Related papers: Evidence for Low-Dimensional Chaos in Semiregular …
We demonstrate how, with a purely empirical analysis of the irregular lightcurve data, one can extract a great deal of information about the stellar pulsation mechanism. An application to R Sct thus shows that the irregular lightcurve is…
It is first shown that the observational light curve data of R Scuti, a star of the RV Tau type, is not multi-periodic, and that it cannot have been generated by a linear stochastic (AR) process. By default, the signal must be a…
We present a detailed lightcurve analysis for a sample of bright semiregular variables based on long-term (70--90 years) visual magnitude estimates carried out by amateur astronomers. Fundamental changes of the physical state (amplitude…
The AAVSO lightcurve data of the irregularly pulsating star AC Herculis of the RV Tau class are analysed. The lightcurve is shown to be incompatible with a periodic, or even multiperiodic pulsation, even if allowance is made for evolution.…
The light curves of the two large amplitude variable stars, R Scuti and AC Herculis, display irregular pulsation cycles with 'periods' of 75 and 35 days, respectively. We review the evidence that the observed time-series are generated by…
Pulsations of RV Tauri-type variable stars can be governed by chaotic dynamics. However, observational evidence for this happening is usually hard to come by. Here we use the continuous, 4-year-long observations of the Kepler space…
The light curves (time series of the radiated energy) of most large amplitude, pulsating stars such as the well known Cepheid stars are regular. However, a smaller group of variable stars that are located next to them in the Hertzsprung-…
CCD photometry in the V band is presented for 7 field RR Lyrae stars selected from a sample of eight variables which, according to data collected in the literature, are expected to be {\it ab}-type pulsators, to have short periods and hence…
Random changes in pulsation period occur in cool pulsating Mira variables, Type A, B, and C semiregular variables, RV Tauri variables, and in most classical Cepheids. The physical processes responsible for such fluctuations are uncertain,…
The recent precise photometric observations and successes of the modelling efforts transformed our picture of the pulsation of RR Lyrae stars. The discovery of additional frequencies and the period doubling phenomenon revealed that a…
The lower part of the classical instability strip and the surrounding main sequence are populated by a large variety of pulsating variable stars. In the past years a great effort was made by the stellar group of Brera Observatory to collect…
In this paper we present radial velocity curves of AGB variables that exhibit various kinds of anomalies: Semiregular variables (SRVs) with typical mira periods, SRVs exceeding the mira 2.5 mag amplitude limit, miras with secondary maxima…
Stars exhibit a bewildering variety of rapidly variable behaviors ranging from explosive magnetic flares to stochastically changing accretion to periodic pulsations or rotation. The principal Rubin Observatory Legacy Survey of Space and…
The RV Tauri stars constitute a small group of classical pulsating stars with some dozen known members in the Milky Way. The light variation is caused predominantly by pulsations, but these alone do not explain the full complexity of the…
The r-mode instability in rotating relativistic stars has been shown recently to have important astrophysical implications (including the emission of detectable gravitational radiation, the explanation of the initial spins of young neutron…
RV Tauri variable stars are pulsating evolved stars that are identified by a characterizing feature in their light curves: alternating deep and shallow minima. Many RV Tauri variable stars were originally classified decades ago using visual…
The expert system for time series analysis of irregularly spaced signals is reviewed. It consists of a number of complementary algorithms and programs, which may be effective for different types of variability. Obviously, for a pure sine…
There is growing observational evidence that the irregular changes in the light curves of certain variable stars might be due to deterministic chaos. Supporting these conclusions, several simple models of non-linear oscillators have been…
We present further photometric observations of the unusual F0 V star 9 Aurigae and present evidence that this star's radial velocity, spectroscopic line widths and line depths are also variable with the same frequencies as the photometric…
The study of pulsating stars in eclipsing binaries holds the promise of combining two different ways of measuring the physical properties of a star to obtain improved constraints on stellar theory. Gravity (g) mode pulsations such as those…