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Light Pollution in Beijing and Effects on Xinglong Station of National Astronomical Observatory

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Light Pollution in Beijing and Effects on Xinglong Station o...

Nonlinear time series analysis of the light curves from the black hole system GRS1915+105

中国科协第249次青年科学家论坛——照明对生态环境影响的量化观测与评价

作者： Li-gen Lu Bao-zhou Zhang Jian Liu Shan-shan Zeng dept.of astronomy Beijing Normal university Beijing Key Laboratory of Applied Optics dept.of physics Beijing Normal university

A night-sky luminance survey was carried on in Beijing to assess the level of light *** luminance of the zenith night sky and skies in four directions at six sites almost in line with different distances from the city center was measured by using a photometric luminance *** Xinglong Station of National Astronomical Observatory was included to study the impacts of city lightings on an astronomical *** survey shows that the night-sky luminance at zenith decreases with increasing distance from the city center,and time is also an important determining factor of the night-sky *** with the night-sky luminance at Lingshan observation site which is closer to the city center,the night-sky luminance at Xinglong Station is about 21.4 mag/arcsec,indicating that night sky at Xinglong Station has been brightened by outdoor lighting of the county town of Xinglong.

关键词： night-sky luminance astronomical observatory outdoor lighting light pollution

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Research in astronomy and Astrophysics 2011年第1期11卷 71-90页

作者： K.P.Harikrishnan Ranjeev Misra G.Ambika Department of physics The Cochin College Inter university Centre for astronomy and Astrophysics Indian Institute of Science Education and Research

GRS 1915＋105 is a prominent black hole system exhibiting variability over a wide range of time scales and its observed light curves have been classified into 12 temporal states. Here we undertake a complete analysis of these light curves from all the states using various quantifiers from nonlinear time series analysis, such as the correlation dimension （D2）, the correlation entropy （K2）, singular value decomposition （SVD） and the multifractal spectrum （f（α） spectrum）. An important aspect of our analysis is that, for estimating these quantifiers, we use algorithmic schemes which we have recently proposed and successfully tested on synthetic as well as practical time series from various fields. Though the schemes are based on the conventional delay embedding technique, they are automated so that the above quantitative measures can be computed using conditions prescribed by the algorithm and without any intermediate subjective analysis. We show that nearly half of the 12 temporal states exhibit deviation from randomness and their complex temporal behavior could be approximated by a few （three or four） coupled ordinary nonlinear differential equations. These results could be important for a better understanding of the processes that generate the light curves and hence for modeling the temporal behavior of such complex systems. To our knowledge, this is the first complete analysis of an astrophysical object （let alone a black hole system） using various techniques from nonlinear dynamics.

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

The current status of galaxy formation

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Research in astronomy and Astrophysics 2012年第8期12卷 917-946页

作者： Joseph Silk Gary A.Mamon Institut d'Astrophysique de Paris (UMR 7095:CNRS&UPMC) 98 bis Boulevard AragoParis 75014France Department of physics and astronomy 3701 San Martin DriveThe Johns Hopkins UniversityBaltimore MD 21218USA Beecroft Institute of Particle Astrophysics and Cosmology 1 Keble RoadUniversity of OxfordOxford OX1 3RHUK

Understanding galaxy formation is one of the most pressing issues in cos- mology. We review the current status of galaxy formation from both an observational and a theoretical perspective, and summarize the prospects ... 详细信息

关键词： galaxy: formation -- galaxies: evolution -- galaxies: star formation --galaxies: active

Evolutionary Algorithms

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Evolutionary Algorithms

Mapping the magnetic field in the solar corona through magnetoseismology

CCAST“基因算法及其在物理，生命科学和工程中的应用”研讨会

作者： Dr.HaowenXi dept.of physics and astronomy Bowling Green State university Bowling Green OH 43403

…I have called this principle,by which *** variation,if useful,is preserved,bythe term Natural Selection.

关键词： Evolutionary Algorithms

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Science China(Technological Sciences) 2020年第11期63卷 2357-2368页

作者： YANG ZiHao TIAN Hui TOMCZYK Steven MORTON Richard BAI XianYong SAMANTA Tanmoy CHEN YaJie School of Earth and Space Sciences Peking UniversityBeijing 100871China Key Laboratory of Solar Activity National Astronomical ObservatoriesChinese Academy of SciencesBeijing 100012China High Altitude Observatory National Center for Atmospheric ResearchBoulderCO 80307USA Department of Mathematics Physics and Electrical EngineeringNorthumbria UniversityNewcastle Upon Tyne NE18STUK Department of physics and astronomy George Mason UniversityFairfaxVA 22030USA johns hopkins university Applied physics Laboratory LaurelMD 20723USA Max Planck Institute for Solar System Research 37077 G¨ottingenGermany

Magnetoseismology,a technique of magnetic field diagnostics based on observations of magnetohydrodynamic(MHD)waves,has been widely used to estimate the field strengths of oscillating structures in the solar ***,previously magnetoseismology was mostly applied to occasionally occurring oscillation events,providing an estimate of only the average field strength or one-dimensional distribution of field strength along an oscillating *** restriction could be eliminated if we apply magnetoseismology to the pervasive propagating transverse MHD waves discovered with the Coronal Multi-channel Polarimeter(CoMP).Using several CoMP observations of the Fe xiii 1074.7 nm and 1079.8 nm spectral lines,we obtained maps of the plasma density and wave phase speed in the corona,which allow us to map both the strength and direction of the coronal magnetic field in the plane of *** also examined distributions of the electron density and magnetic field strength,and compared their variations with height in the quiet Sun and active *** measurements could provide critical information to advance our understanding of the Sun's magnetism and the magnetic coupling of the whole solar atmosphere.

关键词： solar corona solar magnetic field waves magnetoseismology

A report on TypeⅡX-ray bursts from SMC X-1

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Research in astronomy and Astrophysics 2018年第12期18卷 43-52页

作者： Binay Rai Pragati Pradhan Bikash Chandra Paul dept.of physics North Bengal UniversityDarjeelingWest Bengal734013India Department of astronomy and Astrophysics Pennsylvania State UniversityPennsylvania16802USA St.Joseph's College Darjeeling-734104West BengalIndia

We study RXTE PCA data for the high mass X-ray binary source SMC X-1 between 2003–10 and 2003–12 when the source was in its high *** source is found to be frequently bursting which can be seen as flares in lightcurves that occur at a rate of one every 800 s, with an average of 4–5 Type Ⅱ X-ray bursts per *** note that typically a burst was short, lasting for a few tens of seconds in addition to a few long bursts spanning more than a hundred seconds that were also *** flares apparently occupied 2.5% of the total observing time of 225.5 *** note a total of 272 flares with mean FWHM of the flare ～21 *** rms variability and aperiodic variability are independent of *** observed, the pulse profiles of the lightcurves do not change their shape, implying that there is no change in the geometry of an accretion disk due to a *** hardness ratio and rms variability of lightcurves exhibit no correlation with the *** flare fraction shows a positive correlation with the peak-to-peak ratio of the primary and secondary peaks of the pulse *** observed hardening or softening of the spectrum cannot be correlated with the flaring rate but may be due to the interstellar absorption of X-rays as evident from the change in hydrogen column density(n_H).It is found that the luminosity of the source increases with the flaring *** that the viscous timescale is equal to the mean recurrence time of flares, we fixed the viscosity parameter α ～ 0.16.

关键词： accretion accretion discs pulsar:individual(SMC X-1) stars:neutron X-rays:binaries X-ray:burst

Universal Magnetic Behaviors in Strongly Spin-Orbit Coupled d4 and d5 ions

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Universal Magnetic Behaviors in Strongly Spin-Orbit Coupled ...

PROBING THE EARLY UNIVERSE WITH DEEP OBSERVATIONS AND LARGE SURVEYS

中国化学会2019年中西部地区无机化学化工学术研讨会

作者： Hongcheng Lu Juan R.Chamorro Cheng Wan Tyrel McQueen School of Chemistry and Chemical Engineering Huazhong University of Science and Technology Institute for Quantum Matter and Department of physics and astronomy The Johns Hopkins University Department of Chemistry The Johns Hopkins University Department of Materials Science and Engineering The Johns Hopkins University

Geometric spin frustration has been intensively investigated recently because of its leading to exotic states of matter, such as spin liquid. Much recent interest is focused on 4d and 5d systems due to their larger spin-orbit coupling(SOC) compared to those in 3d systems, which could significantly affect magnetic properties including resulting in unexpected insulating ground states and stabilizing Kitaev spin liquid state.2,3 To clearly investigate the importance and effect of SOC on magnetic behavior, we hydrothermally-synthesized three new Ru(4d) and three Ru(4d) materials with isolated RuCl octahedra for negligible magnetic superexchange interactions. Magnetization measurements indicate that the d compounds show effective magnetic moments comparable to the expected moment for a J = 1/2 system, whereas the d compounds show temperature independent magnetic susceptibilities indicative of a J = 0 singlet ground state, both of which can be attributed to the significant strength of SOC. We find that these compounds very closely match theoretical Kotani curves for isolated magnetic units with single ion physics, and find that such behavior is nearly universal in d and d systems.

关键词： Antiferromagnetism Spin-Orbit Coupling Spin Frustration Hydrothermal Synthesis

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中国科学院上海天文台年刊 2001年 147-163页

作者： Zheng Wei (Department of physics and astronomy, The johns hopkins university Baltimore, MD 21218-2686, USA) (Center for Astrophysics university of Science and Technology of China, Hefei, AnHui, 230026) Department of physics and astronomy The Johns Hopkins University BaltimoreMD 21218 - 2686USA Center for Astrophysics university of Science and Technology of China HefeiAnHui230026

Recent advances in astronomy have enabled scientists to reach the early universe to an unprecedented depth. With the new telescopes such as the Chandra, FUSE, and with the Sloan Digital Sky Survey (SDSS), we have gained critical insights into the "Origin of our Universe", i.e. how the intergalactic medium evolves to form galaxies and quasars. SDSS has broken a ten-year barrier of z=5 to reach the very early universe, with the discovery of five quasars at z  5.0. The survey will find more than ten thousands of quasars, enabling us to carry out the most comprehensive classification of quasars. FUSE finds traces of the primordial matter at z ～3, which corresponds to hydrogen column density as low as 10 -11 cm -2 and cannot be detected even with the largest optical telescope. The finding suggests that the intergalactic medium is an evolving and complex entity, and it is ionized mainly by the accumulated radiation from quasars. The Chandra telescope has taken a million second deep exposure of a selected region, reaching about twenty times deeper than ROSAT to a limiting flux of 5 × 10 -17 ergs s -1 cm -2 in the 0.5-2 keV band. The sources found so far can account for up to 90% of the hard X-ray background field, and they consist of Seyfert-2 and normal galaxies at z < 1 and quasars at z < 4.5. In the near future, the Next Generation Space Telescope and others will reveal the first generation of baryonic objects after the Big Bang.

关键词： SPIE Nature

Physical and geometrical parameters of VCBS XIII: HIP 105947

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Research in astronomy and Astrophysics 2018年第6期18卷 109-120页

作者： Suhail Gumaan Masda Mashhoor Ahmed Al-Wardat Jiyaulla Khan Moula Khan Pathan physics Department Dr. Babasaheb Ambedkar Marathwada University Aurangabad-431001 Maharashtra India physics Department Hadhramout University PO Box 50511 Mukalla Yemen dept. of physics and Institute of astronomy and Space Sciences A1 al-Bayt University PO Box 130040 Mafraq25113 Jordan physics Department Maulana Azad College Aurangabad-431001 Maharashtra India

The best physical and geometrical parameters of the main sequence close visual binary system(CVBS), HIP 105947, are presented. These parameters have been constructed conclusively using Al-Wardat’s complex method for analyzing CVBSs, which is a method for constructing a synthetic spectral energy distribution(SED) for the entire binary system using individual SEDs for each component star. The model atmospheres are in its turn built using the Kurucz(ATLAS9) line-blanketed plane-parallel models. At the same time, the orbital parameters for the system are calculated using Tokovinin’s dynamical method for constructing the best orbits of an interferometric binary system. Moreover, the mass-sum of the components, as well as the ?θ and ?ρ residuals for the system, is introduced. The combination of Al-Wardat’s and Tokovinin’s methods yields the best estimations of the physical and geometrical parameters. The positions of the components in the system on the evolutionary tracks and isochrones are plotted and the formation and evolution of the system are discussed.

关键词： binaries: close binaries: visual stars: fundamental parameters stars: individual(HIP 105947)