Project A6: "Multimessenger signatures of tidal disruption events"

Tidal disruption events (TDEs) are extreme panchromatic transients, which are caused when a star becomes disrupted by the tidal forces in the vicinity of a massive black hole and the stellar debris forms an accretion disk. In some cases, powerful relativistic jets are launched. TDEs are considered unique probes of non-active massive black holes. They might shed light on the demographics of massive black holes, accretion physics, and the launching of jets. Furthermore, TDEs are promising cosmic-ray accelerators and might host dense targets for cosmic-ray interaction and thus neutrino production. Many of the ample new multimessenger observations of TDEs in recent years cannot be described by current models of fallback of the stellar debris and accretion.

We will utilize radio, gamma-ray, and neutrino observations to receive a better understanding of the magnetic field configuration and particle acceleration in those sources. We start with detailed investigations of the closest detected TDE in the galaxy NGC 4845. To get a multimessenger view on this event, we will analyze Very Long Baseline Interferometry (VLBI) radio, Fermi-LAT gamma-ray, and IceCube high-energy neutrino data. We will model the processes in the source and constrain the model parameters with our observations. Interestingly, this source shows circular polarized radio emission, which could be a tracer for activity related to TDEs. We are in a unique position to compile a catalog of circular polarized sources using the Apertif survey. In the next step, we will search for gamma rays and neutrinos from a sample of radio-loud TDEs and a sub-sample of circular polarized sources. We will develop a better understanding of the magnetic field configuration and how it is influenced by the onset of accretion, which is an important ingredient to understand the formation of outflows and jets. Furthermore, we will probe TDEs as particle accelerators and their possible contribution to the diffuse neutrino and cosmic-ray flux, whose origin is currently unknown.