We present time-series spectroscopy of the rapidly oscillating Ap star HR 3831. This star has a dominant pulsation period of 11.7 minutes and a rotation period of 2.85d. We have analysed 1400 intermediate-resolution spectra of the wavelength region 6100– 7100Å obtained over one week, using techniques similar to those we applied to another roAp star, α Cir. We confirm that the Hα velocity amplit...

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 HertzsprungRussell diagram undergoes irregular light variations and exhibits irregular radial velocities as well. The mechanism behind this irregular behavior was a long st...

We present a study of a sample of LMC red giants exhibiting Long Secondary Periods (LSPs). We use radial velocities obtained from VLT spectral observations and MACHO and OGLE light curves to examine properties of the stars and to evaluate models for the cause of LSPs. This sample is much larger than the combined previous studies of Hinkle et al. (2002) and Wood, Olivier & Kawaler (2004). Binary...

We discuss in detail the pulsation properties of variable stars in globular clusters (GCs) and in Local Group (LG) dwarf galaxies. Data available in the literature strongly support the evidence that we still lack a complete census of variable stars in these stellar systems. This selection bias is even more severe for small-amplitude variables such as Oscillating Blue Stragglers (OBSs) and new e...

ABSTRACT Pulsations and binarity are both common features of massive stars. The study pulsating stars in eclipsing binary systems holds great potential for constraining stellar structure evolution theory. However, prior to the all-sky Transiting Exoplanet Survey Satellite (TESS) mission, few such had been discovered or studied detail. We have inspected TESS light curves a large number binaries ...

The Vienna nonlinear code for modelling pulsating stars is applied to the problem of RR Lyrae double mode pulsation. For stellar parameters of M = 0.65 M , log(L/L ) = 1.72 and XYZ=(0.760, 0.239, 0.001) we find a stable double mode solution in a small effective temperature range around 6820 K. The fundamental period is given by P0 = 0.5279 days and period and amplitude ratios corresponding to P...

Luminosities and effective temperatures are calculated for 17 nonvariable yellow giants and supergiants and nine Cepheids which were previously identified as members of open clusters. These stars are identified as being in the helium core burning stage of evolution. A comparison with the predictions of pulsation theory does not show any disagreement. O n the other hand, several comparisons with...

SPEC_PULS describes a suite of computer programs to simulate the emergent spectrum from radially-pulsating star. It combines Christy-type non-linear pulsation code with classical stellar atmosphere codes. The principal aim is interpret dynamical radially pulsating extreme helium star V652 Her, which shows strong shock at minimum radius. components are general enough treat other classes radial p...