TIDAL DISRUPTION EDDINGTON ENVELOPES AROUND MASSIVE BLACK-HOLES

Optically-thick envelopes may form following the tidal disruption of a star by a massive black hole. Such envelopes would reprocess hard rad iation from accretion close to the black hole into the UV and optical bands producing AGN-luminosity flares with duration similar to 1 year. We show that due to relativistic effects, the envelopes are convectiv e. If convection is efficient, then the structure of the envelopes is similar to that described in previous work; however, the photospheric radius is shown to be very sensitive to the luminosity at the envelope base, suggesting that either the envelope collapses or the envelope e xpands to a maximum radius at which point a wind may set in. For an en velope without winds, we find a maximum photospheric radius of similar to 10(16) cm (i.e. minimum effective temperature similar to 6, 000 K) . The evolution of the envelopes is described based on simple energy a rguments.