Rubidium and zirconium abundances in massive Galactic asymptotic giant branch stars revisited

Pérez-Mesa, V.; Zamora, Olga; García-Hernández, D. A.; Plez, B.; Manchado, A.; Karakas, Amanda I.; Lugaro, Maria

doi:10.1051/0004-6361/201731245

Cited by 25 publications

(25 citation statements)

References 55 publications

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“…11 are located where they were expected to be. Nevertheless, several studies (García-Hernández et al 2006Pérez-Mesa et al 2017) point out that some of these stars are intermediate rather than low-mass O-rich AGB stars, i.e. they should be found in Fig.…”

Section: Characterisation Of Carbon Stars With the Gaia-2mass Diagrammentioning

confidence: 99%

Properties of carbon stars in the solar neighbourhood based on Gaia DR2 astrometry

Abia

Laverny

Cristallo

et al. 2020

A&A

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Context. Stars evolving along the Asymptotic Giant Branch can become carbon-rich in the final part of their evolution. The detailed description of their spectra has led to the definition of several spectral types, namely: N, SC, J and R types. Up to now, differences among them have been partially established only on the basis of their chemical properties.Aims. An accurate determination of the luminosity function (LF) and kinematics together with their chemical properties is extremely important for testing the reliability of theoretical models and establishing on a solid basis the stellar population membership of the different carbon star types. Methods. Using Gaia Data Release 2 (Gaia DR2) astrometry, we determine the LF and kinematic properties of a sample of 210 carbon stars with different spectral types in the Solar neighbourhood, including some R-hot stars, with measured parallaxes better than 20%. Their spatial distribution and velocity components are also derived. Furthermore, the use of the infrared Wesenheit function allows us to identify the different spectral types in a Gaia-2MASS diagram.Results. We find that the combined LF of N-and SC-type stars are consistent with a Gaussian distribution peaking at M bol ∼ −5.2 mag. The resulting LF however shows two tails at lower and higher luminosities more extended than those previously found, indicating that AGB carbon stars with Solar metallicity may reach M bol ∼ −6.0 mag. This contrasts with the narrower LF derived in Galactic carbon Miras from previous studies. We find that J-type stars are about half a magnitude fainter on average than N-and SC-type stars, while R-hot stars are half a magnitude brighter than previously found although, in any case, fainter by several magnitudes than the rest of carbon types. Part of these differences are due to systematically lower parallaxes measured by Gaia DR2 with respect to Hipparcos ones, in particular for sources with parallax ̟ < 1 mas. The Galactic spatial distribution and velocity components of the N-, SC-and J-type stars are very similar, while about 30% of the R-hot stars in the sample are located at distances larger than ∼ 500 pc from the Galactic Plane, and show a significant drift with respect to the local standard of rest. Conclusions. The LF derived for N-and SC-type in the Solar neighbourhood fully agrees with the expected luminosity of stars of 1.5-3 M ⊙ on the AGB. On a theoretical basis, the existence of an extended low luminosity tail would require a contribution of extrinsic low mass carbon stars, while the high luminosity one would imply that stars with mass up to ∼ 5 M ⊙ may become carbon stars on the AGB. J-type stars not only differ significantly in their chemical composition with respect to the N-and SC-types but also in their LF, which reinforces the idea that these carbon stars belong to a dvifferent type whose origin is still unknown. The derived luminosities of R-hot stars make these stars unlikely to be in the red-clump as previously claimed. On the other hand, the derived spatial distributi...

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Section: Characterisation Of Carbon Stars With the Gaia-2mass Diagrammentioning

confidence: 99%

Properties of carbon stars in the solar neighbourhood based on Gaia DR2 astrometry

Abia

Laverny

Cristallo

et al. 2020

A&A

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“…The s-process element Rb, being a good indicator of the progenitor mass in AGB stars (see e.g. García-Hernández et al 2006;Pérez-Mesa et al 2017), has been also measured in these stars. Contrary to the synthesis of Li, strong Rb production is expected towards the end of the AGB phase, when a significant number of TPs have been experienced (see e.g.…”

Section: Lithiummentioning

confidence: 99%

“…i) AGB stars: both C-rich and O-rich AGB stars may not display the final chemical composition and their chemical abundance analysis (especially towards the end of the AGB, where they are usually dust enshrouded; i.e., optically invisible) is very complicated due to their complex dynamical atmospheres, which can dramatically affect the derived abundances (see e.g. Zamora et al 2014;Pérez-Mesa et al 2017). The CNO elemental and isotopic abundances, as obtained from high-resolution optical and/or near-IR spectroscopy, are only available in some Galactic C-rich AGB stars (e.g.…”

Section: Observational Facts and Future Directionsmentioning

confidence: 99%

“…The possible circumstellar effects (if any) on the near-IR molecular (CO, OH, CN) and atomic lines (Al, Mg, Na) remained to be explored. Finally, observations of heavy neutron-rich elements in AGB stars may provide clues to test these theoretical models but their uncertainties are very large, ranging from 0.3−0.4 dex to as high as 0.7 dex for Rb (e.g., Abia et al 2001;García-Hernández et al 2006;Pérez-Mesa et al 2017), highlighting the need for independent complementary observations (e.g., in post-AGB stars and PNe; see below). Also, the simulations of the nucleosynthesis due to slow-neutron captures (the s-process) in the ATON AGB models are still under construction .…”

Section: Observational Facts and Future Directionsmentioning

confidence: 99%

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Gas and dust from solar metallicity AGB stars

Ventura

Karakas

Dell’Agli

et al. 2018

Monthly Notices of the Royal Astronomical Society

118

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We study the asymptotic giant branch (AGB) evolution of stars with masses between 1 M − 8.5 M . We focus on stars with a solar chemical composition, which allows us to interpret evolved stars in the Galaxy. We present a detailed comparison with models of the same chemistry, calculated with a different evolution code and based on a different set of physical assumptions. We find that stars of mass ≥ 3.5 M experience hot bottom burning at the base of the envelope. They have AGB lifetimes shorter than ∼ 3 × 10 5 yr and eject into their surroundings gas contaminated by proton-capture nucleosynthesis, at an extent sensitive to the treatment of convection. Low mass stars with 1.5 M ≤ M ≤ 3 M become carbon stars. During the final phases the C/O ratio grows to ∼ 3. We find a remarkable agreement between the two codes for the low-mass models and conclude that predictions for the physical and chemical properties of these stars, and the AGB lifetime, are not that sensitive to the modelling of the AGB phase. The dust produced is also dependent on the mass: low-mass stars produce mainly solid carbon and silicon carbide dust, whereas higher mass stars produce silicates and alumina dust. Possible future observations potentially able to add more robustness to the present results are also discussed.

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“…18 of Karinkuzhi et al (2018b). Observations of massive AGB stars have confirmed that these stars in fact produce Rb (García-Hernández et al 2006, although a quantitative mismatch with the models is still present (van Raai et al 2012;Karakas et al 2012) and currently being investigated (Pérez-Mesa et al 2017).…”

Section: The Case Of Stellar Rotationmentioning

confidence: 99%

The s process in AGB stars as constrained by a large sample of barium stars

Cseh

Lugaro

D’Orazi

et al. 2018

A&A

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Context. Barium (Ba) stars are dwarf and giant stars enriched in elements heavier than iron produced by the slow neutron-capture process (s process). They belong to binary systems where the primary star evolved through the asymptotic giant branch (AGB) phase, during which it produced the s-process elements and transferred them onto the secondary, now observed as a Ba star. Aims. We compare the largest homogeneous set of Ba giant star observations of the s-process elements Y, Zr, La, Ce, and Nd with AGB nucleosynthesis models to reach a better understanding of the s process in AGB stars. Methods. By considering the light-s (ls: Y and Zr) heavy-s (hs: La, Ce, and Nd) and elements individually, we computed for the first time quantitative error bars for the different hs-element/ls-element abundance ratios, and for each of the sample stars. We compared these ratios to low-mass AGB nucleosynthesis models. We excluded La from our analysis because the strong La lines in some of the sample stars cause an overestimation and unreliable abundance determination, as compared to the other observed hs-type elements. Results. All the computed hs-type to ls-type element ratios show a clear trend of increasing with decreasing metallicity with a small spread (less than a factor of 3). This trend is predicted by low-mass AGB models where 13 C is the main neutron source. The comparison with rotating AGB models indicates the need for the presence of an angular momentum transport mechanism that should not transport chemical species, but significantly reduce the rotational speed of the core in the advanced stellar evolutionary stages. This is an independent confirmation of asteroseismology observations of the slow down of core rotation in giant stars, and of rotational velocities of white dwarfs lower than predicted by models without an extra angular momentum transport mechanism.

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Rubidium and zirconium abundances in massive Galactic asymptotic giant branch stars revisited

Cited by 25 publications

References 55 publications

Properties of carbon stars in the solar neighbourhood based on Gaia DR2 astrometry

Properties of carbon stars in the solar neighbourhood based on Gaia DR2 astrometry

Gas and dust from solar metallicity AGB stars

The s process in AGB stars as constrained by a large sample of barium stars

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