Hα observations on the Be binary ζ Tauri First some introduction words asking for patience by Ernst Pollmann VdS Spectroscopy Group Germany

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3 The binary system  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 H  -profile  (2003/09 to 2007/03) Dispersion = 27Ǻ/mm R= λ/  λ ≈

5 Temporal development of the Hα- profile between 2000 and 2006 All Profiles from 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

6 Hα equivalent widths of ζ Tau since

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 The measured values vs. Julian date (open symbols) and the sine wave with P = 1471 d (plus signs). 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. 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 11  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 Questions of the V/R variations

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

14 13 Radial velocity of the HeI line 6678Ǻ

15 …thanks for attention…. 14