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arXiv · 2608.06709

Say Hello, Wave Goodbye: Gravitational Waves from Hyperbolic PBH-SMBH Interactions

Laura Burn·Nelson Christensen·Richard Easther
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Abstract

Primordial black holes (PBHs) formed in the early Universe remain a viable dark matter candidate. Since dark matter is expected to be concentrated toward galactic centres, a significant population of PBHs would reside near a supermassive black hole (SMBH), providing a promising environment for gravitational wave emission. We consider PBHs with masses from $10^{-15}$ to $10$ solar masses on hyperbolic trajectories past an SMBH, that produce bursts of gravitational radiation during periastron passage. Sagittarius A* is an obvious location for these events, but we show that both M31* and M87* would generate similar signals, albeit at lower frequencies. We assess the detectability of both individual bursts and "popcorn" backgrounds, relative to LISA and the proposed $\mu$Ares mission. Comparing these results to plausible central halo densities, we find that unbound PBHs are unlikely to yield detectable signals.

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Laura Burn, Nelson Christensen, Richard Easther. 2026-08-07. Say Hello, Wave Goodbye: Gravitational Waves from Hyperbolic PBH-SMBH Interactions. https://arxiv.org/abs/2608.06709

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