The structural properties of Cepheid light curves

Simon, Norman R.; Lee, A. S.

doi:10.1086/159153

Cited by 233 publications

(237 citation statements)

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“…The shape of the light curve can be described quantitatively by properly defined parameters based on Fourier coefficients. The most useful set of parameters was proposed by Simon & Lee (1981). Following their suggestion and notation, the amplitude ratios, R i j = A i /A j , and the φ i j = jφ i − iφ j phase differences are commonly investigated.…”

Section: Pulsation Amplitudesmentioning

confidence: 99%

Observational studies of Cepheid amplitudes

Klagyivik

Szabados

2009

A&A

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Context. The dependence of amplitude on the pulsation period differs from other Cepheid-related relationships. Aims. We attempt to revise the period-amplitude (P-A) relationship of Galactic Cepheids based on multi-colour photometric and radial velocity data. Reliable P-A graphs for Galactic Cepheids constructed for the U, B, V, R C , and I C photometric bands and pulsational radial velocity variations facilitate investigations of previously poorly studied interrelations between observable amplitudes. The effects of both binarity and metallicity on the observed amplitude, and the dichotomy between short-and long-period Cepheids can both be studied. Methods. A homogeneous data set was created that contains basic physical and phenomenological properties of 369 Galactic Cepheids. Pulsation periods were revised and amplitudes were determined by the Fourier method. P-A graphs were constructed and an upper envelope to the data points was determined in each graph. Correlations between various amplitudes and amplitude-related parameters were searched for, using Cepheids without known companions. Results. Large amplitude Cepheids with companions exhibit smaller photometric amplitudes on average than solitary ones, as expected, while s-Cepheids pulsate with an arbitrary (although small) amplitude. The ratio of the observed radial velocity to blue photometric amplitudes, A V RAD /A B , is not as good an indicator of the pulsation mode as predicted theoretically. This may be caused by an incorrect mode assignment to a number of small amplitude Cepheids, which are not necessarily first overtone pulsators. The dependence of the pulsation amplitudes on wavelength is used to identify duplicity of Cepheids. More than twenty stars previously classified as solitary Cepheids are now suspected to have a companion. The ratio of photometric amplitudes observed in various bands confirms the existence of a dichotomy among normal amplitude Cepheids. The limiting period separating short-and long-period Cepheids is 10.47 days. Conclusions. Interdependences of pulsational amplitudes, the period dependence of the amplitude parameters, and the dichotomy have to be taken into account as constraints in modelling the structure and pulsation of Cepheids. Studies of the P-L relationship must comply with the break at 10. d 47 instead of the currently used "convenient" value of 10 days.

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Section: Pulsation Amplitudesmentioning

confidence: 99%

Observational studies of Cepheid amplitudes

Klagyivik

Szabados

2009

A&A

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“…Multi-mode nonlinear pulsation results in interaction among the base frequencies and their harmonics that give rise to sum and difference combination frequencies of the form nfi ± mfj. Studying the relationships among the amplitudes and phases of the Fourier components has been standard practice for RR Lyr stars and Cepheids since the pioneering work of Simon & Lee (1981), and the study of combination frequencies and their astrophysical implications is well established for white dwarf stars (see, e.g. Wu 2001 andMontgomery 2005).…”

Section: Introductionmentioning

confidence: 99%

A unifying explanation of complex frequency spectra of γ Dor, SPB and Be stars: combination frequencies and highly non-sinusoidal light curves

Kurtz¹,

Shibahashi²,

Murphy³

et al. 2015

Monthly Notices of the Royal Astronomical Society

146

199

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There are many Slowly Pulsating B (SPB) stars and γ Dor stars in the Kepler Mission data set. The light curves of these pulsating stars have been classified phenomenologically into stars with symmetric light curves and with asymmetric light curves. In the same effective temperature ranges as the γ Dor and SPB stars, there are variable stars with downward light curves that have been conjectured to be caused by spots. Among these phenomenological classes of stars, some show 'frequency groups' in their amplitude spectra that have not previously been understood. While it has been recognised that nonlinear pulsation gives rise to combination frequencies in a Fourier description of the light curves of these stars, such combination frequencies have been considered to be a only a minor constituent of the amplitude spectra. In this paper we unify the Fourier description of the light curves of these groups of stars, showing that many of them can be understood in terms of only a few base frequencies, which we attribute to g mode pulsations, and combination frequencies, where sometimes a very large number of combination frequencies dominate the amplitude spectra. The frequency groups seen in these stars are thus tremendously simplified. We show observationally that the combination frequencies can have amplitudes greater than the base frequency amplitudes, and we show theoretically how this arises. Thus for some γ Dor and SPB stars combination frequencies can have the highest observed amplitudes. Among the B stars are pulsating Be stars that show emission lines in their spectra from occasional ejection of material into a circumstellar disk. Our analysis gives strong support to the understanding of these pulsating Be stars as rapidly rotating SPB stars, explained entirely by g mode pulsations.

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“…Following the notation proposed by Simon and Lee (1981), the Fourier decomposition consists in interpolating the measurements by means of the series…”

Section: The Application Of Fourier Decomposition To Cepheid Light Cumentioning

confidence: 99%

Asteroseismology of Cepheids

Poretti

2000

Variable Stars as Essential Astrophysical Tools

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The structural properties of Cepheid light curves

Cited by 233 publications

References 6 publications

Observational studies of Cepheid amplitudes

Observational studies of Cepheid amplitudes

A unifying explanation of complex frequency spectra of γ Dor, SPB and Be stars: combination frequencies and highly non-sinusoidal light curves

Asteroseismology of Cepheids

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