Abstract
We perform a systematic study of merging black hole (BH) binaries with compact star (CS) companions, including black hole–white dwarf (BH–WD), black hole–neutron star (BH–NS), and black ...hole–black hole (BH–BH) systems. Previous studies have shown that mass transfer stability and common envelope evolution can significantly affect the formation of merging BH–CS binaries through isolated binary evolution. With detailed binary evolution simulations, we obtain easy-to-use criteria for the occurrence of the common envelope phase in mass-transferring BH binaries with a nondegenerate donor, and incorporate the criteria into population synthesis calculations. To explore the impact of a possible mass gap between NSs and BHs on the properties of merging BH–CS binary population, we adopt different supernova mechanisms involving the
rapid
,
delayed
, and
stochastic
prescriptions to deal with the compact remnant masses and the natal kicks. Our calculations show that there are ∼10
5
–10
6
BH–CS binaries in the Milky Way, among which dozens are observable by future space-based gravitational wave detectors. We estimate that the local merger rate density of all BH–CS systems is ∼60–200 Gpc
−3
yr
−1
. While there are no low-mass BHs formed via
rapid
supernovae, both
delayed
and
stochastic
prescriptions predict that ∼100%/∼70%/∼30% of merging BH–WD/BH–NS/BH–BH binaries are likely to have BH components within the mass gap.
We present a systematic study of the X-ray binaries (XRBs) containing a black hole (BH) and a nondegenerate companion, in which mass transfer takes place via either capturing the companion's wind or ...Roche lobe overflow (RLO). As shown in our previous work, which focused on the formation and evolution of detached BH binaries, our assumed models relevant to BHs' progenitors predicted significantly different binary properties. In this paper, we further follow the evolutionary paths of BH systems that appear as XRBs. By use of both binary population synthesis and detailed binary evolution calculations, we can obtain the potential population of BH XRBs. Distributions at the current epoch of various binary parameters have been computed. The observed sample of wind-fed XRBs can be well reproduced under the assumptions of all of our models. Wind-fed XRBs are expected to be so rare ( 100) that only a couple such systems have been detected. Comparison of known RLO XRBs with the calculated distributions of various binary parameters indicates that only the models assuming relatively small masses for BH progenitors can roughly match the observations. Accordingly we estimate that there are hundreds of RLO XRBs in the Milky Way, of which the majority are low-mass XRBs. RLO systems may become ultraluminous X-ray sources (ULXs) if the BH accretes at a very high rate, and we expect that about a dozen ULXs with a BH accretor may exist in a Milky Way-like galaxy.
One great challenge in understanding the history of life is resolving the influence of environmental change on biodiversity. Simulated annealing and genetic algorithms were used to synthesize data ...from 11,000 marine fossil species, collected from more than 3000 stratigraphic sections, to generate a new Cambrian to Triassic biodiversity curve with an imputed temporal resolution of 26 ± 14.9 thousand years. This increased resolution clarifies the timing of known diversification and extinction events. Comparative analysis suggests that partial pressure of carbon dioxide (
co
) is the only environmental factor that seems to display a secular pattern similar to that of biodiversity, but this similarity was not confirmed when autocorrelation within that time series was analyzed by detrending. These results demonstrate that fossil data can provide the temporal and taxonomic resolutions necessary to test (paleo)biological hypotheses at a level of detail approaching those of long-term ecological analyses.
Optical observations of normal stars in binary systems with massive unseen objects have been proposed to search for candidate black holes (BHs) and provide a direct measurement of their dynamical ...masses. In this paper, we have performed binary population synthesis calculations to simulate the potential population of detached binaries containing BHs and normal-star companions in the Galaxy. We focus on the influence of the BH progenitors. In the traditional model, BHs in binaries evolve from stars more massive than ∼25M . However, it is difficult for this model to produce BH low-mass X-ray binaries. Recent investigations of massive star evolution have suggested that the BH progenitors have masses as low as ∼15M . Based on this model, we provide the expected distributions of various parameters for detached BH binaries with normal-star companions, including the component masses, the orbital parameters of the binary systems, the radial velocity semi-amplitudes, and the astrometric signatures of the optical companions. Our calculations show that there are thousands of such detached binaries in the Galaxy, and hundreds of them are potentially observable systems with luminous companions brighter than 20 mag. In addition, detached BH binaries are dominated by those with main-sequence companions and only a small percent of them are expected to have giant companions.
Gastric cancer is a deadly disease and remains the third leading cause of cancer-related death worldwide. The 5-year overall survival rate of patients with early-stage localized gastric cancer is ...more than 60%, whereas that of patients with distant metastasis is less than 5%. Surgical resection is the best option for early-stage gastric cancer, while chemotherapy is mainly used in the middle and advanced stages of this disease, despite the frequently reported treatment failure due to chemotherapy resistance. Therefore, there is an unmet medical need for identifying new biomarkers for the early diagnosis and proper management of patients, to achieve the best response to treatment. Long non-coding RNAs (lncRNAs) in body fluids have attracted widespread attention as biomarkers for early screening, diagnosis, treatment, prognosis, and responses to drugs due to the high specificity and sensitivity. In the present review, we focus on the clinical potential of lncRNAs as biomarkers in liquid biopsies in the diagnosis and prognosis of gastric cancer. We also comprehensively discuss the roles of lncRNAs and their molecular mechanisms in gastric cancer chemoresistance as well as their potential as therapeutic targets for gastric cancer precision medicine.
Amyotrophic lateral sclerosis (ALS) was initially thought to be associated with oxidative stress when it was first linked to mutant superoxide dismutase 1 (SOD1). The subsequent discovery of ...ALS-linked genes functioning in RNA processing and proteostasis raised the question of how different biological pathways converge to cause the disease. Both familial and sporadic ALS are characterized by the aggregation of the essential DNA- and RNA-binding protein TDP-43, suggesting a central role in ALS etiology. Here we report that TDP-43 aggregation in neuronal cells of mouse and human origin causes sensitivity to oxidative stress. Aggregated TDP-43 sequesters specific microRNAs (miRNAs) and proteins, leading to increased levels of some proteins while functionally depleting others. Many of those functionally perturbed gene products are nuclear-genome-encoded mitochondrial proteins, and their dysregulation causes a global mitochondrial imbalance that augments oxidative stress. We propose that this stress-aggregation cycle may underlie ALS onset and progression.
Be stars are rapidly rotating B-type stars. The origin of their rapid rotation is not certain, but binary interaction remains as a possibility. In this work, we investigate the formation of Be stars ...resulting from mass transfer in binaries in the Galaxy.We calculate binary evolution with both stars evolving simultaneously and consider different possible mass accretion histories for the accretor. From the calculated results, we obtain the critical mass ratios q sub(cr) that determine the stability of the mass transfer. We also numerically calculate the parameter lambda in common envelope evolution and then incorporate both q sub(cr) and lambda into the population synthesis calculations. We present the predicted numbers and characteristics of Be stars in binary systems with different types of companions, including helium stars, white dwarfs, neutron stars, and black holes. We find that in Be/neutron star binaries, the Be stars can have a lower mass limit ~8 M sub(middot in cicle) if they are formed by stable (i.e., without the occurrence of common envelope evolution) and nonconservative mass transfer. We demonstrate that isolated Be stars may originate from both mergers of two main-sequence stars and disrupted Be binaries during the supernova explosions of the primary stars, but mergers seem to play a much more important role. Finally, the fraction of Be stars that have involved binary interactions in all B-type stars can be as high as ~13%-30%, implying that most Be stars may result from binary interaction.
In this work, we interpreted the high braking index of PSR J1640−4631 with a combination of the magneto-dipole radiation and dipole magnetic field decay models. By introducing a mean rotation energy ...conversion coefficient , the ratio of the total high-energy photon energy to the total rotation energy loss in the whole life of the pulsar, and combining the pulsar's high-energy and timing observations with a reliable nuclear equation of state, we estimate the pulsar's initial spin period, ms, corresponding to the moment of inertia g cm2. Assuming that PSR J1640−4631 has experienced a long-term exponential decay of the dipole magnetic field, we calculate the true age , the effective magnetic field decay timescale , and the initial surface dipole magnetic field at the pole of the pulsar to be 2900−3100 yr, yr, and G, respectively. The measured braking index of for PSR J1640−4631 is attributed to its long-term dipole magnetic field decay and a low magnetic field decay rate, G yr−1. Our model can be applied to both the high braking index ( ) and low braking index ( ) pulsars, tested by the future polarization, timing, and high-energy observations of PSR J1640−4631.
Abstract
Recent gravitational-wave observations showed that binary black hole (BBH) mergers with massive components are more likely to have high effective spins. In the model of isolated binary ...evolution, BH spins mainly originate from the angular momenta of the collapsing cores before BH formation. Both observations and theories indicate that BHs tend to possess relatively low spins; the origin of fast-spinning BHs remains a puzzle. We investigate an alternative process that stable Case A mass transfer may significantly increase BH spins during the evolution of massive BH binaries. We present detailed binary evolution calculations and find that this process can explain the observed high spins of some massive BBH mergers under the assumption of mildly super-Eddington accretion.
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