Gamma-ray binaries are extreme systems that produce non-thermal emission from radio to very-high-energy (>TeV) gamma rays, with the energy output in the spectral energy distribution (SED) dominated by the MeVâ€“GeV photons. Their broadband emission is usually modulated by the orbital cycle of the system, which suggests that the physical conditions are also periodic and reproducible. The diversity of systems, together with the reproducibility of the conditions within each system, makes gamma-ray binaries excellent physical laboratories in which high energy particle acceleration, diffusion, absorption, and radiation mechanisms can be explored. Nevertheless, the number of known gamma-ray binaries is still very limited, and only a six binary systems have been classified as gamma-ray binaries. These systems produce outflows of relativistic particles emitting synchrotron radio emission that extend up to several astronomical units, which correspond to projected angular scales of a few milliarcseconds (mas) at typical distances of 2-3 kpc. Very Long Baseline Interferometry (VLBI) provide mas resolution and therefore can be used to directly see this radio outflow. In this thesis we present VLBI observations of five of the six gamma-ray binaries known. We have revealed for the first time the radio structure of two gamma-ray binaries, and found periodic changes in the structure of other two. Based on these results, we have established the basic properties and behaviour of the radio emission of gamma-ray binaries on AU scales, and we have contributed to find characteristics that are common to all of them.
Moldón Vara, Francisco Javier
Directors: Marc Ribó i Gomis i Josep Maria Paredes i Poy.
Dijous, 5 Juliol, 2012
Sala de Graus Eduard Fontseré. Planta 1 Física
Eduardo Ros Ibarra. Profesor Titular de Universidad. Universitat de València. (President). Valentí Bosch i Ramon.Postdoctoral Researcher (Marie Curie Fellow).Dublin Institute for Advanced Studies. (Secretari). James Carl Alexander Miller-Jones.Curtin University Early Career Research Fellow. International Centre for Radio Astronomy Research - Curtin University, Australia. (Vocal).