Interacting Stellar EMRIs as Sources of Quasi-Periodic Eruptions in Galactic Nuclei

Understand

A star that approaches a supermassive black hole (SMBH) on a circular extreme mass ratio inspiral (EMRI) can undergo Roche lobe overflow (RLOF), resulting in a phase of long-lived mass-transfer onto the SMBH.

• If the interval separating consecutive EMRIs is less than the mass-transfer timescale driven by gravitational wave emission (typically ~1-10 Myr), the semi-major axes of the two stars will approach each another on scales of <~ hundreds to thousands of gravitational radii.
• Close flybys tidally strip gas from one or both RLOFing stars, briefly enhancing the mass-transfer rate onto the SMBH and giving rise to a flare of transient X-ray emission.
• If both stars reside in an common orbital plane, these close interactions will repeat on a timescale as short as hours, generating a periodic series of flares with properties (amplitudes, timescales, sources lifetimes) remarkably similar to the &#34;quasi-periodic eruptions&#34; (QPEs) recently observed from galactic nuclei hosting low-mass SMBHs.