Abstract
This Thesis revolves around the topic of black holes (BHs) in X-ray binaries (XRBs). The trigger of this work was to understand how stellar-mass BHs form, a question which we tackled both with theoretical as well as observational studies. The formation mechanism of BHs is an unsolved problem in high-energy astrophysics, in particular when it comes to the amount of mass ejected at formation and to how large is the velocity BHs acquire at birth (the so-called natal kick), if they acquire a velocity at all. One way of tackling these uncertainties is to perform physically-motivated simulations of the core-collapse supernova, which is computationally challenging. Another way is to study the birth and evolution of XRBs hosting a BH accreting from a stellar companion, which is the method we use in this Thesis. On the theoretical side, we combine an approach typical of binary population synthesis calculations with a more detailed approach which solves for the binary evolution of each source. When possible, we describe the different evolutionary paths of the binary via analytical calculations and time-scale arguments. On the observational side, we combine the techniques of optical spectroscopy and photometry, with the goal of increasing the sample of Galactic BHs
