Light Curves and Period Changes of Type Ii Cepheids in the Globular Clusters M3 and M5

Rabidoux, K.; Smith, Horace A.; Pritzl, B. J.; Osborn, W.; Kuehn, Charles A.; Randall, Jill; Lustig, R.; Wells, Kenneth; Taylor, L.; Lee, Nathan De; Kinemuchi, Karen; Lacluyzé, A.; Hartley, D. P.; Greenwood, Charles R.; Ingber, M.; Ireland, Michael; Pellegrini, E.; Anderson, Mary; Purdum, Gene; Lacy, J.; Curtis, Michael; Smolinski, J.; Danford, S.

doi:10.1088/0004-6256/139/6/2300

Cited by 16 publications

(10 citation statements)

References 40 publications

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“…4) for more than two hundred galactic Cepheids spread out over more than a century of observations. Similar observations of decreases and increases of periods for Cepheids of type II in M 13 and M 5 have been recently reported by Rabidoux et al (2010). As the models computed with CHeB cross the instability strip with a monotonous increase of the radius, the temporal derivative of the period is always positive.…”

Section: Discussionsupporting

confidence: 87%

Implications of a new triple-αnuclear reaction rate

Morel

Provost

Pichon

et al. 2010

A&A

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Context. Recently the triple-α reaction rate has been re-evaluated. In the temperature range, 10 7 −10 8 K, with respect to the NACRE rate, the new rate is enhanced by up to 20 orders-magnitude. Aims. To validate this new rate, we investigate its consequences for the evolution of Cepheid models. Methods. The stellar evolutionary tracks are calculated with the CESAM code and displayed in the domain 4−10 M . Results. With the new rate, the first dredge-up does not occur. For masses larger than > 4.5 M each evolutionary track crosses the instability strip only once. The luminosities are higher than with the previous rate, then leading to smaller theoretical masses that better agree with the pulsational mass. Conversely, and inconsistently with one century of observations of more than two hundred Cepheids, the temporal derivative of the period keeps a positive sign. Moreover the observed depletions of atmospheric lithium and C/N ratio do not occur. A slight modification of only a few percents of the new nuclear rate allows us however to restore the loops inside the instability strip and the changes of sign of the temporal derivative of periods. Conclusions. This preliminary work indicates that the new rate may solve some of the long-lasting unsolved theoretical problems of Cepheids. Yet indisputable observations argue against its pertinence. Nonetheless, with regard to its theoretical importance, the triple-α new reaction rate still needs to be confirmed or revisited.

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Section: Discussionsupporting

confidence: 87%

Implications of a new triple-αnuclear reaction rate

Morel

Provost

Pichon

et al. 2010

A&A

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“…The phase variation of M80-V1 suggests that it also experienced a significant period change during the 1970s (sometime between JD 2441000 and 2444000), and it has been pulsating with a longer period since then. These findings agree with previous studies: large and abrupt changes can often be observed in the periods of W Vir-type stars (Percy & Hoss 2000;Rabidoux et al 2010).…”

Section: Period Changessupporting

confidence: 94%

First observations of W Virginis stars with K2: detection of period doubling

Plachy

Molnár

Jurković

et al. 2016

Mon. Not. R. Astron. Soc.

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We present the first analysis of W Vir stars observed by the Kepler space telescope in the K2 mission. Clear cycle-to-cycle variation were detected in the light curves of KT Sco and the globular cluster member M80-V1. While the variations in the former star seems to be irregular on the short time scale of the K2 data, the latter appears to experience period doubling in its pulsation. Ground-based colour data confirmed that both stars are W Vir-type pulsators, while a comparison with historical photometric time-series data revealed drastic period changes in both stars. For comparison we reexamine ground-based observations of W Vir, the prototype of the class, and conclude that it shows period doubling instead of mode beating. These results support the notion that nonlinear dynamics plays an important role in the pulsation of W Virginis-type stars.Large ground-and space-based surveys have potential to map these domains, although the former are limited by accuracy, and the latter by small sample size per mission so far. The only Type II Cepheid observed from space, the

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“…However, RVTs have been identified in the MCs (Soszyński et al 2008;Ripepi et al 2015). b) Alternating cycle behaviour -There is evidence of an interaction between the central star and the circumstellar envelope possibly causing the alternating cycle behaviour (Feast et al 2008;Rabidoux et al 2010). The final crossing of the instability strip before approaching the WD cooling sequence either for PEAGB or for TPAGB models appears a very plausible explanation.…”

Section: Pulsation and Evolutionary Implications For Type II Cepheidsmentioning

confidence: 99%