A new face of PKS 1510-089

Michael Zacharias

The flat spectrum radio quasar PKS 1510-089 is known for a complex behavior requiring different theoretical explanations at different times. In 2016 another set of observations produced an addition to the complexity of the source : The detection of a strong very-high-energy flare (E>100GeV) without strong counterparts at lower energies. The fit of the gamma-ray spectrum above 100MeV allows to derive a lower limit on the distance from the black hole, implying that the emission region must be located outside of the broad-line region. At the same time, radio VLBI observations showed a fast moving knot passing through a standing shock in the jet some 40pc from the black hole. If related, very-high-energy gamma-ray emission was produced at a large distance from the black hole — far away from the typically considered blazar zone at 1pc or less from the black hole. In this talk, I will summarize the fascinating story of this event and describe its many theoretical challenges.