scholarly journals 129I and 247Cm in meteorites constrain the last astrophysical source of solar r-process elements

Science ◽  
2021 ◽  
Vol 371 (6532) ◽  
pp. 945-948 ◽  
Author(s):  
Benoit Côté ◽  
Marius Eichler ◽  
Andrés Yagüe López ◽  
Nicole Vassh ◽  
Matthew R. Mumpower ◽  
...  
Keyword(s):  
Neutron Star ◽  
Solar System ◽  
Neutron Capture ◽  
Nuclear Physics ◽  
Early Solar System ◽  
Capture Process ◽  
Astrophysical Source ◽  
R Process ◽  
Process Elements

The composition of the early Solar System can be inferred from meteorites. Many elements heavier than iron were formed by the rapid neutron capture process (r-process), but the astrophysical sources where this occurred remain poorly understood. We demonstrate that the near-identical half-lives (≃15.6 million years) of the radioactive r-process nuclei iodine-129 and curium-247 preserve their ratio, irrespective of the time between production and incorporation into the Solar System. We constrain the last r-process source by comparing the measured meteoritic ratio 129I/247Cm = 438 ± 184 with nucleosynthesis calculations based on neutron star merger and magneto-rotational supernova simulations. Moderately neutron-rich conditions, often found in merger disk ejecta simulations, are most consistent with the meteoritic value. Uncertain nuclear physics data limit our confidence in this conclusion.

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 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 Turbulent mixing of r-process elements in the Milky Way

2020 ◽  
Vol 496 (2) ◽  
pp. 1891-1901 ◽  
Author(s):  
Paz Beniamini ◽  
Kenta Hotokezaka
Keyword(s):  
Solar System ◽  
Milky Way ◽  
Gas Diffusion ◽  
Star Formation History ◽  
Model Parameters ◽  
Early Solar System ◽  
Element Abundances ◽  
Process Event ◽  
R Process ◽  
Process Elements

ABSTRACT We study turbulent gas diffusion affects on r-process abundances in Milky Way stars, by a combination of an analytical approach and a Monte Carlo simulation. Higher r-process event rates and faster diffusion, lead to more efficient mixing corresponding to a reduced scatter of r-process abundances and causing r-process enriched stars to start appearing at lower metallicities. We use three independent observations to constrain the model parameters: (i) the scatter of radioactively stable r-process element abundances, (ii) the largest r-process enrichment values observed in any solar neighborhood stars, and (iii) the isotope abundance ratios of different radioactive r-process elements (244Pu/238U and 247Cm/238U) at the early Solar system as compared to their formation. Our results indicate that the Galactic r-process rate and the diffusion coefficient are respectively r < 4 × 10−5 yr−1, D > 0.1 kpc2 Gyr−1 (r < 4 × 10−6 yr−1, D > 0.5 kpc2 Gyr−1 for collapsars or similarly prolific r-process sources) with allowed values satisfying an approximate anticorrelation such that D ≈ r−2/3, implying that the time between two r-process events that enrich the same location in the Galaxy, is τmix ≈ 100−200 Myr. This suggests that a fraction of ∼0.8 (∼0.5) of the observed 247Cm (244Pu) abundance is dominated by one r-process event in the early Solar system. Radioactively stable element abundances are dominated by contributions from ∼10 different events in the early Solar system. For metal poor stars (with [Fe/H] ≲ −2), their r-process abundances are dominated by either a single or several events, depending on the star formation history.

scholarly journals Using failed supernovae to constrain the Galactic r-process element production

2019 ◽  
Vol 487 (2) ◽  
pp. 1745-1753 ◽  
Author(s):  
B Wehmeyer ◽  
C Fröhlich ◽  
B Côté ◽  
M Pignatari ◽  
F-K Thielemann
Keyword(s):  
Black Hole ◽  
Neutron Star ◽  
Large Fraction ◽  
Capture Process ◽  
Compact Binary ◽  
Halo Stars ◽  
The Galaxy ◽  
Binary Mergers ◽  
R Process ◽  
Process Elements

ABSTRACT Rapid neutron capture process (r-process) elements have been detected in a large fraction of metal-poor halo stars, with abundances relative to iron (Fe) that vary by over two orders of magnitude. This scatter is reduced to less than a factor of 3 in younger Galactic disc stars. The large scatter of r-process elements in the early Galaxy suggests that the r-process is made by rare events, like compact binary mergers and rare sub-classes of supernovae. Although being rare, neutron star mergers alone have difficulties to explain the observed enhancement of r-process elements in the lowest metallicity stars compared to Fe. The supernovae producing the two neutron stars already provide a substantial Fe abundance where the r-process ejecta from the merger would be injected. In this work we investigate another complementary scenario, where the r-process occurs in neutron star-black hole mergers in addition to neutron star mergers. Neutron star-black hole mergers would eject similar amounts of r-process matter as neutron star mergers, but only the neutron star progenitor would have produced Fe. Furthermore, a reduced efficiency of Fe production from single stars significantly alters the age–metallicity relation, which shifts the onset of r-process production to lower metallicities. We use the high-resolution [(20 pc)3/cell] inhomogeneous chemical evolution tool ‘ICE’ to study the outcomes of these effects. In our simulations, an adequate combination of neutron star mergers and neutron star-black hole mergers qualitatively reproduces the observed r-process abundances in the Galaxy.

scholarly journals Chemical evolution of r-process elements in the Draco dwarf spheroidal galaxy

2015 ◽  
Vol 11 (S317) ◽  
pp. 310-311
Author(s):  
M. N. Ishigaki ◽  
T. Tsujimoto ◽  
T. Shigeyama ◽  
W. Aoki
Keyword(s):  
Neutron Star ◽  
High Resolution ◽  
Neutron Capture ◽  
Milky Way ◽  
Origin And Evolution ◽  
Dwarf Spheroidal Galaxies ◽  
Giant Stars ◽  
Upper Limits ◽  
R Process ◽  
Process Elements

AbstractA dominant astrophysical site for r-process, which is responsible for producing heavy neutron-capture elements, is unknown. Dwarf spheroidal galaxies around the Milky Way halo provide ideal laboratories to investigate the origin and evolution of r-process elements. We carried out high-resolution spectroscopic observations of three giant stars in the Draco dwarf spheroidal galaxy to estimate their europium abundances. We found that the upper-limits of [Eu/H] are very low in the range [Fe/H] < −2, while this ratio is nearly constant at higher metallicities. This trend is not well reproduced with models which assume that Eu is produced together with Fe by SNe, and may suggest the contribution from other objects such as neutron-star mergers.

scholarly journals Silver Stars

2009 ◽  
Vol 5 (S265) ◽  
pp. 67-68
Author(s):  
Camilla Juul Hansen ◽  
Francesca Primas
Keyword(s):  
Neutron Capture ◽  
Heavy Elements ◽  
Capture Process ◽  
Elemental Abundances ◽  
The Galaxy ◽  
Formation And Evolution ◽  
R Process ◽  
Process Elements ◽  
Heaviest Elements ◽  
Process Element

AbstractThe rapid neutron-capture process (r-process), which produces some of the heaviest elements, is not well understood. Obtaining accurate abundances of these heavy elements (Z > 38) is important, both in the context of the chemical evolution of the Galaxy and for understanding the site(s) and process(es) of formation of those elements. We have determined elemental abundances for several r-process elements, notably silver, from high resolution VLT/UVES spectra. Silver was chosen because it is predominantly a light r-process element (38 < Z < 50), and little is known about its formation and evolution in the Galaxy. Here, we present our preliminary results.

A nearby neutron-star merger explains the actinide abundances in the early Solar System

Nature ◽  
2019 ◽  
Vol 569 (7754) ◽  
pp. 85-88 ◽  
Author(s):  
Imre Bartos ◽  
Szabolcs Marka
Keyword(s):  
Neutron Star ◽  
Solar System ◽  
Early Solar System

60Fe and 244Pu deposited on Earth constrain the r-process yields of recent nearby supernovae

Science ◽  
2021 ◽  
Vol 372 (6543) ◽  
pp. 742-745
Author(s):  
A. Wallner ◽  
M. B. Froehlich ◽  
M. A. C. Hotchkis ◽  
N. Kinoshita ◽  
M. Paul ◽  
...  
Keyword(s):  
Pacific Ocean ◽  
Neutron Stars ◽  
Neutron Capture ◽  
Half Life ◽  
Massive Stars ◽  
Chemical Elements ◽  
Capture Process ◽  
Isotopic Signatures ◽  
Supernova Explosions ◽  
R Process

Half of the chemical elements heavier than iron are produced by the rapid neutron capture process (r-process). The sites and yields of this process are disputed, with candidates including some types of supernovae (SNe) and mergers of neutron stars. We search for two isotopic signatures in a sample of Pacific Ocean crust—iron-60 (60Fe) (half-life, 2.6 million years), which is predominantly produced in massive stars and ejected in supernova explosions, and plutonium-244 (244Pu) (half-life, 80.6 million years), which is produced solely in r-process events. We detect two distinct influxes of 60Fe to Earth in the last 10 million years and accompanying lower quantities of 244Pu. The 244Pu/60Fe influx ratios are similar for both events. The 244Pu influx is lower than expected if SNe dominate r-process nucleosynthesis, which implies some contribution from other sources.

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.

scholarly journals Search for neutron star binaries in the Local Group galaxies using LISA

2019 ◽  
Vol 489 (4) ◽  
pp. 4513-4519 ◽  
Author(s):  
Naoki Seto
Keyword(s):  
Neutron Star ◽  
Local Group ◽  
Design Sensitivity ◽  
Signal To Noise ◽  
Frequency Distributions ◽  
Current Design ◽  
R Process ◽  
Merger Rate ◽  
Process Elements

ABSTRACT We discuss the prospects of LISA for detecting neutron star binaries (NSBs) in the Local Group galaxies such as LMC and M31. Using the recently estimated merger rate ${\rm 1540 \, Gpc^{-3}\, yr^{-1}}$ and inversely applying the conventional arguments based on the B-band galaxy luminosities, we estimate the frequency distributions of NSBs in the local galaxies. We find that, after 10 yr observation with its current design sensitivity, LISA might detect ∼5 NSBs both in LMC and M31 with signal-to-noise ratios larger than 10. Some of the NSBs might be three-dimensionally localized well within LMC. These binaries will be useful for studying various topics including the origin of r-process elements.

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