Modeling the Diverse FUV Spectra of Disk-Dominated Cataclysmic Variables

The FUSE and HST spectra of dwarf novae in outburst, and of nova-like variables exhibit a wide range of characteristics. In a few systems, there are obvious signatures of a fast wind in the form of P-Cygni-like profiles of OVI and other relatively high ionization state ions. But this is rare. More common are systems with FUV spectra, showing a complex mixture of high and low ionization state lines. Here we describe attempts to reproduce the spectra using a Monte Carlo radiative transfer code developed to model bi-conical winds in disk systems.

Emission and absorption spectroscopy of X-ray-heated plastic foils

Spherical gold Hohlraums were heated by the iodine laser ASTERIX IV (200 J/0.4 ns at 440 nm) and were used to investigate radiative heating of low-Z plastic foils at temperatures up to 100 eV by time-resolved XUV emission and absorption spectroscopy. Spectra of the reemitted radiation (the albedo) for different C-, O-, F-, or Cl-containing plastic materials are presented. Depending on the material, the typical total (frequency-integrated) reemission is in the range of ≈10% of the gold reemission. By measuring the absorption spectra it was possible to follow the burnthrough in carbon from the initial solid degenerate state up to a high ionization state with absorption lines due to hydrogen-like carbon corresponding to a temperature of about 100 eV. The propagation of the heat wave into the material also has been studied by observing the emission from boron tracer layers embedded at different depths in the plastic foil. The experimental observations are compared with MULTI simulations.