Flares from the Tidal Disruption of Stars by Massive Black Holes

Tidal disruption flares are differentiated into two classes: those that are sub-Eddington and those that radiate near the Eddington limit. Flares from black holes above ~2×10⁷ M_solar will generally not radiate above the Eddington limit. For a Schwarzschild black hole, the maximum bolometric luminosity of a tidal disruption is ~L_Edd(5×10⁷ M_solar), which is substantially below the Eddington luminosities of the most massive disrupting black holes (~2×10⁸ M_solar). Bolometric corrections to the spectra of the brightest flares are found to be large, ~7.5 mag. Nevertheless, the brightest flares are likely to have absolute magnitudes in excess of -19 in V and -21 in U (in the absence of reddening). Because the spectra are so blue, K-corrections may actually brighten the flares in optical bands. If such flares are as frequent as believed, they may soon be detected in low- or high-redshift supernovae searches. The He II ionizing radiation produced in the flares may dominate that which is produced by all other sources in the centers of quiescent galaxies, creating a steady state, highly ionized, fossil nebula with an extent of ~1 kpc that may be observable in recombination lines.