Studying the evolution of AGB stars in the<i>Gaia</i>epoch

Criscienzo, M. Di; Ventura, P.; García-Hernández, D. A.; Dell’Agli, F.; Castellani, M.; Marrese, P. M.; Marinoni, S.; Giuffrida, G.; Zamora, Olga

doi:10.1093/mnras/stw1685

Cited by 36 publications

(30 citation statements)

References 72 publications

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“…While this is a common property of all M ≥ 3.5 M⊙ models, the destruction of the surface oxygen, which requires higher HBB temperatures (∼ 80 MK), is sensitive to the metallicity, and is higher the lower is Z . The destruction of oxygen is extremely sensitive to the modelling of convection: in the present analysis, based on the FST description, we find significant depletion of oxygen in metal poor AGB stars; conversely, when a less efficient convective model is used, the HBB experienced is weaker, thus limiting the efficiency of oxygen burning (Ventura & D'Antona 2005;Di Criscienzo et al 2016). In this context, the detection of oxygen-poor PNe, enriched in nitrogen, would be an Table 1.…”

Section: Hot Bottom Burning and Helium Enrichment In Massive Agb Starsmentioning

confidence: 56%

The evolution of Galactic planetary nebula progenitors through the comparison of their nebular abundances with AGB yields

Ventura

Stanghellini

Dell’Agli

et al. 2017

Monthly Notices of the Royal Astronomical Society

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We study the chemical abundances of a wide sample of 142 Galactic planetary nebulae (PNe) with good quality observations, for which the abundances have been derived more or less homogeneously, thus allowing a reasonable comparison with stellar models. The goal is the determination of mass, chemical composition and formation epoch of their progenitors, through comparison of the data with results from AGB evolution. The dust properties of PNe, when available, were also used to further support our interpretation.We find that the majority (∼ 60%) of the Galactic PNe studied has nearly solar chemical composition, while ∼ 40% of the sources investigated have sub-solar metallicities. About half of the PNe have carbon star progenitors, in the 1.5 M ⊙ < M < 3 M ⊙ mass range, which have formed between 300 Myr and 2 Gyr ago. The remaining PNe are almost equally distributed among PNe enriched in nitrogen, which we interpret as the progeny of M > 3.5 M ⊙ stars, younger than 250 Myr, and a group of oxygen-rich PNe, descending from old (> 2 Gyr) low-mass (M < 1.5 M ⊙ ) stars that never became C-stars.This analysis confirms the existence of an upper limit to the amount of carbon which can be accumulated at the surface of carbon stars, probably due to the acceleration of mass loss in the late AGB phases. The chemical composition of the present sample suggests that in massive AGB stars of solar (or slightly sub-solar) metallicity, the effects of third dredge up combine with hot bottom burning, resulting in nitrogenrich -but not severely carbon depleted -gaseous material to be ejected.

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Section: Hot Bottom Burning and Helium Enrichment In Massive Agb Starsmentioning

confidence: 56%

The evolution of Galactic planetary nebula progenitors through the comparison of their nebular abundances with AGB yields

Ventura

Stanghellini

Dell’Agli

et al. 2017

Monthly Notices of the Royal Astronomical Society

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“…This feature is most likely due to the anticorrelation between C and N abundances (see, e.g., Smith et al 1996;Cohen et al 2005). In the multiple population paradigm, the mechanism responsible for the Na-O anticorrelation would also produce C-N anticorrelation (Ventura et al 2013;Di Criscienzo et al 2016). Our previous studies, however, found a significant CN-CH positive correlation, instead of an anticorrelation, among RGB stars in M22 and NGC 6273 Lim et al 2015).…”

Section: The Cn-ch Positive Correlation In Globular Clusters With Heamentioning

confidence: 71%

The CN–CH Positive Correlation in the Globular Cluster NGC 5286

Lim¹,

Hong²,

Lee³

2017

ApJ

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We performed low-resolution spectroscopy for the red giant stars in the Galactic globular cluster (GC) NGC 5286, which is known to show intrinsic heavy element abundance variations. We found that the observed stars in this GC are clearly divided into three subpopulations by CN index (CN-weak, CN-intermediate, and CN-strong). The CN-strong stars are also enhanced in the calcium HK (7.4σ) and CH (5.1σ) indices, while the CN-intermediate stars show no significant difference in the strength of HK index with CN-weak stars. From the comparison with high-resolution spectroscopic data, we found that the CN-and HK -strong stars are also enhanced in the abundances of Fe and s-process elements. It appears, therefore, that these stars are later generation stars affected by some supernovae enrichment in addition to the asymptotic giant branch ejecta. In addition, unlike normal GCs, sample stars in NGC 5286 show the CN-CH positive correlation, strengthening our previous suggestion that this positive correlation is only discovered in GCs with heavy element abundance variations such as M22 and NGC 6273.

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“…In this circumstance TDU leads to the mixing of M TDU ≃ 0.003M ⊙ from the H-free core into a H-rich envelope of M H env ≃ 0.027M ⊙ , significantly increasing the surface carbon abundance of the star. This example shows why it is necessary to keep in mind that final AGB thermal pulses coupled with low envelope masses can significantly change the surface abundances from those predicted by AGB stellar evolution models 8 We note that oxygen may not be a reliable metallicity indicator if significant amounts of O are dredged up to the surface or destroyed by hot bottom burning during the TP-AGB as predicted by some models -see section 3.1.1 in Di Criscienzo et al (2016) and Table 3 in Miller Bertolami (2016).…”

Section: Discussionmentioning

confidence: 90%

“…We now briefly review the treatment of these key ingredients in the four grids adopted here for the comparison: the MONASH grid (Karakas 2014;, the LPCODE grid (Miller Bertolami 2016), the ATON grid (Ventura et al 2015;Di Criscienzo et al 2016) and the FRUITY database (Cristallo et al 2011(Cristallo et al , 2015. While all the models discussed here include an upto-date treatment of the microphysics, and all of them neglect the impact of rotation, the theoretical models discussed in this section have some key differences in the modeling of winds and convective boundary mixing processes.…”

Section: Description Of the Model Codesmentioning

confidence: 99%

“…The purpose of our investigation here is to confront recently published stellar model predictions of PN abundances with the observed abundances of He, C, N and O. We consider the models of four 2 We qualify this seemingly tidy picture by pointing out that oxygen enrichment in PN has been reported by Péquignot et al (2000) and more recently in C-rich PN by Delgado-Inglada et al (2015) and García-Hernández et al (2016).…”

Section: Introductionmentioning

confidence: 99%

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On the production of He, C, and N by low- and intermediate-mass stars: a comparison of observed and model-predicted planetary nebula abundances

Henry

Stephenson

Bertolami

et al. 2017

Monthly Notices of the Royal Astronomical Society

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The primary goal of this paper is to make a direct comparison between the measured and modelpredicted abundances of He, C and N in a sample of 35 well-observed Galactic planetary nebulae (PN). All observations, data reductions, and abundance determinations were performed in house to ensure maximum homogeneity. Progenitor star masses (M ≤ 4 M ⊙ ) were inferred using two published sets of post-AGB model tracks and L and T ef f values. We conclude the following: 1) the mean values of N/O across the progenitor mass range exceeds the solar value, indicating significant N enrichment in the majority of our objects; 2) the onset of hot bottom burning appears to begin around 2 M ⊙ , i.e., lower than ∼ 5 M ⊙ implied by theory; 3) most of our objects show a clear He enrichment, as expected from dredge-up episodes; 4) the average sample C/O value is 1.23, consistent with the effects of third dredge-up; and 5) model grids used to compare to observations successfully span the distribution over metallicity space of all C/O and many He/H data points but mostly fail to do so in the case of N/O. The evident enrichment of N in PN and the general discrepancy between the observed and model-predicted N/O abundance ratios signal the need for extra-mixing as an effect of rotation and/or thermohaline mixing in the models. The unexpectedly high N enrichment that is implied here for low mass stars, if confirmed, will likely impact our conclusions about the source of N in the Universe.

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Studying the evolution of AGB stars in theGaiaepoch

Cited by 36 publications

References 72 publications

The evolution of Galactic planetary nebula progenitors through the comparison of their nebular abundances with AGB yields

The evolution of Galactic planetary nebula progenitors through the comparison of their nebular abundances with AGB yields

The CN–CH Positive Correlation in the Globular Cluster NGC 5286

On the production of He, C, and N by low- and intermediate-mass stars: a comparison of observed and model-predicted planetary nebula abundances

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