Constraining the rate of transients in ultra-magnetised neutron stars with magnetothermal simulations.

Neutron stars are one of the possible end points of the life of a massive star. They are characterized by having a mass comparable to that of the sun, condensed in 10 km radius, and extremely strong magnetic fields. Magnetars are the subclass of neutron stars with the highest value of the magnetic field. This characteristic is believed to be responsible for their high brightness in the soft X-rays and the emission of powerful transients in the hard X-rays. These transients are believed to be associated to the re-organization of the magnetic field within the crust, that can induce an excess of stress in some points, with the consequent mechanical failure for the crust itself. This process can rapidly release large amounts of energy through the plastic deformation of the crust, which is then emitted, at least in part, radiatively. This thesis studies the properties of crustal failures in the framework of magneto-thermal evolution numerical models. A detailed statistical analysis is performed on the failure rate, waiting time, position, and released energy associated to the failures, exploring their dependence on different stellar parameters such as mass, structure, magnetic field intensity and geometry. Although the phenomenology found in the results is very diverse, a tentative analogy between the final findings and the observations of a prolific FRB is proposed.