From high-mass X-ray binaries to ultraluminous X-ray sources: A (very personal!) journey through the realm of X-ray binaries

X-ray binary systems are among the best astrophysical sources to study the processes of accretion of matter onto compact objects. Their broad phenomenology enables us to investigate distinct elements using a variety of analysis tools. In this talk, I will cover two main categories: high-mass X-ray binaries, represented by the archetypal Vela X-1, and ultraluminous and hyperluminous X-ray sources (ULXs and HLXs). For the first source, I will illustrate how high-resolution spectroscopy studies can help us investigate not only the compact object, but also the wind of the companion star. For the other classes, I will discuss an alternative method to determine the nature of the compact object in ULXs and I will present a population study of HLXs aiming at finding the best ULX-like candidates. This (very personal!) journey in the realm of X-ray binaries will also be a journey from sub- to super-Eddington accretion regimes.