检索结果-内蒙古大学图书馆

学校读者我要写书评

暂无评论

一颗大质量恒星在死亡前猛烈抛射出星周物质

Science Bulletin 2023年第21期68卷 2548-2554,M0005页

作者：张居甲林含王晓锋赵泽毅李丽萍刘嘉联闫圣钰向丹凤王汇娟白金明 Yunnan Observatories(YNAO) Chinese Academy of SciencesKunming 650216China Key Laboratory for the Structure and Evolution of Celestial Objects Chinese Academy of SciencesKunming 650216China International Centre of Supernovae Yunnan Key LaboratoryKunming 650216China Key Laboratory of Radio Astronomy and Technology CASBeijing 100101China Department of Physics Tsinghua UniversityBeijing 100084China Beijing Planetarium Beijing Academy of Science and TechnologyBeijing 100044China National Astronomical Observatories Chinese Academy of SciencesBeijing 100101China School of Astronomy and Space Science University of Chinese Academy of SciencesBeijing 101408China

Ⅱ型超新星是宇宙中最常见的恒星爆炸,其富氢的大质量前身星最后阶段的演变让人捉摸不透.这类恒星晚期演化和由此产生的星周环境的差异导致了超新星丰富的观测多样性.为了建立Ⅱ型超新星爆炸与大质量恒星晚期演化之间的联系,有必要捕捉... 详细信息

Ⅱ型超新星是宇宙中最常见的恒星爆炸,其富氢的大质量前身星最后阶段的演变让人捉摸不透.这类恒星晚期演化和由此产生的星周环境的差异导致了超新星丰富的观测多样性.为了建立Ⅱ型超新星爆炸与大质量恒星晚期演化之间的联系,有必要捕捉超新星爆炸的第一缕光,即由激波爆发冷却产生的高能光子电离星周物质造成的闪亮光谱.近邻星系M 101中爆发的SN 2023ixf为探索这个问题提供了难得的机会.本文利用爆炸后1~5天内频繁拍摄地闪亮光谱,对这颗超新星周围物质的性质进行严格的约束.计算得出,SN 2023ixf前身星在爆炸前最后2~3年中以高达M≈6×10^(-4)M⊙a^(-1)速率损失物质.这些物质以55 km s^(-1)的速度运动,在距离前身星不到7×10^(14)cm的位置形成致密的星周物质壳层.考虑到如此高的质量损失率和相对较大的风速,以及20年前的前身星图像,SN2023ixf可能是刚从红超巨星演化而来的黄巨超巨星产生的超新星爆炸.

关键词：超新星爆炸星周物质前身星 Ⅱ型超新星红超巨星近邻星系质量损失率

Simulating the Escaping Atmosphere of GJ436 b with two-fluid Magnetohydrodynamic Models-

学校读者我要写书评

暂无评论

arXiv 2024年

作者： Xing, Lei Guo, Jianheng Yan, Dongdong Yang, Chuyuan Yunnan Observatories Chinese Academy of Sciences P.0.Box110 Kunming650216 China Yuquan Road Shijingshan District Beijing100049 China Key Laboratory for Structure and Evolution of Celestial Objects Chinese Academy of Sciences P.0.Box110 Kunming650216 China International Centre of Supernovae Yunnan Key Laboratory Kunming650216 China

Observations of transmission spectra reveals that hot Jupiters and Neptunes are likely to possess escaping atmospheres driven by stellar radiation. Numerous models predict that magnetic fields may exert significant influences on the atmospheres of hot planets. Generally, the escaping atmospheres are not entirely ionized, and magnetic fields only directly affect the escape of ionized components within them. Considering the chemical reactions between ionized components and neutral atoms, as well as collision processes, magnetic fields indirectly impact the escape of neutral atoms, thereby influencing the detection signals of planetary atmospheres in transmission *** order to simulate this process, we developed a magneto-hydrodynamic multi-fluid model based on MHD code PLUTO. As an initial exploration, we investigated the impact of magnetic fields on the decoupling of H+ and H in the escaping atmosphere of the hot Neptune GJ436 b. Due to the strong resonant interactions between H and H+. The coupling between them is tight even if the magnetic field is strong. However, our simulation results indicate that under the influence of magnetic fields, there are noticeable regional differences in the decoupling of H+ and H. With the increase in magnetic field strength, the degree of decoupling also increases. For heavier particles such as O, the decoupling between O and H+ is more pronounced. our findings provide important insights for future studies on the decoupling processes of heavy atoms in the escaping atmospheres of hot Jupiters and hot Neptunes under the influence of magnetic fields. © 2024, CC BY-NC-ND.

关键词： Magnetohydrodynamics

Prospects of the multi-channel photometric survey telescope in the cosmological application of Type Ia supernovae

学校读者我要写书评

暂无评论

arXiv 2024年

作者： Wang, Zhenyu Zhang, Jujia Er, Xinzhong Bai, Jinming Yunnan Observatories Chinese Academy of Sciences Kunming650216 China University of Chinese Academy of Sciences Beijing100049 China Key Laboratory for the Structure and Evolution of Celestial Objects Chinese Academy of Sciences Kunming650216 China International Centre of Supernovae Yunnan Key Laboratory Kunming50216 China South-Western Institute for Astronomy Research Yunnan University Kunming650500 China

The Multi-channel Photometric Survey Telescope (Mephisto) is a real-time, threecolor photometric system designed to capture the color evolution of stars and transients accurately. This telescope system can be crucial in cosmological distance measurements of low-redshift (low-z, z 0.1) Type Ia supernovae (SNe Ia). To optimize the capabilities of this instrument, we perform a comprehensive simulation study before its official operation is scheduled to start. By considering the impact of atmospheric extinction, weather conditions, and the lunar phase at the observing site involving the instrumental features, we simulate the light curves of SNe Ia obtained by the Mephisto. The best strategy in the case of SN Ia cosmology is to take the image at an exposure time of 130 s with a cadence of 3 days. In this condition, Mephisto can obtain hundreds of high-quality SNe Ia to achieve a distance measurement better than 4.5%. Given the on-time spectral classification and monitoring of the Lijiang 2.4 m Telescope at the same observatory, Mephisto, in the whole operation, can significantly enrich the well-calibrated sample of supernovae at low-z and improve the calibration accuracy of high-z SNe Ia. © 2024, CC BY.

关键词： Supernovae

A New Magnetically Active Binary System Discovered in Yunnan-Hong Kong Wide Field Survey

学校读者我要写书评

暂无评论

Chinese Astronomy and Astrophysics 2021年第1期45卷 67-81页

作者： Jian-hua, W.A.N.G. Sheng-hong, G.U. Xiao-bin, W.A.N.G. YEUNG, Bill NG, Eric Yunnan Observatories Chinese Academy of Sciences Kunming 650216 Key Laboratory for the Structure and Evolution of Celestial Objects Chinese Academy of Sciences Kunming 650216 School of Astronomy and Space Science University of Chinese Academy of Sciences Beijing 101408 Hong Kong Astronomical Society Hong Kong 999077

We present a newly discovered magnetically active binary system detected by Yunnan-Hong Kong wide field survey, with an orbital period of 0.60286 days. Two color photometry for the system was performed using the 1 m Cassegrain telescope of Yunnan Observatories with its CCD (Charge-Coupled Device) camera. In the observed light curves, there are clearly different light maxima existed in the out-of-eclipse regions. We made spectroscopic observations for the binary system using the 2.4 m telescope and YFOSC (Yunnan Faint Object Spectrograph and Camera) of Lijiang station of Yunnan Observatories, China. The radial velocity curve was derived for primary star of the binary system. The primary star exhibited strong chromospheric activity, which confirms that the distortion of the light curves results from the starspot activity on the primary star. Through analyzing the light curves and RV (Radial Velocity) curve mentioned above by means of the W-D (Wilson-Devinney) code, orbital parameters and starspot configuration of the binary system are obtained. Finally, we have discussed the properties of the binary system, and given the prospects on the future work. © 2021

关键词： Binary: eclipsing Stars: activity stars: magnetic field starspots

Constraining evolution of magnetic field strength in the dissipation region of two BL Lac objects

学校读者我要写书评

暂无评论

Research in Astronomy and Astrophysics 2021年第12期21卷 351-356页

作者： Xu-Liang Fan Da-Hai Yan Qing-Wen Wu Xu Chen School of Mathematics Physics and StatisticsShanghai University of Engineering ScienceShanghai 201620China Yunnan Observatories Chinese Academy of SciencesKunming 650011China Key Laboratory for the Structure and Evolution of Celestial Objects Chinese Academy of SciencesKunming 650011China School of Physics Huazhong University of Science and TechnologyWuhan 430074China Shandong Provincial Key Laboratory of Optical Astronomy and Solar-Terrestrial Environment Institute of Space SciencesShandong UniversityWeihai 264209China

With the assumption that the optical variability timescale is dominated by the cooling time of the synchrotron process for BL Lac objects,we estimate time dependent magnetic field strength of the emission region for two BL Lac *** average magnetic field strengths are consistent with those estimated from core shift measurement and spectral energy distribution *** of magnetic field strength in the dissipation region is *** of flux and magnetic field strength shows no clear correlation,which indicates the variation of magnetic field is not the dominant reason of the variability *** evolution of magnetic field strength can provide another approach to constrain the energy dissipation mechanism in jets.

关键词： BL Lacertae objects:general BL Lacertae objects:individual(S50716+714 BL Lacertae) galaxies:magnetic fields

The Application of Machine Learning in Tidal evolution Simulation of Star-Planet Systems

学校读者我要写书评

暂无评论

arXiv 2024年

作者： Guo, Shuaishuai Guo, Jianheng Ji, KaiFan Liu, Hui Xing, Lei Yunnan Observatories Chinese Academy of Sciences P.O. Box 110 Kunming650011 China School of Astronomy and Space Science University of Chinese Academy of Sciences Beijing China Key Laboratory for the Structure and Evolution of Celestial Objects CAS Kunming650011 China Yunnan Key Laboratory of SolarPhysics and Space Science 650216 China International Centre of Supernovae Yunnan Key Laboratory Kunming650216 China

With the release of a large amount of astronomical data, an increasing number of close-in hot Jupiters have been discovered. Calculating their evolutionary curves using star-planet interaction models presents a challenge. To expedite the generation of evolutionary curves for these close-in hot Jupiter systems, we utilized tidal interaction models established on MESA to create 15,745 samples of star-planet systems and 7,500 samples of stars. Additionally, we employed a neural network (Multi-Layer Perceptron - MLP) to predict the evolutionary curves of the systems, including stellar effective temperature, radius, stellar rotation period, and planetary orbital period. The median relative errors of the predicted evolutionary curves were found to be 0.15%, 0.43%, 2.61%, and 0.57%, respectively. Furthermore, the speed at which we generate evolutionary curves exceeds that of model-generated curves by more than four orders of magnitude. We also extracted features of planetary migration states and utilized lightGBM to classify the samples into 6 categories for prediction. We found that by combining three types that undergo long-term double synchronization into one label, the classifier effectively recognized these features. Apart from systems experiencing long-term double synchronization, the median relative errors of the predicted evolutionary curves were all below 4%. Our work provides an efficient method to save significant computational resources and time with minimal loss in accuracy. This research also lays the foundation for analyzing the evolutionary characteristics of systems under different migration states, aiding in the understanding of the underlying physical mechanisms of such systems. Finally, to a large extent, our approach could replace the calculations of theoretical models. Copyright © 2024, The Authors. All rights reserved.

关键词： Stars

Stellar Spectral Classification Based on Capsule Network

学校读者我要写书评

暂无评论

Chinese Astronomy and Astrophysics 2021年第3期45卷 352-363页

作者： Li-ting, D.U. Li-hua, H.O.N.G. Jin-tao, Y.A.N.G. Ting-ting, X.U. Jing-min, ZHANG Lin-pin, A.I. Wei-hong, Z.H.O.U. School of Mathematics and Computer Science Yunnan Minzu University Kunming 650500 School of Software Engineering Xiamen Institute of Software Technology Xiamen 361000 Center for Astrophysics Guangzhou University Guangzhou 510006 Key Laboratory of the Structure and Evolution of Celestial Objects Chinese Academy of Sciences Kunming 650011

The rapid development of large-scale sky survey project has produced a large amount of stellar spectral data, which make the automatic classification of stellar spectral data a challenging task. In this paper, we have proposed a stellar spectral classification method based on a capsule network. At first, by using the one-dimensional convolutional network and short-time Fourier transform (STFT), the one-dimensional spectra of the F5, G5, and K5 types selected from the LAMOST Data Release 5 (DR5) are converted into the two-dimensional Fourier spectrum images. Then, the two-dimensional Fourier spectrum images are classified automatically by the capsule network. Because the capsule network can preserve the hierarchical pose relationships among the entities in the image, and it does not need any pooling layers, the experimental results show that the capsule network has a better classification performance, for the classifications of the F5, G5, and K5-type stellar spectra, its classification accuracy is superior to other classification methods. © 2021

关键词： methods: data analysis Stars: fundamental parameters techniques: spectral analysis

The force-free dipole magnetosphere in nonlinear electrodynamics

学校读者我要写书评

暂无评论

Research in Astronomy and Astrophysics 2020年第3期20卷 136-141页

作者： Hui-Quan Li Xiao-Lin Yang Jian-Cheng Wang Yunnan Observatories Chinese Academy of SciencesKunming 650216China Key Laboratory for the Structure and Evolution of Celestial Objects Chinese Academy of SciencesKunming 650216China Center for Astronomical Mega-Science Chinese Academy of SciencesBeijing 100101China

Quantum electrodynamics(QED)effects may be included in physical processes of magnetar and pulsar magnetospheres with strong magnetic *** the quantum corrections,Maxwell electrodynamics is modified to nonlinear *** this work,we study the force-free magnetosphere in nonlinear electrodynamics in a general *** pulsar equation describing a steady and axisymmetric magnetosphere is derived,which now admits solutions with *** derive the first-order nonlinear corrections to the near-zone dipole magnetosphere in some popular nonlinear effective *** field lines of the corrected dipole tend to converge on the rotational axis so that the fields in the polar region are stronger compared to the pure dipole case.

关键词： stars: neutron stars: magnetars stars: magnetic field

evolution of double oxygen-neon white dwarf merger remnant

学校读者我要写书评

暂无评论

arXiv 2023年

作者： Wu, Chengyuan Xiong, Heran Han, Zhanwen Wang, Bo Yunnan Observatories Chinese Academy of Sciences Kunming650216 China Key Laboratory for the Structure and Evolution of Celestial Objects Yunnan Observatories CAS Kunming650216 China International Centre of Supernovae Yunnan Key Laboratory Kunming650216 China Research School of Astronomy and Astrophysics The Australian National University CanberraACT2611 Australia

Double white dwarf (WD) merger process and their post-merger evolution are important in many fields of astronomy, such as supernovae, gamma-ray bursts, gravitational waves, etc. The evolutionary outcomes of double ultra-massive WD merger remnants are still a subject of debate, though the general consensus is that the merger remnant will collapse to form a neutron star. In this work, we investigate the evolution of a 2.20Mo merger remnant stemmed from the coalescence of double 1.10Mo ONe WDs. We find that the remnant ignites off-centre neon burning at the position near the surface of primary WD soon after the merger, resulting in the stable inwardly propagating oxygen/neon (O/Ne) flame. The final outcomes of the merger remnant are sensitive to the effect of convective boundary mixing. If the mixing cannot stall the O/Ne flame, the flame will reach the centre within 20 years, leading to the formation of super Chandrasekhar mass silicon core, and its final fate probably be neutron star (NS) through iron-core-collapse supernova. In contrast, if the convective mixing is effective enough to prevent the O/Ne flame from reaching the centre, the merger remnant will undergo electron capture supernova to form an ONeFe WD. Meanwhile, we find that the wind mass loss process may hardly alter the final fate of the remnant due to its fast evolution. Our results imply that the coalescence of double ONe WDs can form short lived giant like object, but the final outcomes (NS or ONeFe WD) are influenced by the uncertain convective mixing in O/Ne flame. © 2023, CC BY.

关键词： Oxygen