Observational Appearance and Spectrum of Black-Hole Winds with Supercritical Accretion Disks

Abstract

Abstract We examine the observational appearance and expected spectra of an optically thick, spherically symmetric, relativistic wind (a black-hole wind), blowing off from the central region of a geometrically thick supercritical accretion disk. Due to the relativistic limb-darkening (center-brightening) effect as well as the usual Doppler boost, the black-hole wind becomes luminous as the wind speed increases. We found that the spectra of the black-hole wind is somewhat similar to a blackbody one, while the spectra of a naked supercritical accretion disk is known to have a flat spectral energy distribution (SED) when viewing from the pole-on direction. In the case of a black-hole wind with a supercritical accretion disk, the spectra generally becomes a hybrid type, but we found that in almost all cases the characteristic flat SED of a supercritical disk disappears. That is, when the speed of the wind gas is low, the apparent photosphere of the black-hole wind becomes larger than the supercritical region. In this case the spectra of a black-hole wind dominates. As the wind speed increases, the apparent photosphere shrinks and the spectra of the disk emergent. However, when the wind speed becomes sufficiently high, the inner part of the naked supercritical disk is not seen, even if the inclination angle is small.