We propose a new neutron-capture site in early metal-poor and metal-free stars of ∼20-30 M that results from proton ingestion in the He shell during late stages of the stars' lives. Most of the ...neutron capture occurs in the first 106 s following proton ingestion when 13C( , n)16O produces neutron densities typical of the intermediate neutron-capture process. This phase may be followed by another lasting 107 s with 17O( , n)20Ne producing much lower neutron densities typical of the slow neutron-capture process. We explore the dependence of the proposed neutron-capture nucleosynthesis on the amount and time of proton ingestion, the initial metallicity, and the ensuing supernova shock. We obtain a range of heavy-element abundance patterns, including those attributed to the slow neutron-capture process or a combination of the slow and rapid neutron-capture processes. Our results can account for the observed ubiquity of heavy elements such as Sr and Ba in the early Galaxy and explain puzzling abundance patterns of these elements in at least some very metal-poor (VMP) stars, including those of the carbon-enhanced varieties. In the latter case, the explanation by the single site proposed here differs from the existing paradigm that attributes various classes of VMP stars to enrichment by multiple different sites.
The wind driven by the intense neutrino emission from a protoneutron star (PNS) is an important site for producing nuclei heavier than the Fe group. Because of certain features in the neutrino ...angular distributions, the so-called fast flavor oscillations may occur very close to the PNS surface, effectively resetting the neutrino luminosities and energy spectra that drive the wind. Using the unoscillated neutrino emission characteristics from two core-collapse supernova simulations representative of relevant progenitors at the lower and higher mass end, we study the potential effects of fast flavor oscillations on neutrino-driven winds and their nucleosynthesis. We find that such oscillations can increase the total mass loss by factors up to ∼1.5-1.7 and lead to significantly more proton-rich conditions. The latter effect can greatly enhance the production of 64Zn and the so-called light p-nuclei 74Se, 78Kr, and 84Sr. Implications for abundances in metal-poor stars, Galactic chemical evolution in general, and isotopic anomalies in meteorites are discussed.
We present a method to find the stationary solutions for fast flavor oscillations of a homogeneous dense neutrino gas. These solutions correspond to collective precession of all neutrino polarization ...vectors around a fixed axis in the flavor space on average, and are conveniently studied in the co-rotating frame. We show that these solutions can account for the numerical results of explicit evolution calculations, and that even with the simplest assumption of adiabatic evolution, they can provide the average survival probabilities to good approximation. We also discuss improvement of these solutions and their use as estimates of the effects of fast oscillations in astrophysical environments.
Collective Neutrino Oscillations Duan, Huaiyu; Fuller, George M.; Qian, Yong-Zhong
Annual review of nuclear and particle science,
11/2010, Letnik:
60, Številka:
1
Journal Article
Recenzirano
Odprti dostop
We review the rich phenomena associated with neutrino flavor transformation in the presence of neutrino self-coupling. Our exposition centers on three collective neutrino oscillation scenarios: (a) a ...simple bipolar neutrino system that initially consists of monoenergetic ν
e
and Formula: see text, (b) a homogeneous and isotropic neutrino gas with multiple neutrino/antineutrino species and continuous energy spectra, and (c) a generic neutrino gas in an anisotropic environment. We use each of these scenarios to illustrate key facets of collective neutrino oscillations. We discuss the implications of collective neutrino flavor oscillations for core-collapse supernova physics and for the prospects of obtaining and/or constraining fundamental neutrino properties, such as the neutrino mass hierarchy and θ
13
from a future observed supernova neutrino signal.
We report a new mechanism for the s-process in rotating massive metal-poor stars. Our models show that above a critical rotation speed, such stars evolve in a quasi-chemically homogeneous fashion, ...which gives rise to a prolific s-process. Rotation-induced mixing results in primary production of 13C, which subsequently makes neutrons via during core He burning. Neutron capture can last up to (∼3 × 105 yr) with the peak central neutron density ranging from ∼107 to 108 . Depending on the rotation speed and the mass loss rate, a strong s-process can occur with production of elements up to Bi for progenitors with initial metallicities of Z −1.5. This result suggests that rapidly rotating massive metal-poor stars are likely the first sites of the main s-process. We find that these stars can potentially explain the early onset of the s-process and some of the carbon-enhanced metal-poor (CEMP-s and CEMP-r/s) stars with strong enrichment attributed to the s-process or a mixture of the r-process and the s-process.
ABSTRACT
We present a suite of seven 3D supernova simulations of non-rotating low-mass progenitors using multigroup neutrino transport. Our simulations cover single star progenitors with zero-age ...main-sequence masses between $9.6$ and $12.5 \, \mathrm{M}_\odot$ and (ultra)stripped-envelope progenitors with initial helium core masses between $2.8$ and $3.5 \, \mathrm{M}_\odot$. We find explosion energies between $0.1$ and $0.4\, \mathrm{Bethe}$, which are still rising by the end of the simulations. Although less energetic than typical events, our models are compatible with observations of less energetic explosions of low-mass progenitors. In six of our models, the mass outflow rate already exceeds the accretion rate on to the proto-neutron star, and the mass and angular momentum of the compact remnant have closely approached their final value, barring the possibility of later fallback. While the proto-neutron star is still accelerated by the gravitational tug of the asymmetric ejecta, the acceleration can be extrapolated to obtain estimates for the final kick velocity. We obtain gravitational neutron star masses between $1.22$ and $1.44 \, \mathrm{M}_\odot$, kick velocities between $11$ and $695\, \mathrm{km}\, \mathrm{s}^{-1}$, and spin periods from $20\, \mathrm{ms}$ to $2.7\, \mathrm{s}$, which suggest that typical neutron star birth properties can be naturally obtained in the neutrino-driven paradigm. We find a loose correlation between the explosion energy and the kick velocity. There is no indication of spin–kick alignment, but a correlation between the kick velocity and the neutron star angular momentum, which needs to be investigated further as a potential point of tension between models and observations.
Human infections with zoonotic coronaviruses (CoVs), including severe acute respiratory syndrome (SARS)-CoV and Middle East respiratory syndrome (MERS)-CoV, have raised great public health concern ...globally. Here, we report a novel bat-origin CoV causing severe and fatal pneumonia in humans.
We collected clinical data and bronchoalveolar lavage (BAL) specimens from five patients with severe pneumonia from Wuhan Jinyintan Hospital, Hubei province, China. Nucleic acids of the BAL were extracted and subjected to next-generation sequencing. Virus isolation was carried out, and maximum-likelihood phylogenetic trees were constructed.
Five patients hospitalized from December 18 to December 29, 2019 presented with fever, cough, and dyspnea accompanied by complications of acute respiratory distress syndrome. Chest radiography revealed diffuse opacities and consolidation. One of these patients died. Sequence results revealed the presence of a previously unknown β-CoV strain in all five patients, with 99.8% to 99.9% nucleotide identities among the isolates. These isolates showed 79.0% nucleotide identity with the sequence of SARS-CoV (GenBank NC_004718) and 51.8% identity with the sequence of MERS-CoV (GenBank NC_019843). The virus is phylogenetically closest to a bat SARS-like CoV (SL-ZC45, GenBank MG772933) with 87.6% to 87.7% nucleotide identity, but is in a separate clade. Moreover, these viruses have a single intact open reading frame gene 8, as a further indicator of bat-origin CoVs. However, the amino acid sequence of the tentative receptor-binding domain resembles that of SARS-CoV, indicating that these viruses might use the same receptor.
A novel bat-borne CoV was identified that is associated with severe and fatal respiratory disease in humans.
A protoneutron star produced in a core-collapse supernova (CCSN) drives a wind by its intense neutrino emission. We implement active-sterile neutrino oscillations in a steady-state model of this ...neutrino-driven wind to study their effects on the dynamics and nucleosynthesis of the wind in a self-consistent manner. Using vacuum mixing parameters indicated by some experiments for a sterile s of ∼1 eV in mass, we observe interesting features of oscillations due to various feedback. For the higher s mass values, we find that oscillations can reduce the mass-loss rate and the wind velocity by a factor of ∼1.6-2.7 and change the electron fraction critical to nucleosynthesis by a significant to large amount. In the most dramatic cases, oscillations shift nucleosynthesis from dominant production of 45Sc to that of 86Kr and 90Zr during the early epochs of the CCSN evolution.
The next Galactic core-collapse supernova (SN) should yield a large number of observed neutrinos. Here, using Bayesian techniques, we show that with a SN at a known distance up to 25 kpc, the ...neutrino events in a water Cherenkov detector similar to Super-Kamiokande (SK) could be used to distinguish between seven one-dimensional neutrino emission models assuming no flavor oscillations or the standard Mikheyev-Smirnov-Wolfenstein effect. Some of these models could still be differentiated with a SN at a known distance of 50 kpc. We also consider just the relative distributions of neutrino energy and arrival time predicted by the models and find that a detector like SK meets the requirement to distinguish between these distributions with a SN at an unknown distance up to $\mathrm{\sim 10 kpc.}$
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