Exploring the Mass Segregation Effect of X-ray Sources in Globular Clusters. IV. Evidence of Black Hole Burning in $ω$ Centauri

Abstract

Using X-ray sources as sensitive probes of stellar dynamical interactions in globular clusters (GCs), we study the mass segregation and binary burning processes in $ω$ Cen. We show that the mass segregation of X-ray sources is quenched in $ω$ Cen, while the X-ray source abundance of $ω$ Cen is much smaller than other GCs, and the binary hardness ratio (defined as $L_{\rm X}/(L_{\rm K}f_{b})$, with $f_{b}$ the binary fraction, $L_{\rm X}$ and $L_{\rm K}$ the cumulative X-ray and K band luminosity of GCs, respectively) of $ω$ Cen is located far below the $L_{\rm X}/(L_{\rm K}f_{b})-σ_{c}$ correlation line of the dynamically normal GCs. These evidences suggest that the binary burning processes are highly suppressed in $ω$ Cen, and other "heating mechanisms", very likely a black hole subsystem (BHS), are essential in the dynamical evolution of $ω$ Cen. Through the "black hole burning" processes (i.e., dynamical hardening of the BH binaries), the BHS is dominating the energy production of $ω$ Cen, which also makes $ω$ Cen a promising factory of gravitational-wave sources in the Galaxy.