نتایج جستجو برای: stellar pulsation
تعداد نتایج: 90649 فیلتر نتایج به سال:
Abstract In this work, the pulsation analysis is performed on 83 high-amplitude δ Scuti stars (HADS), which have been observed by Transiting Exoplanet Survey Satellite. The results show that 49 of these HADS single-mode pulsation, 27 them radial double-modes (in 22 pulsate with fundamental and first overtone modes five second modes), seven triple-modes (three are newly confirmed triple-mode HAD...
It is well known that the mere location of a Beat Cepheid model in a Period Ratio vs. Period diagram (Petersen diagram) puts constraints on its metallicity Z . But these bounds are sensitive to the mixture of elements that are lumped into the parameter Z . In this short paper we update the previous results that were based on the Grevesse-Noels solar mixture to the recent, revised Asplund, Greve...
I investigate the discrepancy between the evolution and pulsation masses for Cepheid variables. A number of recent works have proposed that non-canonical mass-loss can account for the mass discrepancy. This mass-loss would be such that a 5M⊙ star loses approximately 20% of its mass by arriving at the Cepheid instability strip; a 14M⊙ star, none. Such findings would pose a serious challenge to o...
By performing detailed frequency-dependent radia-tive transfer computations we have obtained UBVI light curves of nonlinear RR Lyrae models, which recently have been calculated by the Vienna nonlinear convective pulsation code. For two sets of stellar parameters (M = 0. the fundamental and the first overtone limit cycle solutions have been calculated for effective temperatures ranging from 6000...
Recent analyses of photometric data on globular clusters and galaxies enabled us to study more closely the long-periodic amplitude/phase modulation (Blazhko effect) in classical variables. In the frequency spectra of these stars we see either a doublet or an equallyspaced triplet with a very small frequency separation close to the main component. None of the available theoretical models are abl...
Our analysis of the Deep CFHT M33 variability survey database has uncovered 5 Beat Cepheids (BCs) that are pulsating in the fundamental and first overtone modes. With only the help of stellar pulsation theory and of mass–luminosity (M -L) relations, derived from evolutionary tracks, we can accurately determine the metallicities Z of these stars. The [O/H] metallicity gradient of −0.16 dex/kpc t...
Pulsating stars have given important information in classical astronomy and are still an active research field, e.g. asteroseismology or helioseismology. By studying the rich oscillation stellar spectra, optical astronomy makes predictions for the stellar equations of state (EOS), the evolutionary age of the stars, and in the case of Cepheids one can make exact predictions for the distance of t...
Context. There are many unknowns in the formation of subdwarf B stars. Different formation channels are considered to be possible and to lead to a variety of helium-burning subdwarfs. All seismic models to date, however, assume that a subdwarf B star is a posthelium-flash-core surrounded by a thin inert layer of hydrogen. Aims. We examine an alternative formation channel, in which the subdwarf ...
NASA’s Kepler Mission has revealed two transiting planets orbiting Kepler-68. Follow-up Doppler measurements have established the mass of the innermost planet and revealed a third jovian-mass planet orbiting beyond the two transiting planets. Kepler-68b, in a 5.4 day orbit, has MP = 8.3 +2.2 −2.4 M⊕, RP = 2.31 +0.06 −0.09 R⊕, and ρP = 3.32 +0.86 −0.98 g cm , giving Kepler-68b a density intermed...
A comparison between linear stability analysis and observations of pulsation modes in five δ Scuti stars, belonging to the same cluster, is presented. The study is based on the work by Michel et al. (1999), in which such a comparison was performed for a representative set of model solutions obtained independently for each individual star considered. In this paper we revisit the work by Michel e...
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