On the Cepheid Metallicity Dichotomy

Kovács, G.

doi:10.1051/eas/0938009

Cited by 3 publications

(2 citation statements)

References 13 publications

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“…If metallicity is the main cause of these differences then it follows that the most metal-rich RRd stars in the LMC, those with the smallest period ratios, are more metal-rich than those in the SMC, a result consistent with the LMC having a higher mean metallicity than the SMC (see fig. 2 of Kovács 2009, andfig. 1 of Mucciarelli 2014).…”

Section: Introductionmentioning

confidence: 98%

Four 'Peculiar' RRd Stars Observed by K2

Nemec,

Moskalik

2021

Preprint

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Four stars pulsating simultaneously with a dominant period P D ∈(0.28, 0.39) d and an additional period P A ∈(0.20, 0.27) d have been identified from among the more than 3000 RR Lyrae stars observed by the Kepler space telescope during NASA's K2 Mission. All four stars are located in the direction of the Galactic Bulge and have period ratios, P A /P D , significantly smaller than those of most double-mode RR Lyrae (RRd) stars: P A /P D ∈(0.694, 0.710) vs. P 1 /P 0 ∈(0.726, 0.748). Three of the stars are faint (=18-20 mag) and distant and are among the 'peculiar' RRd (pRRd) stars discovered by Prudil et al. (2017); the fourth star, EPIC 216764000 (= V1125 Sgr), is a newly discovered pRRd star several magnitudes brighter than the other three stars. In this paper the high-precision long-cadence K2 photometry is analyzed in detail and used to study the cycle-to-cycle light variations. The pulsational characteristics of pRRd stars are compared with those of 'classical' and 'anomalous' RRd (cRRd, aRRd) stars. The conclusion by Prudil et al. that pRRd stars form a separate group of double-mode pulsators and are not simply very-short-period cRRd stars is confirmed. V1127 Aql and AH Cam are identified as other probable members of the class of pRRd stars.

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Section: Introductionmentioning

confidence: 98%

Four 'Peculiar' RRd Stars Observed by K2

Nemec,

Moskalik

2021

Preprint

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“…The period ratios can be measured very accurately and have been found to correlate with the Cepheid masses, luminosities, T eff , and the abundances of the heavy elements. For example, from the OGLE photometry and the stellar atmosphere models, Kovács (2009) showed that in both Magellanic Clouds the average metallicity of the P1 Cepheids is lower than those pulsating in the fundamental mode.…”

Section: Introductionmentioning

confidence: 99%

Discovery of the first Super-Lithium rich Beat Cepheid: V371 Per

Kovtyukh,

Gorlova,

Hillen

2013

Preprint

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Four high-resolution spectra of the double-mode Cepheid V371 Per, obtained for the first time, showed the presence of the abnormally strong Li i 6707.76 Å line. Our analysis of the light element abundances indicates that the star did not go through the evolutionary dredge-up stage. Large distance from the galactic plane and the low metallicity suggest that V371 Per may belong to the thick disc (or to the halo) of the Galaxy, which is consistent with its low metallicity [Fe/H]=-0.42 and the enhancement of the α-and s-elements relative to iron. Line splitting is observed in one of the spectra, which can be due to the non-radial pulsations.

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Four ‘Peculiar’ RRd stars observed by K2

Nemec

Moskalik

2021

Monthly Notices of the Royal Astronomical Society

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Four stars pulsating simultaneously with a dominant period PD∈(0.28, 0.39) d and an additional period PA∈(0.20, 0.27) d have been identified from among the more than 3000 RR Lyrae stars observed by the Kepler space telescope during NASA’s K2 Mission. All four stars are located in the direction of the Galactic Bulge and have period ratios, PA/PD, significantly smaller than those of most double-mode RR Lyrae (RRd) stars: PA/PD∈(0.694, 0.710) vs. P1/P0∈(0.726, 0.748). Three of the stars are faint (<V>=18–20 mag) and distant and are among the ‘peculiar’ RRd (pRRd) stars discovered by Prudil et al. (2017); the fourth star, EPIC 216764000 (= V1125 Sgr), is a newly discovered pRRd star several magnitudes brighter than the other three stars. In this paper the high-precision long-cadence K2 photometry is analyzed in detail and used to study the cycle-to-cycle light variations. The pulsational characteristics of pRRd stars are compared with those of ‘classical’ and ‘anomalous’ RRd (cRRd, aRRd) stars. The conclusion by Prudil et al. that pRRd stars form a separate group of double-mode pulsators and are not simply very-short-period cRRd stars is confirmed. V1127 Aql and AH Cam are identified as other probable members of the class of pRRd stars.

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On the Cepheid Metallicity Dichotomy

Cited by 3 publications

References 13 publications

Four 'Peculiar' RRd Stars Observed by K2

Four 'Peculiar' RRd Stars Observed by K2

Discovery of the first Super-Lithium rich Beat Cepheid: V371 Per

Four ‘Peculiar’ RRd stars observed by K2

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