We model the spectral changes of late oxygen-rich Miras observed in diierent pulsation phases. From a combination of variable near-IR spectra and UKIRT spectro-photometry of the 9:7 m silicate dust emission feature in diierent phases we study the innuence of the changing atmospherical circumstances on the conditions in the circumstellar dust shell. From a detailed modelling of TiO and VO bands ...

Aims. We examine a recently–proposed evolutionary scenario that could explain the existence of the low–mass, helium– enriched PG1159 stars. We focus in particular on the study of the pulsational stability properties of the evolutionary models predicted by such scenario. Methods. We assess the overstability of pulsation g−modes of stellar models as evolution proceeds along the PG1159 domain. Ste...

ASTRONOMY AND ASTROPHYSICS Period-luminosity-color-radius relationships of Cepheids as a function of metallicity: evolutionary effects. Abstract. Based on consistent evolutionary and pulsation calculations, we analyse the effect of metallicity and of different convection treatments in the stellar models on period-magnitude,-color and-radius relationships. In order to perform an accurate compari...

We present a preliminary theoretical seismic study of the astronomically famous star 51 Peg. This is done by first performing a detailed analysis within the Hertzsprung-Russell diagram (HRD). Using the Yale stellar evolution code (YREC), a grid of stellar evolutionary tracks has been constructed for the masses 1.00M ⊙ , 1.05M ⊙ and 1.10M ⊙ , in the metallicity range Z = 0.024 − 0.044, and for v...

WASP-33 is one of the few $\delta$ Sct stars with a known planetary companion. By analyzing stellar oscillations, we search for possible star-planet interactions in pattern pulsation. We made use Transit and Light Curve Modeller (TLCM) to solve light curve from Transiting Exoplanet Survey Satellite (TESS). include gravity darkening into our analysis. The oscillation clearly shows signs several ...

Based on consistent evolutionary and pulsation calculations, we analyse the effect of metallicity and of different convection treatments in the stellar models on period– magnitude, –color and –radius relationships. In order to perform an accurate comparison with observations, we have computed grids of atmosphere models and synthetic spectra for different metallicities, covering the range of eff...

it is inferred from the symmetrical and luminous x-ray emission of fossil groups that they are mature, relaxed galaxy systems. cosmological simulations and observations focusing on their dark halo and inter-galactic medium properties confirm their early formation. recent photometric observations suggest that, unlike the majority of non-fossil brightest group galaxies (bggs), the central early-t...