Event details

Date
March 8, 2027  – March 12, 2027
Location
Sport & Kurhotel at Bad Moos - Via Val Fiscalina 27, 39030, Sexten

Scientific Rationale

Accretion onto compact objects represents the most efficient mechanism for converting gravitational energy into radiation. It powers a broad range of astrophysical sources across the mass scale, from stellar-mass black holes in X-ray binaries to the supermassive black holes (SMBHs) shining as active galactic nuclei (AGN). Growing evidence over the last two decades of observations called for accretion above the Eddington limit being no longer a theoretical curiosity, but rather a recurring hypothesis, invoked to explain some of the most pressing open problems in high-energy astrophysics and cosmology.

From a cosmological perspective, the existence of SMBHs with masses exceeding 10^8 M⊙ within the first billion years of cosmic history, observed as luminous quasars, challenges standard growth scenarios. If these systems originated from light seeds (~10^2–10^3 M⊙), prolonged or recurrent phases of super-Eddington accretion appear unavoidable. On galactic scales, extreme accretion episodes are ideal conditions for launching powerful radiation-driven winds and relativistic outflows, widely recognized as key ingredients to drive the black hole–galaxy co-evolution in place through feedback. On intermediate mass scales, super-critical accretion onto ~10^5–10^6 M⊙ black holes has been proposed to explain the recently identified population of faint, compact AGN dubbed “little red dots,” potentially revealing a previously hidden mode of black hole growth. Transient phenomena such as tidal disruption events (TDEs) may also provide nearby laboratories where super-Eddington flows can be studied in real time.

Despite its broad relevance, super-Eddington accretion still lacks both unambiguous observational confirmation and a predictive theoretical framework capable of linking microphysical mechanisms to macroscopic, observable consequences. Radiation-hydrodynamic simulations have made substantial progress, yet key uncertainties remain regarding geometry, radiative efficiency, duty cycles, and the interplay between inflows and outflows. Observationally, degeneracies between obscuration, anisotropy, and intrinsic luminosity further complicate the interpretation.

This workshop will bring together a wide and transversal community working on accretion onto SMBH at all cosmic epochs, bridging steady and transient phenomena. By fostering dialogue between observers, theorists, and simulation experts, we aim to critically assess the state of the field and identify synergies across traditionally separate sub-communities.

We will organize the discussion around four fundamental questions concerning super-Eddington accretion:

  • How well can we measure the Eddington ratio? Since the Eddington ratio is defined as the bolometric luminosity to BH mass ratio, it inherits the uncertainties from these fundamental quantities. This leads us to ask: how confident are we on this type of measurement?
  • When does super-Eddington accretion occur? Is it preferentially associated with specific evolutionary stages, environments, or cosmic epochs?
  • Where does it take place? Which classes of sources and physical conditions most naturally give rise to sustained super-critical flows?
  • How does accretion cross the Eddington limit? What physical mechanisms, from photon trapping to geometric beaming and magnetically driven turbulence, enable it, and what are the robust observational diagnostics and feedback signatures?

By addressing these questions in a coherent framework, this workshop aims to determine whether super-Eddington accretion represents an exceptional, short-lived phenomenon or a fundamental and widespread phase in black hole growth. Establishing this will have far-reaching consequences for our understanding of early SMBH formation, AGN demographics, and black hole–galaxy co-evolution across cosmic time.

Confirmed Invited Speakers

Elena dalla Bontà – University of Padova, INAF-OAPd
Matthew Temple – Durham University
Tommaso Zana – Sapienza University
Claudio Ricci – University of Geneva
Alessia Tortosa – INAF-OAS
Hannah Übler – MPE
Stefano Carniani – Scuola Normale Superiore
Erini Lambrides – NASA Goddard Space Flight Center

Organizers

SOC:  Bartolomeo Trefoloni (Scuola Normale Superiore, INAF-Arcetri), Andrea Sacchi (INAF-IASF Milano, CFA | Harvard & Smithsonian), Matilde Signorini (ESA-ESTEC, INAF-Arcetri).

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Payment details

Registration Fee
370,00 EUR
Workshop code for bus and payment
SCON27