MULTI-COMPONENT VARIABILITY OF PULSATING VARIABLE STARS OF RV TAURI TYPE

Анотація

For the group of pulsating variable stars
with multi-component variability – which are currently
classified as the RV Tau-type stars – the classification
based on complexity of the periodograms is discussed. Per-
iodograms were computed using the least approximation of
the data with a sinusoid. The periodograms previously clas-
sified by their shape into three groups according to the pres-
ence or absence of certain structures: two peaks in a 2:1
ratio, (biharmonic signal with two waves during a main pe-
riod, or the phase curve is significantly asymmetric), the
presence of satellites of these peaks at the periodogram in-
dicating the result of modulation of characteristics of oscil-
lations. Group I includes objects showing the periodogram
typical for the RV-type stars, and the ratio of the periods of
the two main peaks is indicated. These oscillations appear
to be relatively stable during the observations. The Group
II includes objects, the periodograms of which contain
signs of multi-periodicity or, vice-versa, only one clear
peak, instead of two. The presence of multiple peaks may
be due to multiple periods, or due to variability of the main
period. The Group III includes objects, the periodograms of
which are highly noisy, mainly due to a small number of
observations or they do not show typical structures of RV-
type stars. Such stars may be classified in the catalogue
wrongly, so, additional study is needed. For periodogram
analysis, the photometric observations from the interna-
tional databases of AFOEV, AAVSO and ASAS were used.
A least squares method is used for the analysis, to compare
the variance in the deviations from the smoothed function
with the variance in the initial observations. The mean light
curves and the phase plane diagrams dx _C ( ф )/d ф” vs” x_C (ф)
was compiled and analyzed for the values of the periods
corresponding to the peaks in the periodograms.