123 results on '"Meng-Ru, Wu"'
Search Results
2. Collisional flavor instability in dense neutrino gases
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Zewei Xiong, Lucas Johns, Meng-Ru Wu, and Huaiyu Duan
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- 2023
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3. The production of actinides in neutron star mergers
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Meng-Ru Wu and Projjwal Banerjee
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r-process ,Neutron star merger ,Physics ,QC1-999 - Abstract
Abstract Although the multimessenger detection of the neutron star merger event GW170817 confirmed that mergers are promising sites producing the majority of nature’s heavy elements via the rapid neutron-capture process (r-process), a number of issues related to the production of translead nuclei—the actinides—remain to be answered. In this short review paper, we summarize the general requirements for actinide production in r-process and the impact of nuclear physics inputs. We also discuss recent efforts addressing the actinide production in neutron star mergers from different perspectives, including signatures that may be probed by future kilonova and γ-ray observations, the abundance scattering in metal-poor stars, and constraints put by the presence of short-lived radioactive actinides in the Solar system.
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- 2022
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4. MVIN: Learning Multiview Items for Recommendation.
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Chang-You Tai, Meng-Ru Wu, Yun-Wei Chu, Shao-Yu Chu, and Lun-Wei Ku
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- 2020
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5. Progress in nuclear astrophysics of east and southeast Asia
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Azni Abdul Aziz, Nor Sofiah Ahmad, S. Ahn, Wako Aoki, Muruthujaya Bhuyan, Ke-Jung Chen, Gang Guo, K. I. Hahn, Toshitaka Kajino, Hasan Abu Kassim, D. Kim, Shigeru Kubono, Motohiko Kusakabe, A. Li, Haining Li, Z. H. Li, W. P. Liu, Z. W. Liu, Tohru Motobayashi, Kuo-Chuan Pan, T.-S. Park, Jian-Rong Shi, Xiaodong Tang, W. Wang, Liangjian Wen, Meng-Ru Wu, Hong-Liang Yan, and Norhasliza Yusof
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Nuclear astrophysics ,East and southeast Asia ,Physics ,QC1-999 - Abstract
Abstract Nuclear astrophysics is an interdisciplinary research field of nuclear physics and astrophysics, seeking for the answer to a question, how to understand the evolution of the universe with the nuclear processes which we learn. We review the research activities of nuclear astrophysics in east and southeast Asia which includes astronomy, experimental and theoretical nuclear physics, and astrophysics. Several hot topics such as the Li problems, critical nuclear reactions and properties in stars, properties of dense matter, r-process nucleosynthesis, and ν-process nucleosynthesis are chosen and discussed in further details. Some future Asian facilities, together with physics perspectives, are introduced.
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- 2021
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6. COSEν: A collective oscillation simulation engine for neutrinos.
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Manu George, Chun-Yu Lin, Meng-Ru Wu, Tony G. Liu, and Zewei Xiong
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- 2023
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7. Dirammox Is Widely Distributed and Dependently Evolved in Alcaligenes and Is Important to Nitrogen Cycle
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Ting-Ting Hou, Li-Li Miao, Ji-Sen Peng, Lan Ma, Qiang Huang, Ying Liu, Meng-Ru Wu, Guo-Min Ai, Shuang-Jiang Liu, and Zhi-Pei Liu
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nitrogen cycle ,Dirammox ,Alcaligenes ,DnfA ,environmental distribution ,Microbiology ,QR1-502 - Abstract
Nitrogen cycle is an essential process for environmental health. Dirammox (direct ammonia oxidation), encoded by the dnfT1RT2ABCD cluster, was a novel pathway for microbial N2 production defined in Alcaligenes ammonioxydans HO-1. Here, a copy of the cluster dnfT1RT2ABCD as a whole was proved to have existed and very conserved in all Alcaligenes genomes. Phylogenetic analyses based on 16S rRNA gene sequences and amino acid sequences of DnfAs, together with G + C content data, revealed that dnf cluster was evolved associated with the members of the genus Alcaligenes. Under 20% O2 conditions, 14 of 16 Alcaligenes strains showed Dirammox activity, which seemed likely taxon-related. However, the in vitro activities of DnfAs catalyzing the direct oxidation of hydroxylamine to N2 were not taxon-related but depended on the contents of Fe and Mn ions. The results indicated that DnfA is necessary but not sufficient for Dirammox activity. The fact that members of the genus Alcaligenes are widely distributed in various environments, including soil, water bodies (both freshwater and seawater), sediments, activated sludge, and animal–plant-associated environments, strongly suggests that Dirammox is important to the nitrogen cycle. In addition, Alcaligenes species are also commonly found in wastewater treatment plants, suggesting that they might be valuable resources for wastewater treatment.
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- 2022
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8. GraphSW: a training protocol based on stage-wise training for GNN-based Recommender Model.
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Chang-You Tai, Meng-Ru Wu, Yun-Wei Chu, and Shao-Yu Chu
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- 2019
9. Searching for Afterglow: Light Dark Matter Boosted by Supernova Neutrinos
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Yen-Hsun Lin, Wen-Hua Wu, Meng-Ru Wu, and Henry Tsz-King Wong
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High Energy Astrophysical Phenomena (astro-ph.HE) ,High Energy Physics - Phenomenology ,High Energy Physics - Phenomenology (hep-ph) ,Astrophysics::High Energy Astrophysical Phenomena ,General Physics and Astronomy ,FOS: Physical sciences ,Astrophysics - High Energy Astrophysical Phenomena - Abstract
A novel analysis is performed, incorporating time-of-flight (TOF) information to study the interactions of dark matter (DM) with standard model particles. After supernova (SN) explosions, DM with mass $m_\chi\lesssim\mathcal{O}({\rm MeV})$ in the halo can be boosted by SN neutrinos (SN$\nu$) to relativistic speed. The SN$\nu$ boosted DM (BDM) arrives on Earth with TOF which depends only on $m_\chi$ and is independent of the cross section. These BDMs can interact with detector targets in low-background experiments and manifest as afterglow events after the arrival of SN$\nu$. The characteristic TOF spectra of the BDM events can lead to large background suppression and unique determination of $m_\chi$. New cross section constraints on $\sqrt{\sigma_{\chi e} \sigma_{\chi\nu}}$ are derived from SN1987a in the Large Magellanic Cloud with data from the Kamiokande and Super-Kamiokande experiments. Potential sensitivities for the next galactic SN with Hyper-Kamiokande are projected. This analysis extends the existing bounds on $\sqrt{\sigma_{\chi e}\sigma_{\chi \nu}}$ over a broad range of $r_\chi=\sigma_{\chi \nu}/\sigma_{\chi e}$. In particular, the improvement is by 1-3 orders of magnitude for $m_\chi, Comment: PRL accepted, matched published version
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- 2023
10. Near-Infrared Multichannel Filter in a Finite Semiconductor Metamaterial Photonic Crystal
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Meng-Ru Wu, Jia-Ren Chang Chien, Chien-Jang Wu, and Shoou-Jinn Chang
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Photonic crystal ,multichannel filter ,semiconductor ,metamaterial ,Applied optics. Photonics ,TA1501-1820 ,Optics. Light ,QC350-467 - Abstract
A near-infrared (NIR) multichannel filter based on the use of a finite 1-D semiconductor metamaterial (MTM) photonic crystal (PC) is proposed. We consider a PC air/(AB)N/air, where N is the stack number, A is a dielectric layer, and B is a semiconductor MTM made of Al-doped ZnO (AZO) and ZnO. Resonant transmission peaks can be found in the frequency region where the permittivity of AZO/ZnO is negative. It is found that the channel number is equal to N - 1 for a given N and that resonant channels are located in a passband of the photonic band structure. Additionally, the channel positions are tunable, i.e., they can be tuned by the thicknesses of A and B, the filling factor of AZO, and the incidence angle as well. The design of NIR tunable multichannel filter is of technical use for semiconductor optoelectronics.
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- 2016
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11. Physics of neutrino flavor transformation through matter–neutrino resonances
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Meng-Ru Wu, Huaiyu Duan, and Yong-Zhong Qian
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Neutrino oscillations ,Dense neutrino medium ,Black hole accretion disk ,Core-collapse supernova ,Physics ,QC1-999 - Abstract
In astrophysical environments such as core-collapse supernovae and neutron star–neutron star or neutron star–black hole mergers where dense neutrino media are present, matter–neutrino resonances (MNRs) can occur when the neutrino propagation potentials due to neutrino–electron and neutrino–neutrino forward scattering nearly cancel each other. We show that neutrino flavor transformation through MNRs can be explained by multiple adiabatic solutions similar to the Mikheyev–Smirnov–Wolfenstein mechanism. We find that for the normal neutrino mass hierarchy, neutrino flavor evolution through MNRs can be sensitive to the shape of neutrino spectra and the adiabaticity of the system, but such sensitivity is absent for the inverted hierarchy.
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- 2016
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12. Fingerprints of Heavy-Element Nucleosynthesis in the Late-Time Lightcurves of Kilonovae
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Meng-Ru Wu, J. Barnes, G. Martínez-Pinedo, and B. D. Metzger
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- 2019
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13. Resonant production of light sterile neutrinos in compact binary merger remnants
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Garðar Sigurðarson, Irene Tamborra, and Meng-Ru Wu
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High Energy Astrophysical Phenomena (astro-ph.HE) ,High Energy Physics - Phenomenology ,High Energy Physics - Phenomenology (hep-ph) ,FOS: Physical sciences ,Astrophysics - High Energy Astrophysical Phenomena - Abstract
The existence of eV-mass sterile neutrinos is not ruled out because of persistent experimental anomalies. Upcoming multi-messenger detections of neutron-star merger remnants could provide indirect constraints on the existence of these particles. We explore the active-sterile flavor conversion phenomenology in a two-flavor scenario (1 active + 1 sterile species) as a function of the sterile neutrino mixing parameters, neutrino emission angle from the accretion torus, and temporal evolution of the merger remnant. The torus geometry and the neutron richness of the remnant are responsible for the occurrence of multiple resonant active-sterile conversions. The number of resonances strongly depends on the neutrino emission direction above or inside the remnant torus and leads to large production of sterile neutrinos (and no antineutrinos) in the proximity of the polar axis as well as more sterile antineutrinos than neutrinos in the equatorial region. As the black hole torus evolves in time, the shallower baryon density is responsible for more adiabatic flavor conversion, leading to larger regions of the mass-mixing parameter space being affected by flavor mixing. Our findings imply that the production of sterile states could have indirect implications on the disk cooling rate, its outflows, and related electromagnetic observables which remain to be assessed., Comment: 16 pages, including 12 figures. Minor changes in the text; conclusions unchanged. Matches version accepted for publication in Phys. Rev. D
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- 2022
14. Evolution of collisional neutrino flavor instabilities in spherically symmetric supernova models
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Zewei Xiong, Meng-Ru Wu, Gabriel Martínez-Pinedo, Tobias Fischer, Manu George, Chun-Yu Lin, and Lucas Johns
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High Energy Astrophysical Phenomena (astro-ph.HE) ,Nuclear Theory (nucl-th) ,High Energy Physics - Phenomenology ,High Energy Physics - Phenomenology (hep-ph) ,Nuclear Theory ,FOS: Physical sciences ,Astrophysics - High Energy Astrophysical Phenomena - Abstract
We implement a multi-group and discrete-ordinate neutrino transport model in spherical symmetry which allows to simulate collective neutrino oscillations by including realistic collisional rates in a self-consistent way. We utilize this innovative model, based on strategic parameter rescaling, to study a recently proposed collisional flavor instability caused by the asymmetry of emission and absorption rates between $\nu_e$ and $\bar\nu_e$ for four different static backgrounds taken from different stages in a core-collapse supernova simulation. Our results confirm that collisional instabilities generally exist around the neutrinosphere during the SN accretion and post-accretion phase, as suggested by [arXiv:2104.11369]. However, the growth and transport of flavor instabilities can only be fully captured by models with global simulations as done in this work. With minimal ingredient to trigger collisional instabilities, we find that the flavor oscillations and transport mainly affect (anti)neutrinos of heavy lepton flavors around their decoupling sphere, which then leave imprints on their energy spectra in the free-streaming regime. For electron (anti)neutrinos, their properties remain nearly intact. We also explore various effects due to the decoherence from neutrino-nucleon scattering, artificially enhanced decoherence from emission and absorption, neutrino vacuum mixing, and inhomogeneous matter profile, and discuss the implication of our work., Comment: 20 pages, 13 figures
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- 2022
15. Comparison of two methods for extracting exosomes from the nucleus accumbens in mice
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Xiao-Lu Yu, Meng-Ru Wu, Mannan Abdul, Xian Liu, Shuai Zhang, Zheng Xu, Guangchao Zhang, and Jun-Li Cao
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General Neuroscience - Abstract
Exosomes bind to and are endocytosed by neurons of various brain regions. Methods for isolating and extracting exosomes from specific brain samples are critical. At present, the most important extractive methods for exosomes are Ultracentrifugation and exosome isolation kit extraction. Both of these extraction methods have applications in neuroscience. We compare these methods to reveal the differences.We sectioned the nucleus accumbens of mice, and isolated exosomes. A culture medium containing exosomes was extracted using ultracentrifugation (UC) and a total exosome isolation kit (TEI). The exosomes were examined using transmission electron microscopy (TEM), measurement regarding the diameter of the exosomes was done, and the thermal allodynia and western blotting analysis were also conducted, respectively.Transmission electron microscopy observations showed that the ultracentrifugation samples had higher purity and fewer impurities than the kit samples. The results from the two methods were then compared with a number ratio regarding the percentage was not statistically significant. Marker protein tests showed that proteins were expressed under both methods. The thermal allodynia testing observed that the two extraction methods did not affect pain behavior regarding the detection. After the kit extraction method, there were substantial white subjects suspended by PBS.Our study compared the different protocols regarding exosome extraction from the nucleus accumbens and compared the quality of two principal methods for exosome extraction from a culture medium containing exosomes. It was found that the extraction quality of exosomes by ultracentrifugation was better, but the technical difficulty was greater.
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- 2022
16. A fully parallelized scheme of constructing independent spanning trees on Möbius cubes.
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Jinn-Shyong Yang, Meng-Ru Wu, Jou-Ming Chang, and Yu-Huei Chang
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- 2015
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17. Transmission Properties in Lossy Single-Negative Materials
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Meng-Ru Wu, Jia-Ren Chang Chien, Chien-Jang Wu, and Shoou-Jinn Chang
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Transmission ,refractive angle ,single-negative materials ,negative refraction ,Applied optics. Photonics ,TA1501-1820 ,Optics. Light ,QC350-467 - Abstract
We theoretically investigate the transmission properties at an interface between a dielectric and a lossy single-negative (SNG) material. The transmission property is specifically investigated in the refractive angle calculated by the inhomogeneous wave theory. With the existence of a loss in an SNG material, the calculated refractive angle can be negative. That is, the negative refraction phenomenon, which is an important consequence in a double-negative (DNG) material, can also be found in an SNG material. We analyze the refractive angle as functions of the angle of incidence, the wave frequency, and the loss. For the epsilon-permittivity SNG material, the frequency-dependent negative refractive angle is shown to possess a critical frequency at which the absolute value in the negative refractive angle attains a maximum.
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- 2015
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18. Astrophysical Neutrino I_Neutrinos in supernovae and binary neutron star mergers
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Meng-Ru Wu
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Physics::Instrumentation and Detectors ,Astrophysics::High Energy Astrophysical Phenomena ,High Energy Physics::Phenomenology ,High Energy Physics::Experiment - Abstract
Plenary Talk from Neutrino 2022
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- 2022
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19. Code Comparison for Fast Flavor Instability Simulation
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Sherwood Richers, Huaiyu Duan, Meng-Ru Wu, Soumya Bhattacharyya, Masamichi Zaizen, Manu George, Chun-Yu Lin, and Zewei Xiong
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High Energy Astrophysical Phenomena (astro-ph.HE) ,Astrophysics::High Energy Astrophysical Phenomena ,FOS: Physical sciences ,ddc:530 ,Astrophysics - High Energy Astrophysical Phenomena ,Astrophysics - Instrumentation and Methods for Astrophysics ,Instrumentation and Methods for Astrophysics (astro-ph.IM) - Abstract
The fast flavor instability (FFI) is expected to be ubiquitous in core-collapse supernovae and neutron star mergers. It rapidly shuffles neutrino flavor in a way that could impact the explosion mechanism, neutrino signals, mass outflows, and nucleosynthesis. The variety of initial conditions and simulation methods employed in simulations of the FFI prevent an apples-to-apples comparison of the results. We simulate a standardized test problem using five independent codes and verify that they are all faithfully simulating the underlying quantum kinetic equations under the assumptions of axial symmetry and homogeneity in two directions. We quantify the amount of numerical error in each method and demonstrate that each method is superior in at least one metric of this error. We make the results publicly available to serve as a benchmark., Accepted to PRD
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- 2022
20. Fast neutrino conversion in hydrodynamic simulations of neutrino-cooled accretion disks
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Oliver Just, Sajad Abbar, Meng-Ru Wu, Irene Tamborra, Hans-Thomas Janka, Francesco Capozzi, European Commission, and Generalitat Valenciana
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High Energy Astrophysical Phenomena (astro-ph.HE) ,Astrophysics - Solar and Stellar Astrophysics ,Astrophysics::High Energy Astrophysical Phenomena ,High Energy Physics::Phenomenology ,FOS: Physical sciences ,High Energy Physics::Experiment ,ddc:530 ,Astrophysics::Earth and Planetary Astrophysics ,Astrophysics - High Energy Astrophysical Phenomena ,Solar and Stellar Astrophysics (astro-ph.SR) ,Astrophysics::Galaxy Astrophysics - Abstract
The outflows from neutrino-cooled black-hole (BH) accretion disks formed in neutron-star mergers or cores of collapsing stars are expected to be neutron-rich enough to explain a large fraction of elements created by the rapid neutron-capture (r-) process, but their precise chemical composition remains elusive. Here, we investigate the role of fast neutrino flavor conversion, motivated by the findings of our post-processing analysis that shows evidence of electron-neutrino lepton-number (ELN) crossings deep inside the disk, hence suggesting possibly non-trivial effects due to neutrino flavor mixing. We implement a parametric, dynamically self-consistent treatment of fast conversion in time-dependent simulations and examine the impact on the disk and its outflows. By activating the, otherwise inefficient, emission of heavy-lepton neutrinos, fast conversions enhance the disk cooling rates and reduce the absorption rates of electron-type neutrinos, causing a reduction of the electron fraction in the disk by 0.03-0.06 and in the ejected material by 0.01-0.03. The r-process yields are enhanced by typically no more than a factor of two, rendering the overall impact of fast conversions modest. The kilonova is prolonged as a net result of increased lanthanide opacities and enhanced radioactive heating rates. We observe only mild sensitivity to the disk mass, the condition for the onset of flavor conversion, and to the considered cases of flavor mixing. Remarkably, parametric models of flavor mixing that conserve the lepton numbers per family result in an overall smaller impact than models invoking three-flavor equipartition, often assumed in previous works., 25 pages, 10 figures, 1 table; accepted to PRD
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- 2022
21. Frequency Response of a Ferroelectric Material in Double-Negative Region
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Meng-Ru Wu, Heng-Tung Hsu, Chien-Jang Wu, and Shoou-Jinn Chang
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Surface impedance ,ferroelectric ,double-negative region ,Applied optics. Photonics ,TA1501-1820 ,Optics. Light ,QC350-467 - Abstract
In this work, we investigate the far-infrared wave properties for a ferroelectric material, i.e., lithium tantalate $(\hbox{LiTaO}_{3})$, in the double-negative region, i.e., both the real parts of permittivity and permeability are negative. The analysis has been done based on the calculated surface impedances for three model structures, i.e., material occupying semi-infinite space (structure I), material of a slab immersed in free space (structure II), and a layered structure made of film on a dielectric substrate (structure III). It is found that the surface impedance spectrum exhibits resonant behavior. In structure I, there are only two resonant points, which arise mainly from the pole of permeability and the zero of permittivity. In structure II, multiple resonances can be found, and they strongly rely on the film thickness. Finally, we specifically investigate the substrate resonant phenomenon in structure III.
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- 2014
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22. Development and validation of a novel chemiluminescent immunoassay for diagnosing primary aldosteronism
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Li Ge, Jian-Jun Ma, Meng-Ru Wu, Yun Jia, Ya-Li Xu, and Hong-Feng Xu
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Pharmaceutical Science ,Pharmacology (medical) ,Primary aldosteronism, Chemiluminescence immunoassay, Radioimmunoassay, Aldosterone Plasma renin activity, Aldosterone-to-renin ratio, Receiver operating characteristic ,hormones, hormone substitutes, and hormone antagonists - Abstract
Purpose: To compare the diagnostic accuracy of plasma aldosterone concentration (PAC), plasma renin activity (PRA) and aldosterone-to-renin ratio (ARR) in primary aldosteronism (PA) using radioimmunoassay (RIA) and chemiluminescence immunoassay (CLIA) methods. Methods: Both RIA and CLIA were used to analyze the PAC, PRA and ARR with subjects in standing or supine position, before and after a saline infusion test (SIT). The correlation between RIA and CLIA was measured by regression analysis. The receiver operating characteristic (ROC) curve was used to evaluate the diagnostic accuracy by RIA and CLIA. Results: A positive correlation was found between PAC and PRA after SIT using RIA and CLIA (0.1745 and 0.3085, respectively). A positive correlation was found between the PAC and PRA in standing and supine position using RIA and CLIA (0.3979 vs 0.2399 and 0.1885 vs 0.4032, respectively). There was no obvious difference in AUCs of PAC, PRA, and ARR between RIA and CLIA (PAC: 0.91 vs. 0.89; PRA: 0.88 vs. 0.87; ARR: 0.93 vs. 0.92). In standing posture, the AUCs of PAC, PRA and ARR using RIA were 0.63, 0.72 and 0.78, respectively, and the results of CLIA were 0.65, 0.75 and 0.82, respectively. In supine posture, the AUC of PAC, PRA and ARR using RIA was 0.65, 0.68 and 0.71, respectively, and the results of CLIA were 0.68, 0.70 and 0.79, respectively. Conclusion: Chemiluminescent assay is reliable for diagnosis of PA when compared with radioimmunoassay.
- Published
- 2022
23. Finding the Remnants of the Milky Way's Last Neutron Star Mergers
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Meng-Ru Wu, Projjwal Banerjee, Brian D. Metzger, Gabriel Martínez-Pinedo, Tsuguo Aramaki, Eric Burns, Charles J. Hailey, Jennifer Barnes, and Georgia Karagiorgi
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- 2019
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24. Progress in nuclear astrophysics of east and southeast Asia
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Ke-Jung Chen, Xiaodong Tang, Norhasliza Yusof, Zhi Li, M. Bhuyan, Jianrong Shi, A. Li, Motohiko Kusakabe, Zhuoran Liu, Kuo-Chuan Pan, Shigeru Kubono, Tae-Sun Park, Wei Wang, Tohru Motobayashi, Dong Ha Kim, Meng-Ru Wu, Haining Li, Liangjian Wen, Hasan Abu Kassim, K. I. Hahn, Wako Aoki, Azni Abdul Aziz, W. Liu, Toshitaka Kajino, Gang Guo, Hong-Liang Yan, Su Ahn, and Nor Sofiah Ahmad
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Nuclear reaction ,Physics ,Nuclear Theory ,QC1-999 ,Astrophysics::Instrumentation and Methods for Astrophysics ,FOS: Physical sciences ,Astronomy ,General Medicine ,Southeast asia ,Nuclear Theory (nucl-th) ,Hot topics ,Astrophysics - Solar and Stellar Astrophysics ,Nucleosynthesis ,Nuclear astrophysics ,Nuclear Experiment (nucl-ex) ,Nuclear Experiment ,East and southeast Asia ,Nuclear theory ,Dense matter ,Solar and Stellar Astrophysics (astro-ph.SR) - Abstract
Nuclear astrophysics is an interdisciplinary research field of nuclear physics and astrophysics, seeking for the answer to a question, how to understand the evolution of the Universe with the nuclear processes which we learn. We review the research activities of nuclear astrophysics in east and southeast Asia which includes astronomy, experimental and theoretical nuclear physics and astrophysics. Several hot topics such as the Li problems, critical nuclear reactions and properties in stars, properties of dense matter, r-process nucleosynthesis and $\nu$-process nucleosynthesis are chosen and discussed in further details. Some future Asian facilities, together with physics perspectives, are introduced., Comment: 49 pages, 10 figures, published in AAPPS (Association of Asia Pacific Physical Societies) Bulletin
- Published
- 2021
25. Novel Alcaligenes ammonioxydans sp. nov. from wastewater treatment sludge oxidizes ammonia to N
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Meng-Ru, Wu, Ting-Ting, Hou, Ying, Liu, Li-Li, Miao, Guo-Min, Ai, Lan, Ma, Hai-Zhen, Zhu, Ya-Xin, Zhu, Xi-Yan, Gao, Craig W, Herbold, Michael, Wagner, De-Feng, Li, Zhi-Pei, Liu, and Shuang-Jiang, Liu
- Subjects
Sewage ,Ammonia ,Nitrogen ,Denitrification ,Escherichia coli ,Alcaligenes ,Nitrification ,Oxidation-Reduction ,Aerobiosis ,Nitrites ,Water Purification - Abstract
Heterotrophic nitrifiers are able to oxidize and remove ammonia from nitrogen-rich wastewaters but the genetic elements of heterotrophic ammonia oxidation are poorly understood. Here, we isolated and identified a novel heterotrophic nitrifier, Alcaligenes ammonioxydans sp. nov. strain HO-1, oxidizing ammonia to hydroxylamine and ending in the production of N
- Published
- 2021
26. Identification and characterization of a novel hydroxylamine oxidase, DnfA, that catalyzes the oxidation of hydroxylamine to N2
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Meng-Ru Wu, Li-Li Miao, Ying Liu, Xin-Xin Qian, Ting-Ting Hou, Guo-Min Ai, Lu Yu, Lan Ma, Xi-Yan Gao, Ya-Ling Qin, Hai-Zhen Zhu, Lei Du, Sheng-Ying Li, Chang-Lin Tian, De-Feng Li, Zhi-Pei Liu, and Shuang-Jiang Liu
- Subjects
Cell Biology ,Molecular Biology ,Biochemistry - Published
- 2022
27. Supernova constraint on self-interacting dark sector particles
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Gang Guo, Meng-Ru Wu, and Allan Sung
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Physics ,High Energy Astrophysical Phenomena (astro-ph.HE) ,Particle physics ,Star (game theory) ,Astrophysics::High Energy Astrophysical Phenomena ,FOS: Physical sciences ,Fermion ,Astrophysics::Cosmology and Extragalactic Astrophysics ,Dark photon ,Luminosity ,Standard Model ,High Energy Physics - Phenomenology ,Supernova ,High Energy Physics - Phenomenology (hep-ph) ,Neutrino ,Astrophysics - High Energy Astrophysical Phenomena ,Energy (signal processing) - Abstract
We examine the constraints on sub-GeV dark sector particles set by the proto-neutron star cooling associated with the core-collapse supernova event SN1987a. Considering explicitly a dark photon portal dark sector model, we compute the relevant interaction rates of dark photon ($A'$) and dark fermion ($\chi$) with the Standard Model particles as well as their self-interaction inside the dark sector. We find that even with a small dark sector fine structure constant $\alpha_D\ll 1$, dark sector self-interactions can easily lead to their own self-trapping. This effect strongly limits the energy luminosity carried away by dark sector particles from the supernova core and thus drastically affects the parameter space that can be constrained by SN1987a. We consider specifically two mass ratios $m_{A'}=3m_\chi$ and $3m_{A'}=m_\chi$ which represent scenarios where the decay of $A'$ to $\chi\bar\chi$ is allowed or not. We show that SN1987a can only place bounds on the dark sector when $\alpha_D\lesssim 10^{-15}$ ($10^{-7}$) for the former (latter) for $m_\chi\lesssim 20$ MeV. Furthermore, this evades the supernova bounds on the widely-examined dark photon parameter space completely if $\alpha_D\lesssim 10^{-7}$ for the former, while lifts the bounds when $\alpha_D\lesssim 10^{-7}$ if $m_\chi\lesssim 100$ MeV. Our findings thus imply that the existing supernova bounds on light dark particles can be generally evaded by a similar self-trapping mechanism. This also implies that non-standard strongly self-interacting neutrino is not consistent with the SN1987a observation. Same effects can also take place for other known stellar bounds on dark sector particles., Comment: 24 pages, 6 figures
- Published
- 2021
28. Novel Alcaligenes ammonioxydans sp. nov. from wastewater treatment sludge oxidizes ammonia to N2 with a previously unknown pathway
- Author
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De-Feng Li, Ting-Ting Hou, Ying Liu, Hai-Zhen Zhu, Shuang-Jiang Liu, Michael Wagner, Xi-Yan Gao, Craig W. Herbold, Zhi-Pei Liu, Meng-Ru Wu, Li-Li Miao, Lan Ma, Guo-Min Ai, and Yaxin Zhu
- Subjects
biology ,Strain (chemistry) ,Denitrification pathway ,Monooxygenase ,biology.organism_classification ,Microbiology ,chemistry.chemical_compound ,Ammonia ,Hydroxylamine ,chemistry ,Biochemistry ,Aerobic denitrification ,Nitrite ,Alcaligenes ,Ecology, Evolution, Behavior and Systematics - Abstract
Heterotrophic nitrifiers are able to oxidize and remove ammonia from nitrogen-rich wastewaters but the genetic elements of heterotrophic ammonia oxidation are poorly understood. Here, we isolated and identified a novel heterotrophic nitrifier, Alcaligenes ammonioxydans sp. nov. strain HO-1, oxidizing ammonia to hydroxylamine and ending in the production of N2 gas. Genome analysis revealed that strain HO-1 encoded a complete denitrification pathway but lacks any genes coding for homologous to known ammonia monooxygenases or hydroxylamine oxidoreductases. Our results demonstrated strain HO-1 denitrified nitrite (not nitrate) to N2 and N2O at anaerobic and aerobic conditions respectively. Further experiments demonstrated that inhibition of aerobic denitrification did not stop ammonia oxidation and N2 production. A gene cluster (dnfT1RT2ABCD) was cloned from strain HO-1 and enabled E. coli accumulated hydroxylamine. Sub-cloning showed that genetic cluster dnfAB or dnfABC already enabled E. coli cells to produce hydroxylamine and further to 15N2 from (15NH4)2SO4. Transcriptome analysis revealed these three genes dnfA, dnfB and dnfC were significantly upregulated in response to ammonia stimulation. Taken together, we concluded that strain HO-1 has a novel dnf genetic cluster for ammonia oxidation and this dnf genetic cluster encoded a previously unknown pathway of direct ammonia oxidation (Dirammox) to N2.
- Published
- 2021
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29. Collective fast neutrino flavor conversions in a 1D box: Initial conditions and long-term evolution
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Zewei Xiong, Meng-Ru Wu, Chun-Yu Lin, and Manu George
- Subjects
High Energy Astrophysical Phenomena (astro-ph.HE) ,Physics ,Particle physics ,010308 nuclear & particles physics ,High Energy Physics::Phenomenology ,FOS: Physical sciences ,Inverse ,Electron ,01 natural sciences ,Lepton number ,Spectral line ,High Energy Physics - Phenomenology ,High Energy Physics - Phenomenology (hep-ph) ,Phase space ,0103 physical sciences ,Periodic boundary conditions ,ddc:530 ,High Energy Physics::Experiment ,Neutrino ,Astrophysics - High Energy Astrophysical Phenomena ,010306 general physics ,Translational symmetry - Abstract
We perform numerical simulations of fast collective neutrino flavor conversions in an one-dimensional box mimicking a system with the periodic boundary condition in one spatial direction and translation symmetry in the other two dimensions. We evolve the system over several thousands of the characteristic timescale (inverse of the interaction strength) with different initial $\bar\nu_e$ to $\nu_e$ number density ratios and different initial seed perturbations. We find that small scale structures are formed due to the interaction of the flavor waves. This results in nearly flavor depolarization in a certain neutrino phase space, when averaged over the entire box. Specifically, systems with initially equal number of $\nu_e$ and $\bar\nu_e$ can reach full flavor depolarization for the entire neutrino electron lepton number ($\nu$ELN) angular spectra. For systems with initially unequal $\nu_e$ and $\bar\nu_e$, flavor depolarization can only be reached in one side of the $\nu$ELN spectra, dictated by the net neutrino $e-x$ lepton number conservation. Quantitatively small differences depending on the initial perturbations are also found when different perturbation seeds are applied. Our numerical study here provides new insights for efforts aiming to include impact of fast flavor conversions in astrophysical simulations while calls for better analytical understanding accounting for the evolution of fast flavor conversions., Comment: published version in PRD
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- 2021
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30. Constraints on $R$-process Nucleosynthesis from $^{129}$I and $^{247}$Cm in the Early Solar System
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Projjwal Banerjee, Jeena S K, and Meng-Ru Wu
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Astrophysics - Solar and Stellar Astrophysics ,Space and Planetary Science ,Astrophysics of Galaxies (astro-ph.GA) ,FOS: Physical sciences ,Astronomy and Astrophysics ,Astrophysics - Astrophysics of Galaxies ,Solar and Stellar Astrophysics (astro-ph.SR) - Abstract
GW170817 has confirmed binary neutron star mergers as one of the sites for rapid neutron capture ($r$) process. However, there are large theoretical and experimental uncertainties associated with the resulting nucleosynthesis calculations and additional sites may be needed to explain all the existing observations. In this regard, abundances of short-lived radioactive isotopes (SLRIs) in the early solar system (ESS), that are synthesized exclusively by $r$-process, can provide independent clues regarding the nature of $r$-process events. In this work, we study the evolution of $r$-process SLRIs $^{129}$I and $^{247}$Cm as well as the corresponding reference isotopes $^{127}$I and $^{235}$U at the Solar location. We consider up to three different sources that have distinct $^{129}$I/$^{247}$Cm production ratios corresponding to the varied $r$-process conditions in different astrophysical scenarios. In contrast to the results found by C\^ot\'e et al. (2021), we find that $^{129}$I and $^{247}$Cm in the ESS do not come entirely from a single major event but get contributions from at least two more minor contributors. This has a dramatic effect on the evolution of the $^{129}$I/$^{247}$Cm ratio, such that the measured ESS value in meteorites may not correspond to that of the "$last$" major $r$-process event. Interestingly, however, we find that the $^{129}$I/$^{247}$Cm ratio, in combination with the observed $^{129}$I/$^{127}$I and $^{247}$Cm/$^{235}$U ratio in the ESS, can still provide important constraints on the properties of proposed $r$-process sources operating in the Milky Way., Comment: 14 pages, 5 figures, 7 tables
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- 2021
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31. Identification and characterization of a novel hydroxylamine oxidase, DnfA, that catalyzes the oxidation of hydroxylamine to N2.
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Meng-Ru Wu, Li-Li Miao, Ying Liu, Xin-Xin Qian, Ting-Ting Hou, Guo-Min Ai, Lu Yu, Lan Ma, Xi-Yan Gao, Ya-Ling Qin, Hai-Zhen Zhu, Lei Du, Sheng-Ying Li, Chang-Lin Tian, De-Feng Li, Zhi-Pei Liu, and Shuang-Jiang Liu
- Subjects
- *
HYDROXYLAMINE , *ELECTRON paramagnetic resonance , *OXIDATION-reduction reaction , *NITROGEN , *ENZYME kinetics , *OXIDATION , *NITROGEN removal (Water purification) - Abstract
Nitrogen (N2) gas in the atmosphere is partially replenished by microbial denitrification of ammonia. Recent study has shown that Alcaligenes ammonioxydans oxidizes ammonia to dinitrogen via a process featuring the intermediate hydroxylamine, termed "Dirammox" (direct ammonia oxidation). However, the unique biochemistry of this process remains unknown. Here, we report an enzyme involved in Dirammox that catalyzes the conversion of hydroxylamine to N2. We tested previously annotated proteins involved in redox reactions, DnfA, DnfB, and DnfC, to determine their ability to catalyze the oxidation of ammonia or hydroxylamine. Our results showed that none of these proteins bound to ammonia or catalyzed its oxidation; however, we did find DnfA bound to hydroxylamine. Further experiments demonstrated that, in the presence of NADH and FAD, DnfA catalyzed the conversion of 15N-labeled hydroxylamine to 15N2. This conversion did not happen under oxygen (O2)-free conditions. Thus, we concluded that DnfA encodes a hydroxylamine oxidase. We demonstrate that DnfA is not homologous to any known hydroxylamine oxidoreductases and contains a diiron center, which was shown to be involved in catalysis via electron paramagnetic resonance experiments. Furthermore, enzyme kinetics of DnfA were assayed, revealing a Km of 92.9 ± 3.0 μM for hydroxylamine and a kcat of 0.028 ± 0.001 s-1. Finally, we show that DnfA was localized in the cytoplasm and periplasm as well as in tubular membrane invaginations in HO-1 cells. To the best of our knowledge, we conclude that DnfA is the first enzyme discovered that catalyzes oxidation of hydroxylamine to N2. [ABSTRACT FROM AUTHOR]
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- 2022
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32. A novel oxidase from Alcaligenes sp. HO-1 oxidizes hydroxylamine to N2
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Meng-Ru Wu, Li-Li Miao, Ying Liu, Ting-Ting Hou, Guo-Min Ai, Lan Ma, Hai-Zhen Zhu, Ya-Xin Zhu, Xi-Yan Gao, Xin-Xin Qian, Ya-Ling Qin, Tong Wu, Xi-Hui Shen, Cheng-Ying Jiang, Craig W. Herbold, Michael Wagner, De-Feng Li, Zhi-Pei Liu, and Shuang-Jiang Liu
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chemistry.chemical_classification ,Oxidase test ,Cytochrome ,biology ,Strain (chemistry) ,biology.organism_classification ,chemistry.chemical_compound ,Hydroxylamine ,Enzyme ,Biochemistry ,chemistry ,biology.protein ,Ammonium ,Heterologous expression ,Alcaligenes - Abstract
Hydroxylamine is a key intermediate of microbial ammonia oxidation and plays an important role in the biogeochemical cycling of N-compounds. Hydroxylamine is oxidized to NO or N2O by hydroxylamine oxidases or cytochrome P460 from heterotrophic or autotrophic bacteria, but its enzymatic oxidation to N2 has not yet been observed. Here, we report on the discovery of a novel oxidase that converts hydroxylamine to N2 from the newly isolated heterotrophic nitrifier Alcaligenes strain HO-1. Strain HO-1 accumulated hydroxylamine and produced N2 from ammonia oxidation. Using transcriptome analysis and heterologous expression via fosmid library screening, we identified three genes (dnfABC) of strain HO-1 that enabled E. coli cells not only to produce hydroxylamine from 15N-labelled ammonium but also to further convert it to 15N2. The three genes were individually cloned and expressed, and their translational products DnfA, DnfB, and DnfC were purified. In vitro DnfA bound to hydroxylamine and catalyzed the conversion of hydroxylamine to N2 in the presence of FAD, NADH and O2. Thus, DnfA was identified as a novel hydroxylamine oxidase and catalyzed a previously unknown N-N bond forming reaction with a yet-to-be discovered mechanism. DnfA homologs were detected in different bacterial groups, suggesting that hydroxylamine oxidation to nitrogen might occur in additional microbial taxa.
- Published
- 2020
33. Lifting the core collapse supernova bounds on keV mass sterile neutrinos
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Meng-Ru Wu, Suliga, Anna Malgorzata, and Tamborra, Irene
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Astrophysics::High Energy Astrophysical Phenomena ,High Energy Physics::Phenomenology ,High Energy Physics::Experiment - Abstract
We develop a radial- and time-dependent calculation of the $\nu_e$-$\nu_s$ mixing inside the supernovae core by taking into account matter enhanced resonances, reconversions, and collisional production of the sterile neutrinos. The dynamical feedback, generated by the sterile neutrino production on the chemical potentials of leptons and baryons as well as the thermodynamic properties of the core, has major consequences for the supernovae physics for large mixing angles ($\sin^2 2\theta > 10^{-10}$). We find that the self-consistent treatment of the electron-sterile neutrino mixing in the supernova core lifts the bounds on the sterile neutrino mass and mixing in the parameter space ($m_s$, $\sin^2 2\theta$) relevant for the dark matter searches.
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- 2020
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34. Probing Cosmic-Ray Accelerated Light Dark Matter with IceCube
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Yue-Lin Sming Tsai, Meng-Ru Wu, and Gang Guo
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Physics ,High Energy Astrophysical Phenomena (astro-ph.HE) ,010308 nuclear & particles physics ,Scattering ,Astrophysics::High Energy Astrophysical Phenomena ,Dark matter ,FOS: Physical sciences ,Astronomy and Astrophysics ,Cosmic ray ,Scale (descriptive set theory) ,Astrophysics ,01 natural sciences ,High Energy Physics - Experiment ,High Energy Physics - Experiment (hep-ex) ,High Energy Physics - Phenomenology ,High Energy Physics - Phenomenology (hep-ph) ,Neutrino detector ,0103 physical sciences ,Nucleon ,Astrophysics - High Energy Astrophysical Phenomena ,Light dark matter ,Energy (signal processing) - Abstract
The direct detection of particle dark matter through its scattering with nucleons is of fundamental importance to understand the nature of DM. In this work, we propose that the high-energy neutrino detectors like IceCube can be used to uniquely probe the DM-nucleon cross-section for high-energy DM of $\sim$ PeV, up-scattered by the high-energy cosmic rays. We derive for the first time strong constraints on the DM-nucleon cross-section down to $\sim 10^{-32}$ cm$^2$ at this energy scale for sub-GeV DM candidates. Such independent probe at energy scale far exceeding other existing direct detection experiments can therefore provide useful insights complementary to other searches., 16 pages, 6 figures. Published version
- Published
- 2020
35. Neutrino signal from proto-neutron star evolution: Effects of opacities from charged-current–neutrino interactions and inverse neutron decay
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Andreas Lohs, Yong Zhong Qian, Alan A. Dzhioev, Meng-Ru Wu, Gabriel Martínez-Pinedo, Tobias Fischer, and Gang Guo
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High Energy Astrophysical Phenomena (astro-ph.HE) ,Physics ,Nuclear Theory ,Astrophysics::High Energy Astrophysical Phenomena ,Star (game theory) ,High Energy Physics::Phenomenology ,FOS: Physical sciences ,Inverse ,Nuclear Theory (nucl-th) ,Nuclear physics ,Neutron star ,Stars ,Nucleosynthesis ,High Energy Physics::Experiment ,Neutron ,Neutrino ,Astrophysics - High Energy Astrophysical Phenomena ,Urca process - Abstract
We investigate the impact of charged current neutrino processes on the formation and evolution of neutrino spectra during the deleptonization of proto-neutron stars. To this end we develop the full kinematics of these reaction rates consistent with the nuclear equation of state, including weak magnetism contributions. This allows us to systematically study the impact of inelastic contributions and weak magnetism on the $\nu_e$ and $\bar\nu_e$ luminosities and average energies. Furthermore, we explore the role of the inverse neutron decay, also known as the direct Urca process, on the emitted spectra of $\bar\nu_e$. This process is commonly considered in the cooling scenario of cold neutron stars but has so far been neglected in the evolution of hot proto-neutron stars. We find that the inverse neutron decay becomes the dominating opacity source for low-energy $\bar\nu_e$. Accurate three-flavor Boltzmann neutrino transport enables us to relate the magnitude of neutrino fluxes and spectra to details of the treatment of weak processes. This allows us to quantify the corresponding impact on the conditions relevant for the nucleosynthesis in the neutrino-driven wind, which is ejected from the proto-neutron star surface during the deleptonization phase., Comment: 16 pages, 7 figures
- Published
- 2020
36. Fast neutrino flavor conversion, ejecta properties, and nucleosynthesis in newly-formed hypermassive remnants of neutron-star mergers
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Manu George, Irene Tamborra, Hans-Thomas Janka, Meng-Ru Wu, and Ricard Ardevol-Pulpillo
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High Energy Astrophysical Phenomena (astro-ph.HE) ,Physics ,010308 nuclear & particles physics ,Astrophysics::High Energy Astrophysical Phenomena ,High Energy Physics::Phenomenology ,FOS: Physical sciences ,Astrophysics ,Kilonova ,Mass ratio ,01 natural sciences ,7. Clean energy ,Neutron star ,13. Climate action ,Nucleosynthesis ,0103 physical sciences ,Astrophysics::Solar and Stellar Astrophysics ,Neutron ,Neutrino ,010306 general physics ,Ejecta ,Astrophysics - High Energy Astrophysical Phenomena ,Mass fraction ,Astrophysics::Galaxy Astrophysics - Abstract
Neutrinos emitted in the coalescence of two neutron stars affect the dynamics of the outflow ejecta and the nucleosynthesis of heavy elements. In this work, we analyze the neutrino emission properties and the conditions leading to the growth of flavor instabilities in merger remnants consisting of a hypermassive neutron star and an accretion disk during the first 10 ms after the merger. The analyses are based on hydrodynamical simulations that include a modeling of neutrino emission and absorption effects via the "Improved Leakage-Equilibration-Absorption Scheme" (ILEAS). We also examine the nucleosynthesis of the heavy elements via the rapid neutron-capture process (r-process) inside the material ejected during this phase. The dominant emission of $\bar\nu_e$ over $\nu_e$ from the merger remnant leads to favorable conditions for the occurrence of fast pairwise flavor conversions of neutrinos, independent of the chosen equation of state or the mass ratio of the binary. The nucleosynthesis outcome is very robust, ranging from the first to the third r-process peaks. In particular, more than $10^{-5}$ $M_\odot$ of strontium are produced in these early ejecta that may account for the GW170817 kilonova observation. We find that the amount of ejecta containing free neutrons after the $r$-process freeze-out, which may power early-time UV emission, is reduced by roughly a factor of 10 when compared to simulations that do not include weak interactions. Finally, the potential flavor equipartition between all neutrino flavors is mainly found to affect the nucleosynthesis outcome in the polar ejecta within $\lesssim 30^\circ$, by changing the amount of the produced iron-peak and first-peak nuclei, but it does not alter the lanthanide mass fraction therein., Comment: matches the published version
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- 2020
37. MVIN: Learning Multiview Items for Recommendation
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Yun-Wei Chu, Lun-Wei Ku, Shao-Yu Chu, Chang-You Tai, and Meng-Ru Wu
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FOS: Computer and information sciences ,Computer Science - Machine Learning ,Information retrieval ,Computer science ,Aggregate (data warehouse) ,Perspective (graphical) ,02 engineering and technology ,Recommender system ,Computer Science - Information Retrieval ,Machine Learning (cs.LG) ,Cold start ,020204 information systems ,0202 electrical engineering, electronic engineering, information engineering ,020201 artificial intelligence & image processing ,Layer (object-oriented design) ,Information Retrieval (cs.IR) - Abstract
Researchers have begun to utilize heterogeneous knowledge graphs (KGs) as auxiliary information in recommendation systems to mitigate the cold start and sparsity issues. However, utilizing a graph neural network (GNN) to capture information in KG and further apply in RS is still problematic as it is unable to see each item's properties from multiple perspectives. To address these issues, we propose the multi-view item network (MVIN), a GNN-based recommendation model which provides superior recommendations by describing items from a unique mixed view from user and entity angles. MVIN learns item representations from both the user view and the entity view. From the user view, user-oriented modules score and aggregate features to make recommendations from a personalized perspective constructed according to KG entities which incorporates user click information. From the entity view, the mixing layer contrasts layer-wise GCN information to further obtain comprehensive features from internal entity-entity interactions in the KG. We evaluate MVIN on three real-world datasets: MovieLens-1M (ML-1M), LFM-1b 2015 (LFM-1b), and Amazon-Book (AZ-book). Results show that MVIN significantly outperforms state-of-the-art methods on these three datasets. In addition, from user-view cases, we find that MVIN indeed captures entities that attract users. Figures further illustrate that mixing layers in a heterogeneous KG plays a vital role in neighborhood information aggregation.
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- 2020
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38. Neutron Star Mergers as the Main Source of R-process: Natal Kicks And Inside-Out Evolution to The Rescue
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Projjwal Banerjee, Meng-Ru Wu, Zhen Yuan, Observatoire astronomique de Strasbourg (ObAS), and Université de Strasbourg (UNISTRA)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)
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High Energy Astrophysical Phenomena (astro-ph.HE) ,Physics ,010504 meteorology & atmospheric sciences ,Milky Way ,FOS: Physical sciences ,Binary number ,Astronomy and Astrophysics ,Astrophysics ,Astrophysics - Astrophysics of Galaxies ,01 natural sciences ,Omega ,Galaxy ,Neutron star ,Stars ,Space and Planetary Science ,Astrophysics of Galaxies (astro-ph.GA) ,0103 physical sciences ,r-process ,Astrophysics - High Energy Astrophysical Phenomena ,[PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph] ,010303 astronomy & astrophysics ,0105 earth and related environmental sciences ,Delay time - Abstract
Binary neutron star mergers (BNSMs) is currently the most promising source of \textsl{r}-process thanks to the detection of GW170817. The estimated occurring frequency and the amount of mass ejected per merger indicate that BNSMs by itself can account for all the \textsl{r}-process enrichment in the Galaxy. However, the decreasing trend of [Eu/Fe] vs [Fe/H] of disk stars for [Fe/H]$\gtrsim -1$ in the solar neighborhood is inconsistent with the flat trend expected from BNSMs with a standard delay time distribution (DTD) $\propto t^{-1}$. This has led to the suggestion that either additional sources or modification to the DTD of BNSMs is required to match the observations. We investigate the effects of natal kicks received during the birth of neutron star binaries on the chemical evolution of \textsl{r}-process element Eu in the Milky Way by combining the results from the galactic dynamics code \textsc{galpy} with a one-zone Galactic chemical evolution model \textsc{omega}. We show that when key inputs from simulations of the inside-out disk evolution are combined with natal kicks, BNSMs can naturally reproduce the observed decreasing trend of [Eu/Fe] with [Fe/H] in the solar neighborhood without the need for modification to the DTD or additional \textsl{r}-process sources., Comment: 12 pages, 8 figures, text updated and figures added after review
- Published
- 2020
39. Elastic and Inelastic Scattering of Cosmic-Rays on Sub-GeV Dark Matter
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Gang Guo, Qiang Yuan, Meng-Ru Wu, and Yue-Lin Sming Tsai
- Subjects
Physics ,High Energy Astrophysical Phenomena (astro-ph.HE) ,Particle physics ,Annihilation ,Meson ,010308 nuclear & particles physics ,Astrophysics::High Energy Astrophysical Phenomena ,Dark matter ,FOS: Physical sciences ,Cosmic ray ,Inelastic scattering ,01 natural sciences ,MiniBooNE ,High Energy Physics - Phenomenology ,High Energy Physics - Phenomenology (hep-ph) ,0103 physical sciences ,High Energy Physics::Experiment ,Neutrino ,010306 general physics ,Astrophysics - High Energy Astrophysical Phenomena ,Nuclear Experiment ,Fermi Gamma-ray Space Telescope - Abstract
We revisit the signatures from collisions of cosmic-rays on sub-GeV dark matter (DM) in the Milky Way. In addition to the upscattered DM component that can be probed by existing DM and neutrino experiments widely discussed, we examine the associated signals in $\gamma$-rays and neutrinos that span a wide energy range due to the inelastic scatterings. Assuming a simple vector portal DM model for illustration, we compute both the upscattered DM flux by cosmic-ray protons, and the resulting emission of secondary $\gamma$-rays and high-energy neutrinos from proton excitation, hadronization, and the subsequent meson decay. We derive limits on coupling constants in the vector portal model using data from the $\gamma$-ray and high-energy neutrino telescopes including Fermi, H.E.S.S. and IceCube. These limits are compared to those obtained by considering the upscattered DM signals at the low-energy DM/neutrino detectors XENON1T/MiniBooNE and the IceCube. For this particular model, the limits are set predominantly by non-detection of the upscattered DM events in XENON1T, for most of the DM mass range due to the large scattering cross section at low energies. Nevertheless, our study demonstrates that the $\gamma$-ray and neutrino signals, traditionally considered as indirect probes for DM annihilation and decay, can also be directly used to constrain the DM--nucleon interaction in complementary to the direct search experiments., Comment: 17 pages, 7 figures; Published version
- Published
- 2020
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40. Lifting the core-collapse supernova bounds on keV-mass sterile neutrinos
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Anna M. Suliga, Irene Tamborra, and Meng-Ru Wu
- Subjects
Physics ,High Energy Astrophysical Phenomena (astro-ph.HE) ,Sterile neutrino ,Particle physics ,010308 nuclear & particles physics ,Astrophysics::High Energy Astrophysical Phenomena ,Dark matter ,High Energy Physics::Phenomenology ,FOS: Physical sciences ,Astronomy and Astrophysics ,Electron ,Type II supernova ,01 natural sciences ,Lepton number ,Supernova ,High Energy Physics - Phenomenology ,High Energy Physics - Phenomenology (hep-ph) ,0103 physical sciences ,High Energy Physics::Experiment ,Neutrino ,Astrophysics - High Energy Astrophysical Phenomena ,Mixing (physics) - Abstract
We explore the energy and entropy transport as well as the lepton number variation induced from the mixing between electron and sterile neutrinos with keV mass in the supernova core. We develop a radial- and time-dependent treatment of the sterile-electron neutrino mixing, by including ordinary matter effects, reconversions between sterile and electron antineutrinos, as well as the collisional production of sterile particles for the first time. The dynamical feedback due to the production of sterile particles on the composition and thermodynamic properties of the core only leads to major implications for the supernova physics for large mixing angles ($\sin^2 2 \theta > 10^{-10}$). Our findings suggest that a self-consistent appraisal of the electron-sterile conversion physics in the supernova core would relax the bounds on the sterile neutrino mixing parameters reported in the literature for mixing angles smaller than $10^{-6}$, leaving the parameter space of the mass and mixing angles of sterile neutrinos relevant to dark matter searches unconstrained by supernovae., Comment: 30 pages, 15 figures. Minor changes, conclusions unchanged. Matches version accepted in JCAP
- Published
- 2020
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41. r-Process Sites, their Ejecta Composition, and their Imprint in Galactic Chemical Evolution
- Author
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Meng-Ru Wu, Benjamin Wehmeyer, and Friedrich-Karl Thielemann
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Chemical evolution ,Physics ,History ,r-process ,ddc:530 ,Composition (combinatorics) ,Ejecta ,Computer Science Applications ,Education ,Astrobiology - Abstract
Nuclear Physics in Astrophysics IX, NPA-IX, Frankfurt am Main, Germany, 15 Sep 2019 - 20 Sep 2019; Journal of physics / Conference series 1668, 012044 (2020). doi:10.1088/1742-6596/1668/1/012044, Published by IOP Publ., Bristol
- Published
- 2020
42. Multimessenger Asteroseismology of Core-Collapse Supernovae
- Author
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Irene Tamborra, Meng-Ru Wu, John Ryan Westernacher-Schneider, Sean M. Couch, Evan O'Connor, Felix Malmenbeck, and E. O’Sullivan
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Physics ,High Energy Astrophysical Phenomena (astro-ph.HE) ,Gravitational wave ,Astrophysics::High Energy Astrophysical Phenomena ,Mode (statistics) ,Collapse (topology) ,FOS: Physical sciences ,Astrophysics ,General Relativity and Quantum Cosmology (gr-qc) ,Asteroseismology ,General Relativity and Quantum Cosmology ,Core (optical fiber) ,Supernova ,Neutrino ,Astrophysics - High Energy Astrophysical Phenomena - Abstract
We investigate correlated gravitational wave and neutrino signals from rotating core-collapse supernovae with simulations. Using an improved mode identification procedure based on mode function matching, we show that a linear quadrupolar mode of the core produces a dual imprint on gravitational waves and neutrinos in the early post-bounce phase of the supernova. The angular harmonics of the neutrino emission are consistent with the mode energy around the neutrinospheres, which points to a mechanism for the imprint on neutrinos. Thus, neutrinos carry information about the mode amplitude in the outer region of the core, whereas gravitational waves probe deeper in. We also find that the best-fit mode function has a frequency bounded above by $\sim 420$ Hz, and yet the mode's frequency in our simulations is $\sim 15\%$ higher, due to the use of Newtonian hydrodynamics and a widely used pseudo-Newtonian gravity approximation. This overestimation is particularly important for the analysis of gravitational wave detectability and asteroseismology, pointing to limitations of pseudo-Newtonian approaches for these purposes, possibly even resulting in excitation of incorrect modes. In addition, mode frequency matching (as opposed to mode function matching) could be resulting in mode misidentification in recent work. Lastly, we evaluate the prospects of a multimessenger detection of the mode using current technology. The detection of the imprint on neutrinos is most challenging, with a maximum detection distance of $\sim\!1$ kpc using the IceCube Neutrino Observatory. The maximum distance for detecting the complementary gravitational wave imprint is $\sim\!5$ kpc using Advanced LIGO at design sensitivity., 25 pages, 16 figures. Version accepted to PRD. Error corrected, new appendices and figures added
- Published
- 2019
43. Acoustical simulation of a muffler internally inserted with an extended tube using the FEM
- Author
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Meng-Ru Wu, Min-Chie Chiu, and Ying-Chun Chang
- Subjects
Muffler ,Materials science ,Acoustics ,fungi ,food and beverages ,Baffle ,010103 numerical & computational mathematics ,02 engineering and technology ,01 natural sciences ,Finite element method ,law.invention ,Noise ,law ,0202 electrical engineering, electronic engineering, information engineering ,020201 artificial intelligence & image processing ,Tube (fluid conveyance) ,0101 mathematics - Abstract
A reactive muffler has been widely used in depressing venting noise emitted from industrial plants. As can be seen in a previous study, a perforated/ non-perforated tube inserted inside a chamber w...
- Published
- 2018
44. Fingerprints of Heavy-Element Nucleosynthesis in the Late-Time Lightcurves of Kilonovae
- Author
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Jennifer Barnes, Brian D. Metzger, Gabriel Martínez-Pinedo, and Meng-Ru Wu
- Subjects
High Energy Astrophysical Phenomena (astro-ph.HE) ,Mass number ,Physics ,Nuclear Theory ,FOS: Physical sciences ,General Physics and Astronomy ,Order (ring theory) ,Astrophysics ,Kilonova ,01 natural sciences ,Nuclear Theory (nucl-th) ,Neutron star ,Decay energy ,Nucleosynthesis ,0103 physical sciences ,Production (computer science) ,Astrophysics - High Energy Astrophysical Phenomena ,010306 general physics ,Energy (signal processing) - Abstract
The kilonova emission observed following the binary neutron star merger event GW170817 provided the first direct evidence for the synthesis of heavy nuclei through the r-process. The late-time transition in the spectral energy distribution to near-infrared wavelengths was interpreted as indicating the production of lanthanide nuclei, with atomic mass number A>140. However, compelling evidence for the presence of heavier third-peak r-process elements (e.g., gold, platinum) or translead nuclei remains elusive. At early times (~days) most of the r-process heating arises from a large statistical ensemble of beta-decays, which thermalize efficiently while the ejecta is still dense, generating a heating rate that is reasonably approximated by a single power-law. However, at later times (weeks to months), the decay energy input can possibly be dominated by a discrete number of alpha-decays, 223Ra (half-life t_{1/2}=11.43d), 225Ac (t_{1/2}=10.0d, following the beta-decay of 225Ra with t_{1/2}=14.9d), and the fissioning isotope 254Cf (t_{1/2}=60.5d), which liberate more energy per decay and thermalize with greater efficiency than beta-decay products. Late-time nebular observations of kilonovae which constrain the radioactive power provide the potential to identify signatures of these individual isotopes, thus confirming the production of heavy nuclei. In order to constrain the bolometric light to the required accuracy, multi-epoch & wide-band observations are required with sensitive instruments like the James Webb Space Telescope. In addition, by comparing the nuclear heating rate obtained with an abundance distribution following the Solar r abundance pattern, to the bolometric lightcurve of AT2017gfo, we find that the yet-uncertain r abundance of 72Ge plays a decisive role in powering the lightcurve, if one assumes that GW170817 has produced a full range of the Solar r abundances down to A~70., 11 pages, 8 figures including supplemental material, accepted by PRL
- Published
- 2019
45. Deregulation of phytoene-β-carotene synthase results in derepression of astaxanthin synthesis at high glucose concentration in Phaffia rhodozyma astaxanthin-overproducing strain MK19
- Author
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Meng-Ru Wu, Ying Li, Shuang Chi, Zhi-Pei Liu, and Li-Li Miao
- Subjects
Microbiology (medical) ,Metabolite ,lcsh:QR1-502 ,Biology ,Carbohydrate metabolism ,Xanthophylls ,Microbiology ,lcsh:Microbiology ,Gene Expression Regulation, Enzymologic ,Fungal Proteins ,03 medical and health sciences ,chemistry.chemical_compound ,Phytoene ,Astaxanthin ,Gene Expression Regulation, Fungal ,Gene expression ,Carotenoid ,Derepression ,Phaffia rhodozyma ,chemistry.chemical_classification ,0303 health sciences ,Glucose metabolism ,030306 microbiology ,Basidiomycota ,Gene Expression Profiling ,beta Carotene ,Yeast ,Biosynthetic Pathways ,Culture Media ,Phytoene-β-carotene synthase ,Glucose ,Biochemistry ,chemistry ,Geranylgeranyl-Diphosphate Geranylgeranyltransferase ,Research Article - Abstract
Background A major obstacle to industrial-scale astaxanthin production by the yeast Phaffia rhodozyma is the strong inhibitory effect of high glucose concentration on astaxanthin synthesis. We investigated, for the first time, the mechanism of the regulatory effect of high glucose (> 100 g/L) at the metabolite and transcription levels. Results Total carotenoid, β-carotene, and astaxanthin contents were greatly reduced in wild-type JCM9042 at high (110 g/L) glucose; in particular, β-carotene content at 24–72 h was only 14–17% of that at low (40 g/L) glucose. The inhibitory effect of high glucose on astaxanthin synthesis appeared to be due mainly to repression of lycopene-to-β-carotene and β-carotene-to-astaxanthin steps in the pathway. Expression of carotenogenic genes crtE, pbs, and ast was also strongly inhibited by high glucose; such inhibition was mediated by creA, a global negative regulator of carotenogenic genes which is strongly induced by glucose. In contrast, astaxanthin-overproducing, glucose metabolic derepression mutant strain MK19 displayed de-inhibition of astaxanthin synthesis at 110 g/L glucose; this de-inhibition was due mainly to deregulation of pbs and ast expression, which in turn resulted from low creA expression. Failure of glucose to induce the genes reg1 and hxk2, which maintain CreA activity, also accounts for the fact that astaxanthin synthesis in MK19 was not repressed at high glucose. Conclusion We conclude that astaxanthin synthesis in MK19 at high glucose is enhanced primarily through derepression of carotenogenic genes (particularly pbs), and that this process is mediated by CreA, Reg1, and Hxk2 in the glucose signaling pathway.
- Published
- 2019
46. Fission and the r-process nucleosynthesis of translead nuclei in neutron star mergers
- Author
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L. M. Robledo, Gabriel Martínez-Pinedo, Meng-Ru Wu, and Samuel A. Giuliani
- Subjects
Nuclear Theory ,Fission ,Astrophysics::High Energy Astrophysical Phenomena ,FOS: Physical sciences ,Kilonova ,01 natural sciences ,7. Clean energy ,Nuclear physics ,Nuclear Theory (nucl-th) ,Nucleosynthesis ,0103 physical sciences ,Astrophysics::Solar and Stellar Astrophysics ,Neutron ,010306 general physics ,Ejecta ,Nuclear Experiment ,Astrophysics::Galaxy Astrophysics ,Spontaneous fission ,Physics ,High Energy Astrophysical Phenomena (astro-ph.HE) ,010308 nuclear & particles physics ,Neutron star ,13. Climate action ,r-process ,Astrophysics - High Energy Astrophysical Phenomena - Abstract
We study the impact of fission on the production and destruction of translead nuclei during the r-process nucleosynthesis occurring in neutron-star mergers. Abundance patterns and rates of nuclear energy production are obtained for different ejecta conditions using three sets of stellar reaction rates, one of which is based on microscopic and consistent calculations of nuclear masses, fission barriers, and collective inertias. We show that the accumulation of fissioning material during the r process can strongly affect the free neutron abundance after the r-process freeze-out. This leads to a significant impact on the abundances of heavy nuclei that undergo $\alpha$ decay or spontaneous fission, affecting the radioactive energy production by the ejecta at timescales relevant for kilonova emission., Comment: 10 pages, 9 figures
- Published
- 2019
- Full Text
- View/download PDF
47. Tau lepton asymmetry by sterile neutrino emission -- Moving beyond one-zone supernova models
- Author
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Irene Tamborra, Meng-Ru Wu, and Anna M. Suliga
- Subjects
Physics ,High Energy Astrophysical Phenomena (astro-ph.HE) ,Sterile neutrino ,Energy loss ,010308 nuclear & particles physics ,media_common.quotation_subject ,Astrophysics::High Energy Astrophysical Phenomena ,High Energy Physics::Phenomenology ,FOS: Physical sciences ,Astronomy and Astrophysics ,Astrophysics ,01 natural sciences ,Asymmetry ,Accretion (astrophysics) ,High Energy Physics - Phenomenology ,Supernova ,High Energy Physics - Phenomenology (hep-ph) ,0103 physical sciences ,High Energy Physics::Experiment ,Neutrino ,Astrophysics - High Energy Astrophysical Phenomena ,Mixing (physics) ,Lepton ,media_common - Abstract
The mixing of active neutrinos with their sterile counterparts with keV mass is known to have a potentially major impact on the energy loss from the supernova core. By relying on a set of three static hydrodynamical backgrounds mimicking the early accretion phase and the Kelvin-Helmoltz cooling phase of a supernova, we develop the first self-consistent, radial- and time-dependent treatment of sterile and tau neutrinos mixing in the dense stellar core. We follow the flavor evolution by including ordinary matter effects, collisional production of sterile neutrinos, as well as reconversions of sterile states into active ones. The dynamical feedback of the sterile neutrino production on the matter background leads to the development of a tau lepton asymmetry that grows in time until it reaches a value larger than 0.15. Our results hint towards significant implications for the supernova physics, and call for a self-consistent modeling of the sterile neutrino transport in the supernova core to constrain the mixing parameters of sterile neutrinos., Comment: 31 pages, including 18 figures. Discussion on supernova bounds on sterile neutrinos expanded; conclusions unchanged. Matches version accepted for publication in JCAP
- Published
- 2019
- Full Text
- View/download PDF
48. New constraint from supernova explosions on light particles beyond the Standard Model
- Author
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Allan Sung, Huitzu Tu, and Meng-Ru Wu
- Subjects
Physics ,High Energy Astrophysical Phenomena (astro-ph.HE) ,Photon ,010308 nuclear & particles physics ,Physics beyond the Standard Model ,Star (game theory) ,Astrophysics::High Energy Astrophysical Phenomena ,FOS: Physical sciences ,Astrophysics ,Astrophysics::Cosmology and Extragalactic Astrophysics ,Computer Science::Digital Libraries ,01 natural sciences ,Dark photon ,High Energy Physics - Phenomenology ,Supernova ,High Energy Physics - Phenomenology (hep-ph) ,0103 physical sciences ,Astrophysics::Solar and Stellar Astrophysics ,Astrophysics - High Energy Astrophysical Phenomena ,010306 general physics ,Mixing (physics) ,Energy (signal processing) ,Order of magnitude ,Astrophysics::Galaxy Astrophysics - Abstract
We propose a new constraint on light (sub-GeV) particles beyond the Standard Model that can be produced inside the proto-neutron star core resulting from the core-collapse supernova explosion. It is derived by demanding that the energy carried by exotic particles being transferred to the progenitor stellar envelopes must not exceed the explosion energy of $\lesssim 2\cdot 10^{51}$ erg of observed supernovae. We show specifically that for the case of a dark photon which kinetically mixes with the SM photon and decays predominantly to an $e^\pm$ pair, a smaller mixing parameter of one order of magnitude below the well-established supernova cooling bound can be excluded. Furthermore, our bound fills the gap between the cooling bound and the region constrained by (non)observation of gamma rays produced from supernovae for dark photons lighter than ~ 20 MeV. Our result also rules out the possibility of aiding successful supernova explosions by transferring energy from the supernova core to the shock with exotic particles., Comment: 6 pages, 3 figures, matches version published in PRD
- Published
- 2019
- Full Text
- View/download PDF
49. Constraining sterile neutrinos by core-collapse supernovae with multiple detectors
- Author
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J. Tang, TseChun Wang, and Meng-Ru Wu
- Subjects
High Energy Astrophysical Phenomena (astro-ph.HE) ,Physics ,Sterile neutrino ,Physics::Instrumentation and Detectors ,010308 nuclear & particles physics ,Astrophysics::High Energy Astrophysical Phenomena ,High Energy Physics::Phenomenology ,FOS: Physical sciences ,Astronomy and Astrophysics ,Astrophysics ,Astrophysics - Astrophysics of Galaxies ,01 natural sciences ,Cosmology ,Luminosity ,High Energy Physics - Phenomenology ,Supernova ,High Energy Physics - Phenomenology (hep-ph) ,Neutrino detector ,Astrophysics of Galaxies (astro-ph.GA) ,0103 physical sciences ,High Energy Physics::Experiment ,Neutrino ,Astrophysics - High Energy Astrophysical Phenomena ,Event (particle physics) ,Mixing (physics) - Abstract
The eV-scale sterile neutrino has been proposed to explain some anomalous results in experiments, \textit{such as} the deficit of reactor neutrino fluxes and the excess of $\bar{\nu}_\mu\to\bar{\nu}_e$ in LSND. This hypothesis can be tested by future core-collapse supernova neutrino detection independently since the active-sterile mixing scheme affects the flavor conversion of neutrinos inside the supernova. In this work, we compute the predicted supernova neutrino events in future detectors -- DUNE, Hyper-K, and JUNO -- for neutrinos emitted during the neutronization burst phase when the luminosity of $\nu_e$ dominates the other flavors. We find that for a supernova occurring within 10 kpc, the difference in the event numbers with and without sterile neutrinos allows to exclude the sterile neutrino hypothesis at more than $99\%$ confidence level robustly. The derived constraints on sterile neutrinos mixing parameters are comparably better than the results from cosmology and on-going or proposed reactor experiments by more than two orders of magnitude in the $\sin^22\theta_{14}$-$\Delta m_{41}^2$ plane., Comment: 24 pages, 12 figures, 4 tables
- Published
- 2020
50. Production of the entire range ofr-process nuclides by black hole accretion disc outflows from neutron star mergers
- Author
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Gabriel Martínez-Pinedo, Meng-Ru Wu, Brian D. Metzger, and Rodrigo Fernández
- Subjects
Nuclear reaction ,Solar System ,Nuclear Theory ,Astrophysics::High Energy Astrophysical Phenomena ,FOS: Physical sciences ,General Relativity and Quantum Cosmology (gr-qc) ,Astrophysics::Cosmology and Extragalactic Astrophysics ,Astrophysics ,Kilonova ,01 natural sciences ,7. Clean energy ,General Relativity and Quantum Cosmology ,Nuclear Theory (nucl-th) ,Nucleosynthesis ,0103 physical sciences ,Astrophysics::Solar and Stellar Astrophysics ,010303 astronomy & astrophysics ,Solar and Stellar Astrophysics (astro-ph.SR) ,Astrophysics::Galaxy Astrophysics ,High Energy Astrophysical Phenomena (astro-ph.HE) ,Physics ,010308 nuclear & particles physics ,Astronomy ,Astronomy and Astrophysics ,Galaxy ,Stars ,Neutron star ,Astrophysics - Solar and Stellar Astrophysics ,13. Climate action ,Space and Planetary Science ,r-process ,Astrophysics - High Energy Astrophysical Phenomena - Abstract
We consider $r$-process nucleosynthesis in outflows from black hole accretion discs formed in double neutron star and neutron star -- black hole mergers. These outflows, powered by angular momentum transport processes and nuclear recombination, represent an important -- and in some cases dominant -- contribution to the total mass ejected by the merger. Here we calculate the nucleosynthesis yields from disc outflows using thermodynamic trajectories from hydrodynamic simulations, coupled to a nuclear reaction network. We find that outflows produce a robust abundance pattern around the second $r$-process peak (mass number $A \sim 130$), independent of model parameters, with significant production of $A < 130$ nuclei. This implies that dynamical ejecta with high electron fraction may not be required to explain the observed abundances of $r$-process elements in metal poor stars. Disc outflows reach the third peak ($ A \sim 195$) in most of our simulations, although the amounts produced depend sensitively on the disc viscosity, initial mass or entropy of the torus, and nuclear physics inputs. Some of our models produce an abundance spike at $A = 132$ that is absent in the Solar system $r$-process distribution. The spike arises from convection in the disc and depends on the treatment of nuclear heating in the simulations. We conclude that disc outflows provide an important -- and perhaps dominant -- contribution to the $r$-process yields of compact binary mergers, and hence must be included when assessing the contribution of these systems to the inventory of $r$-process elements in the Galaxy., minor modifications, matches the published version
- Published
- 2016
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