Coffee talks
Friday 11/04/2025 @ 11:30, Sala riunioni quarto piano e on line (meet.google.com/sue-bwvk-axf)
Thalia Traianou (Instituto de Astrofísica de Andalucía, IAA - CSIC, Granada, Spain), "Unveiling the Jet and Magnetic Field Dynamics of the Best Sub-Parsec Binary Black Hole Candidate OJ 287 with Space VLBI"
OJ 287 is one of the most fascinating blazars, believed to host a binary supermassive black hole system and exhibiting a rich history of multi-wavelength variability. In this talk, I will present high-resolution 22 GHz space VLBI observations of OJ 287 from RadioAstron (April 2016), offering an unique look at its jet structure and magnetic field topology at sub-milliarcsecond scales. Our imaging reveals a bent jet morphology, significantly more extended than in previous years. Using regularized maximum-likelihood imaging and polarimetric analysis, we observe a transition in the magnetic field from a toroidal-dominated core to a helical structure downstream, indicating an evolving jet. Additionally, model-fitting suggests the emergence of a new component, likely linked to the December 2015 optical outburst and the passage of the secondary black hole through the primary’s accretion disk.