Related papers: Nonlinear Analysis of the Lightcurve of the Variab…
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…
We introduce the reader to the "global flow reconstruction method". The purpose of the method is to see if a given temporal sequence has been generated by a low dimensional dynamics, and to determine that dimension and other properties of…
An analysis of the photometric observations of the light curves of the five large amplitude, irregularly pulsating stars R UMi, RS Cyg, V CVn, UX Dra and SX Her is presented. First, multi-periodicity is eliminated for these pulsations, i.e.…
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…
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 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-…
Combination frequencies are not solutions of the perturbed stellar structure equations. In dense power spectra from a light curve of a given multi-periodic pulsating star, they can compromise the mode identification in an asteroseismic…
Inspection of the periodograms of TESS delta Scuti stars indicates that there is little, if any, similarity between the frequencies of stars in the same region of the H-R diagram. This is difficult to understand because pulsation models…
In this paper we investigate theoretical pulsation models for the delta Scuti star 44 Tau. The star was monitored during several multisite campaigns which confirmed the presence of radial and nonradial oscillations. Moreover, its…
Stars exhibit a bewildering variety of variable behaviors ranging from explosive magnetic flares to stochastically changing accretion to periodic pulsations or rotations. The principal LSST surveys will have cadences too sparse and…
$\delta$ Scuti stars are pulsating variable stars that exhibit both radial and non-radial pulsations, making them key objects for understanding stellar evolution and internal structures. The current classification of $\delta$ Scuti stars…
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…
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…
Space missions have produced an incredibly large database on pulsating stars. The light curves via the frequency content contain a detailed description of each star. The critical point is the identification of modes, especially in the…
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…
We analyze ISO/SWS spectra of the RV Tau star R Scuti. The infrared spectra are dominated by H2O emission bands. The near- and mid-infrared excess is attributed to H2O; the dust contribution is less important. We also identify CO, SiO and…
A series of spectra of the RV Tauri star R Scuti taken as it rose from a deep minimum to a bright maximum during 2013 October and November reveals major changes taking place in the photosphere and outer atmosphere of the star. This may be…
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-modes of neutron stars can be driven unstable by gravitational radiation. While linear perturbation theory predicts the existence of this instability, linear theory can't provide any information about the nonlinear development of the…