Origin of quasar variability timescales

Determine whether most quasar variability arises from rapid, small-scale fluctuations in the accretion flow or from longer-term secular changes tied to galaxy and halo evolution.

Background

The BAQARO framework models quasar activity as a stochastic process characterized by a coherence timescale, which sets the duration of individual luminous episodes. The authors note that the physical processes governing this timescale are not yet established. Resolving whether variability is controlled primarily by small-scale accretion physics or by longer-timescale host-galaxy evolution would provide a physical basis for the model’s phenomenological coherence-time prescription.

References

it is still unclear whether most variability arises from rapid, small-scale fluctuations in the accretion flow or from longer-term, secular changes tied to galaxy and halo evolution.

— BAQARO: Tracing Stochastic Black Hole Growth Histories and Quasar Lightcurves in a Cosmological Context  (2609.12061 - Pizzati et al., 10 Sep 2026) in Section 5.2, “The duty cycle and episodic lifetime of quasars”