X-ray Quasi-Periodic Eruptions &

Repeating Nuclear Transients
​​​​​

16-19 June 2025

European Space Astronomy Centre (ESAC), Madrid

A series of extreme-variability phenomena associated with supermassive black holes (SMBHs) in galactic nuclei are being revealed with increasing frequency in recent years thanks to enhanced survey capabilities across the electromagnetic spectrum. The observation of these extreme phenomena has opened the way to the study of the physics of SMBHs in real time - something that, until a decade ago, was exclusively associated with stellar-mass black holes.

As the baseline of follow-up observations extends, repeating events have gathered more and more observational evidence in the recent past. These Repeating Nuclear Transients could be associated, for instance, with episodic mass transfer and partial Tidal Disruption Events; the interaction between the central SMBH - or its accretion flow - and a secondary orbiting object in an Extreme or Intermediate Mass-Ratio Inspiral system; or with the presence of SMBH binaries in some galactic nuclei. 

Understanding the diverse phenomena presented by multi-wavelength observations - a non-exhaustive list of which is given below - is challenging and competing interpretations are being actively debated. With this workshop, we aim at providing an environment where observers and theorists can gather together to investigate whether a detailed look at individual sources, and the broader characteristics of source samples, can reveal common threads which will enable us to advance our understanding of the dynamic and complex environments which exist in galactic nuclei.

Topics:

• Full and partial Tidal Disruption Events​​​​

• Multi-wavelength emission and outflows in nuclear transients​​​​​​

• X-ray Quasi-Periodic Eruptions in galactic nuclei

• Quasi-Periodic Oscillations from supermassive black holes

• Changing-look and changing-state Active Galactic Nuclei

• Supermassive black hole binaries, Extreme Mass-Ratio Inspirals, Gravitational Waves

• Theory and numerical simulations ​​​​​​​

Invited speakers:

Kate Alexander​​​​​ - University of Arizona

Iair Arcavi - Tel Aviv University

Eric Coughlin - Syracuse University

Margherita Giustini - Centro de Astrobiología

Itai Linial - Institute for Advanced Studies and Columbia University

Megan Masterson - MIT Kavli Institute

Elena Maria Rossi - Leiden University

Benny Trakhtenbrot - Tel Aviv University

Sjoert van Velzen - Leiden University

Thomas Wevers - Space Telescope Science Institute

Acknowledgements:

The workshop is funded by the ESA Space Science Faculty