed by $g$-mode oscillations to quark matter in a homogeneous or mixed phase and find that the $g$-mode can probe the fraction of quark matter inside the star.