2011A&A...525A..87V

The spectacular variability of microquasars has led to many efforts to classify their observed behaviors in a few states. The progress made in the understanding of the quasi-periodic oscillations observed in these objects now makes it possible to develop a new way of identifying order in their behavior, based on the theorized physical processes associated with these oscillations. This development will also help us to reunite microquasars in a single classification based on the physical processes at work and therefore independent of their specific properties (mass, variation timescale, outburst history, etc.). This classification is intended to be a tool to improve our understanding of microquasar behavior and not to replace phenomenological states. We start by considering three instabilities that can cause accretion in the disk. We compare the conditions for their development, and the quasi-periodic oscillations they can be expected to produce, with the spectral states in which these quasi-periodic oscillations are observed and sometimes coexist. From the three instabilities that we proposed to explain the three states of GRS 1915+105 we actually found the theoretical existence of four states. We compared those four states with observations and also how those four states can be seen in a model-independent fashion. Those four state can be used to find an order in microquasar observations, based on the properties of the quasi-periodic oscillations and the physics of the associated instabilities.