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Analysis and Interpretation of Astronomical Spectra 77

The following formula is applicable for the –values at the emission lines Hβ
(4861.3) and FE II (5317, 5169, 6384, 4584 Å).

,

The Distribution of the Rotation Velocity on the Disk R

Assuming that the disk rotation obeys the kinematic laws of Kepler, v <
the highest rotational velocity occurs on its inner edge – In many
cases, probably identical with the star equator. It decreases to- <
wards the outside (formula according to Robinson [5]).

The application of this formula is limited to high values ( or known inclina-
tion angle .

The Analysis of Double Peak Profiles ∆V peak

The emission lines of Be stars often show a double
peak. The gap between the two peaks is explained
with the Doppler-, self-absorption- and perspective
effects. Looking at the edge of the disk in the range R
of the symmetry axis the gas masses apparently Normalised Intensity V
move perpendicularly to our line of sight, ie the ra-
dial velocity there is . Indicated are important 1 Continuum level Ic=1

dimensions, which are used in the literature.

Ic

0 λHα

Wavelength λ

Distance between the Peaks

The chart on the right shows according to K. Robinson [5]
the modelled emission lines for different inclination angles
(sect. 16.1). It seems obvious that the distance
i=82°

increases with growing inclination . At the same time also 65°

the –values are increasing, if for all inclination an-

gles a similar effective equatorial velocity and a fixed disc 30°

radius are assumed. is expressed as a velocity

value according to the Doppler principle: according to 15°

{15}: . 0° Wavelength
λHα
Also according to Hanuschik [143] a rough correlation ex-
ists between the [km / s] at the Hα line and .