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

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 ${\bm~{Einstein~~Probe}}$

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Distortion mapping correction in the AIMS primary mirror testing by a computer-generated hologram

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Research in Astronomy and Astrophysics 2021年第7期21卷 99-106页

作者： Ke-Wei E Jian-Ke Zhao Bo Wang Dong-Guang Wang Yu-Liang Shen Xin Fu Song-Bo Xu Jing Li Xun Xue Ming Chang Yan Zhou Xi’an Institute of Optics and Precision Mechanics Chinese Academy of SciencesXi’an 710119China nanjing astronomical instruments Chinese Academy of SciencesNanjing 210042China National astronomical Observatories Chinese Academy of SciencesBeijing 100101China

The National Solar Observatory is currently developing the Accurate Infrared Magnetic Field Measurements of the Sun(AIMS). The primary mirror of the AIMS solar telescope is an off-axis parabolic with a diameter of 1 m and with a large off-axis amount of 1 m. Due to the surface figure of the primary mirror under the used state is directly related to image quality of the whole system, a computer-generated hologram(CGH) is carried out to test the primary mirror, and the test results are used to polish the mirror to a higher surface accuracy. However, the fact that the distortion exists in the testing results leads to the failure of a further guide to deterministic optical processing. In this paper, a distortion correction method is proposed, which uses an orthogonal set of vector polynomials to mapping the coordinates of the mirror and the pixels of fringes, and then an interpolation method is adopted to obtain the corrected results. The testing accuracy by using CGH is also verified by an auto-collimate test experiment. According to the distorted corrected results, the root-mean-square of the surface figure is about 1/50λ(λ=632.8 nm) after polishing.

关键词： telescopes techniques:interferometric methods:astronomical instrumentation methods and techniques

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H_∞ controller design for a 4-meter direct-drive azimuth axis

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Research in Astronomy and Astrophysics 2015年第11期15卷 1931-1944页

作者： Li-Yan Chen Zhen-Chao Zhang Xiao-Li Song Da-Xing Wang National astronomical Observatories Nanjing Institute of Astronomical Optics & TechnologyChinese Academy of Sciences Key Laboratory of astronomical Optics & Technology Nanjing Institute of Astronomical Optics & Technology Chinese Academy of Sciences University of chinese academy of sciences

To pursue a higher imaging resolution for exploring more details in the information conveyed by the Universe, the next generation of optical telescopes based on a direct drive widely employ the extremely large aperture structure, which also introduces more disturbances and uncertain factors to the control system. Facing this new challenge, the PID control method in main-axis control systems of traditional astronomical telescopes cannot suffice for the requirement of the tracking precision and disturbance sensitivity in angular velocity. To overcome this shortcoming, we establish a dynamic model and propose an H∞ controller for a 4-meter azimuth direct drive control system that consists of a revolving platform（azimuth axis）, a three-phase torque motor, a motor drive, an encoder, a data acquisition card and a small computers. Simulations are carried out to analyze the model and guide the real *** results show that the proposed H∞ controller reduces the tracking error by a maximum of 80.69%（average 57.8%） and the disturbance sensitivity by a maximum of 82.3%（average 50.96%） compared with the traditional tuned PI controller;furthermore, the order of the model describing the proposed controller can be reduced to three, thus its feasibility in real systems is guaranteed.

关键词： disturbance azimuth uncertain guaranteed torque details encoder aperture conveyed pursue

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A possible mechanism for magnetar soft X-ray/γ-ray emission

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chinese Physics B 2012年第5期21卷 542-554页

作者：高志福彭秋和王娜邹志刚 Xinjiang astronomical Observatory Chinese Academy of Sciences Key Laboratory of Radio Astronomy Chinese Academy of Sciences Graduate University of the chinese academy of sciences Department of Astronomy Nanjing University National astronomical Observatories Chinese Academy of Sciences

Once the energies of electrons near the Fermi surface obviously exceed the threshold energy of the inverse β decay,electron capture（EC） dominates inside the *** the maximal binding energy of the 3 P 2 neutron cooper pair is only about 0.048 MeV,the outgoing high-energy neutrons（E k（n） 60 MeV） created by the EC can easily destroy the 3 P 2 neutron cooper pairs through the interaction of nuclear *** the anisotropic neutron superfluid,each 3 P 2 neutron cooper pair has magnetic energy 2μ n B in the applied magnetic field B,where μ n = 0.966 × 10 23 erg.G 1 is the absolute value of the neutron abnormal magnetic *** being destroyed by the high-energy EC neutrons,the magnetic moments of the 3 P 2 cooper pairs are no longer arranged in the paramagnetic direction,and the magnetic energy is *** released energy can be transformed into thermal *** a small fraction of the generated thermal energy is transported from the interior to the surface by conduction,and then it is radiated in the form of thermal photons from the *** highly efficient modulation within the star＇s magnetosphere,the thermal surface emission is shaped into a spectrum of soft X-rays/γ-rays with the observed characteristics of *** introducing related parameters,we calculate the theoretical luminosities of *** calculation results agree well with the observed parameters of magnetars.

关键词： Landau levels Fermi surface thermal radiation heat conduction

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The First Spectral Analysis of Solar Radio Spike Event

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chinese Physics Letters 2000年第6期17卷 460-462页

作者： XU Fu-Ying LIU Yu-Ying FU Qi-jun WU Hong-Ao Purple Mountain Observatory Chinese Academy of SciencesNanjing 210008 Beijing astronomical Observatory Chinese Academy of SciencesBeijing 100012 National astronomical Observatories Chinese Academy of Sciences

The first spectral analysis of a spike event has been *** was found that the peak frequency of spectrum of the spike event on Oct.2,1993 drifted from higher to lower frequency for the first group of spikes,but the frequency remained almost the same for the second *** if the mean energy of electron beam is a monotonic or random function of time and its pitch angle is a monotonically decreasing function of mean energy,then the different observed characteristics of evolution of the peak frequency with time may be interpreted by the location of resonant *** spike radio emissions with one and the same peak frequency probably originated from the same region of electron cyclotron maser instability.

关键词： originated monotonic spectrum

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Excess Carrier Lifetime Improvement in c-Si Solar Cells by YAG:Ce^(3+)-Yb^(3+)

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chinese Physics Letters 2016年第5期33卷 140-143页

作者： Talib Hussain 叶慧琪肖东 National astronomical Observatories Nanjing Institute of Astronomical Optics &TechnologyKey Laboratory of Astronomical Optics & TechnologyNanjing Institute of Astronomical Optics&TechnologyChinese Academy of Sciences University of chinese academy of sciences

Ce3＋-Yb3＋ doped Y3Al5O12 （YAG） is a luminescent down-conversion material which could convert visible pho- tons to near infrared photons. In this work, YAG：Ce3＋-Yb3＋ is applied on the front surface of mass-produced mono crystalline Si solar cells. For the coated cells, the external quantum efficiencv from the visible to the near infrared is improved, and the energy conversion efficiency enhances from 11.70% to 12.2% under ***. Furthermore, the phosphor down-conversion effect on the solar cell is characterized by the microwave detected photoconductivity technique on the n-type silicon wafer under the 977nm excitation. The down-conversion materials improve the average excess carrier lifetime from 22.5μs to 24.2#s and the average surface recombi- nation velocity reduces from ***/s to 371.6cm/s, which reveal the significant reduction in excess carrier recombination by the phosphors.

关键词： by on Yb Excess Carrier Lifetime Improvement in c-Si Solar Cells by YAG:Ce Si YAG of in is down

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Some New Observing Features of a Solar Radio Spectral Event on August 25,1999

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chinese Physics Letters 2000年第11期17卷 850-852页

作者： XU Fu-Ying LIU Yu-Ying YAO Qi-Jun FU Qi-Jun MENG Xuan WU Hong-Ao Purple Mountain Observatory Chinese Academy of SciencesNanjing 210008 Beijing astronomical Observatory Chinese Academy of SciencesBeijing 100012 National astronomical Observatories Chinese Academy of Sciences

A broadband solar radio type III burst was observed on August 25,1999 at Purple Mountain Observatory with waveband of 4.5-7.5 *** was also observed at Beijing astronomical Observatory with waveband of 5.2-7.6 ***,it is the first common spectral event observed in *** type III bursts are gathered into more than 10 groups and drift in opposite directions,but the reverse drifting *** largest bandwidth of type III burst reaches≥3 GHz and may be the broadest bandwidth of the reverse type III burst ever observed up to the *** new observing characteristics of fine structures are found,for example,fiber-like,V-shaped and neck-ring-like ***,the neck-ring-like structure is probably first discovered in cm waveband and may be the evidence of twisted rope of magnetic lines.

关键词： Solar twisted shaped

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Candidate members of star clusters from LAMOST DR2

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Research in Astronomy and Astrophysics 2015年第8期15卷 1197-1208页

作者： Bo Zhang Xiao-Yan Chen Chao Liu Li Chen Li-Cai Deng Jin-Liang Hou Zheng-Yi Shao Fan Yang Yue Wu Ming Yang Yong Zhang Yong-Hui Hou Yue-Fei Wang Key Laboratory of Optical Astronomy National Astronomical ObservatoriesChinese Academy of Sciences University of chinese academy of sciences Shanghai astronomical Observatory Chinese Academy of Sciences nanjing Institute of astronomical Optics & Technology National Astronomical ObservatoriesChinese Academy of Sciences

In this work, we provide 2189 photometrically- and kinematically-selected candidate members of 24 star clusters from the LAMOST DR2 catalog. We perform two-step membership identification： selection along the stellar track in the colormagnitude diagram, i.e., photometric identification, and selection from the distribution of radial velocities, i.e. the kinematic identification. We find that the radial velocities from the LAMOST data are very helpful in the membership identification. The mean probability of membership is 40% for the sample selected with radial velocity. With these 24 star clusters, we investigate the performance of the radial velocity and metallicity estimated with the LAMOST pipeline. We find that the systematic offsets in radial velocity and metallicity are 0.85 ± 1.26 km s-1and-0.08 ± 0.04 dex, with dispersions of 5.47＋1.16-0.71 km s-1and 0.13＋0.04-0.02 dex, respectively. Finally, we propose that the photometrically-selected candidate members of the clusters covered by the LAMOST footprint should be assigned higher priority so that more candidate stars can be observed.

关键词： open clusters and associations: general—stars: statistics—catalogs—surveys—methods: data analysis

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Introduction of Ag nanoparticles by picosecond LIFT to improve the photoelectric property of AZO films

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chinese Optics Letters 2020年第4期18卷 102-108页

作者： Xiaofang Xu Jingbo Li Xiaohan Yang Sen Pan Yong Bi School of Mechanical EngineeringJiangsu University Zhenjiang 212013China nanjing astronomical instruments co.ltd.chinese academy of sciences Nanjing 210000China

The photoelectric properties of conductive films are improved by doping Ag on aluminum-doped zinc oxide(AZO)films by laser induced forward transfer(LIFT).Firstly,the picosecond laser induced transfer mechanism of Ag films was revealed by numerical simulation;then,different-thickness Ag films were deposited on the AZO films by picosecond *** the film thickness is 30 nm and,50 nm,we have successfully obtained some Ag-AZO films with better optoelectronic properties by adjusting the laser parameters.

关键词： LIFT surface treatment AZO film Ag-nanoparticles optoelectronic property

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Numerical model of the influence function of deformable mirrors based on Bessel Fourier orthogonal functions

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Research in Astronomy and Astrophysics 2014年第11期14卷 1504-1510页

作者： Shun Li Sijiong Zhang National astronomical Observatories / nanjing Institute of astronomical Optics & Technology Chinese Academy of Sciences Key Laboratory of astronomical Optics & Technology Nanjing Institute of Astronomical Optics &TechnologyChinese Academy of Sciences

A numerical model is presented to simulate the influence function of de- formable mirror actuators. The numerical model is formed by Bessel Fourier orthog- onal functions, which are constituted of Bessel orthogonal functions and a Fourier basis. A detailed comparison is presented between the new Bessel Fourier model, the Zernike model, the Gaussian influence function and the modified Gaussian influence function. Numerical experiments indicate that the new numerical model is easy to use and more accurate compared with other numerical models. The new numerical model can be used for describing deformable mirror performances and numerical simulations of adaptive optics systems.

关键词： instrumentation adaptive optics -- deformable mirror

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