2025/02/18 by Barak Rom, Re'em Sari, Rom, Barak +1 · 1 voice · 2 citations
Physics and Astronomy · #Astro and Planetary Science #Astronomy and Astrophysical Research #Astrophysics of Galaxies (astro-ph.GA) #FOS: Physical sciences #Gamma-ray bursts and supernovae #High Energy Astrophysical Phenomena (astro-ph.HE) #astro-ph.GA #astro-ph.HE
paper · pdf · doi:10.48550/arxiv.2502.13209
openalex publication_date 2025/02/18 · arxiv published 2025/02/18 · openalex created_date 2025/02/21 · arxiv updated 2025/09/09 · openalex updated_date 2026/07/28
Supermassive black holes at the centers of galaxies occasionally disrupt stars or consume stellar-mass black holes (BHs) that wander too close, producing observable electromagnetic or gravitational wave signals. We examine how mass segregation impacts the rates and distributions of such events. Assuming a relaxed stellar cluster, composed of stars and stellar-mass BHs, we show that the tidal disruption rate of massive stars (m\gtrsim M_\odot) is enhanced relative to their abundance in the stellar population. For stars up to m≈3M_\odot, this enhancement is roughly m/M_\odot and it is driven by segregation within the sphere of influence. Stars with masses m\gtrsim3M_\odot, if relaxed, are predominantly scattered by more massive stellar-mass BHs, leading to a constant enhancement factor of ≈ 9, independent of mass. This aligns with observational evidence suggesting an over-representation of massive stars in tidal disruption events. For stellar-mass BHs, we predict an enhancement factor scaling as m_\bullet1/2 for plunges and m_\bullet3/2 for extreme-mass-ratio inspirals (EMRIs). The power of one-half in both cases reflects the shorter relaxation times of heavier BHs, allowing them to segregate into the sphere of influence from greater distances, thereby increasing their abundance. The additional power in the EMRIs' rate arises from the tendency of heavier BHs to circularize and sink inward more efficiently. Finally, we estimate the rate of main-sequence star inspirals and find that it favors low-mass stars (m\lesssim M_\odot). This seems compatible with the observationally estimated rate of quasiperiodic eruptions.