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20 pages, 1789 KiB

Open AccessArticle

On the Nucleosynthetic Origin of Presolar Silicon Carbide X-Grains

by Waheed Akram, Oliver Hallmann, Bernd Pfeiffer and Karl-Ludwig Kratz

Universe 2022, 8(12), 629; https://doi.org/10.3390/universe8120629 - 28 Nov 2022

Viewed by 1514

Abstract

In this paper we present an extension of our nucleosynthesis parameter study within the classical neutrino-driven wind scenario of core-collapse supernovae (ccSNe). The principal aim of this decade-old study was to shine light on the production of the historical ‘p-only’ isotopes of the [...] Read more.

In this paper we present an extension of our nucleosynthesis parameter study within the classical neutrino-driven wind scenario of core-collapse supernovae (ccSNe). The principal aim of this decade-old study was to shine light on the production of the historical ‘p-only’ isotopes of the light trans-Fe elements in the Solar System (S.S.). One of our earliest key findings was the co-production of neighbouring classical ‘s-only’ and ‘r-only’ isotopes between Zn (Z = 30) and Ru (Z = 44), alongside the synthesis of light p-isotopes, under similar conditions of a moderately neutron-rich, low-entropy, charged-particle component of Type II SNe wind ejecta. We begin this analysis by expressing the need for nuclear-structure input from detailed spectroscopic experiments and microscopic models in the relevant shape-transition mass region between N = 50 and N = 60. Then, we focus on the unique nucleosynthetic origin of the anomalous isotopic compositions of Zr (Z = 40), Mo (Z = 42) and Ru (Z = 44) in presolar silicon carbide X-grains. In contrast to the interpretation of other studies, we show that these grains do not reflect the signature of a ‘clean’ stellar scenario but are mixtures of an exotic rapid (r-process like) nucleosynthesis component and different fractions of S.S. material. Thus, the synthesis of these light isotopes through a ‘primary’ production mode provides further means to revise the abundance estimates of the light trans-Fe elements in the S.S., reducing our dependence on still favoured ‘secondary’ scenarios like Type Ia SNe or neutron-bursts in exploding massive stars. Full article

(This article belongs to the Special Issue AGB Stars—In Honor of Professor Maurizio Busso on the Occasion of His 70th Birthday)

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23 pages, 499 KiB

Open AccessArticle

Chemical Tracing and the Origin of Carbon in the Galactic Disk

by Bengt Gustafsson

Universe 2022, 8(8), 409; https://doi.org/10.3390/universe8080409 - 4 Aug 2022

Cited by 2 | Viewed by 1575

Abstract

A basic problem in studies of the evolution of chemical elements in galaxies is the uncertainties in the yields of elements produced by different types of stars. The possibilities of tracing the sites producing chemical elements and corresponding yields in stellar populations by [...] Read more.

A basic problem in studies of the evolution of chemical elements in galaxies is the uncertainties in the yields of elements produced by different types of stars. The possibilities of tracing the sites producing chemical elements and corresponding yields in stellar populations by studying ratios of abundances in stars of different ages and metallicities, with an approach with minimal assumptions concerning the yields, is explored by means of simple models of Galactic chemical evolution. Elemental abundances of carbon and oxygen, obtained by recent observations of samples of solar-type stars with estimated ages in the thin disk of the Galaxy, are analysed. Constraints on the yields from winds of intermediate-mass stars and of hot massive stars, including core-collapse supernovae, are derived. It is found that a dominating contribution of carbon from massive stars is most probable, although stars in the mass interval of two to three solar masses may have provided some amounts of carbon in the Sun. The results are consistent with those obtained by using theoretical yields and more elaborate models of Galactic evolution. The uncertainties as regards the mixing of stellar populations due to migration of stars in the Galactic disk may be important for the conclusions. Variations in the star formation rates, lack of chemical homogeneity in the Galactic gas, the inflow of gas from the intergalactic space and possible variations in the Initial mass function may also limit conclusions about the sites and their yields. Very accurate abundance ratios and the determination of stellar ages provide further important constraints on the yields. Full article

(This article belongs to the Special Issue AGB Stars—In Honor of Professor Maurizio Busso on the Occasion of His 70th Birthday)

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11 pages, 1560 KiB

Open AccessArticle

The Initial-Final Mass Relation of White Dwarfs: A Tool to Calibrate the Third Dredge-Up

by Paola Marigo

Universe 2022, 8(4), 243; https://doi.org/10.3390/universe8040243 - 14 Apr 2022

Cited by 10 | Viewed by 1824

Abstract

The initial mass-final mass relationship (IFMR) of white dwarfs (WD) represents a crucial benchmark for stellar evolution models, especially for the efficiency of mixing episodes and mass loss during the asymptotic giant branch (AGB) phase. In this study, we argue that this relation [...] Read more.

The initial mass-final mass relationship (IFMR) of white dwarfs (WD) represents a crucial benchmark for stellar evolution models, especially for the efficiency of mixing episodes and mass loss during the asymptotic giant branch (AGB) phase. In this study, we argue that this relation offers the opportunity to constrain the third dredge-up (3DU), with important consequences for chemical yields. The results are discussed in light of recent studies that have identified a kink in the IFMR for initial masses close to

2 M_{⊙}

. Adopting a physically-sound approach in which the efficiency

λ

of the 3DU varies as a function of core and envelope masses, we calibrate

λ

in solar-metallicity TP-AGB models in order to reproduce the final masses of their WD progeny, over the range of initial masses

0.9 \leq M_{i} / M_{⊙} \leq 6

. In particular, we find that in low-mass stars with

1.4 ≲ M_{i} / M_{⊙} ≲ 2.0

the efficiency is small,

λ \leq 0.3

, it steeply rises to about

λ ≃ 0.65

in intermediate-mass stars with

2.0 \leq M_{i} / M_{⊙} \leq 4.0

, and then it drops in massive TP-AGB stars with

4.0 ≲ M_{i} / M_{⊙} ≲ 6.0

. Our study also suggests that a second kink may show up in the IFMR at the transition between the most massive carbon stars and those that are dominated by hot-bottom burning. Full article

(This article belongs to the Special Issue AGB Stars—In Honor of Professor Maurizio Busso on the Occasion of His 70th Birthday)

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10 pages, 558 KiB

Open AccessArticle

The NuGrid AGB Evolution and Nucleosynthesis Data Set

by Umberto Battino, Marco Pignatari, Ashley Tattersall, Pavel Denissenkov and Falk Herwig

Universe 2022, 8(3), 170; https://doi.org/10.3390/universe8030170 - 9 Mar 2022

Cited by 2 | Viewed by 2890

Abstract

Asymptotic Giant Branch (AGB) stars play a key role in the chemical evolution of galaxies. These stars are the fundamental stellar site for the production of light elements such as C, N and F, and half of the elements heavier than Fe via [...] Read more.

Asymptotic Giant Branch (AGB) stars play a key role in the chemical evolution of galaxies. These stars are the fundamental stellar site for the production of light elements such as C, N and F, and half of the elements heavier than Fe via the slow neutron capture process (s-process). Hence, detailed computational models of AGB stars’ evolution and nucleosynthesis are essential for galactic chemical evolution. In this work, we discuss the progress in updating the NuGrid data set of AGB stellar models and abundance yields. All stellar models have been computed using the MESA stellar evolution code, coupled with the post-processing mppnp code to calculate the full nucleosynthesis. The final data set will include the initial masses M

_{i n i}

/M

_{⊙}

= 1, 1.65, 2, 3, 4, 5, 6 and 7 for initial metallicities Z = 0.0001, 0.001, 0.006, 0.01, 0.02 and 0.03. Observed s-process abundances on the surfaces of evolved stars as well as the typical light elements in the composition of H-deficient post-AGB stars are reproduced. A key short-term goal is to complete and expand the AGB stars data set for the full metallicity range. Chemical yield tables are provided for the available models. Full article

(This article belongs to the Special Issue AGB Stars—In Honor of Professor Maurizio Busso on the Occasion of His 70th Birthday)

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14 pages, 5310 KiB

Open AccessArticle

The Achievements of the RockStar Group (Perugia) on Astrophysical Modelling and Pallasite Geochemistry

by Lisa Ricci, Maurizio Petrelli, Francesco Frondini, Azzurra Zucchini, Paola Comodi, Andrea Bisciotti, Diego Vescovi and Oscar Trippella

Universe 2022, 8(3), 156; https://doi.org/10.3390/universe8030156 - 28 Feb 2022

Cited by 1 | Viewed by 2253

Abstract

In the present work we summarize the first achievements of the RockStar Group of the Department of Physics and Geology (at the University of Perugia, Italy), which is made of a strict collaboration between Physicists and Geologists on astrophysical and planetological studies. The [...] Read more.

In the present work we summarize the first achievements of the RockStar Group of the Department of Physics and Geology (at the University of Perugia, Italy), which is made of a strict collaboration between Physicists and Geologists on astrophysical and planetological studies. The RockStar Group acts on two research lines: (i) astrophysical modeling and (ii) mineralogical and geochemical studies of meteorites. In the first part of the article we review the recent results concerning the development of theoretical modeling of nucleosynthesis and mixing process in asymptotic giant branch. In the second part we report (1) the catalog of the Meteorite collection of University of Perugia and (2) major and trace elements mapping, performed through EPMA and LA-ICP-MS, of the Mineo pallasite, a unique sample hosted by the collection. The new data constrain the Mineo meteorite among the Main Group Pallasites and support the hypothesis of the “early giant impact” formation. Full article

(This article belongs to the Special Issue AGB Stars—In Honor of Professor Maurizio Busso on the Occasion of His 70th Birthday)

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16 pages, 2066 KiB

Open AccessArticle

The RADIOSTAR Project

by Maria Lugaro, Benoit Côté, Marco Pignatari, Andrés Yagüe López, Hannah Brinkman, Borbála Cseh, Jacqueline Den Hartogh, Carolyn Louise Doherty, Amanda Irene Karakas, Chiaki Kobayashi, Thomas Lawson, Mária Pető, Benjámin Soós, Thomas Trueman and Blanka Világos

Universe 2022, 8(2), 130; https://doi.org/10.3390/universe8020130 - 17 Feb 2022

Cited by 2 | Viewed by 2057

Abstract

Radioactive nuclei are the key to understanding the circumstances of the birth of our Sun because meteoritic analysis has proven that many of them were present at that time. Their origin, however, has been so far elusive. The ERC-CoG-2016 RADIOSTAR project is dedicated [...] Read more.

Radioactive nuclei are the key to understanding the circumstances of the birth of our Sun because meteoritic analysis has proven that many of them were present at that time. Their origin, however, has been so far elusive. The ERC-CoG-2016 RADIOSTAR project is dedicated to investigating the production of radioactive nuclei by nuclear reactions inside stars, their evolution in the Milky Way Galaxy, and their presence in molecular clouds. So far, we have discovered that: (i) radioactive nuclei produced by

s l o w

(

^{107}

Pd and

^{182}

Hf) and

r a p i d

(

^{129}

I and

^{247}

Cm) neutron captures originated from stellar sources —asymptotic giant branch (AGB) stars and compact binary mergers, respectively—within the galactic environment that predated the formation of the molecular cloud where the Sun was born; (ii) the time that elapsed from the birth of the cloud to the birth of the Sun was of the order of 10

^{7}

years, and (iii) the abundances of the very short-lived nuclei

^{26}

Al,

^{36}

Cl, and

^{41}

Ca can be explained by massive star winds in single or binary systems, if these winds directly polluted the early Solar System. Our current and future work, as required to finalise the picture of the origin of radioactive nuclei in the Solar System, involves studying the possible origin of radioactive nuclei in the early Solar System from core-collapse supernovae, investigating the production of

^{107}

Pd in massive star winds, modelling the transport and mixing of radioactive nuclei in the galactic and molecular cloud medium, and calculating the galactic chemical evolution of

^{53}

Mn and

^{60}

Fe and of the p-process isotopes

^{92}

Nb and

^{146}

Sm. Full article

(This article belongs to the Special Issue AGB Stars—In Honor of Professor Maurizio Busso on the Occasion of His 70th Birthday)

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11 pages, 440 KiB

Open AccessArticle

The Complex Behaviour of s-Process Element Abundances at Young Ages

by Valentina D’Orazi, Martina Baratella, Maria Lugaro, Laura Magrini and Marco Pignatari

Universe 2022, 8(2), 110; https://doi.org/10.3390/universe8020110 - 9 Feb 2022

Cited by 8 | Viewed by 2401

Abstract

Open clusters appear as simple objects in many respects, with a high degree of homogeneity in their (initial) chemical composition, and the typical solar-scaled abundance pattern that they exhibit for the majority of the chemical species. The striking singularity is represented by heavy [...] Read more.

Open clusters appear as simple objects in many respects, with a high degree of homogeneity in their (initial) chemical composition, and the typical solar-scaled abundance pattern that they exhibit for the majority of the chemical species. The striking singularity is represented by heavy elements produced from the slow process of the neutron-capture reactions. In particular, young open clusters (ages less than a few hundred Myr) give rise to the so-called barium puzzle: that is an extreme enhancement in their [Be/Fe] ratios, up to a factor of four of the solar value, which is not followed by other nearby s-process elements (e.g., lanthanum and cerium). The definite explanation for such a peculiar trend is still wanting, as many different solutions have been envisaged. We review the status of this field and present our new results on young open clusters and the pre-main sequence star RZ Piscium. Full article

(This article belongs to the Special Issue AGB Stars—In Honor of Professor Maurizio Busso on the Occasion of His 70th Birthday)

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19 pages, 4209 KiB

Open AccessArticle

n_TOF: Measurements of Key Reactions of Interest to AGB Stars

by Cristian Massimi, Sergio Cristallo, César Domingo-Pardo and Claudia Lederer-Woods

Universe 2022, 8(2), 100; https://doi.org/10.3390/universe8020100 - 4 Feb 2022

Cited by 8 | Viewed by 1774

Abstract

In the last 20 years, the neutron time-of-flight facility n_TOF at CERN has been providing relevant data for the astrophysical slow neutron capture process (s process). At n_TOF, neutron-induced radiative capture (n,

γ

) as well as (n,p) and (n,

α

) [...] Read more.

In the last 20 years, the neutron time-of-flight facility n_TOF at CERN has been providing relevant data for the astrophysical slow neutron capture process (s process). At n_TOF, neutron-induced radiative capture (n,

γ

) as well as (n,p) and (n,

α

) reaction cross sections are measured as a function of energy, using the time-of-flight method. Improved detection systems, innovative ideas and collaborations with other neutron facilities have lead to a considerable contribution of the n_TOF collaboration to studying the s process in asymptotic giant branch stars. Results have been reported for stable and radioactive samples, i.e.,

^{24, 25, 26}

Mg,

^{26}

Al,

^{33}

S,

^{54, 57}

Fe,

^{58, 59, 62, 63}

Ni,

^{70, 72, 73}

Ge,

^{90, 91, 92, 93, 94, 96}

Zr,

^{139}

La,

^{140}

Ce,

^{147}

Pm,

^{151}

Sm,

^{154, 155, 157}

Gd,

^{171}

Tm,

^{186, 187, 188}

Os,

^{197}

Au,

^{203, 204}

Tl,

^{204, 206, 207}

Pb and

^{209}

Bi isotopes, while others are being studied or planned to be studied in the near future. In this contribution, we present an overview of the most successful achievements, and an outlook of future challenging measurements, including ongoing detection system developments. Full article

(This article belongs to the Special Issue AGB Stars—In Honor of Professor Maurizio Busso on the Occasion of His 70th Birthday)

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16 pages, 4832 KiB

Open AccessArticle

A Novel Approach to β-Decay: PANDORA, a New Experimental Setup for Future In-Plasma Measurements

by David Mascali, Domenico Santonocito, Simone Amaducci, Lucio Andò, Vincenzo Antonuccio, Sándor Biri, Alfio Bonanno, Vincenza Piera Bonanno, Stefan Briefi, Maurizio Busso, Luigi Celona, Luigi Cosentino, Sergio Cristallo, Marco Cuffiani, Costantino De Angelis, Giacomo De Angelis, Davide De Salvador, Loreto Di Donato, Jean-Eric Ducret, Aref Eshkevar Vakili, Ursel Fantz, Alessio Galatà, Carmelo Sebastiano Gallo, Santo Gammino, Tommaso Isernia, Hannu Koivisto, Karl-Ludwig Kratz, Risto Kronholm, Marco La Cognata, Silvia Leoni, Andrea Locatelli, Mario Maggiore, Fabio Maimone, Luciana Malferrari, Giorgio Mancini, Laurent Maunoury, Giorgio Sebastiano Mauro, Maria Mazzaglia, Alberto Mengoni, Andrea Miraglia, Bharat Mishra, Mario Musumeci, Daniel Ricardo Napoli, Eugenia Naselli, Fabrizio Odorici, Libero Palladino, Giuseppe Palmisano, Santi Pavone, Salvatore Pennisi, Albino Perego, Angelo Pidatella, Richard Rácz, Riccardo Reitano, Danilo Rifuggiato, Matteo Rinaldi, Antonio Domenico Russo, Filippo Russo, Gaetano Schillaci, Stefano Selleri, Stefano Simonucci, Gino Sorbello, Roberta Spartà, Simone Taioli, Klaus Tinschert, Giuseppe Torrisi, Antonio Trifirò, Sedina Tsikata, Aurora Tumino, Diego Vescovi and Luca Vincetti Show full author list Hide full author list

Universe 2022, 8(2), 80; https://doi.org/10.3390/universe8020080 - 27 Jan 2022

Cited by 26 | Viewed by 4664

Abstract

Theoretical predictions as well as experiments performed at storage rings have shown that the lifetimes of β-radionuclides can change significantly as a function of the ionization state. In this paper we describe an innovative approach, based on the use of a compact plasma [...] Read more.

Theoretical predictions as well as experiments performed at storage rings have shown that the lifetimes of β-radionuclides can change significantly as a function of the ionization state. In this paper we describe an innovative approach, based on the use of a compact plasma trap to emulate selected stellar-like conditions. It has been proposed within the PANDORA project (Plasmas for Astrophysics, Nuclear Decay Observation and Radiation for Archaeometry) with the aim to measure, for the first time in plasma, nuclear β-decay rates of radionuclides involved in nuclear-astrophysics processes. To achieve this task, a compact magnetic plasma trap has been designed to reach the needed plasma densities, temperatures, and charge-states distributions. A multi-diagnostic setup will monitor, on-line, the plasma parameters, which will be correlated with the decay rate of the radionuclides. The latter will be measured through the detection of the γ-rays emitted by the excited daughter nuclei following the β-decay. An array of 14 HPGe detectors placed around the trap will be used to detect the emitted γ-rays. For the first experimental campaign three isotopes, ¹⁷⁶Lu, ¹³⁴Cs, and ⁹⁴Nb, were selected as possible physics cases. The newly designed plasma trap will also represent a tool of choice to measure the plasma opacities in a broad spectrum of plasma conditions, experimentally poorly known but that have a great impact on the energy transport and spectroscopic observations of many astrophysical objects. Status and perspectives of the project will be highlighted in the paper. Full article

(This article belongs to the Special Issue AGB Stars—In Honor of Professor Maurizio Busso on the Occasion of His 70th Birthday)

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10 pages, 950 KiB

Open AccessCommunication

The Abundance of S-Process Elements: Temporal and Spatial Trends from Open Cluster Observations

by Laura Magrini, Carlos Viscasillas Vázquez, Giada Casali, Martina Baratella, Valentina D’Orazi, Lorenzo Spina, Sofia Randich, Sergio Cristallo and Diego Vescovi

Universe 2022, 8(2), 64; https://doi.org/10.3390/universe8020064 - 21 Jan 2022

Cited by 4 | Viewed by 2567

Abstract

Spectroscopic observations of stars belonging to open clusters, with well-determined ages and distances, are a unique tool for constraining stellar evolution, nucleosynthesis, mixing processes, and, ultimately, Galactic chemical evolution. Abundances of slow (s) process neutron capture elements in stars that retain their initial [...] Read more.

Spectroscopic observations of stars belonging to open clusters, with well-determined ages and distances, are a unique tool for constraining stellar evolution, nucleosynthesis, mixing processes, and, ultimately, Galactic chemical evolution. Abundances of slow (s) process neutron capture elements in stars that retain their initial surface composition open a window into the processes that generated them. In particular, they give us information on their main site of production, i.e., the low- and intermediate-mass Asymptotic Giant Branch (AGB) stars. In the present work, we review some observational results obtained during the last decade that contributed to a better understanding of the AGB phase: the growth of s-process abundances at recent epochs, i.e., in the youngest stellar populations; the different relations between age and [s/Fe] in distinct regions of the disc; and finally the use of s-process abundances combined with those of

α

elements, [s/

α

], to estimate stellar ages. We revise some implications that these observations had both on stellar and Galactic evolution, and on our ability to infer stellar ages. Full article

(This article belongs to the Special Issue AGB Stars—In Honor of Professor Maurizio Busso on the Occasion of His 70th Birthday)

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19 pages, 1494 KiB

Open AccessArticle

Nucleosynthesis, Mixing Processes, and Gas Pollution from AGB Stars

by Paolo Ventura, Flavia Dell’Agli, Marco Tailo, Marco Castellani, Ester Marini, Silvia Tosi and Marcella Di Criscienzo

Universe 2022, 8(1), 45; https://doi.org/10.3390/universe8010045 - 11 Jan 2022

Cited by 6 | Viewed by 1794

Abstract

We discuss the evolution of stars through the asymptotic giant branch, focusing on the physical mechanisms potentially able to alter the surface chemical composition and on how changes in the chemistry of the external regions affect the physical properties of the star and [...] Read more.

We discuss the evolution of stars through the asymptotic giant branch, focusing on the physical mechanisms potentially able to alter the surface chemical composition and on how changes in the chemistry of the external regions affect the physical properties of the star and the duration of this evolutionary phase. We focus on the differences between the evolution of low-mass stars, driven by the growth of the core mass and by the surface carbon enrichment, and that of their higher mass counterparts, which experience hot bottom burning. In the latter sources, the variation of the surface chemical composition reflects the equilibria of the proton capture nucleosynthesis experienced at the base of the convective envelope. The pollution expected from this class of stars is discussed, outlining the role of mass and metallicity on the chemical composition of the ejecta. To this aim, we considered evolutionary models of 0.7–8

M_{⊙}

stars in a wide range of metallicities, extending from the ultra-metal-poor domain to super-solar chemistries. Full article

(This article belongs to the Special Issue AGB Stars—In Honor of Professor Maurizio Busso on the Occasion of His 70th Birthday)

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17 pages, 917 KiB

Open AccessArticle

Extremely Metal-Poor Asymptotic Giant Branch Stars

by Mario Cirillo, Luciano Piersanti and Oscar Straniero

Universe 2022, 8(1), 44; https://doi.org/10.3390/universe8010044 - 11 Jan 2022

Cited by 1 | Viewed by 1602

Abstract

Little is known about the first stars, but hints on this stellar population can be derived from the peculiar chemical composition of the most metal-poor objects in the Milky Way and in resolved stellar populations of nearby galaxies. In this paper, we review [...] Read more.

Little is known about the first stars, but hints on this stellar population can be derived from the peculiar chemical composition of the most metal-poor objects in the Milky Way and in resolved stellar populations of nearby galaxies. In this paper, we review the evolution and nucleosynthesis of metal-poor and extremely metal-poor (EMP) stars with low and intermediate masses. In particular, new models of 6 M

_{⊙}

with three different levels of metallicity, namely

Z = 10^{- 4}

,

10^{- 6}

and

10^{- 10}

, are presented. In addition, we illustrate the results obtained for a 2 M

_{⊙}

,

Z = 10^{- 5}

model. All these models have been computed by means of the latest version of the FuNS code. We adopted a fully coupled scheme of solutions for the complete set of differential equations describing the evolution of the physical structure and the chemical abundances, as modified by nuclear processes and convective mixing. The scarcity of CNO in the material from which these stars formed significantly affects their evolution, their final fate and their contribution to the chemical pollution of the ISM in primordial galaxies. We show the potential of these models for the interpretation of the composition of EMP stars, with particular emphasis on CEMP stars. Full article

(This article belongs to the Special Issue AGB Stars—In Honor of Professor Maurizio Busso on the Occasion of His 70th Birthday)

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22 pages, 6873 KiB

Open AccessEditor’s ChoiceArticle

Underground Measurements of Nuclear Reaction Cross-Sections Relevant to AGB Stars

by Chemseddine Ananna, Francesco Barile, Axel Boeltzig, Carlo Giulio Bruno, Francesca Cavanna, Giovanni Francesco Ciani, Alessandro Compagnucci, Laszlo Csedreki, Rosanna Depalo, Federico Ferraro, Eliana Masha, Denise Piatti, David Rapagnani and Jakub Skowronski

Universe 2022, 8(1), 4; https://doi.org/10.3390/universe8010004 - 23 Dec 2021

Cited by 8 | Viewed by 4442

Abstract

Nuclear reaction cross sections are essential ingredients to predict the evolution of AGB stars and understand their impact on the chemical evolution of our Galaxy. Unfortunately, the cross sections of the reactions involved are often very small and challenging to measure in laboratories [...] Read more.

Nuclear reaction cross sections are essential ingredients to predict the evolution of AGB stars and understand their impact on the chemical evolution of our Galaxy. Unfortunately, the cross sections of the reactions involved are often very small and challenging to measure in laboratories on Earth. In this context, major steps forward were made with the advent of underground nuclear astrophysics, pioneered by the Laboratory for Underground Nuclear Astrophysics (LUNA). The present paper reviews the contribution of LUNA to our understanding of the evolution of AGB stars and related nucleosynthesis. Full article

(This article belongs to the Special Issue AGB Stars—In Honor of Professor Maurizio Busso on the Occasion of His 70th Birthday)

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Review

Jump to: Research, Other

18 pages, 4906 KiB

Open AccessReview

Slow Neutron-Capture Process: Low-Mass Asymptotic Giant Branch Stars and Presolar Silicon Carbide Grains

by Nan Liu, Sergio Cristallo and Diego Vescovi

Universe 2022, 8(7), 362; https://doi.org/10.3390/universe8070362 - 30 Jun 2022

Cited by 6 | Viewed by 1664

Abstract

Presolar grains are microscopic dust grains that formed in the stellar winds or explosions of ancient stars that died before the formation of the solar system. The majority (~90% in number) of presolar silicon carbide (SiC) grains, including types mainstream (MS), Y, and [...] Read more.

Presolar grains are microscopic dust grains that formed in the stellar winds or explosions of ancient stars that died before the formation of the solar system. The majority (~90% in number) of presolar silicon carbide (SiC) grains, including types mainstream (MS), Y, and Z, came from low-mass C-rich asymptotic giant branch (AGB) stars, which is supported by the ubiquitous presence of SiC dust observed in the circumstellar envelope of AGB stars and the signatures of slow neutron-capture process preserved in these grains. Here, we review the status of isotope studies of presolar AGB SiC grains with an emphasis on heavy element isotopes and highlight the importance of presolar grain studies for nuclear astrophysics. We discuss the sensitives of different types of nuclei to varying AGB stellar parameters and how their abundances in presolar AGB SiC grains can be used to provide independent, detailed constraints on stellar parameters, including ¹³C formation, stellar temperature, and nuclear reaction rates. Full article

(This article belongs to the Special Issue AGB Stars—In Honor of Professor Maurizio Busso on the Occasion of His 70th Birthday)

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12 pages, 841 KiB

Open AccessReview

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

by Devika Kamath and Hans Van Winckel

Universe 2022, 8(4), 233; https://doi.org/10.3390/universe8040233 - 11 Apr 2022

Cited by 6 | Viewed by 2612

Abstract

The chemical evolution of galaxies is governed by the chemical yields from stars, and here we focus on the important contributions from asymptotic giant branch (AGB) stars. AGB nucleosynthesis is, however, still riddled with complexities. Observations from post-asymptotic giant branch (post-AGB) stars serve [...] Read more.

The chemical evolution of galaxies is governed by the chemical yields from stars, and here we focus on the important contributions from asymptotic giant branch (AGB) stars. AGB nucleosynthesis is, however, still riddled with complexities. Observations from post-asymptotic giant branch (post-AGB) stars serve as exquisite tools to quantify and understand AGB nucleosynthesis. In this contribution, we review the invaluable constraints provided by post-AGB stars with which to study AGB nucleosynthesis, especially the slow neutron capture nucleosynthesis (i.e., the s-process). Full article

(This article belongs to the Special Issue AGB Stars—In Honor of Professor Maurizio Busso on the Occasion of His 70th Birthday)

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12 pages, 985 KiB

Open AccessReview

Insights into AGB Nucleosynthesis Thanks to Spectroscopic Abundance Measurements in Intrinsic and Extrinsic Stars

by Sophie Van Eck, Shreeya Shetye and Lionel Siess

Universe 2022, 8(4), 220; https://doi.org/10.3390/universe8040220 - 29 Mar 2022

Cited by 3 | Viewed by 2253

Abstract

The foundations of stellar nucleosynthesis have been established more than 70 years ago. Since then, much progress has been made, both on the theoretical side, with stellar evolution and nucleosynthesis models of increasing complexity, using more and more accurate nuclear data, and on [...] Read more.

The foundations of stellar nucleosynthesis have been established more than 70 years ago. Since then, much progress has been made, both on the theoretical side, with stellar evolution and nucleosynthesis models of increasing complexity, using more and more accurate nuclear data, and on the observational side, with the number of analyzed stars growing tremendously. In between, the complex machinery of abundance determination has been refined, taking into account model atmospheres of non-solar chemical composition, three-dimensional, non-LTE (non-local thermodynamic equilibrium) effects, and a growing number of atomic and molecular data. Neutron-capture nucleosynthesis processes, and in particular the s-process, have been scrutinized in various types of evolved stars, among which asymptotic giant branch stars, carbon-enhanced metal-poor stars and post-AGB stars. We review here some of the successes of the comparison between models and abundance measurements of heavy elements in stars, including in binaries, and outline some remaining unexplained features. Full article

(This article belongs to the Special Issue AGB Stars—In Honor of Professor Maurizio Busso on the Occasion of His 70th Birthday)

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13 pages, 2270 KiB

Open AccessReview

Impact of AGB Stars on the Chemical Evolution of Neutron-Capture Elements

by Gabriele Cescutti and Francesca Matteucci

Universe 2022, 8(3), 173; https://doi.org/10.3390/universe8030173 - 9 Mar 2022

Cited by 9 | Viewed by 2470

Abstract

In this review, we discuss the impact of s-process nucleosynthesis in asymptotic giant branch stars on the enrichment of heavy elements. We review the main steps made on this subject in the last 40 years and discuss the importance of modelling the evolution [...] Read more.

In this review, we discuss the impact of s-process nucleosynthesis in asymptotic giant branch stars on the enrichment of heavy elements. We review the main steps made on this subject in the last 40 years and discuss the importance of modelling the evolution of the abundances of such elements in our Milky Way. From the comparison between model results and observations, we can impose strong constraints on stellar nucleosynthesis, as well as on the evolution of the Milky Way. Full article

(This article belongs to the Special Issue AGB Stars—In Honor of Professor Maurizio Busso on the Occasion of His 70th Birthday)

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13 pages, 785 KiB

Open AccessReview

Recent Achievements of the ERNA Collaboration

by Raffaele Buompane, Antonino Di Leva, Lucio Gialanella, Gianluca Imbriani, Lizeth Morales-Gallegos and Mauro Romoli

Universe 2022, 8(2), 135; https://doi.org/10.3390/universe8020135 - 21 Feb 2022

Cited by 3 | Viewed by 1887 | Correction

Abstract

For more than two decades, the ERNA collaboration has investigated nuclear processes of astrophysical interest through the direct measurement of cross sections or the identification of the nucleosynthesis effects. Measurements of cross-section, reported in this publication, of radiative capture reactions have been mainly [...] Read more.

For more than two decades, the ERNA collaboration has investigated nuclear processes of astrophysical interest through the direct measurement of cross sections or the identification of the nucleosynthesis effects. Measurements of cross-section, reported in this publication, of radiative capture reactions have been mainly conducted using the ERNA Recoil Mass Separator, and more recently with an array of charged particle detector telescopes designed for nuclear astrophysics measurements. Some results achieved with ERNA will be reviewed, with a focus on the results most relevant for nucleosynthesis in AGB and advanced burning phases. Full article

(This article belongs to the Special Issue AGB Stars—In Honor of Professor Maurizio Busso on the Occasion of His 70th Birthday)

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25 pages, 882 KiB

Open AccessReview

Trojan Horse Investigation for AGB Stellar Nucleosynthesis

by Maria Letizia Sergi, Giuseppe D’Agata, Giovanni Luca Guardo, Giuseppe Gabriele Rapisarda, Vaclav Burjan, Silvio Cherubini, Marisa Gulino, Iolanda Indelicato, Marco La Cognata, Livio Lamia, Dario Lattuada, Jaromir Mrázek, Alessandro Alberto Oliva, Rosario Gianluca Pizzone, Stefano Romano, Roberta Spartá, Oscar Trippella and Aurora Tumino

Universe 2022, 8(2), 128; https://doi.org/10.3390/universe8020128 - 16 Feb 2022

Cited by 5 | Viewed by 2453

Abstract

Asymptotic Giant Branch (AGB) stars are among the most important astrophysical sites influencing the nucleosynthesis and the chemical abundances in the Universe. From a pure nuclear point of view, several processes take part during this peculiar stage of stellar evolution thus requiring detailed [...] Read more.

Asymptotic Giant Branch (AGB) stars are among the most important astrophysical sites influencing the nucleosynthesis and the chemical abundances in the Universe. From a pure nuclear point of view, several processes take part during this peculiar stage of stellar evolution thus requiring detailed experimental cross section measurements. Here, we report on the most recent results achieved via the application of the Trojan Horse Method (THM) and Asymptotic Normalization Coefficient (ANC) indirect techniques, discussing the details of the experimental procedure and the deduced reaction rates. In addition, we report also on the on going studies of interest for AGB nucleosynthesis. Full article

(This article belongs to the Special Issue AGB Stars—In Honor of Professor Maurizio Busso on the Occasion of His 70th Birthday)

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20 pages, 799 KiB

Open AccessReview

Mixing and Magnetic Fields in Asymptotic Giant Branch Stars in the Framework of FRUITY Models

by Diego Vescovi

Universe 2022, 8(1), 16; https://doi.org/10.3390/universe8010016 - 28 Dec 2021

Cited by 5 | Viewed by 2214

Abstract

In the last few years, the modeling of asymptotic giant branch (AGB) stars has been much investigated, both focusing on nucleosynthesis and stellar evolution aspects. Recent advances in the input physics required for stellar computations made it possible to construct more accurate evolutionary [...] Read more.

In the last few years, the modeling of asymptotic giant branch (AGB) stars has been much investigated, both focusing on nucleosynthesis and stellar evolution aspects. Recent advances in the input physics required for stellar computations made it possible to construct more accurate evolutionary models, which are an essential tool to interpret the wealth of available observational and nucleosynthetic data. Motivated by such improvements, the FUNS stellar evolutionary code has been updated. Nonetheless, mixing processes occurring in AGB stars’ interiors are currently not well-understood. This is especially true for the physical mechanism leading to the formation of the

^{13} C

pocket, the major neutron source in low-mass AGB stars. In this regard, post-processing s-process models assuming that partial mixing of protons is induced by magneto-hydrodynamics processes were shown to reproduce many observations. Such mixing prescriptions have now been implemented in the FUNS code to compute stellar models with fully coupled nucleosynthesis. Here, we review the new generation of FRUITY models that include the effects of mixing triggered by magnetic fields by comparing theoretical findings with observational constraints available either from the isotopic analysis of trace-heavy elements in presolar grains or from carbon AGB stars and Galactic open clusters. Full article

(This article belongs to the Special Issue AGB Stars—In Honor of Professor Maurizio Busso on the Occasion of His 70th Birthday)

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