Theoretical rates of pulsation period change in the Galactic Cepheids

Fadeyev, Yu. A.

doi:10.1134/s1063773714050028

Cited by 34 publications

(20 citation statements)

References 19 publications

(19 reference statements)

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“…Turner et al (2007) propose a much lower value of 0.082 ± 0.012 s/yr, which is closer to our own value of 0.124 ± 0.036 s/yr. This period change is that expected for a Cepheid crossing the instability strip for the third time (Fadeyev 2014). Turner et al (2007) observed a sinusoidal trend in the O-C diagram, which is interpreted as a light-time effect produced by a long period orbit companion.…”

Section: Rt Aursupporting

confidence: 62%

“…Meyer (2006) mentioned that the change rate is in the interval of −0.25 ± 0.13 s/yr with a probability of 99%, while Turner (1998) suggests a similar value of −0.24 s/yr. We find a disagreeing value of 0.060 ± 0.035 s/yr, which would place in T Vul rather in the third crossing of the instability strip (Fadeyev 2014). Whether or not we include the interferometric data in the SPIPS fit leads to consistent results, although the amplitude of the diameter variation tends to be slightly underestimated.…”

Section: T Vulcontrasting

confidence: 51%

“…There is no period change reported for this Cepheid. Our study nevertheless leads to the value of dP/dt = 0.016 ± 0.048 s/yr, which places Y Sgr in the third crossing of the instability strip (Fadeyev 2014). Kovtyukh et al (2008) publish a color excess E(B − V) = 0.182 ± 0.021, and Benedict et al (2007) give the value of 0.205.…”

Section: Y Sgrmentioning

confidence: 56%

“…This small instability could be due to the lack of RVs measurements, in particular, at the extrema. We find a linear period variation of 0.371 ± 0.098 s/yr, corresponding for X Sgr to the third crossing of the instability strip (Fadeyev 2014). Szabados (1989) finds a higher value of 0.74 ± 0.09 s/yr, which nevertheless corresponds to the same evolutionary status.…”

Section: Sgrmentioning

confidence: 57%

“…Berdnikov et al (2014) also find a value of dP/dt = 0.072 ± 0.011 s/yr. We find that the Cepheid is close to the center of the instability strip with a very different rate of period change (−0.140 ± 0.036 s/yr), which places the Cepheid in the second crossing of the instability strip (Fadeyev 2014). We do not find any IR excess.…”

Section: Ff Aqlmentioning

confidence: 80%

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Observational calibration of the projection factor of Cepheids

Breitfelder

Mérand

Kervella

et al. 2016

A&A

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Context. The distance to pulsating stars is classically estimated using the parallax-of-pulsation (PoP) method, which combines spectroscopic radial velocity (RV) measurements and angular diameter (AD) estimates to derive the distance of the star. A particularly important application of this method is the determination of Cepheid distances in view of the calibration of their distance scale. However, the conversion of radial to pulsational velocities in the PoP method relies on a poorly calibrated parameter, the projection factor (p-factor). Aims. We aim to measure empirically the value of the p-factors of a homogeneous sample of nine bright Galactic Cepheids for which trigonometric parallaxes were measured with the Hubble Space Telescope (HST) Fine Guidance Sensor. Methods. We use the SPIPS algorithm, a robust implementation of the PoP method that combines photometry, interferometry, and radial velocity measurements in a global modeling of the pulsation of the star. We obtained new interferometric angular diameter measurements using the PIONIER instrument at the Very Large Telescope Interferometer (VLTI), completed by data from the literature. Using the known distance as an input, we derive the value of the p-factor of the nine stars of our sample and study its dependence with the pulsation period. Results. We find the following p-factors: p = 1.20 ± 0.12 for RT Aur, p = 1.48 ± 0.18 for T Vul, p = 1.14 ± 0.10 for FF Aql, p = 1.31 ± 0.19 for Y Sgr, p = 1.39 ± 0.09 for X Sgr, p = 1.35 ± 0.13 for W Sgr, p = 1.36 ± 0.08 for β Dor, p = 1.41 ± 0.10 for ζ Gem, and p = 1.23 ± 0.12 for Car. Conclusions. The values of the p-factors that we obtain are consistently close to p = 1.324 ± 0.024. We observe some dispersion around this average value, but the observed distribution is statistically consistent with a constant value of the p-factor as a function of the pulsation period (χ 2 = 0.669). The error budget of our determination of the p-factor values is presently dominated by the uncertainty on the parallax, a limitation that will soon be waived by Gaia.

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Section: Rt Aursupporting

confidence: 62%

Section: T Vulcontrasting

confidence: 51%

Section: Y Sgrmentioning

confidence: 56%

Section: Sgrmentioning

confidence: 57%

Section: Ff Aqlmentioning

confidence: 80%

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Observational calibration of the projection factor of Cepheids

Breitfelder

Mérand

Kervella

et al. 2016

A&A

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A search for evolutionary changes in the pulsation period of the classical Cepheid V609 Cygni

Бердников

Pastukhova

Дамбис

2019

Astrophys Space Sci

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On the effect of rotation on populations of classical Cepheids

Anderson

Ekström

Georgy

et al. 2014

A&A

113

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Context. Classical Cepheids are among the most important variable star types due to their nature as standard candles and have a long history of modeling in terms of stellar evolution. The effects of rotation on Cepheids have not yet been discussed in detail in the literature, although some qualitative trends have already been mentioned. Aims. We aim to improve the understanding of Cepheids from an evolutionary perspective and establish the role of rotation in the Cepheid paradigm. In particular, we are interested in the contribution of rotation to the problem of Cepheid masses, and explore testable predictions of quantities that can be confronted with observations. Methods. Recently developed evolutionary models including a homogeneous and self-consistent treatment of axial rotation are studied in detail during the crossings of the classical instability strip (IS). The dependence of a suite of parameters on initial rotation is studied. These parameters include mass, luminosity, temperature, lifetimes, equatorial velocity, surface abundances, and rates of period change. Results. Several key results are obtained: i) mass−luminosity (M−L) relations depend on rotation, particularly during the blue loop phase; ii) luminosity increases between crossings of the IS. Hence, Cepheid M−L relations at fixed initial rotation rate depend on crossing number (the faster the rotation, the larger the luminosity difference between crossings); iii) the Cepheid mass discrepancy problem vanishes when rotation and crossing number are taken into account, without a need for high core overshooting values or enhanced mass loss; iv) rotation creates dispersion around average parameters predicted at fixed mass and metallicity. This is of particular importance for the period−luminosity relation, for which rotation is a source of intrinsic dispersion; v) enhanced surface abundances do not unambiguously distinguish Cepheids occupying the Hertzsprung gap from ones on blue loops (after dredgeup), since rotational mixing can lead to significantly enhanced main sequence (MS) abundances; vi) rotating models predict greater Cepheid ages than non-rotating models due to longer MS lifetimes. Conclusions. Rotation has a significant evolutionary impact on classical Cepheids and should no longer be neglected in their study.

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Theoretical rates of pulsation period change in the Galactic Cepheids

Cited by 34 publications

References 19 publications

Observational calibration of the projection factor of Cepheids

Observational calibration of the projection factor of Cepheids

A search for evolutionary changes in the pulsation period of the classical Cepheid V609 Cygni

On the effect of rotation on populations of classical Cepheids

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