Observational studies of Cepheid amplitudes

Klagyivik, P.; Szabados, László

doi:10.1051/0004-6361/200811464

Cited by 77 publications

(82 citation statements)

References 62 publications

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“…For the FO pulsators we adopted the ratio between optical and NIR amplitudes for FU Cepheids with log P ≤ 1.2 (see Klagyivik & Szabados 2009). This assumption relies on the theoretical and empirical evidence that FOs, once their period is fundamentalized, display pulsation properties very similar to FU Cepheids with periods shorter than log P ≤ 1.2.…”

Section: Photometric Datamentioning

confidence: 99%

“…During the last few years the dependence of the luminosity amplitude on metallicity has been investigated both from the theoretical point of view (Bono et al 2000b) and the observational (Klagyivik & Szabados 2009;Pedicelli et al 2010;Klagyivik et al 2013). In particular, Szabados & Klagyivik (2012), by using a large sample (327) of Galactic Cepheids with accurate pulsation parameters and spectroscopic metal abundances, found evidence that the luminosity and the radial velocity amplitudes slightly decrease with increasing iron abundance.…”

Section: Luminosity Amplitudes and Metallicity Dependencementioning

confidence: 99%

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On the fine structure of the Cepheid metallicity gradient in the Galactic thin disk

Genovali

Lemasle

Bono

et al. 2014

A&A

197

262

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We present homogeneous and accurate iron abundances for 42 Galactic Cepheids based on high resolution (R ∼ 38 000) high signal-to-noise ratio (S /N ≥ 100) optical spectra collected with UVES at VLT (128 spectra). The above abundances were complemented with high-quality iron abundances provided either by our group (86) or available in the literature. We were careful to derive a common metallicity scale and ended up with a sample of 450 Cepheids. We also estimated accurate individual distances for the entire sample by using homogeneous near-infrared photometry and the reddening free period-Wesenheit relations. The new metallicity gradient is linear over a broad range of Galactocentric distances (R G ∼ 5-19 kpc) and agrees quite well with similar estimates available in the literature (-0.060 ± 0.002 dex/kpc). We also uncover evidence that suggests that the residuals of the metallicity gradient are tightly correlated with candidate Cepheid groups (CGs). The candidate CGs have been identified as spatial overdensities of Cepheids located across the thin disk. They account for a significant fraction of the residual fluctuations, and also for the large intrinsic dispersion of the metallicity gradient. We performed a detailed comparison with metallicity gradients based on different tracers: OB stars and open clusters. We found very similar metallicity gradients for ages younger than 3 Gyr, while for older ages we found a shallower slope and an increase in the intrinsic spread. The above findings rely on homogeneous age, metallicity, and distance scales. Finally, by using a large sample of Galactic and Magellanic Cepheids for which accurate iron abundances are available, we found that the dependence of the luminosity amplitude on metallicity is vanishing.

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Section: Photometric Datamentioning

confidence: 99%

Section: Luminosity Amplitudes and Metallicity Dependencementioning

confidence: 99%

On the fine structure of the Cepheid metallicity gradient in the Galactic thin disk

Genovali

Lemasle

Bono

et al. 2014

A&A

197

262

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“…Visual estimates from those plates will be needed unless surveyed by DASCH, which is a project aimed at digitizing the Harvard collection (Grindlay et al 2012). However, QZ Nor and V340 Nor are small-amplitude Cepheids (Klagyivik & Szabados 2009), which will exacerbate the uncertainties. Lastly, despite recent gains in bolstering the short and intermediate period regimes of the Galactic Cepheid calibration, considerable effort remains to constrain the long-period domain.…”

Section: Conclusion and Future Researchmentioning

confidence: 99%

Anchors for the cosmic distance scale: the Cepheid QZ Normae in the open cluster NGC 6067

Majaess¹,

Sturch

Bidin

et al. 2013

Astrophys Space Sci

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Cepheids are key to establishing the cosmic distance scale. Therefore it's important to assess the viability of QZ Nor, V340 Nor, and GU Nor as calibrators for Leavitt's law via their purported membership in the open cluster NGC 6067. The following suite of evidence confirms that QZ Nor and V340 Nor are members of NGC 6067, whereas GU Nor likely lies in the foreground: (i) existing radial velocities for QZ Nor and V340 Nor agree with that established for the cluster (−39.4 ± 0.2(σx) ± 1.2(σ) km/s) to within 1 km/s, whereas GU Nor exhibits a markedly smaller value; (ii) a steep velocity-distance gradient characterizes the sight-line toward NGC 6067, thus implying that objects sharing common velocities are nearly equidistant; (iii) a radial profile constructed for NGC 6067 indicates that QZ Nor is within the cluster bounds, despite being 20 ′ from the cluster center; (iv) new BV JH photometry for NGC 6067 confirms the cluster lies d = 1.75 ± 0.10 kpc distant, a result that matches Wesenheit distances computed for QZ Nor/V340 Nor using the Benedict et al. (2007, HST parallaxes) calibration. QZ Nor is a cluster Cepheid that should be employed as a calibrator for the cosmic distance scale.

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“…Motivated by the fact that the dependence of the pulsation amplitude on log P is neither linear nor unique, we studied the P − A relationship of Galactic Cepheids in Paper I (Klagyivik & Szabados 2009). We revised the P − A graphs for the U, B, V, R C , and I C photometric bands.…”

Section: Introductionmentioning

confidence: 99%

Observational studies of Cepheid amplitudes

Szabados

Klagyivik

2012

A&A

Self Cite

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Context. Physical and phenomenological properties (radius, luminosity, shape of the light curve, etc.) of Cepheids strongly depend on the pulsation period, with the exception of the pulsation amplitude. A possible factor causing a wide range of pulsation amplitudes might be the different atmospheric metallicities of individual Cepheids. Aims. We studied the influence exerted by the atmospheric iron content, [Fe/H], on the pulsational amplitude of Galactic Cepheids. Methods. We searched for correlations between the [Fe/H] value and both the observed amplitudes and amplitude related parameters.Results. The amplitude of the Cepheid pulsation slightly decreases with increasing iron abundance. This effect is more pronounced for the radial velocity variations and for the shorter pulsation periods. The wavelength dependence of photometric amplitudes is also found to be sensitive to the metallicity. Some of these effects are not consequences of differential line blanketing. Based on the calibrations of the metallicity sensitivity relationships, we derived photometric iron abundance for 21 Galactic Cepheids. The dichotomic behaviour dividing Galactic Cepheids that pulsate in the fundamental mode into short-and long-period groups at the period of 10. d 47 can be noticed in some diagrams that show metallicity-related dependences. Conclusions. We confirm that variety in atmospheric metallicity in Cepheids contributes to the finite range of pulsation amplitudes at a given period. Effects of metallicity on the amplitudes revealed from observational data and the occurrence of the dichotomy also derived from phenomenological data have to be confirmed by appropriate theoretical models of stellar structure and pulsation.

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Observational studies of Cepheid amplitudes

Cited by 77 publications

References 62 publications

On the fine structure of the Cepheid metallicity gradient in the Galactic thin disk

On the fine structure of the Cepheid metallicity gradient in the Galactic thin disk

Anchors for the cosmic distance scale: the Cepheid QZ Normae in the open cluster NGC 6067

Observational studies of Cepheid amplitudes

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