  We have analysed the asymmetry of lines Fe I and Fe II in spectra of a solar
flux using three FTS atlases and the HARPS atlas and also in spectra of 13
stars using observation data on the HARPS spectrograph. To reduce observation
noise individual line bisectors of each star have been averaged. The obtained
average bisectors in the stellar spectra are more or less similar to the shape
C well known to the Sun. In stars with rotation speeds greater than 5 km/s the
shape of the bisectors is more like /. The curvature and span of the bisectors
increase with the temperature of the star. Our results confirm the known facts
about strong influence of rotation velocity on the span and shape of bisectors.
The average convective speed was determined based on the span of the average
bisector, which shows the largest difference between the velocity of cold
falling and hot rising convective flows of the matter. It's equal to -420 m/s
for the Sun as a star. In solar-type stars, it grows from -150 to -700 m/s with
an effective temperature of 4800 to 6200 K, respectively. For stars with
greater surface gravity and greater metallicity, the average convective
velocity decreases. It also decreases with star age and correlates with the
speed of micro and macroturbulent movements. The results of solar flux analysis
showed that absolute wavelength scales in the FTS atlases used coincide with an
accuracy of about -10 m/s, except for the atlas of Hinkle, etc., whose scale is
shifted and depends on the wavelength. In the range from 450 to 650 nm, the
scale shift of this atlas varies from -100 to -330 m/s, respectively, and it
equals on average of -240 m/s. The resulting average star bisectors contain
information about the fields of convective velocities and may be useful for
hydrodynamic modeling of stellar atmospheres in order to study the
characteristic features of surface convection.
