September 23, 1999 CfA Colloquium

Title: X-Ray Spectra of Photoionized Plasmas

Speaker: Dr. Steven M. Kahn

Abstract: X-ray photoionized plasmas are produced in cosmic accretion-powered sources, such as X-ray binaries and active galactic nuclei, where an intense X-ray continuum irradiates much cooler surrounding gas. X-ray spectra of such systems reveal characteristic discrete emission features produced primarily via radiative cascade following recombination. I will review some of the intricacies of this process, and illustrate the diagnostic potential of future high resolution spectroscopic observations planned for Chandra, XMM, and ASTRO E. I will also discuss thermal instability in X-ray photoionized plasmas, and present some new calculations of the discrete X-ray spectra expected from reflection off of cold irradiated gas.

Student Lunch: Thursday 9/23 at 12:00 in A-101.

Further Reading: