Search

We present the detection of false positive double-lined spectroscopic binaries candidates (SB2) using medium-resolution survey (MRS) spectra from the one time-domain field of LAMOST data release 10 (DR10). The secondary component in all these binaries has near zero radial velocity and solar-like spectral lines. Highly likely this is light from the semi-transparent clouds illuminated by the full Moon. However we also suspect that partially this contamination can be caused by a solar light reflected from the surface of low-orbital artificial satellites launched in the beginning of 2022. We found several possible contaminant candidates using archival orbital data. We propose measures to reduce risk of such contamination for the future observations and methods to find it in archived ones., accepted in MNRAS letters 2023 July 07

The formation path to ultra-compact X-ray binaries (UCXBs) with black hole (BH) accretors is still unclear. In the classical formation scenario, it is difficult to eject the massive envelope of the progenitor star of the BH via common envelope process. Given that some neutron stars (NSs) in binary systems evidently have birth masses close to $\sim 2.0\;M_\odot$, we explore here the possibility that BH-UCXBs may form via accretion-induced collapse (AIC) of accreting NSs, assuming that these previously evolved in LMXBs to masses all the way up to the maximum limit of a NS. We demonstrate this formation path by modelling a few cases of NS-UCXBs with initial NS masses close to the maximum mass of a NS that evolve into BH-UCXBs after the NS accretes material from its He~WD companion. We follow the evolution of the post-AIC BH-UCXB and, based on simple arguments, we anticipate that there is about one BH-UCXB with an AIC origin and a He~WD donor within the current sample of known UCXBs and that 2--5 such BH-UCXBs may be detected in gravitational waves by LISA. In addition, we find that the X-ray luminosity of NS-UCXBs near their orbital period minimum exceeds $\sim 10^{39}\;{\rm erg\;s^{-1}}$ and thus such systems may appear as ultraluminous X-ray sources., Comment: ApJ accepted, 12 pages, 3 figures

Additional file 1.

Mass transfer stability is an essential issue in binary evolution. Ge et al. studied critical mass ratios for dynamically stable mass transfer by establishing adiabatic mass loss model and found that the donor stars on the giant branches tend to be more stable than that based on the composite polytropic stellar model. We would investigate the influence of mass transfer stability on the formation and properties of DWD populations. We performed a series of binary population synthesis, where the critical mass ratios from adiabatic mass loss model (Ge's model) and that from the composite polytropic model are adopted, respectively. For Ge's model, most of the DWDs are produced from the stable non-conservative Roche lobe overflow plus common envelope (CE) ejection channel (RL+CE channel) regardless of the CE ejection efficiency $\alpha_{CE}$. While the results of the polytropic model strongly depend on the adopted value of $\alpha_{ CE}$. We find DWDs produced from the RL+CE channel have comparable WD masses and the mass ratio distribution peaks at around 1. Based on the magnitude-limited sample of DWDs, the space densities for the detectable DWDs and those with extremely low-mass WD (ELM WD) companions in Ge's model is $1347$ and $473 kpc^{-3}$, respectively, close to observations. While the polytropic model overpredicts space density of DWDs by a factor of about $2-3$. We also find that the results of DWD merger rate distribution in Ge's model reproduce the observations better than that of the polytropic model, and the merger rate of DWDs with ELM WD companions in the Galaxy is about $1.8\times 10^{-3} yr^{-1}$ in Ge's model, which is comparable to the observation estimation. We confirm that the mass transfer stability plays important roles in the formation and properties of DWD populations, and then in the progenitors of SNe Ia and detectable GW sources., Comment: 28 pages, 17 figures; A&A version

We present a study of eclipsing binary J064726.39+223431.6 using spectra from the LAMOST-MRS and TESS photometry. We use full-spectrum fitting to derive radial velocities and spectral parameters: ${T_{\rm eff}}_{A,B}=6177,\,5820$ K, $v \sin{i}_{A,B}=59,\,50~\kms$ and ${\rm [Fe/H]}_{A,B}=-0.19$ dex. The orbital solution and light curve analysis suggest that it is a close pair of fast rotating stars on circular orbit. We measure their masses to be $M_{A,B}=1.307\pm0.007,\, 1.129\pm0.005\,M_\odot$ and their radii to be $R_{A,B}=1.405\pm0.052,\, 1.219\pm0.060\,R_\odot$ resulting in surface gravities of $\log{g}_{A,B}=4.259\pm0.033,\,4.319\pm0.042$ (cgs). Theoretical models cannot match all of these properties, predicting significantly higher ${T_{\rm eff}}$ for a given metallicity. Derived age of the system 1.56 Gyr indicates that both components are younger than Sun, which contradicts to much longer orbit's circularisation timescale., submitted to MNRAS. arXiv admin note: text overlap with arXiv:2204.10680

The evolution and stability of mass transfer of CO+He WD binaries are not well understood. Observationally they may emerge as AM CVn binaries and are important gravitational wave (GW) emitters. In this work, we have modeled the evolution of double WD binaries with accretor masses of $0.50 - 1.30\;M_{\odot}$ and donor masses of $0.17\; - 0.45\;M_{\odot}$ using the detailed stellar evolution code MESA. We find that the evolution of binaries with same donor masses but different accretor masses is very similar and binaries with same accretor masses but larger He donor masses have larger maximum mass transfer rates and smaller minimum orbital periods. We also demonstrate that the GW signal from AM CVn binaries can be detected by space-borne GW observatories, such as LISA, TianQin. And there is a linear relation between the donor mass and gravitational wave frequency during mass transfer phase. In our calculation, all binaries can have dynamically stable mass transfer, which is very different from previous studies. The threshold donor mass of Eddington-limited mass transfer for a given accretor WD mass is lower than previous studies. Assuming that a binary may enter common envelope if the mass transfer rate exceeds the maximum stable burning rate of He, we provide a new criterion for double WDs surviving mass transfer, which is below the threshold of Eddington-limit. Finally, we find that some systems with ONe WDs in our calculation may evolve into detached binaries consisting of neutron stars (NSs) and extremely low mass He WDs and further ultra-compact X-ray binaries., 10 pages, 8 figures, accepted for publication in ApJ

Due to an error at the publisher, the unit "mHz"was changed to "MHz"without being identified to the authors at the proof stage. In the published article, all "MHz"should be changed to "mHz". IOP Publishing sincerely regrets this error.

Neutron star-helium white dwarf (NS+He WD) binaries are important evolutionary products of close-orbit binary star systems. They are often observed as millisecond pulsars and may continue evolving into ultra-compact X-ray binaries (UCXBs) and continuous gravitational wave (GW) sources that will be detected by space-borne GW observatories, such as LISA, TianQin and Taiji. Nevertheless, the stability of NS+He WD binaries undergoing mass transfer is not well studied and still under debate. In this paper, we model the evolution of NS+He WD binaries with WD masses ranging from 0.17-0.45 $M_{\odot}$, applying the detailed stellar evolution code mesa. Contrary to previous studies based on hydrodynamics, we find that apparently all NS+He WD binaries undergo stable mass transfer. We find for such UCXBs that the larger the WD mass, the larger the maximum mass-transfer rate and the smaller the minimum orbital period during their evolution. Finally, we demonstrate numerically and analytically that there is a tight correlation between WD mass and GW frequency for UCXBs, independent of NS mass., Accepted by ApJ, 9 pages, 7 figures

The chemical short-range orders (CSRO) are the sub-nanosized entities inherent in high-/medium-entropy alloys (H/MEA). To discern CSRO poses the challenge with pending issues as to under what zone axis in electron diffraction, signature scattering specific to CSRO will appear and what the structure motif of CSRO is. Here, we show extra diffuse scattering by CSRO from [111] and [112] directions in a VCoNi MEA and accordingly, construct the L11-type structure motif, and derive the spacial shape of flat cuboid of CSRO in virtue of diffractions under varying zone axis. Moreover, we demonstrate the methods to identify CSRO in lattice images. The structure motif is constructed as L11-type for chemical short-range order in a medium-entropy alloy in terms of electron diffractions under the multiple zone axis.

At present, the existing Hall current sensor can only accurately measure the current in a single direction, but the bidirectional current flow often occurs in the field of new energy, so the traditional single Hall current sensor cannot solve the problem of bidirectional current measurement. Therefore, this paper proposes and designs a new high current bidirectional Hall current sensor, which uses a single power supply H-bridge circuit, and uses the principle of magnetic balance of the superimposed magnetic field added to the Hall chip. Works the triode in H-bridge circuit in different amplification states, and through collecting the voltage size and direction at both ends of the coil, the problem of high current bidirectional current measurement is solved. The practical test meets the measurement requirements of 0-600A bidirectional DC current.

The dataset includes all data for "A rapid cooling event over the western Pacific region during the Middle Bronze Age" by Xiao et al..

Rationale: Schaaf-Yang syndrome, a rare imprinted hereditary disease caused by MAGEL2 variants, manifests as developmental delay/intellectual disability, neonatal hypotonia, feeding difficulties, contractures, and autism spectrum disorder. Patient concerns: Patient 1 and 2 were infant girls presenting facial dysmorphisms, contractures of interphalangeal joints, neonatal hypotonia, feeding difficulties, congenital heart diseases, and respiratory complications. Besides, Patient 2 presented with delayed psychomotor development. Diagnosis: Whole-exome sequencing was performed and heterozygous mutations of the MAGEL2 gene were detected in the patients. They were diagnosed as Schaaf-Yang syndrome. Interventions: The patients received supportive treatment including mechanical ventilation, parenteral nutrition and gastric tube feeding. Outcomes: Whole-exome sequencing revealed de novo heterozygous c.1996dupC pathogenic mutations in the MAGEL2 gene in the 2 patients. They died due to respiratory failure at the age of 20 days and 98 days, respectively. Lessons: Our results indicate that MAGEL2 variants can cause congenital heart disease and fatal respiratory complications, broadening the phenotypic spectrum and adding to the fatal cases of Schaaf-Yang syndrome. We highly suggest that the MAGEL2 gene should be added to gene-panels or gene-filters in next-generation sequencing-based diagnostics, which is of great significance for early diagnosis and early intervention of Schaaf-Yang syndrome patients.

Since September 2018, LAMOST starts a new 5-year medium-resolution spectroscopic survey (MRS) using bright/gray nights. We present the scientific goals of LAMOST-MRS and propose a near optimistic strategy of the survey. A complete footprint is also provided. Not only the regular medium-resolution survey, but also a time-domain spectroscopic survey is being conducted since 2018 and will be end in 2023. According to the detailed survey plan, we expect that LAMOST-MRS can observe about 2 million stellar spectra with ~7500 and limiting magnitude of around G=15 mag. Moreover, it will also provide about 200 thousand stars with averagely 60-epoch observations and limiting magnitude of G~14 mag. These high quality spectra will give around 20 elemental abundances, rotational velocities, emission line profiles as well as precise radial velocity with uncertainty less than 1 km/s. With these data, we expect that LAMOST can effectively leverage sciences on stellar physics, e.g. exotic binary stars, detailed observation of many types of variable stars etc., planet host stars, emission nebulae, open clusters, young pre-main-sequence stars etc., 25 pages, 10 figues. Submitted to Reseach in Astronomy and Astrophysics

Three-Dimensional (3-D) Interferometric Inverse Synthetic Aperture Radar (InISAR) imaging system based on the orthogonal double baseline can achieve the 3-D geometric reconstruction of a target effectively, which is extremely helpful in target classification and identification. However, only sparse aperture measurements are available in the actual imaging process, which might pose some challenges to the traditional InISAR imaging algorithms. In this study, a new method of 3-D InISAR imaging of a ship with sparse aperture is presented. Minimum entropy algorithms are adopted to realize motion compensation and image coregistration of the sparse echoes. A gradient-based technique is used to achieve highly accurate signal reconstruction for the sparse aperture. A two-Dimensional (2-D) ISAR image was achieved with azimuth compression via the parameters-estimation method, and the 3-D reconstruction of a ship was achieved via the interference approach. The obtained simulation results validate the feasibility of the presented approach.

Extracting event sentences with explicit and significant information is a basic work of semantic analysis based retrieval of text information. Current methods of event extraction normally lack evaluation of the quality of information embedded in a sentence, thus the extracted event sentences usually contain inexplicit or insignificant information that is unusable for real-world applications. In this paper, we introduce ES-ESens, a deep learning based methodology for detecting event sentences with high-quality information. To evaluate the explicitness and significance of the information embedded in a sentence, ES-ESens adopts Recurrent Neural Network with attention mechanism to perform deep semantic analysis on the context of the sentence and the article that explains the background of the event. Based on datasets of practical applications, experiments are presented to show the performance of our methodology.

Al-Mg alloys are a series of low cost and low density Al alloys, which show remarkable strengthening during deformation. In this work, study of commercial purity Al, Al-0.5Mg and Al-4.1Mg alloys was carried out to investigate the effect of Mg on materials strengthening. Slight solid solution strengthening by Mg addition is found in the as-cast alloys. While further significant strengthening effect is achieved in the alloys produced by high pressure torsion. An extraordinarily high strength of ~800 MPa is achieved in the Al-4.1Mg alloy, as a result of deformation induced ultrafine grains, high density stacking faults and Mg segregation.

As sdB stars in wide binary systems can only be created by stable RLOF, they are a great test sample to constrain the theoretical models for stable mass loss on the RGB. We have setup a long term monitoring program using high resolution spectrographs on different telescopes to create a sample of solved long period sdB binaries. An important advantage of using wide sdB binaries in these studies is that all of them are double lined binaries, and the GAIA data shows that it is a uniform population of canonical sdB stars. This way the sdB+MS binaries provide much stronger constraints on theoretical models than many other systems. The first results of our observing program are now available. We found two main features in the orbital parameters. The majority of the systems has eccentric orbits with systems on longer orbital period having a higher eccentricity. As these systems have undergone mass loss near the tip of the RGB, circularisation theory predicts them to be circularized. Our observations suggest that efficient eccentricity pumping mechanisms are active during the mass loss phase. A second finding is a strong correlation between the mass ratio and the orbital period. Using binary evolution models, this relation is used to derive an upper limit on the critical mass ratio for stable RLOF wich depends on the orbital period of the system. Furthermore a split in the P-q relation seems to indicate two different groups with somewhat different formation histories.

Probabilistic time geography (PTG) is suggested as an extension of (classical) time geography, in order to present the uncertainty of an agent located at the accessible position by probability. This may provide a quantitative basis for most likely finding an agent at a location. In recent years, PTG based on normal distribution or Brown bridge has been proposed, its variance, however, is irrelevant with the agent's speed or divergent with the increase of the speed; so they are difficult to take into account application pertinence and stability. In this paper, a new method is proposed to model PTG based on Markov chain. Firstly, a bidirectional conditions Markov chain is modeled, the limit of which, when the moving speed is large enough, can be regarded as the Brown bridge, thus has the characteristics of digital stability. Then, the directed movement is mapped to Markov chains. The essential part is to build step length, the state space and transfer matrix of Markov chain according to the space and time position of directional movement, movement speed information, to make sure the Markov chain related to the movement speed. Finally, calculating continuously the probability distribution of the directed movement at any time by the Markov chains, it can be get the possibility of an agent located at the accessible position. Experimental results show that, the variance based on Markov chains not only is related to speed, but also is tending towards stability with increasing the agent's maximum speed.

In this paper, we discussed the effect mechanism of professional differences and emergency cooperation on inter-organizational partnerships, validated the intermediary effect of information transmission in professional differences and emergency cooperation, and the moderating effects of task uncertainty in professional differences and the way of information transmission (information forwarding and information sharing), then we proposed the conceptual model and research hypothesis. By analyzing 255 emergency teams at all levels and members of the investigation data, the assumptions for the model and analysis results show that professional differences have a negative impact on emergency cooperation and information forwarding and sharing. At the same time, information forwarding and sharing act as an intermediary role between professional differences and emergency cooperation. Task uncertainty has positive moderated effects between professional differences and the information sharing, not the information forwarding.

Generally, there are two types of Chinese public educational policymaking: problem oriented and ideal oriented. The 985 Project policy clearly exhibits the characteristics of the latter. Usually, the goals of ideal-oriented policymaking are long-term and overarching, so they can play a role in propagating, directing, and encouraging people to accelerate society's development. But unexpected problems often arise during its implementation. This article attempts to describe and analyze the background, processes, and problems of the 985 Project policy.

Based on analysis of relationship between ontology and conventional information organization and problems existing in ontology construction study and on authors’ experience of building ontology, the paper focuses on currently well accepted domain knowledge and domain experts’ effective domain which are two indispensable terms to quickly and successfully construct a domain ontology. The paper also reconstructs and reuses existing accepted domain knowledge, establishes a set of depended texts’ ontology learning system, and finally realizes automatic construction of domain ontology concept description system through NLP theory and technology. This would further provide theory and technology support for domain ontology automatic construction

Since the founding of the republic, we have undertaken a number of reforms and adjustments with regard to the departments and faculties, specializations, curriculum, and contents and methods of teaching in the humanities in our institutions of higher education (by this we mean, in this essay, such subjects or departments as language, literature, history, philosophy, financial and economic studies, law, political science, and library science). In general, humanities education at that higher level has developed as an enterprise. Up to 1978, the number of baccalaureate-level humanities specialists trained nationwide was 314,796, and there were 7,500 graduate students. At present there are 78 higher institutions of humanities learning in the country (including universities that have humanities in their curriculum and special institutes for financial and economic studies and for legal and political studies). There are 89 separate specialization programs, and 336 research organs. A total of 101,400 students are...