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What is XSTAR?

XSTAR is a command-driven computer program for calculating the physical conditions and emission spectra of photoionized gases. It may be applied in a wide variety of astrophysical contexts. Stripped to essentials, its job may be described simply: A spherical gas shell surrounding a central source of ionizing radiation absorbs some of this radiation and reradiates it in other portions of the spectrum; XSTAR computes the effects on the gas of absorbing this energy, and the spectrum of reradiated light. In many cases other sources (or sinks) of heat may exist, for example, mechanical compression or expansion, or cosmic ray scattering. XSTAR permits consideration of these effects as well. The user supplies the shape and strength of the incident continuum, the elemental abundances in the gas, its density or pressure, and its thickness; the code returns the ionization balance and temperature, opacity, and emitted line and continuum fluxes. The solution divides into several distinct parts: transfer of the incident radiation into the cloud; calculation of the temperature, ionization, and atomic level populations at each point in the cloud; and transfer of the emitted radiation out of the cloud. XSTAR v2 is written in standard fortran77, and has been tested on a variety of unix platforms


next up previous contents
Next: Scope of This Document Up: Introduction Previous: Introduction   Contents
Tim Kallman 2014-09-12