SIMBAD references

AGN SEDs generally show a turnover at λ ∼ 1000Å, implying a maximal accretion disc (AD) temperature of Tmax ∼ 50000K. Massive O stars display a similar Tmax, associated with a sharp rise in a line-driven mass-loss \skew4{dot}M_wind with increasing surface temperature. AGN AD are also characterized by similar surface gravity to massive O stars. The \skew4{dot}M_wind of O stars reaches ∼ 10^–5M_☉/yr. Since the surface area of AGN AD can be 10⁶ larger, the implied \skew4{dot}M_wind in AGN AD can reach the accretion rate \skew4{dot}M. A rise to \skew4{dot}M_wind∼\skew4{dot}M towards the AD centre may therefore set a similar cap of Tmax ∼ 50000K. To explore this idea, we solve the radial structure of an AD with a mass-loss term, and calculate the implied AD emission using the mass-loss term derived from observations of O stars. We find that \skew4{dot}M_wind becomes comparable to \skew4{dot}M typically at a few tens of GM/c2. Thus, the standard thin AD solution is effectively truncated well outside the innermost stable orbit. The calculated AD SED shows the observed turnover at λ ∼ 1000Å, which is weakly dependent on the AGN luminosity and black hole mass. The AD SED is generally independent of the black hole spin, due to the large truncation radius. However, a cold AD (low \skew4{dot}M, high black hole mass) is predicted to be windless, and thus its SED should be sensitive to the black hole spin. The accreted gas may form a hot thick disc with a low radiative efficiency inside the truncation radius, or a strong line-driven outflow, depending on its ionization state.