2000/02/15 by V. Joergens, Joergens, V., H. C. Spruit +3
Earth and Planetary Sciences · Physics and Astronomy · #Astrophysical Phenomena and Observations #Astrophysics (astro-ph) #FOS: Physical sciences #High-pressure geophysics and materials #Laser-Plasma Interactions and Diagnostics #astro-ph
paper · pdf · doi:10.48550/arxiv.astro-ph/0002302
accepted (A&A Letter)
openalex publication_date 2000/02/15 · arxiv created 2000/03/15 · arxiv updated 2009/12/01 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/28
Observations at high spectral and temporal resolution are presented of the dwarf nova EX Dra in outburst. The disk seen in the He I line reconstructed by Doppler tomography shows a clear two-armed spiral pattern pointing to spiral shocks in the disk. The Balmer and He II maps also give evidence for the presence of spirals. The eclipse as seen in the red continuum indicates a disk radius of 0.31 times the orbital separation, which might be large enough to explain the observed spiral shocks through excitation by the tidal field of the secondary. The eclipse in the Balmer line profiles, well resolved in our observations, indicates a somewhat smaller disk size (0.25). We discuss the possibility that this is related to an optical depth effect in the lines.