Neutron-Capture Elements in the Double-Enhanced Star HE 1305-0007: a New s- and r-Process Paradigm

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.

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Constraining nucleosynthesis in two CEMP progenitors using fluorine

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/staa2610 ◽

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.

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The contribution from rotating massive stars to the enrichment in Sr and Ba of the Milky Way

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/stz2505 ◽

2019 ◽

Cited By ~ 3

Author(s):

F Rizzuti ◽

G Cescutti ◽

F Matteucci ◽

A Chieffi ◽

R Hirschi ◽

...

Keyword(s):

Neutron Capture ◽

Milky Way ◽

Massive Stars ◽

Rotational Velocity ◽

Stellar Rotation ◽

Deep Impact ◽

Low Metallicity ◽

Group Rotation ◽

R Process ◽

Chemical Evolution Model

Abstract Most neutron capture elements have a double production by r- and s-processes, but the question of production sites is complex and still open. Recent studies show that including stellar rotation can have a deep impact on nucleosynthesis. We studied the evolution of Sr and Ba in the Milky Way. A chemical evolution model was employed to reproduce the Galactic enrichment. We tested two different nucleosynthesis prescriptions for s-process in massive stars, adopted from the Geneva group and the Rome group. Rotation was taken into account, studying the effects of stars without rotation or rotating with different velocities. We also tested different production sites for the r-process: magneto rotational driven supernovae and neutron star mergers. The evolution of the abundances of Sr and Ba is well reproduced. The comparison with the the most recent observations shows that stellar rotation is a good assumption, but excessive velocities result in overproduction of these elements. In particular, the predicted evolution of the [Sr/Ba] ratio at low metallicity does not explain the data at best if rotation is not included. Adopting different rotational velocities for different stellar mass and metallicity better explains the observed trends. Despite the differences between the two sets of adopted stellar models, both show a better agreement with the data assuming an increase of rotational velocity toward low metallicity. Assuming different r-process sources does not alter this conclusion.

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Sensitivity studies for the weak r process: neutron capture rates

AIP Advances ◽

10.1063/1.4867191 ◽

2014 ◽

Vol 4 (4) ◽

pp. 041008 ◽

Cited By ~ 27

Author(s):

R. Surman ◽

M. Mumpower ◽

R. Sinclair ◽

K. L. Jones ◽

W. R. Hix ◽

...

Keyword(s):

Neutron Capture ◽

Sensitivity Studies ◽

R Process ◽

Capture Rates

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Insights into the s-process and r-process as revealed by globular clusters

Proceedings of the International Astronomical Union ◽

10.1017/s1743921310000153 ◽

2009 ◽

Vol 5 (S265) ◽

pp. 54-56

Author(s):

D. Yong ◽

A. I. Karakas ◽

D. L. Lambert ◽

A. Chieffi ◽

M. Limongi

Keyword(s):

Relative Abundance ◽

Neutron Capture ◽

Globular Clusters ◽

Giant Stars ◽

The Mean ◽

R Process ◽

Process Material

AbstractWe present abundance measurements for a large number of neutron-capture elements in giant stars of the globular clusters M4, M5, and M13. The relative abundance ratios differ between all three clusters. For all clusters, we find that the mean abundances for the elements from Ba to Hf can be well explained by scaled versions of the solar s- and r-process abundances, albeit with different mixtures of s- and r-process material for each clusters.

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Neutron capture cross sections of light neutron-rich nuclei relevant for r -process nucleosynthesis

Physical Review C ◽

10.1103/physrevc.104.045801 ◽

2021 ◽

Vol 104 (4) ◽

Author(s):

A. Bhattacharyya ◽

Ushasi Datta ◽

A. Rahaman ◽

S. Chakraborty ◽

T. Aumann ◽

...

Keyword(s):

Cross Sections ◽

Neutron Capture ◽

Capture Cross ◽

R Process ◽

Capture Cross Sections

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Nuclear Masses, Neutron Capture, and the r Process: A New Approach

Nuclear Physics News ◽

10.1080/10619127.2019.1642709 ◽

2019 ◽

Vol 29 (3) ◽

pp. 18-21

Author(s):

A. Couture ◽

R. F. Casten ◽

R. B. Cakirli

Keyword(s):

Neutron Capture ◽

New Approach ◽

Nuclear Masses ◽

R Process

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Heavy Element Abundances in the Magellanic Clouds

Publications of the Astronomical Society of Australia ◽

10.1017/s1323358000024978 ◽

1991 ◽

Vol 9 (1) ◽

pp. 82-83 ◽

Cited By ~ 2

Author(s):

Stephen C. Russell

Keyword(s):

Neutron Capture ◽

Heavy Element ◽

Magellanic Clouds ◽

Element Abundances ◽

R Process

AbstractThis paper presents a brief discussion of the apparent underdepletion of the heavy neutron-capture elements (elements heavier than Ba), compared with Fe in the Magellanic Clouds. The s-process appears to have been only effective in forming elements in the light neutron-capture group (Sr, Y, Zr) in the Magellanic Clouds, but to have much reduced effectiveness in forming the heavy neutron-capture group. The abundances of the elements heavier than Ba have a distribution that indicates that they were produced by the r-process alone.

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Abundance patterns of the light neutron-capture elements in very and extremely metal-poor stars

Astronomy and Astrophysics ◽

10.1051/0004-6361/201732096 ◽

2018 ◽

Vol 611 ◽

pp. A30 ◽

Cited By ~ 13

Author(s):

F. Spite ◽

M. Spite ◽

B. Barbuy ◽

P. Bonifacio ◽

E. Caffau ◽

...

Keyword(s):

Thermodynamic Equilibrium ◽

Neutron Capture ◽

Local Thermodynamic Equilibrium ◽

Abundance Patterns ◽

Element Pattern ◽

The Mean ◽

R Process ◽

Peak Abundance ◽

Second Peak

Aims. The abundance patterns of the neutron-capture elements in metal-poor stars provide a unique record of the nucleosynthesis products of the earlier massive primitive objects. Methods. We measured new abundances of so-called light neutron-capture of first peak elements using local thermodynamic equilibrium (LTE) 1D analysis; this analysis resulted in a sample of 11 very metal-poor stars, from [Fe/H] = –2.5 to [Fe/H] = –3.4, and one carbon-rich star, CS 22949-037 with [Fe/H] = –4.0. The abundances were compared to those observed in two classical metal-poor stars: the typical r-rich star CS 31082-001 ([Eu/Fe] > +1.0) and the r-poor star HD 122563 ([Eu/Fe] < 0.0), which are known to present a strong enrichment of the first peak neutron-capture elements relative to the second peak. Results. Within the first peak, the abundances are well correlated in analogy to the well-known correlation inside the abundances of the second-peak elements. In contrast, there is no correlation between any first peak element with any second peak element. We show that the scatter of the ratio of the first peak abundance over second peak abundance increases when the mean abundance of the second peak elements decreases from r-rich to r-poor stars. We found two new r-poor stars that are very similar to HD 122563. A third r-poor star, CS 22897-008, is even more extreme; this star shows the most extreme example of first peak elements enrichment to date. On the contrary, another r-poor star (BD–18 5550) has a pattern of first peak elements that is similar to the typical r-rich stars CS 31082-001, however this star has some Mo enrichment. Conclusions. The distribution of the neutron-capture elements in our very metal-poor stars can be understood as the combination of at least two mechanisms: one that enriches the forming stars cloud homogeneously through the main r-process and leads to an element pattern similar to the r-rich stars, such as CS 31082-001; and another that forms mainly lighter, first peak elements.

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Carbon-Enhanced Metal-Poor (CEMP) stars

Proceedings of the International Astronomical Union ◽

10.1017/s1743921310000311 ◽

2009 ◽

Vol 5 (S265) ◽

pp. 111-116 ◽

Cited By ~ 2

Author(s):

Wako Aoki

Keyword(s):

Neutron Capture ◽

Significant Fraction ◽

Agb Stars ◽

Iron Deficient ◽

R Process ◽

Process Elements

AbstractA significant fraction of metal-poor stars have large over-abundances of carbon, and are called Carbon-Enhanced Metal-Poor (CEMP) stars. Most of CEMP stars also show excesses of heavy neutron-capture elements like Ba, indicating that their origin is the nucleosynthesis in AGB stars. Remaining CEMP stars that have Ba abundances as low as non-carbon-rich stars appear in the lowest metallicity range ([Fe/H]≲−2.5), and connections with the two most iron-deficient stars (so-called Hyper Metal-Poor stars) are suggested. Although the origins of the carbon-excesses in these objects have not been well identified, some objects suggest contributions of faint supernovae. Remaining problems on CEMP stars, such as the binary fraction, excess of r-process elements, are discussed.

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