Multi-wavelength study of binary millisecond pulsars

The main object of my research activity has been the multi-wavelength study of the temporal evolution of binary millisecond pulsars (MSPs), from the accretion phase to the radio pulsar state. Throughout their evolution, binary MSPs show a rich phenomenology, manifesting themselves as accreting millisecond X-ray pulsars (AMXPs), transitional millisecond pulsars (tMSPs) and radio millisecond pulsars (RMSPs). Each of these classes has been object of study in my thesis, with the purpose of addressing open questions about the processes responsible for their multi-wavelength pulsed emission and the physical conditions in which they operate. The rapid variability between low/high and flares modes in tMSPs is another focus of this thesis. To investigate these phenomena, I made use of X-ray spectral analysis techniques, applying it to the study of the tMSPs XSS J12270–4859 and PSR J1023+0038. The presence of an accretion disc and a possible intra-binary shock emission in RMSPs and AMXPs systems has also been investigated in this thesis, given its implications for the study of the evolution of these objects. In this thesis, I present new results on the emission phenomena associated with binary MSPs in different stages of their evolution. The new observational evidences, in particular the discovery of optical/UV pulsations in the AMXP SAX J1808.4–3658 could lead to important developments of the current evolutionary scenario of MSPs.