TAPIR Seminar

Hybrid

In person: 370 Cahill -- Attendees joining in person must have a valid Caltech UID.

To Join via Zoom: https://caltech.zoom.us/j/89695722750

ABSTRACT: A star wandering close enough to a massive black hole (MBH) can be ripped apart by the tidal forces of the black hole. The advent of wide-field surveys at many wavelengths has quickly increased the number of tidal disruption events (TDEs) observed, and has revealed that i) observed TDE rates are lower than theoretical predictions and ii) E+A galaxies are significantly overrepresented. This overrepresentation further worsens the tension between observed and theoretically predicted TDEs for non-E+A galaxies. Classical loss cone theory focuses on the cumulative effect of many weak scatterings. However, a strong scattering can remove a star from the distribution before it can get tidally disrupted. Most stars undergoing TDEs come from within the radius of influence, the densest environments of the universe. In such environments, close encounters rare elsewhere become non-negligible. I will present our revised loss cone theory that takes into account classical two-body interactions as well as strong scattering, collisions, and tidal captures, and study under which conditions close encounters can shield the loss cone. I will show that TDE rates can be reduced by up to an order of magnitude, reconciling theory and observations.

After 11 years of hibernation, another jetted TDE has been observed. During these 11 years, transrelativistic outflows, neutrinos in association with TDEs, and polarization were also detected. Here I will present how polarization can be used to disentangle between jetted and non-jetted TDEs and review our model for GRB afterglow polarization.