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Variability in Relativistic Jets: the Fastest Time Scales at all Wavelengths

Final Report Summary - MULTIFAST (Variability in Relativistic Jets: the Fastest Time Scales at all Wavelengths)

Jets appear to be ubiquitous in accreting systems, but the origin of the observed accretion disc-jet coupling remain largely unknown. The project proposed to fully harness a new window recently opened in Astrophysics: the study of multi-lambda fast variability from relativistic jets from stellar-mass compact objects. The objective has been tackled with a multi-disciplinary approach, working on both observations and theory, maximizing the scientific exploitation of the method. The project has evolved smoothly and overall successfully. The PI of the project was hired with a permanent position at the host institution, and one post-doctoral fellow was hired to work fully on the project. The team has included also two undergraduate students, who have both obtained their Master degree with a thesis on this project under the PI supervision. One of them has entered subsequently a PhD program at the Università dell’Insubria, with a project under the PI co-supervision. Several international collaborators have been invited to work with the team on the various aspects of the projects. The three main objectives of the projects (definition and implementation of timing statistics and software; numerical code for the variable emission from a relativistic jet; analysis of existing datasets) have proceeded as planned, and initial important results have been obtained, including: the discovery of a peculiar quasi-periodic oscillation in the infrared emission, at half the frequency of the one observed simultaneously in X-rays, allowing us to place geometrical constraints to the accretion flow (Kalamkar, Casella et al. 2016, MNRAS, 460, 3284); the discovery of the first sub-second quasi-periodic oscillation in the infrared emission from a jet (Casella et al. 2016, to be submitted); the detailed study of the infrared-X-ray rms-flux relation (Vincentelli et al. 2016, to be submitted); the discovery of important novel re-heating properties of internal jet variability (Pe’er, Long & Casella, submitted to ApJ); the definition and implementation of a new timing technique to obtain an estimate of the Transfer Function in case of non linearity (Vincentelli et al. 2017, to be submitted). Other results have been and are being obtained within the above mentioned international collaborations, from which other publications have resulted and others are foreseen. This project has provided the fellow with an excellent visibility within and outside the host country, helping his re-integration after his years abroad.