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A Fermi-LAT Study of Globular Cluster Dynamical Evolution in the Milky Way:Millisecond Pulsars as the Probe

Research in astronomy and Astrophysics 2024年第2期24卷 1-23页

作者： Li Feng Zhongqun Cheng Wei Wang Zhiyuan Li Yang Chen School of astronomy and Space Science Nanjing UniversityNanjing 210023China Department of astronomy School of Physics and TechnologyWuhan UniversityWuhan 430072China whu-naoc joint center for astronomy Wuhan UniversityWuhan 430072China Key Laboratory of Modern astronomy and Astrophysics Nanjing UniversityNanjing 210023China

Using archival Fermi-LAT data with a time span of~12 yr,we study the population of Millisecond Pulsars(MSPs)in Globular Clusters(GlCs)and investigate their dependence on cluster dynamical evolution in the Milky Way.We show that theγ-ray luminosity(L_(γ))and emissivity(i.e.,ε_(γ)=L_(γ)/M,with M the cluster mass)are good indicators of the population and abundance of MSPs in GlCs,and they are highly dependent on the dynamical evolution history of the host clusters.Specifically speaking,the dynamically older GlCs with more compact structures are more likely to have larger L_(γ)andε_(γ),and these trends can be summarized as strong correlations with cluster stellar encounter rateΓand the specific encounter rate(Λ=Γ/M),with L_(γ)∝Γ^(0.7±0.11)andε_(γ)∝Λ^(0.73±0.13)for dynamically normal GlCs.However,as GlCs evolve into deep core collapse,these trends are found to be reversed,implying that strong encounters may have lead to the disruption of Low-Mass X-ray Binaries and ejection of MSPs from core-collapsed systems.Besides,the GlCs are found to exhibit largerε_(γ)with increasing stellar mass function slope(ε_(γ)∝10^((0.52±0.1)α)),decreasing tidal radius(ε_(γ)∝R_(t)^(-10±0.22))and distances from the Galactic center(GC,ε_(γ)∝R_(gc)^(-1.13±0.21)).These correlations indicate that,as GlCs losing kinetic energy and spiral in toward the GC,tidal stripping and mass segregation have a preference in leading to the loss of normal stars from GlCs,while MSPs are more likely to concentrate to cluster center and be deposited into the GC.Moreover,we gaugeε_(γ)of GlCs is~10-1000 times larger than the Galactic bulge,the latter is thought to reside thousands of unresolved MSPs and may be responsible for the GC 7-ray excess,which supports that GlCs are generous contributors to the population of MSPs in the GC.

关键词： (Galaxy:)globular clusters general-(stars:)pulsars general-Galaxy kinematics and dynamics-Galaxy center-Galaxy bulge-gamma-rays stars-gamma-rays diffuse background-gamma-rays galaxies

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Analysis of Bright Source Hardness Ratios in the 4 yr Insight-HXMT Galactic Plane Scanning Survey Catalog

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Research in astronomy and Astrophysics 2024年第2期24卷 154-170页

作者： Chen Wang Jin-Yuan Liao Ju Guan Yuan Liu Cheng-Kui Li Na Sai Jing Jin Shuang-Nan Zhang Key Laboratory of Space astronomy and Technology National Astronomical ObservatoriesChinese Academy of SciencesBeijing 100101China University of Chinese Academy of Sciences Beijing 100049China Key Laboratory of Particle Astrophysics Institute of High Energy PhysicsChinese Academy of SciencesBeijing 100049China Department of astronomy School of Physics and TechnologyWuhan UniversityWuhan 430072China whu-naoc joint center for astronomy Wuhan UniversityWuhan 430072China

We conduct a statistical analysis of the hardness ratio(HR)for bright sources in the 4 yr Galactic Plane Scanning Survey catalog of Insight-HXMT.Depending on the stable(variable)flux F_(s)(F_(v))or spectrum S_(s)(S_(v))of each source,the bright sources are classified into three groups:F_(v)&S_(v),F_(v)&S_(s),and F_(s)&_(s).Our study of the HR characteristics in different types of sources reveals that accretion-powered neutron star(NS)low-mass X-ray binaries(LMXBs)exhibit softer energy spectra than NS high-mass X-ray binaries(HMXBs),but harder energy spectra than black hole binaries in most cases.This difference is probably due to their different magnetic field strengths.Additionally,Fv&Sv LMXBs tend to be harder than Fv&Ss LMXBs below 7 keV,while the opposite is true for HMXBs.Our results suggest that LMXBs may dominate unclassified sources,and NS binaries are likely to be the primary type of X-ray binaries with ambiguous compact stars.By comparing the HR of transient sources in their outburst and low-flux states,it is found that the averaged HR of four sources in the two states are roughly comparable within uncertainties.We also investigate the spatial properties of the three groups and find that Fv&Sv sources are mainly located in the longitude of-20°

关键词： catalogs-surveys-methods data analysis-X-rays general

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Scintillation Arc from FRB 20220912A

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Science China(Physics,Mechanics & astronomy) 2024年第1期67卷 134-142页

作者： Zi-Wei Wu Robert AMain Wei-Wei Zhu Bing Zhang Peng Jiang Jia-Rui Niu Jin-Lin Han Di Li Ke-Jia Lee Dong-Zi Li Yuan-Pei Yang Fa-Yin Wang Rui Luo Pei Wang Chen-Hui Niu Heng Xu Bo-Jun Wang Wei-Yang Wang Yong-Kun Zhang Yi Feng De-Jiang Zhou Yong-Hua Xu Can-Min Deng Yu-Hao Zhu National Astronomical Observatories Chinese Academy of SciencesBeijing 100101China Max-Planck-Institut für Radioastronomie Bonn 53121Germany Institute for Frontier in astronomy and Astrophysics Beijing Normal UniversityBeijing 102206China Nevada center for Astrophysics and Department of Physics and astronomy University of NevadaLas VegasNV 89154USA CAS Key Laboratory of FAST National Astronomical ObservatoriesChinese Academy of SciencesBeijing 100101China School of astronomy University of Chinese Academy of SciencesBeijing 100049China naoc-UKZN Computational Astrophysics Centre University of KwaZulu-NatalDurban 4000South Africa Department of astronomy Peking UniversityBeijing 100871China Kavli Institute for astronomy and Astrophysics Peking UniversityBeijing 100871China Cahill center for astronomy and Astrophysics California Institute of TechnologyPasadena 91125USA South-Western Institute For astronomy Research Yunnan UniversityKunming 650504China School of astronomy and Space Science Nanjing UniversityNanjing 210093China Key Laboratory of Modern astronomy and Astrophysics(Nanjing University) Ministry of EducationNanjing 210023China CSIRO Space and astronomy Epping 1710Australia Department of astronomy School of Physics and Materials ScienceGuangzhou UniversityGuangzhou 510006China Research center for Intelligent Computing Platforms Zhejiang LaboratoryHangzhou 311100China Yunnan Observatories Chinese Academy of SciencesKunming 650011China Guangxi Key Laboratory for Relativistic Astrophysics Department of PhysicsGuangxi UniversityNanning 530004China

We present the interstellar scintillation analysis of fast radio burst(FRB)20220912A during its extremely active episode in 2022using data from the Five-hundred-meter Aperture Spherical Radio Telescope(FAST).We detect a scintillation arc in the FRB’s secondary spectrum,which describes the power in terms of the scattered FRB signals’time delay and Doppler shift.The arc indicates that the scintillation is caused by a highly localized region.Our analysis favors a Milky Way origin of the ionized interstellar medium(IISM)for the localized scattering medium but cannot rule out a host galaxy origin.We present our method for detecting the scintillation arc,which can be applied generally to sources with irregularly spaced bursts or pulses.These methods could help shed light on the complex interstellar environment surrounding the FRBs and in our Galaxy.

关键词： fast radio burst scintillation FRB 20220912A

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Probing turbulence in galaxies with fast radio burst scintillation

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Science China(Physics,Mechanics & astronomy) 2024年第1期67卷 177-178页

作者： James M.Cordes Department of astronomy the Cornell Center for Astrophysics and Planetary ScienceCornell UniversityIthaca NY 14853USA

Interstellar scintillation(ISS)is a well-known phenomenon observed from pulsars in the Milky Way.It comprises intensity variations vs.time and frequency caused by constructive and destructive interference from multipath propagation,which is due to diffraction from fluctuations in electron density in the interstellar medium(ISM)on scales as small as~100 km.These density fluctuations appear to be part of a turbulence process combined with discrete structures in electron density from other astrophysical processes;together these fluctuations extend to scales of pc or larger.

关键词： scales galaxies turbulence

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A phase separation-fortified bi-specific adaptor for conditional tumor killing

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Science China(Life Sciences) 2024年第7期67卷 1385-1397页

作者： Yuyan Liu Yuting Zhu Weifan Xu Pilong Li State Key Laboratory of Membrane Biology Frontier Research Center for Biological StructureTsinghua University-Peking University Joint Center for Life SciencesSchool of Life SciencesTsinghua UniversityBeijing 100084China

A common approach in therapeutic protein development involves employing synthetic ligands with multivalency,enabling sophisticated control of signal transduction.Leveraging the emerging concept of liquid-liquid phase separation(LLPS)and its ability to organize cell surface receptors into functional compartments,we herein have designed modular ligands with phase-separation modalities to engineer programmable interreceptor communications and precise control of signal pathways,thus inducing the rapid,potent,and specific apoptosis of tumor cells.Despite their simplicity,these“triggers”,named phase-separated Tumor Killers(hereafter referred to as psTK),are sufficient to yield interreceptor clustering of death receptors(represented by DR5)and tumor-associated receptors,with notable features:LLPSmediated robust high-order organization,well-choreographed conditional activation,and broad-spectrum capacity to potently induce apoptosis in tumor cells.The development of novel therapeutic proteins with phase-separation modalities showcases the power of spatially reorganizing signal transduction.This approach facilitates the diversification of cell fate and holds promising potential for targeted therapies against challenging tumors.

关键词： phase separation therapeutic proteins receptor-ligand interactions DR5 tumor apoptosis

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Nickel-Catalyzed Regiodivergent Acylzincation of Styrenes with Organozincs and CO

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Chinese Journal of Chemistry 2024年第6期42卷 599-604页

作者： Chenglong Wang Ning Liu Xianqing Wu Jingping Qu Yifeng Chen Key Laboratory for Advanced Materials and joint International Research Laboratory of Precision Chemistry and Molecular Engineering Feringa Nobel Prize Scientist Joint Research CenterFrontiers Science Center for Materiobiology and Dynamic ChemistrySchool of Chemistry and Molecular EngineeringEast China University of Science and TechnologyShanghai200237 China Dedicated to the Special Issue of C1 Chemistry.

Transition metal-catalyzed carbometallation of unsaturated hydrocarbons constitutes one of the most efficient synthetic methodologies for the construction of C—C bond.Recently,the incorporation of organometallic reagent with the CO gas as a nucleophilic acyl synthon could enable the acylmetallation reaction,which greatly increases the horizon of carbometallation chemistry.Herein,we report a nickel-catalyzed regiodivergent acylzincation of o-cyano cinnamate ester and o-cyano styrene,in which the cyano moiety intramolecularly captures zinc intermediates to trigger the tandem cyclization process.This protocol features mild conditions,broad substrate scope and excellent functional group tolerance,thus affording a diverse array of highly functionalized carbocyclic compounds.

关键词： Carbonylation Carbometallation Styrene Nickel Cyclization

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Remote copper-catalyzed enantioselective substitution of yne-thiophene carbonates

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Science China Chemistry 2024年第4期67卷 1175-1180页

作者： Hao-Dong Qian Xiang Li Tingrui Yin Wei-Feng Qian Chunhui Zhao Cuiju Zhu Hao Xu CCNU-uOttawa joint Research Centre Key Laboratory of Pesticides&Chemical Biology of Ministry of EducationInternational Joint Research Center for Intelligent Biosensing Technology and HealthCollege of ChemistryCentral China Normal UniversityWuhan 430079China

Here,we describe a strategy for the copper-catalyzed asymmetric heteroarylation of yne-thiophene carbonates with indoles via remote substitution.The key to the success of this strategy lies in the design of the alkynyl group at the ortho-position of the heterocycle thiophene,enabling the formation of a triarylmethane moiety via very remote substitution.Thus,the concept of remote copper-catalyzed asymmetric transformation extends not only to yne-allylic esters but also to yne-aryl esters.The reaction readily provides a diverse array of chiral triarylmethanes with high efficiency,enantioselectivity,and excellent functional group compatibility.Moreover,facile follow-up transformations underscore their potential utility in the synthesis of various enantioenriched building blocks.Preliminary mechanistic studies support the plausibility of the remote substitution pathway.

关键词： remote substitution copper catalyst asymmetric catalysis triaryl methanes

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Inelastic Scattering of Dark Matter with Heavy Cosmic Rays

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Research in astronomy and Astrophysics 2024年第6期24卷 70-82页

作者： Keyu Lu Yue-Lin Sming Tsai Qiang Yuan Le Zhang School of Physics and astronomy Sun Yat-sen University Key Laboratory of Dark Matter and Space astronomy Purple Mountain Observatory Chinese Academy of Sciences School of astronomy and Space Science University of Science and Technology of China CSST Science center for the Guangdong-Hong Kong-Macau Greater Bay Area SYSU Peng Cheng Laboratory

We investigate the impact of inelastic collisions between dark matter （DM） and heavy cosmic ray （CR） nuclei on CR propagation.We approximate the fragmentation cross-sections for DM-CR collisions using collider-measured proton-nuclei scattering cross-sections,allowing us to assess how these collisions affect the spectra of CR boron and carbon.We derive new CR spectra from DM-CR collisions by incorporating their cross-sections into the source terms and solving the diffusion equation for the complete network of reactions involved in generating secondary species.In a specific example with a coupling strength of bχ=0.1 and a DM mass of mχ=0.1 GeV,considering a simplified scenario where DM interacts exclusively with oxygen,a notable modification in the boron-to-carbon spectrum due to the DM-CR interaction is observed.Particularly,the peak within the spectrum,spanning from 0.1 to 10 GeV,experiences an enhancement of approximately 1.5 times.However,in a more realistic scenario where DM particles interact with all CRs,this peak can be amplified to twice its original value.Utilizing the latest data from AMS-02 and DAMPE on the boron-to-carbon ratio,we estimate a 95%upper limit for the effective inelastic cross-section of DM-proton as a function of DM mass.Our findings reveal that at mχ?2 MeV,the effective inelastic cross-section between DM and protons must be less than O(10-32) cm2.

关键词： (cosmology:) dark matter abundances astroparticle physics elementary particles nuclear reactions nucleosynthesis scattering

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Understanding adversarial attacks on observations in deep reinforcement learning

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Science China(Information Sciences) 2024年第5期67卷 69-83页

作者： You QIAOBEN Chengyang YING Xinning ZHOU Hang SU Jun ZHU Bo ZHANG Department of Computer Science and Technology Beijing National Research Center for Information Science and Technology Tsinghua-Bosch Joint Center for Machine Learning Institute for Artificial Intelligence Tsinghua University Peng Cheng Laboratory

Deep reinforcement learning models are vulnerable to adversarial attacks that can decrease the cumulative expected reward of a victim by manipulating its observations. Despite the efficiency of previous optimization-based methods for generating adversarial noise in supervised learning, such methods might not achieve the lowest cumulative reward since they do not generally explore the environmental dynamics.Herein, a framework is provided to better understand the existing methods by reformulating the problem of adversarial attacks on reinforcement learning in the function space. The reformulation approach adopted herein generates an optimal adversary in the function space of targeted attacks, repelling them via a generic two-stage framework. In the first stage, a deceptive policy is trained by hacking the environment and discovering a set of trajectories routing to the lowest reward or the worst-case performance. Next, the adversary misleads the victim to imitate the deceptive policy by perturbing the observations. Compared to existing approaches, it is theoretically shown that our adversary is strong under an appropriate noise level. Extensive experiments demonstrate the superiority of the proposed method in terms of efficiency and effectiveness, achieving state-of-the-art performance in both Atari and MuJoCo environments.

关键词： deep learning reinforcement learning adversarial robustness adversarial attack

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Imprints of ultralight axions on the gravitational wave and pulsar timing measurement

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Science China(Physics,Mechanics & astronomy) 2024年第1期67卷 23-29页

作者： Ning Xie Fa Peng Huang MOE Key Laboratory of TianQin Mission TianQin Research Center for Gravitational Physics&School of Physics and AstronomyFrontiers Science Center for TianQinGravitational Wave Research Center of CNSASun Yat-sen University(Zhuhai Campus)Zhuhai 519082China

The axion or axion-like particle motivated from a natural solution of strong CP problem or string theory is a promising dark matter candidate.We study the new observational effects of ultralight axion-like particles by the space-borne gravitational wave detector and the radio telescope.Taking the neutron star-black hole binary as an example,we demonstrate that the gravitational waveform could be obviously modified by the slow depletion of the axion cloud around the black hole formed through the superradiance process.We compare these new effects on the binary with the well-studied effects from dynamical friction with dark matter and dipole radiation in model-independent ways.Finally,we discuss the constraints from LIGO/Virgo and study the detectability of the ultralight axion particles at LISA and TianQin.

关键词： gravitational wave axion dark matter

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