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Einstein Probe discovery of EP240408a: A peculiar X-ray transient with an intermediate timescale

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Science China(physics,Mechanics & Astronomy) 2025年第1期Mechanics & Astronomy) .卷 222-240页

作者： Wenda Zhang Weimin Yuan Zhixing Ling Yong Chen Nanda Rea Arne Rau Zhiming Cai Huaqing Cheng Francesco Coti Zelati Lixin Dai Jingwei Hu Shumei Jia Chichuan Jin Dongyue Li Paul O’Brien Rongfeng Shen Xinwen Shu Shengli Sun Xiaojin Sun Xiaofeng Wang Lei Yang Bing Zhang Chen Zhang Shuang-Nan Zhang Yonghe Zhang Jie An David Buckley Alexis Coleiro Bertrand Cordier Liming Dou Rob Eyles-Ferris Zhou Fan Hua Feng Shaoyu Fu Johan P.U.Fynbo Lluis Galbany Saurabh W.Jha Shuaiqing Jiang Albert Kong Erik Kuulkers Weihua Lei Wenxiong Li Bifang Liu Mingjun Liu Xing Liu Yuan Liu Zhu Liu Chandreyee Maitra Alessio Marino Itumeleng Monageng Kirpal Nandra Jeremy Sanders Roberto Soria Lian Tao Junfeng Wang Song Wang Tinggui Wang Zhongxiang Wang Qingwen Wu Xuefeng Wu Dong Xu Yanjun Xu Suijian Xue Yongquan Xue Zijian Zhang Zipei Zhu Hu Zou Congying Bao Fansheng Chen Houlei Chen Tianxiang Chen Wei Chen Yehai Chen Yifan Chen Chenzhou Cui Weiwei Cui Yanfeng Dai Dongwei Fan Ju Guan Dawei Han Dongjie Hou Haibo Hu Maohai Huang Jia Huo Zhenqing Jia Bowen Jiang Ge Jin Chengkui Li Junfei Li Longhui Li Maoshun Li Wei Li Zhengda Li Tianying Lian Congzhan Liu Heyang Liu Huaqiu Liu Fangjun Lu Laidan Luo Jia Ma Xuan Mao Haiwu Pan Xin Pan Liming Song Hui Sun Yunyin Tan Qingjun Tang Yihan Tao Hao Wang Juan Wang Lei Wang Wenxin Wang Yilong Wang Yusa Wang Qinyu Wu Haitao Xu Jingjing Xu Xinpeng Xu Yunfei Xu Zhao Xu Changbin Xue Yulong Xue Ailiang Yan Haonan Yang Xiongtao Yang Yanji Yang Juan Zhang Mo Zhang Wenjie Zhang Zhen Zhang Zhen Zhang Ziliang Zhang Donghua Zhao Haisheng Zhao Xiaofan Zhao Zijian Zhao Hongyan Zhou Yilin Zhou Yuxuan Zhu Zhencai Zhu National Astronomical Observatories Chinese Academy of Sciences School of Astronomy and Space Sciences University of Chinese Academy of Sciences Key Laboratory of Particle Astrophysics Institute of High Energy physics Chinese Academy of Sciences Institute of Space Sciences (ICE) CSIC Institut d’Estudis Espacials de Catalunya (IEEC) Max Planck Institute for Extraterrestrial physics Innovation Academy for Microsatellites Chinese Academy of Sciences department of physics University of Hong Kong School of physics and Astronomy University of Leicester School of physics and Astronomy Sun Yat-sen University department of physics Anhui Normal University Shanghai Institute of Technical physics Chinese Academy of Sciences physics department Tsinghua University Nevada Center for Astrophysics University of Nevada Las Vegas department of physics and Astronomy University of Nevada Las Vegas South African Astronomical Observatory department of Astronomy University of Cape Town department of physics University of the Free State Université Paris Cité CNRS Astroparticule et Cosmologie Université Paris Cité CEA Paris-Saclay IRFU/DAp-AIM department of Astronomy Guangzhou University Cosmic Dawn Center (DAWN) Niels Bohr Institute University of Copenhagen department of physics and Astronomy Rutgers the State University of New Jersey Institute for Cosmic Ray research The University of Tokyo ESA/ESTEC department of Astronomy School of physics Huazhong University of Science and Technology INAF-Osservatorio Astrofisico di Torino Sydney Institute for Astronomy School of physics The University of Sydney department of Astronomy Xiamen University Institute for Frontiers in Astronomy and Astrophysics Beijing Normal University department of Astronomy University of Science and Technology School of Astronomy and Space Sciences University of Science and Technology of China Institute of Deep Space Sciences Deep Space Exploration Laboratory department of Astronomy School of physics and Astronomy Yunnan University Shanghai Astronomical Observatory Chi

We report the discovery of a peculiar X-ray transient,EP240408a,by Einstein Probe （EP） and follow-up studies made with EP,Swift,NICER,GROND,ATCA and other ground-based multiwavelength *** new transient was first detected with Wide-field X-ray Telescope （WXT） on board EP on April 8th,2024,manifested in an intense yet brief X-ray flare lasting for *** flare reached a peak flux of 3.9×10-9erg cm-2s-1in 0.5-4 ke V,～300 times brighter than the underlying X-ray emission detected throughout the *** and more precise follow-up observations by EP/FXT,Swift and NICER confirmed the finding of this new *** X-ray spectrum is non-thermal in 0.5-10 ke V,with a power-law photon index varying *** X-ray light curve shows a plateau lasting for ～4 d,followed by a steep decay till becoming undetectable ～10 d after the initial *** on its temporal property and constraints from previous EP observations,an unusual timescale in the range of 7-23 d is found for EP240408a,which is intermediate between the commonly found fast and long-term *** counterparts have been found in optical and near-infrared,with the earliest observation at 17 h after the initial X-ray detection,suggestive of intrinsically weak emission in these *** demonstrate that the remarkable properties of EP240408a are inconsistent with any of the transient types known so far,by comparison with,in particular,jetted tidal disruption events,gamma-ray bursts,X-ray binaries and fast blue optical *** nature of EP240408a thus remains an *** suggest that EP240408a may represent a new type of transients with intermediate timescales of the order of～10 *** detection and follow-ups of more of such objects are essential for revealing their origin.

关键词： X-ray transients ${\bm~{Einstein~~Probe}}$

Effect of pH on Crystal Size and Photoluminescence Property of ZnO Nanoparticles Prepared by Chemical Precipitation Method

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Acta Metallurgica Sinica(English Letters) 2015年第3期28卷 394-404页

作者： M.Jay Chithra M.Sathya K.Pushpanathan pg & research department of physics Government Arts College

The effects of pH value on crystal size and optical property of zinc oxide nanoparticles prepared by chemical precipitation method were *** samples have been characterized by means of X-ray diffraction,scanning electron microscopy,ultraviolet-visible spectrometer and photoluminescence *** X-ray diffraction profile,it is found that the particle size of sample increases from 13.8 to 33 nm when the pH value of the solution was increased from 6 to *** study also shows that the particle size increases with pH *** shape of the zinc oxide nanoparticle has been confirmed by the scanning electron microscopy *** recorded ultraviolet-visible spectrum shows excitonic absorption peaks around 381 *** energy gap of the prepared samples has been determined from the ultraviolet-visible absorption spectrum,effective mass model equation and Tauc＇s *** was found that the energy gap of the prepared samples decreases with increase in pH *** recorded blue shift confirmed the quantum confinement effect in the prepared zinc oxide *** spectrum infers that the increase in pH value shifts the ultraviolet-visible emission but not the violet and green emissions.

关键词： Zinc oxide nanoparticles pH value Crystal structure Microstructure Energy gap Photoluminescence

Effect of Fuel to Oxidant Molar Ratio on Structural and DC Electrical Conductivity of ZnO Nanoparticles Prepared by Simple Solution Combustion Method

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Journal of Materials Science & Technology 2013年第10期29卷 898-902页

作者： C.S.Naveen M.L.Dinesha H.S.Jayanna department of pg Studies and research in physics Kuvempu University

ZnO nanoparticles of different sizes were prepared by varying the molar ratio of glycine and zinc nitrate hexahydrate as fuel and oxidizer （0.1, 0.8, 1.11, 1.3, 1.5, 1.7, 2.0） by simple solution combustion method. UV-Visible spectrophotometry studies show that, the band gap of the prepared ZnO nanoparticles increases with increasing fuel to oxidant （F/O） molar ratio up to 1.7 revealing the formation of ZnO nanoparticles. The decrease in band gap for the sample of F/O molar ratio 2.0 is due to an increase in particle size. Powder X-ray diffraction patterns of the prepared samples show the formation of single phase ZnO nanoparticles and the particle size decreases with increasing F/O molar ratio up to 1.7. Surface morphology of the prepared samples was studied by scanning electron microscopy and it was observed that, the porosity increases with increasing F/O molar ratio. DC electrical conductivity at room temperature and in the temperature range of 303-563 K was studied for all the samples and the results revealed that, the sample of F/O molar ratio 1.7 has low electrical conductivity at room temperature and high EAR （high temperature activation energy） compared to other samples.

关键词： ZnO nanoparticles Structural characterization Electrical conductivity

Thermospheric neutral wind studies over the equatorial region:A review

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Earth and Planetary physics 2025年第1期9卷 81-100页

作者： Siti Syazwani Nasuha Idahwati Sarudin Nurul Shazana Abdul Hamid Ahmad Fairuz Omar School of physics Universiti Sains Malaysia11800 USMPulau PinangMalaysia department of Applied physics Faculty of Science and TechnologyUniversiti Kebangsaan Malaysia43600 UKM BangiSelangorMalaysia Space Science centre(ANGKASA) Institute of Climate ChangesUniversiti Kebangsaan Malaysia43600 UKM BangiSelangorMalaysia

Thermospheric neutral winds(TNWs)refer to the neutral gases in the thermosphere circulating as tides,which play a crucial role in the dynamics of the thermosphere-ionosphere system(TIS).Global geospace neutral winds,particularly over the magnetic equator,have been a subject of study for several ***,despite the known importance of neutral winds,a comprehensive understanding and characterization of the winds is still *** ground-based and satellite missions have provided valuable information on the contribution of neutral winds to the global atmospheric ***,efforts in the global monitoring of neutral winds are still lacking,and the drivers behind the behavior of TNWs as well as their influence on the TIS remain *** address these knowledge gaps in the global circulation of TNWs,it is crucial to develop a deep understanding of the neutral wind characteristics over different *** low-latitude equatorial region in particular has been observed to exert complex influences on TNWs because of the unique effects of the Earth’s magnetic field at the dip *** neutral winds over this region will provide valuable insights into the unique dynamics and processes that occur in this region,thereby enhancing our understanding of their role in the overall dynamics of the ***,through empirical observations,an improved ability to accurately model and predict the behavior of this region can be *** review article addresses challenges in understanding equatorial winds by reviewing historical measurements,current missions,and the interactions of ionospheric and thermospheric phenomena,emphasizing the need for comprehensive measurements to improve global atmospheric dynamics and weather forecasting.

关键词： thermospheric neutral wind thermosphere-ionosphere system dip equator equatorial region

Flower-shaped CuO Nanostructures: Synthesis,Characterization and Antimicrobial Activity

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Journal of Materials Science & Technology 2013年第10期29卷 909-914页

作者： K.Mageshwari R.Sathyamoorthy pg & research department of physics Kongunadu Arts and Science College

In the present work, flower-like CuO nanostructures were synthesized by reflux condensation method without using any surfactants or templates. Structural analysis by X-ray diffraction （XRD）, Fourier transform infrared spectroscopy （FTIR） and Raman studies revealed the formation of highly crystalline single phase CuO, exhibiting monoclinic structure. Morphological analysis by field emission scanning electron microscopy （FESEM） showed flower-shaped CuO hierarchical architecture made up of interpenetrating self-assembled nanosheets. Optical analysis by UV-Vis diffused reflectance spectra （DRS） exhibited considerable blue-shift in the optical band gap due to quantum confinement effect. Photoluminescence （PL） spectrum showed both UV as well as visible emissions. The antibacterial activity of flower-shaped CuO nanostructures were tested against gram-positive （Bacillus subtilis, Bacillus thuringiensis） and gram-negative （Salmonella paratyphi, Salmonella paratyphi-a, Salmonella paratyphi-b, Escherichia coil and Pseudomonas aeruginosa） bacteria. Also, the antifungal activity of CuO was investigated against Aspergillus niger, Rhizopus oryzae, Aspergi/lus flavus, Cladosporium carrionii, Mucor, Penicilliurn notatum and Alternaria alternata. Results demonstrate that the flower-shaped CuO nanostructures act as an effective antimicrobial agent against pathogenic bacteria and fungi.

关键词： CuO nanosheets Hierarchical X-ray diffraction Photoluminescence Antibacterial Antifungal

Electronic structure and bonding interactions in Ba1-xSrxZr0.1Ti0.9O3 ceramics

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Frontiers of Materials Science 2017年第2期11卷 182-189页

作者： Jegannathan MANGAIYARKKARASI Subramanian SASIKUMAR Olai Vasu SARAVANAN Ramachandran SARAVANAN pg and research department of physics NMSSVN College Nagamalai Madurai-625 019 Tamil Nadu India research centre and pg department of physics The Madura College Madurai-625 011 Tamil Nadu India

An investigation on the precise electronic structure and bonding interactions has been carried out on Ba1-xSrxZr0.1Ti0.9O3 （short for BSZT, x = 0, 0.05, 0.07 and 0.14） ceramic systems prepared via high-temperature solid state reaction technique. The influence of Sr doping on the BSZT structure has been examined by characterizing the prepared samples using PXRD, UV-visible spectrophotometry, SEM and EDS. Powder profile refinement of X-ray data confirms that all the synthesized samples have been crystallized in cubic perovskite structure with single phase. Charge density distribution of the BSZT systems has been completely analyzed by the maximum entropy method （MEM）. Co-substitution of Sr at the Ba site and Zr at the Ti site into the BaTiOz structure presents the ionic nature between Ba and O ions and the covalent nature between Ti and O ions, revealed from MEM calculations. Optical band gap values have been evaluated from UV-visible absorption spectra. Particles with irregular shapes and well defined grain boundaries are clearly visualized from SEM images. The phase purity of the prepared samples is further confirmed by EDS qualitative spectral analysis.

关键词： barium titanate X-ray diffraction Rietveld refinement maximum entropy method bonding

Boosting hydrocarbon conversion via Cu-doping induced oxygen vacancies on CeO2 in CO2 electroreduction

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Journal of Energy Chemistry 2025年第1期100卷 66-76页

作者： Lei Xue Tong Shi Chenhui Han Heng Zhang Fenrong Liu Haorun Li Yan Wang Xiaojun Gu Shanghong Zeng Inner Mongolia Key Laboratory of Chemistry and physics of Rare Earth Materials School of Chemistry and Chemical Engineering Inner Mongolia University State Key Laboratory of Coal Conversion Institute of Coal Chemistry Chinese Academy of Sciences Institute of Catalysis Department of Chemistry Zhejiang University National Key Laboratory of Baiyunobo Rare Earth Resource research and Comprehensive Utilization Baotou Research Institute of Rare Earths

Conversion of CO2back to hydrocarbons is the most direct way of closing the“carbon cycle”,and its significance is further enlarged if this process is driven by renewable energies such as ***,precisely controlling the product selectivity towards hydrocarbons against the competitive hydrogen evolution remains challenging,especially for Cu-based ***,we report a novel defect engineering strategy,by which Cu-doping-induced oxygen vacancies on CeO2nanorods were effectively created,with adjustable vacancy/Cu *** resulting optimum catalyst shows up to 79% catalytic current density to hydrocarbons （excluding CO）,with 49% faradaic efficiency to *** and density functional theory unveil that the ratio between oxygen vacancy and Cu affects significantly the formation of*CHO and activation of H2O,which leads to the following deep hydrogenation to *** findings may spur new insights for designing and developing more controllable chemical process relevant to CO2utilization.

关键词： Oxygen vacancy Hydrocarbon production Reaction mechanism

Reply to Comments on "Structural,Optical,and Electrical Properties of Zn-Doped CdO Thin Films Fabricated by a Simplified Spray Pyrolysis Technique'' by *** and *** published in Acta ***.(***.) 28(1),64–71(2015)

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Acta Metallurgica Sinica(English Letters) 2018年第9期31卷 1007-1008页

作者： A.R.Balu pg and research department of physics AVVM Sri Pushpam College

Following are the comments for the queries raised by Prof. Pawel E. Tomaszewski on our published paper entitled ＂Structural, Optical, and Electrical Properties of Zn-Doped CdO Thin Films Fabricated by a Simplified Sp... 详细信息

关键词： Cd Engl.Lett Structural,Optical,and Electrical Properties of Zn-Doped CdO Thin Films Fabricated by a Simplified Spray Pyrolysis Technique by K.Usharani and A.R.Balu published in Acta Metall.Sin Zn

Vector meson's spin alignments in high energy reactions

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Science China(physics,Mechanics & Astronomy) 2025年第1期Mechanics & Astronomy) .卷 5-20页

作者： Jin-Hui Chen Zuo-Tang Liang Yu-Gang Ma Xin-Li Sheng Qun Wang Key Laboratory of Nuclear physics and Ion-beam Application (MoE) Institute of Modern PhysicsFudan University Institute of Frontier and Interdisciplinary Science Key Laboratory of Particle Physics and Particle Irradiation (MOE)Shandong University INFN-Firenze department of Modern physics University of Science and Technology of China School of Mechanics and physics Anhui University of Science and Technology

The global spin alignment of vector mesons has been observed by the STAR collaboration at the Relativistic Heavy Ion Collider （RHIC） at Brookhaven National Laboratory （BNL）.It provides a unique opportunity to probe the correlation between the polarized quark and antiquark in the strongly coupled quark-gluon plasma （sQGP） produced in relativistic heavy ion collisions,opening a new window to explore the properties of s *** addition,spin alignments of vector mesons have also been observed in other high-energy particle collisions such as e+e-annihilations at high energies where hadron production is dominated by quark fragmentation *** results obtained are quite different from those obtained in heavy ion collisions where quark coalescence/combination mechanism dominates suggesting strong dependence on hadronization *** comprehensive studies in different hadronization processes are *** this article,we present a brief review of theoretical and experimental advances in the study of vector meson’s spin alignments in a variety of high-energy particle collisions,with emphasis on hadronization mechanisms.

关键词： vector meson spin alignment global polarization relativistic heavy ion collisions fragmentation