Observational signature of tidal disruption of a star by a massive black hole

We have modeled the time-variable profiles of the Hα emission line from the non-axisymmetric disk and debris tail created in the tidal disruption of a solar-type star by a 10⁶ M_⊙ black hole. We find that the line profiles at these very early stages of the evolution of the post-disruption debris do not resemble the double peaked profiles expected from a rotating disk since the debris has not yet settled into such a stable structure. The predicted line profiles vary on fairly short time scales (of order hours to days). As a result of the uneven distribution of the debris and the existence of a "tidal tail" (the stream of returning debris), the line profiles depend sensitively on the orientation of the tail relative to the line of sight. Given the illuminating UV/X-ray light curve, we also model the Hα light curve from the debris.