Showing papers by "Roger Blandford published in 1981"

Compton scattering in a converging fluid flow – III Spherical supercritical accretion

Abstract: Radiative transfer in spherical, supercritical accretion on to a massive black hole is considered. Particular emphasis is placed on the case of non-adiabatic flow in which electron scattering in the converging flow is the dominant source of opacity and photon heating. In escaping diffusively, the photons, which are produced mainly at the trapping radius, undergo ~ (c/utr) 2 scatterings (where Utr is the velocity of the flow at the trapping radius), each one giving a secular fractional energy increase ~ (utr/c) 2 and a total average increase of order unity. The emitted radiation spectrum will be a superposition of the locally produced spectra at low frequencies and a powerlaw at high frequencies. For gas accreting radially with the free-fall speed, the spectral index observed in the outflowing radiation is a~ 2. Both thermal and non-thermal emission processes are discussed. The conditions under which bulk heating of the photons is important are specified.

Relativistic jet production and propagation in active galaxies

Abstract: Recent studies of the phenomena of active galactic nuclei are beginning to identify the most likely physical processes involved in the galactic nuclei cores which give rise to a fast moving plasma that emerges in directed beams and energizes radio sources. In particular, the formation of the beams appears to be a generic property of the flow pattern around collapsed objects, where there is a relativistically deep potential well. These beams are relevant to extended radio sources, superluminal variations in compact sources, and the injection of high-energy plasma into the intergalactic medium. There is a physical similarity, and not merely a superficial analogy, between the physical mechanisms of such objects as SS 433 and Sco X-1 and the processes in active galactic nuclei. The exploration of fluid dynamic and electrodynamic effects around black holes is envisaged as a fruitful line of inquiry in the present field of study.