Tidal processes very near the black hole in the Galactic Center

Abstract

The accessibility of the ∼ 3×106 M⊙massive black hole (MBH) in the Galactic Center (GC) offers a unique opportunity to probe a variety of strong tidal interactions of stars with a MBH or with other stars in the high density cusp around aMBH. We show that such interactions can affect a significant fraction of the stellar population within the MBH radius of influence. We consider three processes that could possibly modify stellar structure and evolution there. (1) Tidal spin-up by hyperbolic star-star encounters. (2) Tidal scattering of stars on the MBH. (3) Tidal heating of tidally captured inspiraling stars — “squeezars”. We discuss the implications for stellar populations near MBHs and for the growth of MBHs by tidal disruption, and the possible signatures of such processes in the GC. We compare the event rates of prompt tidal encounters (tidal disruption and tidal scattering) with slow inspiral events (squeezars / tidal capture), and find that, contrary to what was assumed in past studies, tidal capture in the presence of scattering is an order of magnitude less efficient than prompt disruption and so does not contribute significantly to the growth of the MBH.