2003/11/06 by Stephen B. Potter, S. Potter, E. Romero-Colmenero +4 · 2 citations
Earth and Planetary Sciences · Physics and Astronomy · #Astrophysical Phenomena and Observations #Astrophysics and Star Formation Studies #High-pressure geophysics and materials #astro-ph
paper · pdf · doi:10.1111/j.1365-2966.2004.07379.x
published as Mon.Not.Roy.Astron.Soc. 348 (2004) 316 · 10 pages, 8 figures; Accepted for publication in MNRAS
arxiv created 2003/11/06 · openalex publication_date 2004/01/30 · arxiv updated 2009/12/01 · openalex created_date 2016/06/24 · openalex updated_date 2026/07/28
We report on new simultaneous phase-resolved spectroscopic and polarimetric observations of the polar (AM Herculis star) V834 Cen during a high state of accretion. Strong emission lines and high levels of variable circular and linear polarization are observed over the orbital period. The polarization data are modelled using the Stokes imaging technique of Potter et al. The spectroscopic emission lines are investigated using the Doppler tomography technique of Marsh and Horne and the Roche tomography technique of Dhillon and Watson. Up to now, all three techniques have been used separately to investigate the geometry and accretion dynamics in cataclysmic variables. For the first time, we apply all three techniques to simultaneous data for a single system. This allows us to compare and test each of the techniques against each other and hence to derive a better understanding of the geometry, dynamics and system parameters of V834 Cen. All three techniques are consistent with an interpretation in which a ballistic stream extends to a minimum of ∼40 degrees in azimuth around the white dwarf before becoming threaded by the magnetic field lines. Interestingly, the observed ballistic Doppler velocities do not show a reduced vy component, as found in Doppler imaging of other AM Her systems. Furthermore, the secondary star in V834 Cen shows more He ii (4686 Å) emission on its leading inner face, as opposed to the trailing face like in other AM Her systems. We propose that the accretion shock preferentially illuminates the leading face of the secondary star. In addition, the ballistic stream does not obscure the leading face of the secondary from the accretion shock, and, in fact, our Doppler maps show that the ballistic stream is a strong He ii (4686 Å) emission source in itself and thus adds to the illumination of the leading face of the secondary.