Il viaggio delle stelle iperveloci

Hypervelocity stars (HVSs) are stars that, according to Hills (1988), are ejected by the central super-massive black hole (SMBH) of the Milky Way (MW) at speeds that exceed the MW escape velocity. HVSs are now observed in the halo of the Milky Way and thus they link the outer parts of the MW to its very center. Their unbound trajectories are determined by the gravitational potential of the MW; thus, HVSs represent a unique probe of the MW mass distribution, from its very center out to the outer halo. In this Thesis, I study the time evolution of the positions and velocities for a sample of HVSs ejected by the Galactic SMBH, according to the Hills ejection mechanism. To this aim, I implement a numerical code to perform numerical simulations of the HVS trajectories for two different models of the MW potential. The aim is to investigate how the trajectories of HVSs and their velocities are affected by the MW mass distribution. After considering a simple, spherically symmetric potential for comparison with the literature, I move to a more complex and realistic axisymmetric potential. The code successfully computes the HVS trajectories and velocity distributions in all my case studies, yielding results broadly consistent with the literature, where the comparison can be performed. Minor inconsistencies are still under investigation. The code implemented in this Thesis, represents a useful tool for future work in this field. It is the starting point for the creation of mock catalogs of HVSs that include stars' positions and velocities in different models of the MW potential. These mock catalogs will be used both for comparing the simulates data with the available HVS data and for forecasts for future astrometric missions (as, e.g. Theia), with the aim to constrain the MW mass distribution for any given HVS generation mechanism.