Speaker
Description
Extreme tidal disruption events (eTDEs) are a new type of tidal disruption event (TDE) with a very different observational signature from regular ones. In eTDEs, the disruption takes place just outside the event horizon, where relativistic gravity leads to dramatic effects. Unlike ordinary TDEs, in which the star (and post-disruption, its center-of-mass) follows a parabolic orbit, in eTDEs, the orbit winds several times around the black hole and then leaves. Using fully general relativistic hydrodynamics simulations, we show that eTDEs are easily distinguished from most TDE. The debris is geometrically axisymmetric, undergoing multiple structure transitions until part of the debris forms an accretion flow near the BH while the rest forms an expanding shell, as opposed to the ellipsoidal and eccentric nature of debris in common TDEs. The primary radiation source is the accretion flow near the black hole, producing a light curve in soft X-rays (~100-200eV) that rises rapidly to roughly the Eddington luminosity, maintains this level for between a few weeks and a year (depending on both the stellar mass and the black hole mass), and then drops. Although eTDEs are relatively rare for lower-mass black holes, most tidal disruptions around higher-mass black holes are extreme. Their detection offers a view of an exotic relativistic phenomenon previously inaccessible.
