Spectra of coronae

X-ray spectra of accretion discs with dynamic coronae

We compute the X-ray spectra produced by non-static coronae atop accretion discs around black holes and neutron stars. The hot corona is radiatively coupled to the underlying disc (the reflector) and generates an X-ray spectrum which is sensitive to the bulk velocity of the coronal plasma, β = v/c. We show that an outflowing corona reproduces the hard-state spectrum of Cyg X-1 and similar objec...

Infrared Spectra of Young Stars Embedded in the R Coronae Australis Cloud

Infrared spectra are presented for a magnitude-limited (K < 12:5 mag) sample of stellar objects observed toward the R Coronae Australis molecular core. These spectra, which are used to identify young stellar objects in the cloud, include the wavelengths of emission lines from [Fe II] andH2, four of the Brackett series lines, the CO bandheads, as well as photospheric absorption lines of Al, Na, ...

Physics of Stellar Coronae

Massive Coronae of Galaxies

There is reason to suspect that about half of the baryons are in pressure-supported plasma in the halos of normal galaxies, drawn in by gravity along with about half of the dark matter. To be consistent with the observations this baryonic component, the corona, would have to be hotter than the kinetic temperature of the dark matter in the halo so as to produce acceptable central electron densit...

Forward Modeling of Stellar Coronae: from a 3d Mhd Model to Synthetic Euv Spectra

A forward model is described in which we synthesize spectra from an ab-initio 3D MHD simulation of an outer stellar atmosphere, where the coronal heating is based on braiding of magnetic flux due to photospheric footpoint motions. We discuss the validity of assumptions such as ionization equilibrium and investigate the applicability of diagnostics like the differential emission measure inversio...