Hα observations on the Be binary ζ Tauri

First some introduction wordsasking for patience

by Ernst PollmannVdS Spectroscopy Group Germany

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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

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Temporal development of the H-profile

(2003/09 to 2007/03)

Dispersion = 27Ǻ/mmR= λ/λ ≈ 14000

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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

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Hα equivalent widths of ζ Tau since 1975

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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.

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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

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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.

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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

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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

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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)

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Radial velocity of the HeI line 6678Ǻ

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…thanks for attention….

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