Title: A jet “caught in a speed trap”: revealing particle acceleration and transport using gamma ray observations
Speaker: Laura Olivera-Nieto, Max-Planck-Institut für Kernphysik, Heidelberg, Germany
Abstract: The microquasar SS 433 stands out as one of the most intriguing objects within our Milky Way. At its core, a black hole draws material from a closely orbiting companion star, creating a hot accretion disk. As a result, a pair of oppositely directed beams of plasma ("jets") spirals away perpendicularly from the disk’s surface at just over a quarter of the speed of light. I will discuss the recent detection of high energy gamma rays from the jets of SS 433 by the H.E.S.S. observatory in Namibia. We found that the position of the gamma-ray emitting region changes when considering different photon energies. This allowed us to identifying the location within the jets of one of the galaxy's most effective particle accelerators and measure the jets velocity far beyond their launching site, constraining the acceleration mechanism itself. Finally, I will discuss the implications of this result on the expected contribution of microquasars and other astrophysical jets to the observed cosmic ray flux.