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Probing the peripheral self-generated magnetic field distribution in laser-plasma magnetic reconnection with Martin-Puplett interferometer polarimeter

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Chinese Physics B 2024年第4期33卷 129-134页

作者：张雅芃姚嘉文刘正东马作霖仲佳勇 Department of astronomy Beijing Normal UniversityBeijing 100875China institute for Frontiers in astronomy and Astrophysics Beijing Normal UniversityBeijing 102206China

Magnetic reconnection of the self-generated magnetic fields in laser-plasma interaction is an important laboratory method for modeling high-energy density astronomical and astrophysical phenomena.We use the Martin-Puplett interferometer(MPI)polarimeter to probe the peripheral magnetic fields generated in the common magnetic reconnection configuration,two separated coplanar plane targets,in laser-target interaction.We introduce a new method that can obtain polarization information from the interference pattern instead of the sinusoidal function fitting of the intensity.A bidirectional magnetic field is observed from the side view,which is consistent with the magneto-hydro-dynamical(MHD)simulation results of self-generated magnetic field reconnection.We find that the cancellation of reverse magnetic fields after averaging and integration along the observing direction could reduce the magnetic field strength by one to two orders of magnitude.It indicates that imaging resolution can significantly affect the accuracy of measured magnetic field strength.

关键词： laser-plasma experiment polarimeter self-generated magnetic field magnetic reconnection

BSEC Method for Unveiling Open Clusters and its Application to Gaia DR3:83 New Clusters

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Research in astronomy and Astrophysics 2024年第5期24卷 169-184页

作者： Zhong-Mu Li Cai-Yan Mao institute of astronomy and Information Dali UniversityDali 671003China

Open clusters(OCs) are common in the Milky Way, but most of them remain undiscovered. There are numerous techniques, including some machine-learning algorithms, available for the exploration of OCs. However, each method has its limitations and therefore, different approaches to discovering OCs hold significant values. We develop a comprehensive approach method to automatically explore the data space and identify potential OC candidates with relatively reliable membership determination. This approach combines the techniques of Hierarchical Density-Based Spatial Clustering of Applications with Noise, Gaussian mixture model, and a novel cluster member identification technique, color excess constraint. The new method exhibits efficiency in detecting OCs while ensuring precise determination of cluster memberships. Because the main feature of this technique is to add an extra constraint(EC) for the members of cluster candidates using the homogeneity of color excess,compared to typical blind search codes, it is called Blind Search-Extra Constraint(BSEC) method. It is successfully applied to the Gaia Data Release 3, and 83 new OCs are found, whose color–magnitude diagrams(CMDs) are fitted well to the isochrones. In addition, this study reports 621 new OC candidates with discernible main sequence or red giant branch. It is shown that BSEC technique can discard some false negatives of previous works, which takes about three percentage of known clusters. It shows that as an EC, the color excess(or twocolor) constraint is useful for removing fake cluster member stars from the clusters that are identified from the positions and proper motions of stars, and getting more precise CMDs, when differential reddening of member stars of a cluster is not large(e.g., ΔE(GBP-GRP) < 0.5 mag). It makes the CMDs of 15% clusters clearer(in particular for the region near turnoff) and therefore is helpful for CMD and stellar population studies. Our result suggests that the color excess constraint is more appropriate for clusters with small di

关键词： Galaxy stellar content-(Galaxy:)open clusters and associations general-stars fundamental parameters

An Asymmetric Galactic Stellar Disk Traced by OB-type Stars from LAMOST DR7

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Research in astronomy and Astrophysics 2024年第6期24卷 40-53页

作者： Xiaopeng Liu Hao Tian Wenyuan Cui Linlin Li Jiaming Liu Zhenyan Huo Yawei Gao Department of Physics Hebei Normal University Guo Shoujing institute for astronomy Hebei Normal University Key Laboratory of Space astronomy and Technology National Astronomical Observatories Chinese Academy of Sciences institute for Frontiers in astronomy and Astrophysics Beijing Normal University

Using 9943 OB-type stars from LAMOST DR7 in the solar neighborhood,we fit the vertical stellar density profile with the model including a single exponential distribution at different positions （R,Φ）.The distributions of the scale heights and scale length show that the young disk traced by the OB-type stars is not axisymmetric.The scale length decreases versus the azimuthal angle Φ,i.e.,from.■kpc withΦ=-3°to■kpc withΦ=9°.Meanwhile we find signal of non-symmetry in the distribution of the scale height of the north and south of the disk plane.The scale height in the north side shows signal of flaring of the disk,while that of the south disk stays almost constant around hs=130 pc.The distribution of the displaceeent of the disk plane Z0also shows variance versus the azimuthal angleΦ,which displays significant differences with the warp model constrained by the Cepheid stars.We also test different values for the position of the Sun,and the distance between the Sun and the Galactic center affects the scale heights and the displacement of the disk significantly,but that does not change our conclusion that the disk is not axisymmetric.

关键词： galaxies: spiral Galaxy: disk stars: early-type stars: massive

Recent progress in MnBi2nTe3n+1 intrinsic magnetic topological insulators: crystal growth, magnetism and chemical disorder

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National Science Review 2024年第2期11卷 65-80页

作者： Chaowei Hu Tiema Qian Ni Ni Department of Physics and astronomy and California Nano Systems institute University of California-Los Angeles

The search for magnetic topological materials has been at the forefront of condensed matter research for their potential to host exotic states such as axion insulators, magnetic Weyl semimetals, Chern insulators,etc. To date, the MnBi2nTe3n+1family is the only group of materials showcasing van der Waals-layered structures, intrinsic magnetism and non-trivial band topology without trivial bands at the Fermi level. The interplay between magnetism and band topology in this family has led to the proposal of various topological phenomena, including the quantum anomalous Hall effect, quantum spin Hall effect and quantum magnetoelectric effect. Among these, the quantum anomalous Hall effect has been experimentally observed at record-high temperatures, highlighting the unprecedented potential of this family of materials in fundamental science and technological innovation. In this paper, we provide a comprehensive review of the research progress in this intrinsic magnetic topological insulator family, with a focus on single-crystal growth, characterization of chemical disorder, manipulation of magnetism through chemical substitution and external pressure, and important questions that remain to be conclusively answered.

关键词： MnBi2Te4 magnetic topological insulator magnetism tuning antiferromagnetism ferromagnetism pressure chemical doping

On the Performances of Estimating Stellar Atmospheric Parameters from CSST Broad-band Photometry

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Research in astronomy and Astrophysics 2024年第4期24卷 161-173页

作者： Rui-Feng Shi Yang Huang Xin-Yi Li Hua-Wei Zhang School of astronomy and Space Science University of Chinese Academy of SciencesBeijing 100049China South-Western institute for astronomy Research Yunnan UniversityKunming 650500China CAS Key Lab of Optical astronomy Key Laboratory of Space Astronomy and TechnologyNational Astronomical ObservatoriesChinese Academy of SciencesBeijing 100101China College of Physics and Electronic Engineering Qilu Normal UniversityJinan 250200China Department of astronomy School of PhysicsPeking UniversityBeijing 100871China Kavli institute for astronomy and Astrophysics Peking UniversityBeijing 100871China

Deriving atmospheric parameters of a large sample of stars is of vital importance to understand the formation and evolution of the Milky Way.Photometric surveys,especially those with near-ultraviolet filters,can offer accurate measurements of stellar parameters,with the precision comparable to that from low/medium resolution spectroscopy.In this study,we explore the capability of measuring stellar atmospheric parameters from Chinese Space Station Telescope(CSST)broad-band photometry(particularly in the near-ultraviolet bands),based on synthetic colors derived from model spectra.We find that colors from the optical and near-ultraviolet filter systems adopted by CSST show significant sensitivities to the stellar atmospheric parameters,especially the metallicity.According to our mock data tests,the precision of the photometric metallicity is quite high,with typical values of0.17 and 0.20 dex for dwarf and giant stars,respectively.The precision of the effective temperature estimated from broad-band colors are within 50 K.

关键词： methods:data analysis stars:abundances surveys

Microlensing bias on the detection of strong lensing gravitational wave

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Science China(Physics,Mechanics & astronomy) 2024年第6期67卷 156-165页

作者： Xikai Shan Xuechun Chen Bin Hu Guoliang Li institute for Frontier in astronomy and Astrophysics Beijing Normal UniversityBeijing 102206China Department of astronomy Beijing Normal UniversityBeijing 100875China Purple Mountain Observatory Chinese Academy of SciencesNanjing 210023China

Identifying strong lensing gravitational wave(SLGW)events is of utmost importance in astrophysics as we approach the historic first detection of SLGW amidst the growing number of gravitational wave(GW)events.Currently,one crucial method for identifying SLGW signals involves assessing the overlap of parameters between two GWs.However,the distribution of discrete matter,such as stars and sub-halos,within the strong lensing galaxy can imprint a wave optical(WO)effect on the SLGW waveform.These frequency dependent imprints introduce biases in parameter estimation and impact SLGW identification.In this study,we assess the influence of the stellar microlensing field embedded in a strong lensing galaxy.Our findings demonstrate that the WO effect reduces the detection efficiency of SLGW by 5%-50%for various false alarm probabilities per pair(FAPper pair).Specifically,at an FAPper pairof 10^(-5),the detection efficiency decreases from~10%to~5%.Consequently,the presence of the microlensing field can result in missing half of the strong lensing candidates.Additionally,the microlensing WO effect introduces a noticeable bias in intrinsic parameters,particularly for chirp mass and mass ratio.However,it has tiny influence on extrinsic parameters.Considering all parameters,~30%of events exhibit a 1σparameter bias,~12%exhibit a 2σparameter bias,and~5%exhibit a 3σparameter bias.

关键词： gravitational wave gravitational strong lensing gravitational micro lensing wave optical effect

Accuracy of numerical relativity waveforms with respect to space-based gravitational wave detectors

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Communications in Theoretical Physics 2024年第1期76卷 82-95页

作者： Zun Wang Junjie Zhao Zhoujian Cao institute for Frontiers in astronomy and Astrophysics Beijing Normal UniversityBeijing 102206China Department of astronomy Beijing Normal UniversityBeijing 100875China School of Fundamental Physics and Mathematical Sciences Hangzhou Institute for Advanced StudyUCASHangzhou 310024China

As with the laser interferometer gravitational-wave observatory(LIGO),the matched filtering technique will be critical to the data analysis of gravitational wave detection by space-based detectors,including LISA,Taiji and Tianqin.Waveform templates are the basis for such matched filtering techniques.To construct ready-to-use waveform templates,numerical relativity waveforms are a starting point.Therefore,the accuracy issue of numerical relativity waveforms is critically important.There are many investigations regarding this issue with respect to LIGO.But unfortunately there are few results on this issue with respect to space-based detectors.The current paper investigates this problem.Our results indicate that the existing numerical relativity waveforms are as accurate as 99%with respect to space-based detectors,including LISA,Taiji and Tianqin.Such an accuracy level is comparable to that with respect to LIGO.

关键词： numerical relativity gravitational wave binary black hole

Study of 26 Galactic Open Clusters with Extended Main-sequence Turnoffs

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Research in astronomy and Astrophysics 2024年第6期24卷 30-39页

作者： Yang-Yang Deng Zhong-Mu Li Yunnan Observatories Chinese Academy of Sciences University of Chinese Academy of Sciences institute of astronomy and Information Dali University

Recent studies indicate that some Galactic open clusters(OCs) exhibit extended main-sequence turnoff(eMSTO)in their color–magnitude diagrams(CMDs). However, the number of Galactic OCs with eMSTO structures detected so far is limited, and the reasons for their formation are still unclear. This work identifies 26 Galactic OCs with undiscovered eMSTOs and investigates the causes of these features. Stellar population types and fundamental parameters of cluster samples are acquired using CMD fitting methods. Among them, the results of 11 OCs are reliable as the observed CMDs are well-reproduced. We propose the crucial role of stellar binarity and confirm the importance of stellar rotation in reproducing eMSTO morphologies. The results also show that the impact of age spread is important, as it can adequately explain the structure of young OCs and fit the observed CMDs of intermediate-age OCs better.

关键词： (Galaxy:) open clusters and associations: general (stars:) binaries: general (stars:) Hertzsprung-Russell and C-M-diagrams Galaxy: fundamental parameters

Improving the underwater navigation performance of an IMU with acoustic long baseline calibration

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Satellite Navigation 2024年第1期5卷 224-239页

作者： Paipai Wu Wenfeng Nie Yangfan Liu Tianhe Xu Shandong Key Laboratory of Optical astronomy and Solar-Terrestrial Environment Institute of Space SciencesShandong UniversityWeihai264209ShandongChina Research Group of astronomy and Geomatics(gAGE) Universitat Politecnica de Catalunya(UPC)BarcelonaSpain

Underwater acoustic Long-Baseline System(LBL)is an important technique for submarine positioning and navigation.However,the high cost of the seafloor equipment and complex construction of a seafloor network restrict the distribution of the LBL within a small area,making an underwater vehicle difficult for long-distance and high-precision acoustic-based or inertial-based navigation.We therefore propose an acoustic LBL-based Inertial Measurement Unit(IMU)calibration algorithm.When the underwater vehicle can receive the acoustic signal from a seafloor beacon,the IMU is precisely calibrated to reduce the cumulative error of Strapdown Inertial Navigation System(SINS).In this way,the IMU is expected to maintain a certain degree of accuracy by relying solely on SINS when the vehicle reaches out the range of the LBL network and cannot receive the acoustic signal.We present the acoustic LBL-based IMU online calibration model and analyze the factors that affect the accuracy of IMU calibration.The results fulfill the expectation that the gyroscope bias and accelerometer bias are the main error sources that affect the divergence of SINS position errors,and the track line of the underwater vehicle directly affects the accuracy of the calibration results.In addition,we deduce that an optimal calibration trajectory needs to consider the effects of the three-dimensional observability and position dilution of precision.In the experiment,we compare the effects of seven calibration trajectories:straight and diamond-shaped with and without the change of depth,and three sets of curves with the change of depth:circular,S-shaped,and figure-eight.Among them,we find that the figure-eight is the optimal trajectory for acoustic LBL-based IMU online calibration.We take the maintenance period during which the accumulated SINS Three Dimensional(3D)position errors are below 1 km to evaluate the calibration performance.The filed experimental results show that for the Micro-electromechanical Systems-grade IMU sensor,the maintenance period for th

关键词： Acoustic LBL Online IMU calibration SINS Relay reference network