scholarly journals Constraints on the Astrophysical Nature of r-Process Nucleosynthesis Sites from Inhomogeneous Chemical Evolution Models

2004 ◽  
Vol 21 (2) ◽  
pp. 161-166 ◽  
Author(s):  
Dominik Argast ◽  
Markus Samland
Keyword(s):  
Neutron Star ◽  
Chemical Evolution ◽  
Core Collapse ◽  
Lower Mass ◽  
Evolution Study ◽  
R Process ◽  
First Time

AbstractWe present a detailed inhomogeneous chemical evolution study that considers for the first-time neutron star mergers as major r-process sources, and compare this scenario with the ones in which lower-mass (in the range 8–10 M⊙) or higher-mass core-collapse supernovae (with masses ≥20 M⊙) act as dominant r-process sites. We conclude that it is not possible at present to distinguish between the lower-mass and higher-mass supernovae scenarios within the framework of inhomogeneous chemical evolution. However, neutron-star mergers seem to be ruled out as the dominant r-process source, since their low rates of occurrence would lead to r-process enrichment that is not consistent with observations.

scholarly journals Chemical Evolution of R-process Elements in the Hierarchical Galaxy Formation

2015 ◽  
Vol 11 (S317) ◽  
pp. 318-319
Author(s):  
Yutaka Komiya ◽  
Toshikazu Shigeyama
Keyword(s):  
Neutron Star ◽  
Chemical Evolution ◽  
Galaxy Formation ◽  
Milky Way ◽  
Galactic Chemical Evolution ◽  
Halo Stars ◽  
R Process ◽  
Process Elements ◽  
Milky Way Halo

AbstractThe main astronomical source of r-process elements has not yet been identified. One plausible site is neutron star mergers (NSMs). From the perspective of Galactic chemical evolution, however, it has been pointed out that the NSM scenario is incompatible with observations. Recently, Tsujimoto & Shigeyama (2014) pointed out that NSM ejecta can spread into much larger volume than ejecta from a supernova. We re-examine the chemical evolution of r-process elements under the NSM scenario considering this difference in propagation of the ejecta. We find that the NSM scenario can be compatible with the observed abundances of the Milky Way halo stars.

scholarly journals The overarching framework of core-collapse supernova explosions as revealed by 3D fornax simulations

2019 ◽  
Vol 491 (2) ◽  
pp. 2715-2735 ◽  
Author(s):  
Adam Burrows ◽  
David Radice ◽  
David Vartanyan ◽  
Hiroki Nagakura ◽  
M Aaron Skinner ◽  
...  
Keyword(s):  
Neutron Star ◽  
Massive Star ◽  
State Of The Art ◽  
Mass Range ◽  
Core Collapse ◽  
Final States ◽  
Lower Mass ◽  
Core Collapse Supernova ◽  
Supernova Explosions ◽  
General Range

ABSTRACT We have conducted 19 state-of-the-art 3D core-collapse supernova simulations spanning a broad range of progenitor masses. This is the largest collection of sophisticated 3D supernova simulations ever performed. We have found that while the majority of these models explode, not all do, and that even models in the middle of the available progenitor mass range may be less explodable. This does not mean that those models for which we did not witness explosion would not explode in Nature, but that they are less prone to explosion than others. One consequence is that the ‘compactness’ measure is not a metric for explodability. We find that lower-mass massive star progenitors likely experience lower-energy explosions, while the higher-mass massive stars likely experience higher-energy explosions. Moreover, most 3D explosions have a dominant dipole morphology, have a pinched, wasp-waist structure, and experience simultaneous accretion and explosion. We reproduce the general range of residual neutron-star masses inferred for the galactic neutron-star population. The most massive progenitor models, however, in particular vis à vis explosion energy, need to be continued for longer physical times to asymptote to their final states. We find that while the majority of the inner ejecta have Ye = 0.5, there is a substantial proton-rich tail. This result has important implications for the nucleosynthetic yields as a function of progenitor. Finally, we find that the non-exploding models eventually evolve into compact inner configurations that experience a quasi-periodic spiral SASI mode. We otherwise see little evidence of the SASI in the exploding models.

scholarly journals Evidence for ≳4 Gyr timescales of neutron star mergers from Galactic archaeology

2020 ◽  
Vol 634 ◽  
pp. L2 ◽  
Author(s):  
Á. Skúladóttir ◽  
S. Salvadori
Keyword(s):  
Neutron Star ◽  
Milky Way ◽  
Dwarf Galaxy ◽  
Direct Detection ◽  
Compact Object ◽  
Core Collapse ◽  
Chemical Abundances ◽  
Capture Process ◽  
Process Elements ◽  
First Time

The nucleosynthetic site of the rapid (r) neutron-capture process is currently being debated. The direct detection of the neutron star merger GW170817, through gravitational waves and electromagnetic radiation, has confirmed such events as important sources of the r-process elements. However, chemical evolution models are not able to reproduce the observed chemical abundances in the Milky Way when neutron star mergers are assumed to be the only r-process site and realistic time distributions of such events are taken into account. Now for the first time, we combine all the available observational evidence of the Milky Way and its dwarf galaxy satellites to show that the data can only be explained if there are (at least) two distinct r-process sites: a quick source with timescales comparable to core-collapse supernovae, tquick ≲ 108 yr, and a delayed source with characteristic timescales tdelayed ≳ 4 Gyr. The delayed r-process source most probably originates in neutron star mergers, as the timescale fits well with that estimated for GW170817. Given the short timescales of the quick source, it is likely associated with massive stars, though a specific fast-track channel for compact object mergers cannot be excluded at this point. Our approach demonstrates that only by looking at all the available data will we be able to solve the puzzle that is the r-process.

scholarly journals Neutron star mergers versus core-collapse supernovae as dominant r-process sites in the early Galaxy

2004 ◽  
Vol 416 (3) ◽  
pp. 997-1011 ◽  
Author(s):  
D. Argast ◽  
M. Samland ◽  
F.-K. Thielemann ◽  
Y.-Z. Qian
Keyword(s):  
Neutron Star ◽  
Core Collapse ◽  
R Process ◽  
Early Galaxy

scholarly journals Neutron star mergers and rare core-collapse supernovae as sources of r-process enrichment in simulated galaxies

2020 ◽  
Vol 494 (4) ◽  
pp. 4867-4883 ◽  
Author(s):  
Freeke van de Voort ◽  
Rüdiger Pakmor ◽  
Robert J J Grand ◽  
Volker Springel ◽  
Facundo A Gómez ◽  
...  
Keyword(s):  
Neutron Star ◽  
Milky Way ◽  
Small Variation ◽  
Abundance Ratio ◽  
Core Collapse ◽  
Binary Neutron Star ◽  
Low Metallicity ◽  
Process Event ◽  
R Process ◽  
Process Elements

ABSTRACT We use cosmological, magnetohydrodynamical simulations of Milky Way-mass galaxies from the Auriga project to study their enrichment with rapid neutron capture (r-process) elements. We implement a variety of enrichment models from both binary neutron star mergers and rare core-collapse supernovae. We focus on the abundances of (extremely) metal-poor stars, most of which were formed during the first ∼Gyr of the Universe in external galaxies and later accreted on to the main galaxy. We find that the majority of metal-poor stars are r-process enriched in all our enrichment models. Neutron star merger models result in a median r-process abundance ratio, which increases with metallicity, whereas the median trend in rare core-collapse supernova models is approximately flat. The scatter in r-process abundance increases for models with longer delay times or lower rates of r-process-producing events. Our results are nearly perfectly converged, in part due to the mixing of gas between mesh cells in the simulations. Additionally, different Milky Way-mass galaxies show only small variation in their respective r-process abundance ratios. Current (sparse and potentially biased) observations of metal-poor stars in the Milky Way seem to prefer rare core-collapse supernovae over neutron star mergers as the dominant source of r-process elements at low metallicity, but we discuss possible caveats to our models. Dwarf galaxies that experience a single r-process event early in their history show highly enhanced r-process abundances at low metallicity, which is seen both in observations and in our simulations. We also find that the elements produced in a single event are mixed with ≈108 M⊙ of gas relatively quickly, distributing the r-process elements over a large region.

scholarly journals CONTRIBUTION OF NEUTRON STAR MERGERS TO THE r-PROCESS CHEMICAL EVOLUTION IN THE HIERARCHICAL GALAXY FORMATION

2016 ◽  
Vol 830 (2) ◽  
pp. 76 ◽  
Author(s):  
Yutaka Komiya ◽  
Toshikazu Shigeyama
Keyword(s):  
Neutron Star ◽  
Chemical Evolution ◽  
Galaxy Formation ◽  
R Process

scholarly journals R-Process with Magnetized Nuclei at Dynamo-Explosive Supernovae and Neutron Star Mergers

Universe ◽  
2021 ◽  
Vol 7 (12) ◽  
pp. 487
Author(s):  
Vladimir N. Kondratyev
Keyword(s):  
Neutron Star ◽  
Zeeman Effect ◽  
Magnetic Response ◽  
Core Collapse ◽  
Iron Group ◽  
Noticeable Increase ◽  
Atomic Nuclei ◽  
Low Mass ◽  
R Process ◽  
Neutron Component

Nucleosynthesis at latge magnetic induction levels relevant to core-collapse supernovae and neutron star mergers is considered. For respective magnetic fields of a strength up to ten teratesla, atomic nuclei exhibit a linear magnetic response due to the Zeeman effect. Such nuclear reactivity can be described in terms of magnetic susceptibility. Susceptibility maxima correspond to half-filled shells. The neutron component rises linearly with increasing shell angular momentum, while the contribution of protons grows quadratically due to considerable income from orbital magnetization. For a case j = l + 1/2, the proton contribution makes tens of nuclear magnetons and significantly exceeds the neutron values which give several units. In a case j = l − 1/2, the proton component is almost zero up to the g shell. A noticeable increase in the generation of corresponding explosive nucleosynthetic products with antimagic numbers is predicted for nuclei at charge freezing conditions. In the iron group region, new seeds are also created for the r-process. In particular, the magnetic enhancement of the volume of 44Ti isotopes is consistent with results from observations and indicates the substantial increase in the abundance of the main titanium isotope (48Ti) in the Galaxy’s chemical composition. Magnetic effects are proven to result in a shift of the r-process path towards smaller mass numbers, as well as an increase in the volume of low-mass nuclides in peaks of the r-process nuclei.

scholarly journals Neutron star mergers as sites of r-process nucleosynthesis and short gamma-ray bursts

2018 ◽  
Vol 27 (13) ◽  
pp. 1842005 ◽  
Author(s):  
Kenta Hotokezaka ◽  
Paz Beniamini ◽  
Tsvi Piran
Keyword(s):  
Neutron Star ◽  
Chemical Evolution ◽  
Near Infrared ◽  
Gamma Ray ◽  
Ultra Violet ◽  
Gamma Ray Bursts ◽  
Galactic Model ◽  
Multi Wavelength ◽  
R Process ◽  
Process Elements

Neutron star mergers have been long considered as promising sites of heavy [Formula: see text]-process nucleosynthesis. We overview the observational evidence supporting this scenario including: the total amount of [Formula: see text]-process elements in the galaxy, extreme metal-poor stars, geological radioactive elemental abundances, dwarf galaxies and short gamma-ray bursts (sGRBs). Recently, the advanced LIGO and Virgo observatories discovered a gravitational-wave signal of a neutron star merger, GW170817, as well as accompanying multi-wavelength electromagnetic (EM) counterparts. The ultra-violet, optical and near infrared (n/R) observations point to [Formula: see text]-process elements that have been synthesized in the merger ejecta. The rate and ejected mass inferred from GW170817 and the EM counterparts are consistent with other observations. We however, find that, within the simple one zone chemical evolution models (based on merger rates with reasonable delay time distributions as expected from evolutionary models, or from observations of sGRBs), it is difficult to reconcile the current observations of the Eu abundance history of galactic stars for [Fe/H] [Formula: see text]. This implies that to account for the role of mergers in the galactic chemical evolution, we need a galactic model with multiple populations that have different spatial distributions and/or varying formation rates.

R-Process Nucleosynthesis in Core-Collapse Supernova Explosions and Binary Neutron Star Mergers

2019 ◽  
pp. 437-440
Author(s):  
Toshio Suzuki ◽  
Shota Shibagaki ◽  
Takashi Yoshida ◽  
Toshitaka Kajino ◽  
Takaharu Otsuka
Keyword(s):  
Neutron Star ◽  
Core Collapse ◽  
Core Collapse Supernova ◽  
Binary Neutron Star ◽  
Supernova Explosions ◽  
R Process
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