Normal and Quasinormal Modes of Holographic Multiquark Star

Abstract

The quadrupole normal-mode oscillation frequency $f_{n}$ of multiquark star are computed for $n=1-5$. At the transition from low to high density multiquark in the core region, the first 2 modes jump to larger values, a distinctive signature of the presence of the high-density core. When the star oscillation couples with spacetime, gravitational waves~(GW) will be generated and the star will undergo damped oscillation. The quasinormal modes~(QNMs) of the oscillation are computed using two methods, direct scan and WKB, for QNMs with small and large imaginary parts respectively. The small imaginary QNMs have frequencies $1.5-2.6$ kHz and damping times $0.19-1.7$ secs for multiquark star with mass $M=0.6-2.1 M_{\odot}$~(solar mass). The WKB QNMs with large imaginary parts have frequencies $5.98-9.81$ kHz and damping times $0.13-0.46$ ms for $M\simeq 0.3-2.1 M_{\odot}$. They are found to be the fluid $f-$modes and spacetime curvature $w-$modes respectively.