Post-AGB Stars as Tracers of AGB Nucleosynthesis: An Update

Kamath, D.; Winckel, H. Van

doi:10.3390/universe8040233

Cited by 7 publications

(15 citation statements)

References 70 publications

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“…This is consistent with the dominant sprocess origin from low-and intermediate-mass stars, where the 13 C neutron source is not dependent on metallicity, but the neutron to heavy seed ratio declines with metallicity. Image reproduced with permissions from Kamath and Van Winckel (2022), copyright by the authors from about 1120 down to 0.5 (Hansen et al 2018), and indicating the different decline of the abundance curve as a function of A. Some of the r-process enriched stars show an "actinide boost", i.e.…”

Section: Galactic Chemical Evolution (Gce)mentioning

confidence: 99%

Origin of the elements

Arcones

Thielemann

2022

Astron Astrophys Rev

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What is the origin of the oxygen we breathe, the hydrogen and oxygen (in form of water H2O) in rivers and oceans, the carbon in all organic compounds, the silicon in electronic hardware, the calcium in our bones, the iron in steel, silver and gold in jewels, the rare earths utilized, e.g. in magnets or lasers, lead or lithium in batteries, and also of naturally occurring uranium and plutonium? The answer lies in the skies. Astrophysical environments from the Big Bang to stars and stellar explosions are the cauldrons where all these elements are made. The papers by Burbidge (Rev Mod Phys 29:547–650, 1957) and Cameron (Publ Astron Soc Pac 69:201, 1957), as well as precursors by Bethe, von Weizsäcker, Hoyle, Gamow, and Suess and Urey provided a very basic understanding of the nucleosynthesis processes responsible for their production, combined with nuclear physics input and required environment conditions such as temperature, density and the overall neutron/proton ratio in seed material. Since then a steady stream of nuclear experiments and nuclear structure theory, astrophysical models of the early universe as well as stars and stellar explosions in single and binary stellar systems has led to a deeper understanding. This involved improvements in stellar models, the composition of stellar wind ejecta, the mechanism of core-collapse supernovae as final fate of massive stars, and the transition (as a function of initial stellar mass) from core-collapse supernovae to hypernovae and long duration gamma-ray bursts (accompanied by the formation of a black hole) in case of single star progenitors. Binary stellar systems give rise to nova explosions, X-ray bursts, type Ia supernovae, neutron star, and neutron star–black hole mergers. All of these events (possibly with the exception of X-ray bursts) eject material with an abundance composition unique to the specific event and lead over time to the evolution of elemental (and isotopic) abundances in the galactic gas and their imprint on the next generation of stars. In the present review, we want to give a modern overview of the nucleosynthesis processes involved, their astrophysical sites, and their impact on the evolution of galaxies.

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Section: Galactic Chemical Evolution (Gce)mentioning

confidence: 99%

Origin of the elements

Arcones

Thielemann

2022

Astron Astrophys Rev

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“…This dispersion, on the other hand, is necessary to account for the s-element abundance patterns observed in individual C-stars. We note, nevertheless, that the correlation [hs/ls] vs. [Fe/H] is not clearly observed in post-AGB stars, the progeny of AGB stars, at least in the metallicity range studied [37]. This shows the complexity of the s-process nucleosynthesis in AGB stars.…”

Section: S-elementsmentioning

confidence: 61%

“…In any case, this question remains unsolved. Note that most of post-AGB stars show also C/O ratios very close to 1 [38], which is not either understandable on theoretical grounds.…”

Section: The Observational Frameworkmentioning

confidence: 83%

The carbon star mystery: 40 years later

2023

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In 1981 Icko Iben Jr published a paper entitled “The carbon star mystery: why do the low mass ones become such, and where have all the high mass ones gone?”, where he discussed the discrepancy between the theoretical expectation and its observational counterpart about the luminosity function of AGB carbon stars. After more than 40 years, our understanding of this longstanding problem is greatly improved, also thanks to more refined stellar models and a growing amount of observational constraints. In this paper we review the state of the art of these studies and we briefly illustrate the future perspectives.

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“…Observational studies of post-AGB stars in the Galaxy (e.g. Van Winckel & Reyniers 2000;Rao et al 2012;De Smedt et al 2015;Kamath et al 2022) and the Magellanic Clouds (MCs) (e.g. Kamath et al 2014Kamath et al , 2015 have shown that they are far more chemically diverse than anticipated.…”

Section: Introductionmentioning

confidence: 99%

“…However, a study by Kamath et al (2017) reported a subset of luminous single post-AGB stars (one in the Small Magellanic Cloud (SMC) and two in the Galaxy) that exhibited neither traces of carbon enhancements nor s-process elements, suggesting a likely failure of the third dredge-up (TDU). Further expanding on this, a recent investigation by Kamath et al (2022) categorised single post-AGB stars with similar atmospheric parameters into two groups: those displaying s-process enrichment and those exhibiting no s-process enrichment.…”

Section: Introductionmentioning

confidence: 99%

s-Process Enriched Evolved Binaries in the Galaxy and the Magellanic Clouds

Menon,

Kamath,

Mohorian

et al. 2024

Publ. Astron. Soc. Aust.

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Post-asymptotic giant branch stars (post-AGB) in binary systems, with typical orbital periods between ∼100 to ∼1000 days, result from a poorly understood interaction that terminates their precursory AGB phase. The majority of these binaries display a photospheric anomaly called ‘chemical depletion’, thought to arise froman interaction between the circumbinary disc and the post-AGB star, leading to the reaccretion of pure gas onto the star, devoid of refractory elements due to dust formation. In this paper, we focus on a subset of chemically peculiar binary post-AGBs in the Galaxy and the Magellanic Clouds (MCs). Our detailed stellar parameter and chemical abundance analysis utilising high-resolution optical spectra from VLT+UVES revealed that our targets span a Teff of 4900 - 7250K and [Fe/H] of -0.5 - -1.57 dex. Interestingly, these targets exhibit a carbon ([C/Fe] ranging from 0.5 - 1.0 dex, dependant on metallicity) and s-process enrichment ([s/Fe]≥1dex) contrary to the commonly observed chemical depletion pattern. Using spectral energy distribution (SED) fitting and period-luminosity-colour (PLC) relation methods, we determine the luminosity of the targets (2700 – 8300 L⊙), which enables confirmation of their evolutionary phase and estimation of initial masses (as a function of metallicity) (1 - 2.5M⊙). In conjunction with predictions from dedicated ATON stellar evolutionary models, our results indicate a predominant intrinsic enrichment of carbon and s-process elements in our binary post-AGB targets. We qualitatively rule out extrinsic enrichment and inherited s-process enrichment from the host galaxy as plausible explanations for the observed overabundances. Our chemically peculiar subset of intrinsic carbon and s-process enriched binary post-AGBs also hints at potential variation in the efficiency of chemical depletion between stars with C-rich and O-rich circumbinary disc chemistries. However, critical observational studies of circumbinary disc chemistry, along with specific condensation temperature estimates in C-rich environments, are necessary to address gaps in our current understanding of disc-binary interactions inducing chemical depletion in binary post-AGB systems.

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Post-AGB Stars as Tracers of AGB Nucleosynthesis: An Update

Cited by 7 publications

References 70 publications

Origin of the elements

Origin of the elements

The carbon star mystery: 40 years later

s-Process Enriched Evolved Binaries in the Galaxy and the Magellanic Clouds

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