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The binary system z Tau

H α observations on the Be binary ζ Tauri First some introduction words asking for patience by Ernst Pollmann VdS Spectroscopy Group Germany. 1. The binary system z Tau. Development of a rotating one-armed density wave by disturbed orbits

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The binary system z Tau

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  1. Hα observations on the Be binary ζ Tauri First some introduction wordsasking for patienceby Ernst PollmannVdS Spectroscopy Group Germany

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  3. The binary system z Tau • Development of a rotating one-armed density wave by disturbed orbits • Due to a radial disturbance the gas particles of the disk are moving on excentric Kepler-orbits 2

  4. Temporal development of the Ha-profile  (2003/09 to 2007/03) Dispersion = 27Ǻ/mm R= λ/Dλ ≈ 14000 3

  5. Temporal development of the Hα-profile between 2000 and 2006 All Profiles from 2000-2006. The vertical offset is proportional to time and corresponds to 25 days per continuum unit. The lowermost spectra date from Nov./2000 (left), Sep./2002 (middle) and Aug./2004 (right). The spectra are published electronically in the form of ASCII-tables IBVS-Nr. 5813 4

  6. Hα equivalent widths of ζ Tau since 1975 5

  7. Enlargement of the previous figure showing the data presented in this work in greater detail, also for comparison between values taken with professional and amateur equipment. 6

  8. Development of a rotating one-armed density wave by disturbed orbits • Due to a radial disturbance the gas particles of the disk are moving on excentric Kepler-orbits • This leads to V/R-variations • V/R of Hα show the same period as the radial velocies • Period duration = 1500 d V/R-Variation as function of phase 7

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  10. Hα V/R-ratio The residuals of the left panel, folded with P = 69.3 d and the respective sine fit. Shown are 1.4 cycles for clarification, i.e. 40% of the points are redundant. The measured values vs. Julian date (open symbols) and the sine wave with P = 1471 d (plus signs). 9

  11. Causes of the V/R variations • V/R variations in binary stars may be locked to the orbital phase • follow quasi-cyles typical 5-10 years • or combines these two types of variations with long-term trends • length and amplitude of the quasi-cycle vary from cycle to cycle 10

  12. Questions of the V/R variations • Conditions of the synchronisation of the V/R variations with the orbital periods ? • Several peculiarities of emission lines and their profiles can hardly be explained with one-armed oscillation model 11

  13. Phase variations of the radial velocity of the HeI line 6678 and Ha-V/R (1) (1) Stefl/Okazaki/Rivinius/Baade: V/R- Variations of binary Be stars (ASP-Conference Series, Vol. 361, 2007) 12

  14. Radial velocity of the HeI line 6678Ǻ 13

  15. …thanks for attention…. 14

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