Physical Sciences and Mathematics Commons^™

Infrared Emission And Dynamics Of Outlfows In Late-Type Stars, Željko Ivezić, Moshe Elitzur

Physics and Astronomy Faculty Publications

The dynamical structure and infrared emission of winds around late-type stars are studied in a self-consistent model that couples the equations of motion and radiative transfer. Thanks to its scaling properties, both the dynamics and IR spectrum of the solution are fully characterized by τ_F, the flux-averaged optical depth of the wind. Five types of dust grains are considered: astronomical silicate, crystalline olivine, graphite, amorphous carbon and SiC, as well as mixtures. Analysis of infrared signatures provides constraints on the grain chemical composition and indications for the simultaneous existence of silicate and carbon grains. The abundances of crystalline …

Optically Thin Broad-Line Clouds In Active Galactic Nuclei, Joseph C. Shields, Gary J. Ferland, Bradley M. Peterson

Physics and Astronomy Faculty Publications

The broad-line region (BLR) in Seyfert galaxy nuclei exhibits correlated variations in continuum and emission-line luminosity that are qualitatively consistent with photoionization of ionization-bounded (optically thick) clouds. However, evidence is growing that a nonnegligible fraction of the BLR cloud population is optically thin to the Lyman continuum and fully ionized in hydrogen. We consider the implications of this nebular component for observed line emission and find that inclusion of thin clouds in photoionization calculations can resolve several outstanding puzzles of Seyfert variability, notably the behavior of the C IV λ1549/Lyα ratio as a function of continuum luminosity.

A …