Magellanic Cloud Cepheids: Abundances

Luck, R. E.; Moffett, T. J.; Barnes, Thomas G.; Gieren, W.

doi:10.1086/300227

Cited by 229 publications

(233 citation statements)

References 48 publications

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“…Synthetic CMDs are generated using the latest PARSEC (Bressan et al 2012;Tang et al 2014) isochrones, and assuming a Kroupa IMF and metallicity Z=0.008 (from the mean [Fe/H] for LMC Cepheids of Luck et al 1998, referred to the updated Caffau et al 2011 mixture). 30% of synthetic stars are considered members of binary systems and their flux is combined with a secondary star sampled from the same IMF.…”

Section: Synthetic Cmdsmentioning

confidence: 99%

“…The empirical evidence of a metallicity spread in the young populations of the LMC (see e.g., Luck et al 1998, Romaniello et al 2008) makes Hodge's metallicity inherently uncertain. In order to test the impact of a lower metallicity on the final age, we re-recovered the SFH using PARSEC models with Z=0.005 (about 1σ away from the mean value of Luck's Figure 9.…”

Section: Metallicitymentioning

confidence: 99%

See 1 more Smart Citation

Hubble Tarantula Treasury Project. V. The Star Cluster Hodge 301: The Old Face of 30 Doradus*

Cignoni

Sabbi

Marel

et al. 2016

ApJ

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Based on color-magnitude diagrams (CMDs) from the Hubble Space TelescopeHubble Tarantula Treasury Project (HTTP) survey, we present the star formation history of Hodge301, the oldest star cluster in the Tarantula Nebula. The HTTP photometry extends faint enough to reach, for the first time, the cluster pre-main sequence (PMS) turnon, where the PMS joins the main sequence. Using the location of this feature, along with synthetic CMDs generated with the latest PARSEC models, we find that Hodge301 is older than previously thought, with an age between 26.5 and 31.5 Myr. From this age, we also estimate that between 38 and 61 Type II supernovae exploded in the region. The same age is derived from the main sequence turn-off, whereas the age derived from the postmain sequence stars is younger and between 20 and 25 Myr. Other relevant parameters are a total stellar mass of ≈8800±800M e and average reddening E(B − V ) ≈ 0.22-0.24 mag, with a differential reddening δE (B − V )≈0.04 mag.

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Section: Synthetic Cmdsmentioning

confidence: 99%

Section: Metallicitymentioning

confidence: 99%

Hubble Tarantula Treasury Project. V. The Star Cluster Hodge 301: The Old Face of 30 Doradus*

Cignoni

Sabbi

Marel

et al. 2016

ApJ

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“…3.3. The low iron abundance of J004441.04 with respect to the mean metallicity of the SMC of [Fe/H] ≈ −0.7 (Luck et al 1998) classifies J004441.04 as a low-metallicity star which are generally acknowledged as astrophysical production sites of heavy s-nuclei provided the third dredge-up (TDU) takes place.…”

Section: Atmospheric Parameter Determinationmentioning

confidence: 99%

Post-AGB stars in the SMC as tracers of stellar evolution: the extreme s-process enrichment of the 21 μm star J004441.04-732136.4

Smedt

Winckel

Karakas

et al. 2012

A&A

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Context. This paper is part of a larger project in which we want to focus on the still poorly understood asymptotic giant branch (AGB) third dredge-up processes and associated s-process nucleosynthesis. Aims. We confront accurate spectral abundance analyses of post-AGB stars in both the Magellanic Clouds, to state-of-the-art AGB model predictions. With this comparison we aim at improving our understanding of the 3rd dredge-up phenomena and their dependencies on initial mass and metallicity. Methods. Because of the well constrained distance with respect to Galactic post-AGB stars, we choose an extra-galactic post-AGB star for this contribution, namely the only known 21 μm object of the Small Magellanic Cloud (SMC): J004441.04-732136.4. We used optical UVES spectra to perform an accurate spectral abundance analysis. With photometric data of multiple catalogues we construct a spectral energy distribution (SED) and perform a variability analysis. The results are then compared to predictions of tailored theoretical chemical AGB evolutionary models for which we used two evolution codes. Results. Spectral abundance results reveal J004441.04-732136.4 to be one of the most s-process enriched objects found up to date, while the photospheric C/O ratio of 1.9 ± 0.7, shows the star is only modestly C-rich. J004441.04-732136.4 also displays a low [Fe/H] = −1.34 ± 0.32, which is significantly lower than the mean metallicity of the SMC. From the SED, a luminosity of 7600 ± 200 L is found, together with E(B − V) = 0.64 ± 0.02. According to evolutionary post-AGB tracks, the initial mass should be ≈1.3 M . The photometric variability shows a clear period of 97.6 ± 0.3 days. The detected C/O as well as the high s-process overabundances (e.g. [Y/Fe] = 2.15, [La/Fe] = 2.84) are hard to reconcile with the predictions. The chemical models also predict a high Pb abundance, which is not compatible with the detected spectrum, and a very high 12 C/ 13 C, which is not yet constrained by observations. The predictions are only marginally dependent on the evolution codes used. Conclusions. By virtue of their spectral types, favourable bolometric corrections as well as their constrained distances, post-AGB stars in external galaxies offer unprecedented tests to AGB nucleosynthesis and dredge-up predictions. We focus here on one object J004441.04-732136.4, which is the only known 21 μm source of the SMC. We show that our theoretical predictions match the s-process distribution, but fail in reproducing the detected high overabundances and predict a high Pb abundance which is not detected. Additionally, there remain serious problems in explaining the observed pulsational properties of this source.

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“…In particular Luck et al (1998) One should also take into account the uncertainty on the solar mixture. As already discussed, tridimensional hydrodynamical atmospheric models by Asplund et al (2005) reduced the derived abundances of CNO and other heavy elements with respect to previous estimates (Grevesse & Sauval 1998, hereafter GS98).…”

Section: Effects Of the Chemical Composition Uncertaintiesmentioning

confidence: 99%

Uncertainties on the theoretical predictions for classical Cepheid pulsational quantities

Valle

Marconi²,

Degl’Innocenti

et al. 2009

A&A

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Context. With their period-luminosity relation, "classical Cepheids" (CC) are the most common primary distance indicators within the Local Group, also providing an absolute calibration of important secondary distance indicators. However, the predicted position of these pulsators in the HR diagram, along the so called blue loop, that is the expected distribution of Cepheids within the instability strip is affected by several model inputs, reflecting upon the predicted PL relation. Aims. The aim of this work is to quantitatively evaluate the effects on the theoretical PL relation of current uncertainties on the chemical abundances of Cepheids in the Large Magellanic Cloud (LMC) and on several physical assumptions adopted in the evolutionary models. We will separately analyse how the different factors influence the evolutionary and pulsational observables and the resulting PL relation. Methods. To achieve this goal we computed new sets of updated evolutionary and pulsational models. Results. As a result, we find that present uncertainties on the most relevant H and He burning reaction rates do not influence in a relevant way the loop extension in temperature. On the contrary, current uncertainties on the LMC chemical composition significantly affect the loop extension and also reflect in the morphology of the instability strip; however their influence on the predicted pulsational parameters is negligible. We also discussed how overshooting and mass loss, sometimes suggested as possible solutions for the long-standing problem of the Cepheid mass discrepancy, influence the ML relation and the pulsational parameters. Conclusions. In summary, the present uncertainties on the physical inputs adopted in the evolutionary codes and in the LMC chemical composition are negligible for the prediction of the main pulsational properties. On the other hand, the inclusion of overshooting in the previous hydrogen burning phase and/or of mass loss is expected to significantly change the resulting theoretical pulsational scenario for Cepheids, as well as the calibration of their distance scale. These systematic effects are expected to influence the theoretical Cepheid calibration of the secondary distance indicators and in turn the resulting evaluation of the Hubble constant.

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Magellanic Cloud Cepheids: Abundances

Cited by 229 publications

References 48 publications

Hubble Tarantula Treasury Project. V. The Star Cluster Hodge 301: The Old Face of 30 Doradus*

Hubble Tarantula Treasury Project. V. The Star Cluster Hodge 301: The Old Face of 30 Doradus*

Post-AGB stars in the SMC as tracers of stellar evolution: the extreme s-process enrichment of the 21 μm star J004441.04-732136.4

Uncertainties on the theoretical predictions for classical Cepheid pulsational quantities

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