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Wave effect of gravitational waves intersected with a microlens field Ⅱ:An adaptive hierarchical tree algorithm and population study

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Science China(Physics,Mechanics & Astronomy) 2025年第1期Mechanics & Astronomy) .卷 241-254页

作者： Xikai Shan Guoliang Li Xuechun Chen Wen Zhao Bin Hu Shude Mao Department of Astronomy Tsinghua University Purple Mountain Observatory Chinese Academy of Sciences Institute for Frontier in Astronomy and Astrophysics Beijing Normal University School of Physics and Astronomy Beijing Normal University School of Astronomy and Space Science University of Science and Technology of China CAS key laboratory for researches in galaxies and cosmology Department of Astronomy University of Science and Technology of ChinaChinese Academy of Sciences

The gravitational lensing wave effect generated by a microlensing field embedded in a lens galaxy is an inevitable phenomenon in strong lensed gravitational waves （SLGWs）.This effect presents both challenges and opportunities for the detection and application of ***,investigating this wave effect requires computing a complete diffraction integral over each microlens in the *** is extremely time-consuming due to the large number of microlenses （10～3-10～6）.Therefore,simply adding all the microlenses is ***,the complexity of the time delay surface makes the lens plane resolution a crucial factor in controlling numerical *** this paper,we propose a trapezoid approximation-based adaptive hierarchical tree algorithm to meet the challenges of calculation speed and *** find that this algorithm accelerates the calculation by four orders of magnitude compared to the simple adding method and is one order of magnitude faster than the fixed hierarchical tree algorithm proposed for electromagnetic *** importantly,our algorithm ensures controllable numerical errors,increasing confidence in the *** with our previous work （***.66,239511,2023）,this paper addresses all numerical issues,including integral convergence,precision,and computational time1).Finally,we conducted a population study on the microlensing wave effect of SLGWs using this algorithm and found that the microlensing wave effect cannot be ignored,especially for Type II SLGWs （from saddle position of the time delay surface） due to their intrinsic geometric structures and their typical intersection with a denser microlensing ***,more than 33%（11%） of SLGWs have a mismatch larger than 1%（3%） compared to the unlensed ***,we found that the mismatch between signal pairs in a doubly imaged GW is generally larger than 10-3,and 61%（25%） of signal pairs have a mismatch larger than 1%（3%）.Therefo

关键词： gravitational lensing diffractional integral algorithm gravitational wave

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

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Effect of non-stationary accretion on spectral state transitions:An example of a persistent neutron star LMXB 4U 1636–536

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research in Astronomy and Astrophysics 2018年第3期18卷 91-98页

作者： Hui Zhang Wen-Fei Yu key laboratory for research in galaxies and cosmology Shanghai Astronomical ObservatoryChinese Academy of Sciences

Observations of black hole and neutron star X-ray binaries show that the luminosity of the hard-to-soft state transition is usually higher than that of the soft-to-hard state transition,indicating additional parameters other than mass accretion rate are required to interpret spectral state *** has been found in some individual black hole or neutron star soft X-ray transients that the luminosity corresponding to the hard-to-soft state transition is positively correlated with the peak luminosity of the following soft state. In this work,we report the discovery of the same correlation in the single persistent neutron star low mass X-ray binary（LMXB） 4 U 1636–536 based on data from the All Sky Monitor（ASM） on board RXTE,the Gas Slit Camera（GSC） on board MAXI and the Burst Alert Telescope（BAT） on board Swift. We also found such a positive correlation holds in this persistent neutron star LMXB in a luminosity range spanning about a factor of four. Our results indicate that non-stationary accretion also plays an important role in driving X-ray spectral state transitions in persistent accreting systems with small accretion flares,which is much less dramatic compared with the bright outbursts seen in many Galactic LMXB transients.

关键词： accretion accretion disks - X-rays binaries - stars neutron

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Triggering star formation by both radiative and mechanical AGN feedback

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research in Astronomy and Astrophysics 2013年第8期13卷 899-911页

作者： Chao Liu Zhao-Ming Gan Fu-Guo Xie key laboratory for research in galaxies and cosmology Shanghai Astronomical Observatory Chinese Academy of Sciences University of chinese academy of sciences

We perform two dimensional hydrodynamic numerical simulations to study the positive active galactic nucleus （AGN） feedback which triggers, rather than suppresses, star formation. Recently, it was shown by Nayakshin et al. and Ishibashi et al. that star formation occurs when the cold interstellar medium （ISM） is squeezed by the impact of mass outflow or radiation pressure, respectively. Mass outflow is ubiquitous in this astrophysical context, and radiation pressure is also important if the AGN is luminous. For the first time in this subject, we incorporate both mass outflow feedback and radiative feedback into our model. Consequently, the ISM is shocked into shells by the AGN feedback, and these shells soon fragment into clumps and filaments because of Rayleigh-Taylor and thermal instabilities. We have two major findings：（1） the star formation rate can indeed be very large in the clumps and filaments. However, the resultant star formation rate density is too large compared with previous works, which is mainly because we ignore the fact that most of the stars that are formed would be disrupted when they move away from the galactic center. （2） Although radiation pressure feedback has a limited effect, when mass outflow feedback is also included, they reinforce each other. Specifically, in the gas-poor case, mass outflow is always the dominant contributor to feedback.

关键词： methods: numerical - accretion - shock waves - galaxies: active - galaxies: starburst

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Transient accelerating scalar models with exponential potentials

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research in Astronomy and Astrophysics 2013年第6期13卷 629-634页

作者： Wen-Ping Cui Yang Zhang Zheng-Wen Fu key laboratory for research in galaxies and cosmology The University of Science and Technology of China Chinese Academy of Sciences

We study a known class of scalar dark energy models in which the potential has an exponential term and the current accelerating era is transient. We find that, although a decelerating era will return in the future, when extrapolating the model back to earlier stages （z ≥ 4）, scalar dark energy becomes dominant over matter. So these models do not have the desired tracking behavior, and the predicted transient period of acceleration cannot be adopted into the standard scenario of the Big Bang cosmology. When couplings between the scalar field and matter are introduced, the models still have the same problem; only the time when deceleration returns will be varied. To achieve re-deceleration, one has to turn to alternative models that are consistent with the standard Big Bang scenario.

关键词： cosmology cosmological parameters -- cosmology theory

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Classification study of WISE infrared sources:identification of candidate asymptotic giant branch stars

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research in Astronomy and Astrophysics 2013年第3期13卷 323-333页

作者： Xun Tu Zhong-Xiang Wang key laboratory for research in galaxies and cosmology and Shanghai Astronomical Observatory Chinese Academy of Sciences Graduate University of chinese academy of sciences

In the Wide-field Infrared Survey Explorer （WISE） all-sky source catalog there are 76 million mid-infrared point sources that were detected in the first three WISE bands and have association with only one 2MASS near-IR source within 3. We search for their identifications in the SIMBAD database and find 3.2 million identified sources. Based on these known sources, we establish three criteria for selecting candidate asymptotic giant branch （AGB） stars in the Galaxy, which are three defined zones in a color-color diagram, Galactic latitude ｜b｜〈 20°, and ＂corrected＂ WISE third-band W3c≤ 11. Applying these criteria to the WISE＋2MASS sources, 1.37 million of them are selected. We analyze the WISE third-band W3 distribution of the selected sources, and further establish that W3〈8 is required in order to exclude a large fraction of normal stars from them. We therefore find 0.47 million candidate AGB stars in our Galaxy from the WISE source catalog. Using W3c, we estimate their distances and derive their Galactic distributions. The candidates are generally distributed around the Galactic center uniformly, with 68% （1-σ） of them within approximately 8 kpc. We discuss the idea that optical spectroscopy can be used to verify the C-rich AGB stars in our candidates, and thus a fraction of them （-10%） will be good targets for the Large Sky Area Multi-Object Fiber Spectroscopic Telescope （LAMOST） survey that is planned to start in fall of 2012.

关键词： stars: AGB and post-AGB -- infrared: stars -- stars: carbon

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State transitions triggered by inverse magnetic field: probably applied in high-mass X-ray binaries?

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research in Astronomy and Astrophysics 2016年第3期16卷 107-110页

作者： Shuang-Liang Li Zhen Yan key laboratory for research in galaxies and cosmology Shanghai Astronomical Observatory Chinese Academy of Sciences

Previous works suggested that the state transitions in an X-ray binary can be triggered by accret- ing an inverse magnetic field from its companion star. A key point of this mechanism is the accretion and magnification of large-scale magnetic fields from the outer boundary of a thin disk. However, how such a process can be realized is still an open question. In this work, we check this issue in a realistic X-ray binary system. According to our calculations, a quite strong initial magnetic field, B - 10^2 - 10^3 G, is required in order to assure that the large-scale magnetic field can be effectively dragged inward and magnified with the accretion of gas. Thus, such a picture probably can be present in high-mass X-ray binaries possessing a strong stellar magnetic field, e.g., Cyg X-1.

关键词： accretion accretion disks-- blackhole physics-- (magnetohydrodynamics)MHD--X-rays binaries

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Dynamics and collisions of episodic jets from black holes and accretion disk systems

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research in Astronomy and Astrophysics 2015年第2期15卷 207-214页

作者： Ying Meng Jun Lin Feng Yuan Yunnan Observatories Chinese Academy of Sciences University of chinese academy of sciences key laboratory for research in galaxies and cosmology Shanghai Astronomical ObservatoryChinese Academy of Sciences

In many astrophysical black hole systems, episodic jets of plasma blobs have been observed, which are much faster and more powerful than continuous jets. A magnetohydrodynamical model was proposed by Yuan et al. to study the formation of episodic jets in Sgr A＊. By taking Sgr A＊ and a stellar mass black hole as examples, we modify the model of Yuan et al. by including the effects of relativity, and further study the relativistic motion and expansion of episodic jets of plasma blobs. Then we study the collision between two consecutive ejections in the modified model, and calculate the magnetic energy released in the collision. Our results show two consecutive blobs can collide with each other, and the released magnetic energy is more than 1050 erg, which supports the idea that a gamma-ray burst is powered by the collision of episodic jets, as suggested by Yuan ＆ Zhang.

关键词： accretion, accretion disks black hole physics magnetohydrodynamics (MHD) ISM: jets and outflows gamma-ray bursts: general

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Is BZB J1450+5201 the most distant gamma-ray BL Lacertae object?

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research in Astronomy and Astrophysics 2015年第3期15卷 313-326页

作者： Neng-Hui Liao Jin-Ming Bai Jian-Guo Wang Hong-Tao Liu Jiu-Jia Zhang Ning Jiang Zun-Li Yuan Liang Chen Yunnan Observatories Chinese Academy of Sciences key laboratory for the Structure and Evolution of Celestial Objects Chinese Academy of Sciences University of chinese academy of sciences key laboratory for research in galaxies and cosmology University of Science and Technology of China Chinese Academy of Sciences Department of Astronomy University of Science and Technology of China key laboratory for research in galaxies and cosmology Shanghai Astronomical ObservatoryChinese Academy of Sciences

BL Lacertae （BL Lac） objects at high redshifts （z ≥ 2） are rarely detected. Through careful analysis of its Sloan Digital Sky Survey spectrum, BZB J1450＋5201 is confirmed to be a high-z BL Lac object with z ≥ 2.471 by identifying the Lyα 1216 and CIV 1548/1550 absorption lines. This indicates that BZB J1450＋5201 is the most distant BL Lac object discovered to date. Careful analysis of the five-year Fermi-LAT data of 2FGL J1451.0＋5159 shows that its γ-ray emission is robust with a confidence level of 6.2σ at 1-3 GeV and 6.7σ at 3-10 GeV. This analysis with the five-year data overcomes confusion with its bright neighbor, which is a problem when analyzing the two-year data. In addition, 2FGL J 1451.0＋5159 is confirmed to be associated with BZB J1450＋5201 using the five-year data. The analysis of multiwavelength data, from radio to γ-ray energies, indicates that BZB J1450＋5201 is an intermediate synchrotron peaked （ISP） source. Its multiwavelength properties are consistent with distributions of other ISP sources at lower redshifts in the second Fermi-LAT AGN catalog. The pure synchrotron self-Compton （SSC） model seems to be disfavored, but the scattering of weak external emission plus the SSC process can provide a satisfactory description of the broadband emission.

关键词： galaxies active -- BL Lacertae objects individual (BZB J1450+5201)-- gamma rays galaxies -- radiation mechanisms non-thermal

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Integrated HI emission in galaxy groups and clusters

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research in Astronomy and Astrophysics 2017年第10期17卷 15-26页

作者： Mei Ai Ming Zhu Jian Fu National Astronomical Observatories Chinese Academy of Sciences key laboratory of Radio Astronomy Chinese Academy of Sciences University of chinese academy of sciences key laboratory for research in galaxies and cosmology Shanghai Astronomical Observatory Chinese Academy of Sciences

The integrated HI emission from hierarchical structures such as groups and clusters of galax- ies can be detected by FAST at intermediate redshifts. Here we propose to use FAST to study the evolution of the global HI content of clusters and groups over cosmic time by measuring their integrated HI emissions. We use the Virgo Cluster as an example to estimate the detection limit of FAST, and have estimated the integration time to detect a Virgo type cluster at different redshifts （from z = 0.1 to z ---- 1.5）. We have also employed a semi-analytic model （SAM） to simulate the evolution of HI contents in galaxy clusters. Our simulations suggest that the HI mass of a Virgo-like cluster could be 2-3 times higher and the physical size could be more than 50% smaller when redshift increases from z = 0.3 to z = 1. Thus the integration time could be reduced significantly and gas rich clusters at intermediate redshifts can be detected by FAST in less than 2 hours of integration time. For the local Universe, we have also used SAM simulations to create mock catalogs of clusters to predict the outcomes from FAST all sky surveys. Comparing with the optically selected catalogs derived by cross matching the galaxy catalogs from the SDSS survey and the ALFALFA survey, we find that the HI mass distribution of the mock catalog with 20 s of integration time agrees well with that of observations. However, the mock catalog with 120 s of integration time predicts many more groups and clusters that contain a population of low mass HI galaxies not detected by the ALFALFA survey. A future deep HI blind sky survey with FAST would be able to test such prediction and set constraints on the numerical simulation models. The observational strategy and sample selections for future FAST observations of galaxy clusters at high redshifts are also discussed.

关键词： galaxy clusters -- neutral hydrogen (HI) -- galaxy evolution

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