scholarly journals Stellar origin of the 182Hf cosmochronometer and the presolar history of solar system matter

Science ◽  
2014 ◽  
Vol 345 (6197) ◽  
pp. 650-653 ◽  
Author(s):  
Maria Lugaro ◽  
Alexander Heger ◽  
Dean Osrin ◽  
Stephane Goriely ◽  
Kai Zuber ◽  
...  
Keyword(s):  
Solar System ◽  
Neutron Capture ◽  
Half Life ◽  
Slow Neutron ◽  
Asymptotic Giant Branch ◽  
Asymptotic Giant Branch Stars ◽  
Early Solar System ◽  
Capture Process ◽  
History Of ◽  
Giant Branch Stars

Among the short-lived radioactive nuclei inferred to be present in the early solar system via meteoritic analyses, there are several heavier than iron whose stellar origin has been poorly understood. In particular, the abundances inferred for 182Hf (half-life = 8.9 million years) and 129I (half-life = 15.7 million years) are in disagreement with each other if both nuclei are produced by the rapid neutron-capture process. Here, we demonstrate that contrary to previous assumption, the slow neutron-capture process in asymptotic giant branch stars produces 182Hf. This has allowed us to date the last rapid and slow neutron-capture events that contaminated the solar system material at ∼100 million years and ∼30 million years, respectively, before the formation of the Sun.

scholarly journals The slow-neutron capture process in low-metallicity asymptotic giant branch stars

2009 ◽  
Vol 5 (S265) ◽  
pp. 57-60
Author(s):  
Amanda I. Karakas ◽  
Maria Lugaro ◽  
Simon W. Campbell
Keyword(s):  
Neutron Capture ◽  
Slow Neutron ◽  
Asymptotic Giant Branch ◽  
Observational Constraints ◽  
Asymptotic Giant Branch Stars ◽  
Agb Stars ◽  
Capture Process ◽  
Low Metallicity ◽  
Giant Branch Stars ◽  
Full Network

AbstractElements heavier than iron are produced in asymptotic giant branch (AGB) stars via the slow neutron capture process (s process). Recent observations of s-process-enriched Carbon Enhanced Metal-Poor (CEMP) stars have provided an unprecedented wealth of observational constraints on the operation of the s-process in low-metallicity AGB stars. We present new preliminary full network calculations of low-metallicity AGB stars, including a comparison to the composition of a few s-process rich CEMP stars. We also discuss the possibility of using halo planetary nebulae as further probes of low-metallicity AGB nucleosynthesis.

scholarly journals Direct cross-section measurement of 13C(α,n)16O in the s-process Gamow peak

2020 ◽  
Vol 1643 (1) ◽  
pp. 012043
Author(s):  
J. Balibrea-Correa ◽  
G. F. Ciani ◽  
L. Csedreki ◽  
A. Best ◽  
A. Formicola ◽  
...  
Keyword(s):  
Center Of Mass ◽  
Region Of Interest ◽  
Slow Neutron ◽  
Asymptotic Giant Branch ◽  
Asymptotic Giant Branch Stars ◽  
Capture Process ◽  
Direct Measurements ◽  
Direct Cross ◽  
Low Mass ◽  
Giant Branch Stars

Abstract The main neutron source for the slow neutron capture process in low mass Asymptotic Giant Branch stars is the 13C(α,n)16O reaction. This reaction is responsible for the production of half of the natural heavy elements in the Universe. Up to now, no direct measurements have reached the energy region of interest for astrophysics, the so called Gamow window, which lies between 140 and 230 keV in the center of mass. In this paper we describe the experiment carried out at the LUNA experiment at the Laboratori Nazionali del Gran Sasso and present first preliminary results.

scholarly journals Constraining nucleosynthesis in two CEMP progenitors using fluorine

2020 ◽  
Vol 498 (3) ◽  
pp. 3549-3559
Author(s):  
Aldo Mura-Guzmán ◽  
D Yong ◽  
C Abate ◽  
A Karakas ◽  
C Kobayashi ◽  
...  
Keyword(s):  
Neutron Capture ◽  
Slow Neutron ◽  
Asymptotic Giant Branch ◽  
Capture Process ◽  
Upper Limit ◽  
Infrared Spectrometer ◽  
Binary Evolution ◽  
Vibration Rotation ◽  
R Process ◽  
Process Elements

ABSTRACT We present new fluorine abundance estimations in two carbon enhanced metal-poor (CEMP) stars, HE 1429−0551 and HE 1305+0007. HE 1429−0551 is also enriched in slow neutron-capture process (s-process) elements, a CEMP-s, and HE 1305+0007 is enhanced in both, slow and rapid neutron-capture process elements, a CEMP-s/r. The F abundances estimates are derived from the vibration–rotation transition of the HF molecule at 23358.6 Å  using high-resolution infrared spectra obtained with the Immersion Grating Infrared Spectrometer (IGRINS) at the 4-m class Lowell Discovery Telescope. Our results include an F abundance measurement in HE 1429−0551 of A(F) = +3.93 ([F/Fe] = +1.90) at [Fe/H] = −2.53, and an F upper limit in HE 1305+0007 of A(F) < +3.28 ([F/Fe] < +1.00) at [Fe/H] = −2.28. Our new derived F abundance in HE 1429−0551 makes this object the most metal-poor star where F has been detected. We carefully compare these results with literature values and state-of-the-art CEMP-s model predictions including detailed asymptotic giant branch (AGB) nucleosynthesis and binary evolution. The modelled fluorine abundance for HE 1429−0551 is within reasonable agreement with our observed abundance, although is slightly higher than our observed value. For HE 1429−0551, our findings support the scenario via mass transfer by a primary companion during its thermally pulsing phase. Our estimated upper limit in HE 1305+0007, along with data from the literature, shows large discrepancies compared with AGB models. The discrepancy is principally due to the simultaneous s- and r-process element enhancements which the model struggles to reproduce.

scholarly journals The s-process in stellar sites

2018 ◽  
Vol 184 ◽  
pp. 01004
Author(s):  
Sergio Cristallo
Keyword(s):  
Solar System ◽  
Neutron Capture ◽  
Slow Neutron ◽  
Heavy Elements ◽  
The Sun ◽  
Capture Process ◽  
The Universe ◽  
Pollution Episodes

Stars are marvellous caldrons where all the elements of the Universe (apartfrom hydrogen and helium) have been synthesized. The solar system chemical distri-butionis the result of many pollution episodes from already extinct stellar generations, occurred at different epochs before the Sun formation. Main nucleosynthesis channels re-sponsiblefor the formation of heavy elements are the rapid neutron capture process (ther-process) and the slow neutron capture process (the s-process). Hereafter, I will describethe theory of the s-process and the stellar sites where it is active.

The role of AGB stars in Galactic and cosmic chemical enrichment

2018 ◽  
Vol 14 (S343) ◽  
pp. 247-257
Author(s):  
Chiaki Kobayashi ◽  
Christopher J. Haynes ◽  
Fiorenzo Vincenzo
Keyword(s):  
Electron Capture ◽  
Galaxy Formation ◽  
Neutron Capture ◽  
Slow Neutron ◽  
Asymptotic Giant Branch ◽  
Agb Stars ◽  
Capture Process ◽  
Chemical Enrichment ◽  
Cno Abundances

AbstractThe role of asymptotic giant branch (AGB) stars in chemical enrichment is significant for producing 12,13C, 14N, F, 25,26Mg, 17O and slow neutron-capture process (s-process) elements. The contribution from super-AGB stars is negligible in classical, one-zone chemical evolution models, but the mass ranges can be constrained through the contribution from electron-capture supernovae and possibly hybrid C+O+Ne white dwarfs, if they explode as Type Iax supernovae. In addition to the recent s-process yields of AGB stars, we include various sites for rapid neutron-capture processes (r-processes) in our chemodynamical simulations of a Milky Way type galaxy. We find that neither electron-capture supernovae or neutrino-driven winds are able to adequately produce heavy neutron-capture elements such as Eu in quantities to match observations. Both neutron-star mergers (NSMs) and magneto-rotational supernovae (MRSNe) are able to produce these elements in sufficient quantities. Using the distribution in [Eu/(Fe, α)] – [Fe/H], we predict that NSMs alone are unable to explain the observed Eu abundances, but may be able to together with MRSNe. In order to discuss the role of long-lifetime sources such as NSMs and AGB stars at the early stages of galaxy formation, it is necessary to use a model that can treat inhomogeneous chemical enrichment, such as in our chemodynamical simulations. In our cosmological, chemodynamical simulations, we succeed in reproducing the observed N/O-O/H relations both for global properties of galaxies and for local inter-stellar medium within galaxies, without rotation of stars. We also predict the evolution of CNO abundances of disk galaxies, from which it will be possible to constrain the star formation histories.

scholarly journals Mass and metallicity distribution of parent AGB stars of presolar SiC

2020 ◽  
Vol 644 ◽  
pp. A8
Author(s):  
S. Cristallo ◽  
A. Nanni ◽  
G. Cescutti ◽  
I. Minchev ◽  
N. Liu ◽  
...  
Keyword(s):  
Solar System ◽  
Slow Neutron ◽  
Asymptotic Giant Branch ◽  
Agb Stars ◽  
Detailed Characterization ◽  
Mixing Processes ◽  
Capture Process ◽  
Metallicity Distribution

The vast majority (≳90%) of presolar SiC grains identified in primitive meteorites are relics of ancient asymptotic giant branch (AGB) stars, whose ejecta were incorporated into the Solar System during its formation. Detailed characterization of these ancient stardust grains has revealed valuable information on mixing processes in AGB interiors in great detail. However, the mass and metallicity distribution of their parent stars still remains ambiguous, although such information is crucial to investigating the slow neutron-capture process, whose efficiency depends on mass and metallicity. Using a well-known Milky Way chemo-dynamical model, we followed the evolution of the AGB stars that polluted the Solar System at 4.57 Gyr ago and weighted the stars based on their SiC dust productions. We find that presolar SiC in the Solar System predominantly originated from AGB stars with M ∼ 2 M⊙ and Z ∼ Z⊙. Our finding well explains the grain-size distribution of presolar SiC identified in situ in primitive meteorites. Moreover, it provides complementary results to very recent papers that characterized parent stars of presolar SiC.

scholarly journals Asymptotic Giant Branch Stars and presolar grains

2020 ◽  
Vol 227 ◽  
pp. 01002
Author(s):  
Maurizio Busso ◽  
Sara Palmerini ◽  
Diego Vescovi
Keyword(s):  
Slow Neutron ◽  
Asymptotic Giant Branch ◽  
Radioactive Isotopes ◽  
Red Giants ◽  
Asymptotic Giant Branch Stars ◽  
Heavy Nuclei ◽  
Early Solar System ◽  
Stable Species ◽  
The Galaxy ◽  
Circumstellar Environments

Starting from the recognition that radioactive isotopes were present alive in the Early Solar System, inducing composition anomalies from their decay, and through the discovery that other important anomalies affected also stable species, we shall discuss how the carriers of these abundance peculiarities were identified in very refractory pre-solar dust grains, formed in circumstellar environments. We shall outline how groups of such grains and subsequently in-dividual single crystals of C-rich or O-rich materials (like, e.g., SiC and Al2O3) could be analyzed, providing a new tool to verify the composition of stellar winds. This is so especially for AGB stars, which are the primary factories of dust in the Galaxy. For this reason, pristine meteorites open a crucial window on the details of nucleosynthesis processes occurring in such evolved red giants, for both intermediate-mass elements and rare heavy nuclei affected by slow neutron captures (the s-process).

scholarly journals Characterizing the companion AGBs using surface chemical composition of barium stars

2019 ◽  
Vol 492 (3) ◽  
pp. 3708-3727 ◽  
Author(s):  
J Shejeelammal ◽  
Aruna Goswami ◽  
Partha Pratim Goswami ◽  
Rajeev Singh Rathour ◽  
Thomas Masseron
Keyword(s):  
Neutron Capture ◽  
Detailed Comparison ◽  
Slow Neutron ◽  
Asymptotic Giant Branch ◽  
Agb Stars ◽  
Capture Process ◽  
Origin And Evolution ◽  
Element Abundances ◽  
The Galaxy ◽  
Low Mass

ABSTRACT Barium stars are one of the important probes to understand the origin and evolution of slow neutron-capture process elements in the Galaxy. These are extrinsic stars, where the observed s-process element abundances are believed to have an origin in the now invisible companions that produced these elements at their asymptotic giant branch (AGB) phase of evolution. We have attempted to understand the s-process nucleosynthesis, as well as the physical properties of the companion stars through a detailed comparison of observed elemental abundances of 10 barium stars with the predictions from AGB nucleosynthesis models, FRUITY. For these stars, we have presented estimates of abundances of several elements, C, N, O, Na, Al, α-elements, Fe-peak elements, and neutron-capture elements Rb, Sr, Y, Zr, Ba, La, Ce, Pr, Nd, Sm, and Eu. The abundance estimates are based on high resolution spectral analysis. Observations of Rb in four of these stars have allowed us to put a limit to the mass of the companion AGB stars. Our analysis clearly shows that the former companions responsible for the surface abundance peculiarities of these stars are low-mass AGB stars. Kinematic analysis has shown the stars to be members of Galactic disc population.

The role of asymptotic giant branch stars in the chemical evolution of the Galaxy

2018 ◽  
Vol 14 (S343) ◽  
pp. 510-511
Author(s):  
G. Tautvaišienė ◽  
C. Viscasillas Vázquez ◽  
V. Bagdonas ◽  
R. Smiljanic ◽  
A. Drazdauskas ◽  
...  
Keyword(s):  
High Resolution ◽  
Neutron Capture ◽  
Open Clusters ◽  
Asymptotic Giant Branch ◽  
Asymptotic Giant Branch Stars ◽  
Galactic Disc ◽  
The Galaxy ◽  
Process Elements ◽  
Giant Branch Stars

AbstractAsymptotic giant branch stars play an important role in enriching galaxies by s-process elements. Recent studies have shown that their role in producing s-process elements in the Galactic disc was underestimated and should be reconsidered. Based on high-resolution spectra we have determined abundances of neutron-capture elements in a sample of 310 stars located in the field and open clusters and investigated elemental enrichment patterns according to their age and mean galactocentric distances.

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