Neutron Star Mergers at the Dawn of Multimessenger Astrophysics: massive binaries, accretion disks and phase transitions

Multimessenger astrophysics represents a new paradigm in our understanding of the universe, transcending traditional observational boundaries by combining information from various cosmic messengers. One of the most notable events in multimessenger astrophysics is the merger of two neutron stars, which was first detected in 2017 through the simultaneous observation of gravitational waves (GW) and electromagnetic radiation across the entire spectrum. This groundbreaking discovery provided many insights on different physical phenomena, from the properties of matter at very high densities to the origin of heavy elements. In this thesis we mainly focus on the study of the second binary neutron star (BNS) merger GW190425, detected by the Ligo and Virgo interferometers on the 25th of April, 2019, on the characterization of the accretion discs formed from the merger of a binary system composed by two neutron stars and on the effects of a hadron to quark phase transition that can occurs during such mergers.