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arXiv 2024年

作者： Hu, Xin-Ke Yu, Yu-Wei Zhang, Jin Wang, Xiang-Gao Patra, Kishore C. Brink, Thomas G. Zheng, Wei-Kang Wang, Qi Kong, De-Feng Chen, Liang-Jun Zhou, Ji-Wang Cao, Jia-Xin Lu, Ming-Xuan Zhou, Zi-Min Wei, Yi-Ning Huang, Xin-Bo Li, Xing-Lin Lou, Hao Mao, Ji-Rong Liang, En-Wei Filippenko, Alexei V. Guangxi Key Laboratory for Relativistic Astrophysics School of Physical Science and Technology Guangxi University Nanning530004 China School of Physics Beijing Institute of Technology Beijing100081 China Department of Astronomy University of California BerkeleyCA94720-3411 United States Yunnan Observatories Chinese Academy of Sciences 396 Yangfangwang Guandu District Kunming650216 China Center for Astronomical Mega-Science Chinese Academy of Sciences 20A Datun Road Chaoyang District Beijing100012 China Key Laboratory for the Structure and Evolution of Celestial Objects Chinese Academy of Sciences 396 Yangfangwang Guandu District Kunming650216 China

Mrk 501 is a prototypical high-synchrotron-peaked blazar (HBL) and serves as one of the primary targets for the Imaging X-ray Polarimetry Explorer (IXPE). In this study, we report X-ray polarization measurements of Mrk 501 based on six IXPE observations. The detection of X-ray polarization at a confidence level exceeding 99% is achieved in four out of the six observations conducted across the entire energy range (2–8 keV) of IXPE. The maximum polarization degree (ΠX) is measured to be 15.8% ± 2.8%, accompanied by a polarization angle (ψX) of 98.0◦ ± 5.1◦ at a confidence level of 5.6σ. During the remaining two observations, only an upper limit of ΠX X. The chromatic behavior of Π and the consistent values of ψ across different frequencies from X-rays to radio waves, along with the agreement between ψ and jet position angle, strongly support the interpretation of the energy-stratified model with shock-accelerated particles in the jet of Mrk 501. Additionally, the possibility of the presence of a global helical magnetic field in the jet of Mrk 501 is discussed. Copyright © 2024, The Authors. All rights reserved.

关键词： Active Galactic Nuclei

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Detection of Ubiquitous Circumbinary Matter in Hot Subdwarfs Formed from Common-Envelope Ejections

arXiv

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arXiv 2025年

作者： Li, Jiangdan Wolf, Christian Li, Jiao Luo, Yangping Zhao, Jingkun Chen, Bingqiu Zhang, Lin Jia, Shi Chen, Xuefei Han, Zhanwen 396 Yangfangwang Guandu District Kunming650216 China Key Laboratory for the Structure and Evolution of Celestial Objects CAS Kunming650216 China Research School of Astronomy and Astrophysics Australian National University Weston CreekACT2611 Australia Centre for Gravitational Astrophysics Australian National University CanberraACT2600 Australia Department of Astronomy China West Normal University Nanchong637002 China CAS Key Laboratory of Optical Astronomy National Astronomical Observatories Chinese Academy of Sciences Beijing100101 China South-Western Institute for Astronomy Research Yunnan University Kunming650504 China International Centre of Supernovae Yunnan Key Laboratory Kunming650216 China University of Chinese Academy of Sciences Beijing100049 China

The formation of compact binary systems is largely driven by their evolution through a common envelope (CE) phase, crucial for understanding phenomena such as type Ia supernovae and black hole mergers. Despite their importance, direct observational evidence for CE material has been elusive due to the transient nature of these envelopes. Numerical simulations suggest that some envelope material may persist post-ejection. In this study, we investigate circumstellar material (CSM) surrounding hot subdwarf (sdB) stars, focusing on material ejected during the CE phase of binary evolution. We analyze Ca II K absorption lines in 727 sdB candidates from the LAMOST-LRS survey, selecting 145 stars with strong absorption features, indicating the presence of CSM. We compare the velocities of the Ca II K lines with the systemic velocities of sdB binaries, confirming that the material originates from ejected common-envelope material. The results show that the CSM persists long after the CE event, suggesting the formation of a stable, long-lived circumstellar environment around sdB stars. This study enhances our understanding of the role of CSM in post-CE evolution and provides new insights into the physical processes shaping the evolution of sdB binaries. Copyright © 2025, The Authors. All rights reserved.

关键词： Supernovae

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Temporal Analysis of GRB Precursors in the Third Swift-BAT Catalog

arXiv

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arXiv 2022年

作者： Li, Liande Mao, Jirong Yunnan Observatories Chinese Academy of Sciences Yunnan Province Kunming650011 China Center for Astronomical Mega-Science Chinese Academy of Sciences 20A Datun Road Chaoyang District Beijing100012 China University of Chinese Academy of Sciences Beijing100049 China Key Laboratory for the Structure and Evolution of Celestial Objects Chinese Academy of Sciences Kunming650011 China

We select 52 long gamma-ray bursts(GRBs) having the precursor activity in the third Swift-BAT catalog. Each episode shown in both the precursors and the main bursts is fitted by the Norris function. We systematically analyze the temporal properties for both the precursors and the main bursts. We do not find any significant difference between the temporal profile of the precursor and that of the main burst. The photon count of the precursor is related to that of the main burst. It is indicated that the precursor and the main burst might have the same physical origin, as the precursor and the main burst follow the same τp−ω relation. However, we do not find the explicit relation between the energy release of the precursor and the quiescent time. Some theoretical models, such as the fallback collapsar scenario and the jet-cocoon scenario, may be helpful to explain the GRB-precursor phenomena. © 2022, CC BY.

关键词： Stars

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Transient phenomena from gas-erupting neutron stars

arXiv

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arXiv 2021年

作者： Li, Huiquan Wang, Jiancheng Yunnan Observatories Chinese Academy of Sciences Kunming650216 China Key Laboratory for the Structure and Evolution of Celestial Objects Chinese Academy of Sciences Kunming650216 China Center for Astronomical Mega-Science Chinese Academy of Sciences Beijing100012 China

Starquakes probably occur in rapidly spinning or ultra high field neutron stars. In this article, we argue that highly compressed gas containing electron-positron pairs could evaporate and erupt from inside the neutron star when a crack forms and then heals during a starquake. Under the influence of the existing oscillation modes of the star, the crack may have sufficiently large size and long lifetime. An appropriate amount of gas can erupt into the magnetosphere with relativistic and nearly uniform velocity, producing various transient and bursting phenomena. © 2021, CC0.

关键词： Stars

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Strong magnetic field inside degenerate relativistic plasma and the impacts on the neutrino transport in Core-Collapse Supernovae

arXiv

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arXiv 2024年

作者： Luo, Yudong Zha, Shuai Kajino, Toshitaka School of Physics Peking University Beijing100871 China Kavli Institute for Astronomy and Astrophysics Peking University Beijing100871 China Kunming650216 China Key Laboratory for the Structure and Evolution of Celestial Objects CAS Kunming650216 China International Centre of Supernovae Yunnan Key Laboratory Kunming650216 China School of Physics Peng Huanwu Collaborative Center for Research and Education International Research Center for Big-Bang Cosmology and Element Genesis Beihang University Beijing100191 China Graduate School of Science The University of Tokyo Tokyo113-0033 Japan National Astronomical Observatory of Japan Tokyo181-8588 Japan

We study the impacts of magnetic field on the neutrino transport inside corecollapse supernovae (CCSNe). Magnetic field quantizes the momentum of electrons and positrons, resulting in the modification of weak-interaction cross sections and the chemical potentials of electrons and positrons. We include these changes in the leakage scheme of neutrino transport and perform 1D CCSN simulations with GR1D, assuming the postbounce magnetic field strength of 1016-17 G. The results show that the neutrino opacities are enhanced due to the amplified interaction rates, resulting in a larger neutrinosphere. This further reduces the peak value of neutrino luminosities and their decay rates since neutrinos stay longer inside the neutrinosphere. Meanwhile, the neutrino mean energies are smaller shortly after bounce and reach their peak values at later times. As these neutrino properties are crucial in subsequent nucleosynthesis processes, including the νp-process, ν-process, and r-process, our findings suggest that the magnetic field may leave discernible marks on the abundance pattern of nucleosynthesis in CCSN. Copyright © 2024, The Authors. All rights reserved.

关键词： Magnetic fields

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Distribution and evolution of Li abundance in red clump stars can be explained by the internal gravity waves

arXiv

引用

arXiv 2024年

作者： Li, Xue-Feng Shi, Jian-Rong Li, Yan Yan, Hong-Liang Zhang, Jing-Hua Yunnan Observatories Chinese Academy of Sciences P.O.Box110 Kunming650216 China University of Chinese Academy of Sciences Beijing100049 China CAS Key Laboratory of Optical Astronomy National Astronomical Observatories Beijing100101 China School of Astronomy and Space Science University of Chinese Academy of Sciences Beijing100049 China Key Laboratory for Structure and Evolution of Celestial Objects Chinese Academy of Sciences P.O.Box110 Kunming650216 China Center for Astronomical Mega-Science Chinese Academy of Sciences Beijing100012 China Institute for Frontiers in Astronomy and Astrophysics Beijing Normal University Beijing102206 China

The study of Li phenomena in red clump (RC) stars can give us a deeper understanding of the structure and evolution of stars. Chanamé et al. (2022) explained the RC Li abundance distributions naturally using only standard post main sequence (MS) Li evolution models when the distribution of progenitor masses and the depletion of Li during the MS observed in MS stars were considered, thus neither extra Li depletion nor Li creation mechanism is required. Nevertheless, it is interesting to consider the effects of mixing caused by some extra mechanisms. By constructing different models, we find that the mixing caused by internal gravity waves can explain the observed Li abundances of RC stars with low mass progenitors. To explain that, we rely on the extra mixing induced by internal gravity waves that are excited at the bottom of the convective envelope at the red giant branch (RGB) stage. During the RGB stage, introducing the internal gravity waves can improve the diffusion coefficient and strengthen the mixing effect. The effective enrichment of Li occurs at the late RGB stage and requires the diffusion coefficient of H-burning shell to reach ∼ 108 cm2 s−1. Our models predict that the Li abundance decreases from ∼ 1.5 dex to ∼ 0.0 dex at the end of core He-burning stage, thereby revealing the ∼ 99% of the observed Li abundance distribution. The thermohaline mixing regulates the Li abundance of RGB stars, which combines with the internal gravity waves can explain the Li abundances of most giants. Copyright © 2024, The Authors. All rights reserved.

关键词： Diffusion

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Meridional Circulation. I. A Formation Channel for Lithium-rich and Super Lithium-rich Red Clump Stars

arXiv

引用

arXiv 2025年

作者： Li, Xue-Feng Shi, Jian-Rong Li, Yan Yan, Hong-Liang Zhang, Jing-Hua Yunnan Observatories Chinese Academy of Sciences P.O.Box110 Kunming650216 China CAS Key Laboratory of Optical Astronomy National Astronomical Observatories Beijing100101 China University of Chinese Academy of Sciences Beijing100049 China Key Laboratory for Structure and Evolution of Celestial Objects Chinese Academy of Sciences P.O.Box110 Kunming650216 China Center for Astronomical Mega-Science Chinese Academy of Sciences Beijing100012 China Institute for Frontiers in Astronomy and Astrophysics Beijing Normal University Beijing102206 China South-Western Institute for Astronomy Research Yunnan University Chenggong District Kunming650500 China

Current observations indicate that stars with higher rotation rates appear to maintain more surface lithium, and the majority of lithium-rich giants are indeed red clump stars. Hence, we investigate the mechanisms behind lithium enrichment in rotating red clump stars and the pathways to forming lithium-rich red clump stars. Meridional circulation is prevalent in the radiative zone of rotating giants. We model its radial mixing as a diffusion process and derive the corresponding diffusion coefficient based on its material transfer effect. Due to uncertainties in numerical calculations, we consider an average diffusion effect. Additionally, certain limiting conditions for the radial velocity of meridional circulation are incorporated. With varying input rotation velocities, we simulate the lithium evolution for red clump stars with this model. Our results indicate that the material transfer effect due to meridional circulation can efficiently transport beryllium, produced by H burning, into the convective envelope. This meridional circulation can lead to lithium enrichment, with a maximum lithium abundance increment approaching 3.0 dex. Consequently, it is capable of forming both lithium-rich and super lithium-rich red clump stars. The degree of lithium enrichment exhibits a strong positive correlation with the rotation velocity, i.e., faster red clump stars show more surface lithium. Furthermore, our models indicate that lithium-rich red clump stars are relatively young (∼ 106 yr), which aligns with observation evidences. Copyright © 2025, The Authors. All rights reserved.

关键词： Giant stars

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A photometric study of the high-mass-ratio contact binary AV Puppis

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Research in Astronomy and Astrophysics 2019年第12期19卷 217-222页

作者： Quan-Wang Han Li-Fang Li Deng-Kai Jiang Yunnan Observatories Chinese Academy of SciencesKunming 650216China Key Laboratory of the Structure and Evolution of Celestial Objects Chinese Academy of Sciences.Kunming 650216China University of Chinese Academy of Sciences Beijing 100049China

The multi-color photometric light curves for contact binary AV Puppis(AV Pup) in VRcIc bandpasses are presented and analyzed by using the 2013 version of the Wilson-Devinney(W-D) *** solutions suggest that AV Pup is a peculiar A-subtype W UMa contact binary with a high mass ratio(q = m2/m1 = 0.896) and a low fill-out factor(f = 10%). Combining our newly determined times of minimum with those collected from literatures, the orbital period changes of this system are investigated. The O-C analysis indicates that the orbital period of AV Pup is increasing at a rate of d P/dt = 4.83 × 10-7 days yr-1, which can be explained by mass transfer from the less massive component to the more massive one.

关键词： techniques:photometric stars:magnetic field stars:individual:AV Pupis

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The Common Envelope evolution Outcome-A Case Study on Hot Subdwarf B Stars

arXiv

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arXiv 2022年

作者： Ge, Hongwei Tout, Christopher A. Chen, Xuefei Kruckow, Matthias U. Chen, Hailiang Jiang, Dengkai Li, Zhenwei Liu, Zhengwei Han, Zhanwen Yunnan Observatories Chinese Academy of Sciences 396 YangFangWang Guandu District Kunming650216 China Institute of Astronomy The Observatories University of Cambridge Madingley Road CambridgeCB3 0HA United Kingdom Key Laboratory for Structure and Evolution of Celestial Objects Chinese Academy of Sciences P.O. Box 110 Kunming650216 China

Common envelope evolution (CEE) physics plays a fundamental role in the formation of binary systems, such as mergering stellar gravitational wave sources, pulsar binaries and type Ia supernovae. A precisely constrained CEE has become more important in the age of large surveys and gravitational wave detectors. We use an adiabatic mass loss model to explore how the total energy of the donor changes as a function of the remnant mass. This provides a more self-consistent way to calculate the binding energy of the donor. For comparison, we also calculate the binding energy through integrating the total energy from the core to the surface. The outcome of CEE is constrained by total energy conservation at the point at which both component's radii shrink back within their Roche lobes. We apply our results to 142 hot subdwarf binaries. For shorter orbital period sdBs, the binding energy is highly consistent. For longer orbital period sdBs in our samples, the binding energy can differ by up to a factor of 2. The CE efficiency parameter βCEbecomes smaller than αCEfor the final orbital period log10Porb=d >-0.5. We also find the mass ratios log10q and CE efficiency parameters log10αCEand log10βCElinearly correlate in sdBs, similarly to De Marco et al. (2011) for post-AGB binaries. © 2022, CC0.

关键词： Binding energy

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Magnetic-Reconnection-Heated Corona Model: Implication of Hybrid Electrons for Hard X-ray Emission of Luminous Active Galactic Nuclei

arXiv

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arXiv 2023年

作者： Liu, Jie-Ying Mao, Jirong Liu, B.F. Yunnan Observatories Chinese Academy of Sciences Yunnan Province Kunming650216 China International Centre of Supernovae Yunnan Key Laboratory Kunming650216 China Key Laboratory for the Structure and Evolution of Celestial Objects Chinese Academy of Sciences Kunming650216 China School of Astronomy and Space Sciences University of Chinese Academy of Sciences 19A Yuquan Road Beijing100049 China Center for Astronomical Mega-Science Chinese Academy of Sciences 20A Datun Road Chaoyang District Beijing100012 China Key Laboratory of Space Astronomy and Technology National Astronomical Observatories Chinese Academy of Sciences Beijing100012 China

It is widely accepted that X-ray emission in luminous active galactic nuclei (AGNs) originates from hot corona. To prevent the corona from over-cooling by strong X-ray emission, steady heating to the corona is essential, for which the most promising mechanisms is the magnetic reconnection. Detailed studies of the coupled disc and corona, in the frame of magnetic field transferring accretion-released energy from the disc to the corona, reveal that the thermal electrons can only produce X-ray spectrum with Γ2−10 keV > 2.1, which is an inevitable consequence of the radiative coupling of the thermal corona and disc. In the present work, we develop the magnetic-reconnection-heated corona model by taking into account the potential non-thermal electrons accelerated in the magnetic reconnection process, in addition to the thermal electrons. We show that the features of the structure and spectrum of the coupled disc and corona can be affected by the fraction of magnetic energy allocated to thermal electrons. Furthermore, we investigate the effects of the power-law index and energy range of non-thermal electrons and the magnetic field on the spectrum. It is found that the X-ray spectrum from the Comptonization of the hybrid electrons can be flatter than that from thermal electrons only, in agreement with observations. By comparing with the observed hard X-ray data, we suggest that a large fraction (> 40%) of the magnetic energy be allocated to the non-thermal electrons in the luminous and flat X-ray spectrum AGNs. Copyright © 2023, The Authors. All rights reserved.

关键词： Gamma rays

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