Consequences of strong compression in tidal disruption events

Abstract

The tidal disruption of a star by a supermassive black hole (SMBH) is a highly energetic event with consequences dependent on the degree to which the star plunges inside the SMBH's tidal sphere. We introduce a new analytic model for tidal disruption events (TDEs) to analyse the dependence of these events on beta, the ratio of the tidal radius to the orbital pericentre. We find, contrary to most previous work, that the spread in debris energy for a TDE is largely constant for all beta. This result has important consequences for optical transient searches targeting TDEs, which we discuss. We quantify leading-order general relativistic corrections to this spread in energy and find that they are small. We also examine the role of stellar spin and find that a combination of spin-orbit misalignment, rapid rotation and high beta may alter the spread in debris energy. Finally, we quantify for the first time the gravitational wave emission due to the strong compression of a star in a high-beta TDE. Although this signal is unlikely to be detectable for disruptions of main-sequence stars, the tidal disruption of a white dwarf by an intermediate mass black hole can produce a strong signal visible to Advanced LIGO at tens of megaparsecs.