Strong dynamical interactions among stars and compact objects are expected in a variety of astrophysical settings, such as star clusters and the disks of active galactic nuclei. Via a suite of 3D hydrodynamics simulations using the moving-mesh code AREPO, we investigate the formation of transient phenomena and their properties in close encounters between an 2M⊙ or 20M⊙ equal-mass circular binary star and single 20M⊙ black hole (BH). Stars can be disrupted by the BH during dynamical interactions, naturally producing electromagnetic transient phenomena. Encounters with impact parameters smaller than the semimajor axis of the initial binary frequently lead to a variety of transients whose electromagnetic signatures are qualitatively different from those of ordinary disruption events involving just two bodies. These include the simultaneous or successive disruptions of both stars and one full disruption of one star accompanied by successive partial disruptions of the other star. On the other hand, when the impact parameter is larger than the semimajor axis of the initial binary, the binary is either simply tidally perturbed or dissociated into bound and unbound single stars (“micro-Hills” mechanism). The dissociation of 20M⊙ binaries can produce a runaway star and an active BH moving away from one another. Also, the binary dissociation can either produce an interacting binary with the BH, or a non-interacting, hard binary; both could be candidates of BH high- and low-mass X-ray binaries. Hence our simulations especially confirm that strong encounters can lead to the formation of the (generally difficult to form) BH low-mass X-ray binaries.
The cosmic origin of the elements, the fundamental chemical building blocks of the universe, is still uncertain. Binary interactions play a key role in the evolution of many massive stars, yet their impact on chemical yields is poorly understood. Using the MESA stellar evolution code, we predict the chemical yields ejected in wind mass loss and the supernovae of single and binary-stripped stars. We do this with a large 162-isotope nuclear network at solar metallicity. We find that binary-stripped stars are more effective producers of the elements than single stars, due to their increased mass loss and an increased chance to eject their envelopes during a supernova. This increased production by binaries varies across the periodic table, with F and K being more significantly produced by binary-stripped stars than single stars. We find that the 12C/13C could be used as an indicator of the conservativeness of mass transfer, as 13C is preferentially ejected during mass transfer while 12C is preferentially ejected during wind mass loss. We identify a number of gamma-ray-emitting radioactive isotopes that may be used to help constrain progenitor and explosion models of core-collapse supernovae with next-generation gamma-ray detectors. For single stars we find that 44V and 52Mn are strong probes of the explosion model, while for binary-stripped stars it is 48Cr. Our findings highlight that binary-stripped stars are not equivalent to two single stars and that detailed stellar modeling is needed to predict their final nucleosynthetic yields.
The isospin violating processes ψ′→ψ(11P1)+π° and T′′→T(11P1)+π° are investigated in the framework of the multipole expansion in quantum chromodynamics. Using the rate of ψ′→ψ+π° as an input to determine the isospin violating vertex, we obtain the following branching ratios for the processes for . These are too small to be detected in the present experiments.
Relativistic magnetohydrodynamic shocks are efficient particle accelerators, often invoked in the models of gamma-ray bursts (GRBs) and shock-powered fast radio bursts (FRBs). Most theoretical studies assume a perpendicular shock with an ordered magnetic field perpendicular to the shock normal. However, the degree of magnetization σ and the magnetic field geometry in shock-powered GRB/FRB scenarios are still poorly constrained by observations. Analogous to the magnetization σ associated with the total field strength, we define a tangential magnetization σ⊥ associated with the tangential field component. We explore the jump conditions of magnetized relativistic shocks, either with an ordered field of arbitrary inclination angle or with a random field of arbitrary anisotropy. In either case, we find that the jump conditions of relativistic shocks are governed by the tangential magnetization σ⊥ instead of the total magnetization σ, insensitive to the inclination angles or the anisotropy of the pre-shock magnetic field. The approximated analytical solution developed in this work could serve as a quick check for numerical simulations and apply to theoretical studies of GRBs/FRBs with a more general field geometry.
Background: Many studies had shown that with global warming, heat waves may increase the mortality risk of Chinese populations. However, these findings are not consistent. Therefore, we elucidated the associations by meta-analysis and quantified the magnitude of these risks, as well as the underlying factors. Methods: We searched the China National Knowledge Infrastructure (CNKI), Wanfang database, PubMed, EMBASE, and Web of Science for literature screening up to Nov 10, 2022, to analyze the effect of heat waves on mortality in the Chinese population. Literature screening and data extraction were performed independently by two researchers and the data were merged by meta-analysis. In addition, we conducted subgroup analysis by sex, age, years of education, region, and number of events to explore the source of heterogeneity. Results: Fifteen related studies on the impact on heat waves of the death of Chinese people were included in this study. The results of the meta-analysis showed that heat waves were significantly associated with increased mortality from non-accidental deaths, cardiovascular diseases, stroke, respiratory diseases, and circulatory diseases in the Chinese population: non-accidental mortality (RR = 1.19, 95% CI: 1.13–1.27, P < .01), cardiovascular diseases (RR = 1.25, 95% CI: 1.14–1.38), stroke (RR = 1.11, 95% CI: 1.03–1.20), respiratory diseases (RR = 1.18, 95% CI: 1.09–1.28), and circulatory diseases (RR = 1.11, 95% CI: 1.06–1.17). Subgroup analyses showed that heat waves had a higher risk of non-accidental death for those with <6 years of education than for those with ≥6 years of education. Meta-regression analysis showed that the contribution of the study year to the inter studied heterogeneity was 50.57%. The sensitivity analysis showed that the exclusion of any single study did not materially alter the overall combined effect. The meta-analysis method indicated no obvious evidence of publication bias. Conclusions: The results of the review indicated that heat waves were associated with increased mortality in the Chinese population, that attention should be paid to high-risk groups, and that public health policies and strategies should be implemented to more effectively respond to and adapt to climate change.
Climate change affects ecosystems and human health in multiple dimensions. With the acceleration of climate change, climate-sensitive vector-borne diseases (VBDs) pose an increasing threat to public health. This paper summaries 10 publications on the impacts of climate change on ecosystems and human health; then it synthesizes the other existing literature to more broadly explain how climate change drives the transmission and spread of VBDs through an ecological perspective. We highlight the multi-dimensional nature of climate change, its interaction with other factors, and the impact of the COVID-19 pandemic on transmission and spread of VBDs, specifically including: (1) the generally nonlinear relationship of local climate (temperature, precipitation and wind) and VBD transmission, with temperature especially exhibiting an n-shape relation; (2) the time-lagged effect of regional climate phenomena (the El Niño–Southern Oscillation and North Atlantic Oscillation) on VBD transmission; (3) the u-shaped effect of extreme climate (heat waves, cold waves, floods, and droughts) on VBD spread; (4) how interactions between non-climatic (land use and human mobility) and climatic factors increase VBD transmission and spread; and (5) that the impact of the COVID-19 pandemic on climate change is debatable, and its impact on VBDs remains uncertain. By exploring the influence of climate change and non-climatic factors on VBD transmission and spread, this paper provides scientific understanding and guidance for their effective prevention and control.
Gravitational dynamic collapses of supermassive stars (SMSs) triggered at certain critical stages may give rise to black holes (BHs) in a broad mass range that populate the Universe including the early Universe. SMSs have been speculated to be the progenitors or seeds of supermassive black holes that power quasars and active galactic nuclei. We study magnetostatic equilibria and magnetohydrodynamic (MHD) radial (in)stability properties of non-rotating SMSs with quasi-spherical symmetry involving random transverse magnetic fields (RTMFs) using general relativity (GR). With RTMFs, the maxima of the gravitational binding energy marks the GR MHD transition from stability to instability and the RTMF does not modify the GR stability criterion significantly when ${\cal M}/\left|\Omega \right|\lesssim 0.1$ where $\cal M$ is the total magnetic energy and Ω is the total gravitational potential energy. When $0.1\lesssim {\cal M}/\left|\Omega \right|\lesssim 1$, nevertheless, the critical equilibria on the verge of GR MHD collapses or explosions may change drastically, raising the upper mass limit at the onset of GR MHD instability from ∼105 M⊙ to ∼106 M⊙ and higher. For ${\cal M}/\left|\Omega \right|\sim 1$, the evolution track of SMS is shifted towards the redder part of the H-R diagram, suggesting a sort of “magnetic reddening” associated with the stellar ‘magnetized envelope inflation’. By estimates, the RTMF energy stored in an SMS can be as large as ∼1057 erg, enough to power gamma-ray bursts, fast radio bursts or other forms of powerful electromagnetic wave bursts. It is possible for magnetized massive stars to dynamically form BHs in the mass range from several tens to thousands of solar masses without necessarily triggering the central electron-positron e± instability inside such stars – this fact is closely related to reports of LIGO-Virgo gravitational wave event scenario of binary BH mergers.
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