KIPAC Tea Talk: Quasi-periodic eruptions: a new probe of supermassive black holes and extreme mass-ratio inspirals / The Origin of Supermassive Black Holes from Pop III.1 Seeds and Implications for Particle Physics and Cosmology

Watch the Zoom Recording; Passcode: 1dP@Rb3r

Chakraborty Abstract: Quasi-periodic eruptions (QPEs) are a newly discovered type of recurring X-ray transient originating from supermassive black holes in nearby, low-mass galaxy nuclei. They are thought to be the first observed counterparts to extreme mass-ratio inspirals (EMRIs), long-anticipated gravitational wave sources detectable by future space-based interferometers (e.g. LISA). Thirteen QPEs are known, and in an unexpected twist, several have emerged from the accretion disks formed in tidal disruption events. I will give an overview of the surprising discoveries, observational properties, and theoretical progress in QPEs, including empirical constraints on their emission mechanisms, prospects for probing EMRI orbital dynamics using QPE timings, and estimates of the QPE rate and its implications for EMRI formation.

Tan Abstract: The origin of supermassive black holes (SMBHs) is a key open question for contemporary astrophysics and cosmology. I review various formation scenarios for SMBHs and then discuss the predictions of the Pop III.1 model, i.e., seeding via metal-free stars forming in locally isolated dark matter minihalos, where dark matter annihilation has a chance to alter the structure of the star allowing growth to supermassive scales (Banik, Tan & Monaco 2019; Singh, Monaco & Tan 2023; Cammelli et al. 2025; Sanati et al. 2025a,b; Nandal et al. 2026; for a review see Tan et al. 2024 and this project page:http://cosmicorigins.space/smbh). The model predicts that all SMBHs form very early in the Universe (i.e., by z = 20) with a spatial distribution that is initially relatively unclustered. It also makes predictions for SMBH occupation fractions, host galaxy properties, frequency of binary SMBHs and the gravitational wave background. These predictions are compared to latest results from the Hubble Space Telescope, James Webb Spact Telescope and pulsar timing array observations. Another key prediction is an early phase of “flash” ionization of the universe at z~20, which can help alleviate cosmological tensions (Hubble tension, dynamical dark energy, negative neutrino masses) (Tan 2025; Tan & Komatsu 2026; Aggarwal et al. 2026). Finally, since the Pop III.1 mechanism relies on the process of WIMP dark matter self-annihilation, there are implication for the nature of the dark matter particle.