Lunch talk on Mar. 3, 2025

Gravitational-Wave Signatures from Quasi-Periodic Eruptions

Speaker: Leif Lui (HKU)

Venue: Video Conference

Time: 12:45 PM, Monday, Mar. 3, 2025

Abstract: 

Quasi-periodic eruptions (QPEs) have evaded astronomers for the past several years. Despite the successful detection of their ultraluminous X-ray signatures from XMM-Newton, eROSITA, and Chandra, the mechanism that powers them remains a mystery. The elusive physical origin of QPEs has spawned many theoretical models to explain their electromagnetic (EM) signatures, with the most widely accepted being the extreme-mass-ratio-inspiral (EMRI) secondary disk collision model. In this talk, we provide a theoretical framework to predict the gravitational-wave (GW) signatures from an EMRI where the orbiter interacts with the accretion disk of a supermassive black hole (SMBH). We compute the trajectory of an orbiter with orbiter-disk interactions (ODIs) using geodesic ray tracing accounting for changes in energy and angular momentum due to GW radiation. Then, using the FEW software package, the GW amplitude and phases are calculated by solving the radial Teukolsky equation along the orbiter's trajectory and interpolating the fundamental frequencies from the Kerr geodesic constants $(E, L_z,\\mathscr{C})$, respectively. Finally, we compute the GW spectra to calculate the signal-to-noise ratios (SNR) and mismatch using the noise curves from LISA and TianQin.We plan to extend our analyses to generic Kerr geodesics and perform some Markov-Chain-Monte-Carlo (MCMC) simulations to predict the GW signatures for current QPEs. Assuming the EMRI secondary disk collision model is valid, the objective of this research is to provide novel predictions of the GW signatures of QPEs based on this model, and hopefully, these signatures can be detected by future space-based detectors like LISA, TianQin, or µ-Ares.