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Constraints on smoothness parameter and dark energy using observational H(z) data

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Research in Astronomy and Astrophysics 2011年第2期11卷 125-136页

作者： Hao-Ran Yu1,Tian Lan1,Hao-Yi Wan2,Tong-Jie Zhang1,3 and Bao-Quan Wang4 1 Department of Astronomy,beijing Normal University,beijing 100875,China 2 Business Office,beijing planetarium,beijing 100044,China 3 Center for High Energy Physics,Peking University,beijing 100871,China 4 Department of Physics,Dezhou University,Dezhou 253023,China Department of Astronomy Beijing Normal University Beijing 100875 China Business Office Beijing Planetarium Beijing 100044 China Center for High Energy Physics Peking University Beijing 100871 China Department of Physics Dezhou University Dezhou 253023 China

With large-scale homogeneity,the universe is locally inhomogeneous,clustering into stars,galaxies and larger *** property is described by the smoothness parameter α which is defined as the proportion of matter in the form of intergalactic *** we consider the inhomogeneities over a small scale,there should be modifications of the cosmological distances compared to a homogenous *** and Roeder developed a second-order ordinary differential equation（D-R equation） that describes the angular diameter distance-redshift relation for inhomogeneous cosmological ***,we may obtain the D-R equation for observational H（z） data（OHD）.The density-parameter ΩM,the state of dark energy ω,and the smoothness-parameter α are constrained by a set of OHD in a spatially flat XCDM universe as well as a spatially flat XCDM *** using a χ2 minimization method,we get α = 0.81＋0.19-0.20 and ΩM = 0.32＋0.12-0.06 at the 1σ confidence *** we assume a Gaussian prior of ΩM = 0.26 ± 0.1,we get α = 0.93＋0.07-0.19 and ΩM = 0.31＋*** the XCDM model,α is constrained to α≥ 0.80 but ω is weakly constrained around-1,where ω describes the equation of state of the dark energy（pX = ωρX）.We conclude that OHD constrains the smoothness parameter more effectively than the data of SNe Ia and compact radio sources.

关键词： cosmology -- dark energy -- cosmological parameters

Cosmological constraints on the Undulant Universe

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Research in Astronomy and Astrophysics 2010年第11期10卷 1109-1118页

作者： Tian Lan Yan Gong Hao-Yi Wan Tong-Jie Zhang Department of Astronomy Beijing Normal University Beijing 100875 China National Astronomical Observatories Chinese Academy of Sciences Beijing 100012 China Graduate University of Chinese Academy of Sciences Beijing 100049 China Business Office Beijing Planetarium Beijing 100044 China Center for High Energy Physics Peking University Beijing 100871 China

We use the redshift Hubble parameter H（z） data derived from relative galaxy ages, distant type Ia supernovae （SNe Ia）, the Baryonic Acoustic Oscillation （BAO） peak, and the Cosmic Microwave Background （CMB） shift parameter data, to constrain cosmological parameters in the Undulant Universe. We marginalize the like- lihood functions over h by integrating the probability density 19 ∝ e-x^2/2. By using a Markov Chain Monte Carlo （MCMC） technique, we obtain the best fitting results and give the confidence regions in the b - Ωm0 plane. Then we compare their constraints. Our results show that the H（z） data play a similar role with the SNe Ia data in cosmological study. By presenting the independent and joint constraints, we find that the BAO and CMB data play very important roles in breaking the degeneracy compared with the H（z） and SNe Ia data alone. Combined with the BAO or CMB data, one can remarkably improve the constraints. The SNe Ia data sets constrain Ωm0 much tighter than the H（z） data sets, but the H（z） data sets constrain b much tighter than the SNe Ia data sets. All these results show that the Undulant Universe approaches the ACDM model. We expect more H（z） data to constrain cosmological parameters in the future.

关键词： cosmology observations - dark matter

Effect of Neutrinos on Angular Momentum of Dark Matter Halo

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Research in Astronomy and Astrophysics 2023年第8期23卷 355-363页

作者： Yu Chen Chang-Zhi Lu Yu Lu Tingting Zhang Tong-Jie Zhang Institute for Frontiers in Astronomy and Astrophysics Beijing Normal UniversityBeijing 102206China Department of Astronomy Beijing Normal UniversityBeijing 100875China beijing planetarium Beijing Academy of Science and TechnologyBeijing 100044China College of Command and Control Engineering PLA Army Engineering UniversityNanjing 210017China Institute for Astronomical Science Dezhou UniversityDezhou 253023China

Massive neutrinos are expected to affect the large-scale structure formation,including the major component of solid substances,dark matter *** halos are influenced by neutrinos is vital and interesting,and angular momentum(AM)as a significant feature provides a statistical perspective for this *** halos from TianNu N-body cosmological simulation with the co-evolving neutrino particles,we obtain some concrete ***,by comparing the same halos with and without neutrinos,in contrast to the neutrino-free case,over 89.71%of halos have smaller halo moduli,over 71.06%have smaller particle-mass-reduced(PMR)AM moduli,and over 95.44%change their orientations of less than 0°.***,the relative variation of PMR modulus is more visible for low-mass ***,to explore the PMR moduli of halos in dense or sparse areas,we divide the whole box into big cubes,and search for halos within a small spherical cell in a single *** the two-level divisions,we discover that in denser cubes,the variation of PMR moduli with massive neutrinos decreases more *** distinction suggests that neutrinos exert heavier influence on halos'moduli in compact *** massive neutrinos,most halos(86.60%)have lower masses than without neutrinos.

关键词： (cosmology:)dark matter-neutrinos-(cosmology:)large-scale structure of universe-methods data analysis

K Parameter Analysis of the Radio Emission Region of Pulsars

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Chinese Physics Letters 1999年第1期16卷 74-75页

作者： WU Xin-ji KNYu ZHANG Cheng-min WEN Xue-shi Department of Geophysics Peking Universityand Chinese Academy of Science-Peking University Joint Astrophysical CenterBeijing 100871 Department of Physics and Materials Science City University of Hong KongHong Kong Department of Physics Hebei University of TechnologyTianjin 300130 beijing planetarium Beijing 100044

Using a new method of multi-frequency of K parameter,we estimate the ratio of altitudes of radio emission region of pulsars at 430 and 1418 *** value of the ratio is 1.34±0.12 and the power law index of altitude-frequency is 0.24±*** is indicated that the lower radio frequencies originate further out and the emission region is radially narrow.

关键词： altitude Pulsar narrow

The double helium-white dwarf channel for the formation of AM CVn binaries

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Research in Astronomy and Astrophysics 2018年第1期18卷 101-112页

作者： Xian-Fei Zhang Jin-Zhong Liu C.Simon Jeffery Philip D.Hall Shao-Lan Bi Department of Astronomy Beijing Normal University Xinjiang Astronomical Observatory Chinese Academy of Sciences Armagh Observatory and planetarium College Hill School of Physics Trinity College Dublin

Most close double helium white dwarfs will merge within a Hubble time due to orbital decay by gravitational wave ***,a significant fraction with low mass ratios will survive for a long time as a consequence of stable mass *** stable mass transfer between two helium white dwarfs（He WDs） provides one channel for the production of AM CVn binary *** previous calculations of double He WD progenitors,the accreting He WD was treated as a point *** have computed the evolution of 16 double He WD models in order to investigate the consequences of treating the evolution of both components in *** find that the boundary between binaries having stable and unstable mass transfer is slightly modified by this *** comparing with observed periods and mass ratios,we redetermine masses of eight known AM CVn stars by our double He WDs channel,*** Cnc,AM CVn,V406 Hya,J0926,J1240,GP Com,Gaia14 aae and V396 *** propose that central spikes in the triple-peaked emission spectra of J1240,GP Com and V396 Hya and the surface abundance ratios of N/C/O in GP Com can be explained by the stable double He WD *** mass estimates derived from our calculations are used to discuss the predicted gravitational wave signal in the context of the Laser Interferometer Space Antenna（LISA） project.

关键词： stars:peculiar(helium) stars:white dwarfs binaries:close gravitational waves

EXPLANATION OF UV BAND ABSORPTION SPECTRA CAUSED BY MARTIAN DUST CLOUD IN 1971

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Chinese Science Bulletin 1983年第6期28卷 779-782页

作者：赵南生梁民基 beijing planetarium beijing Light Industry College

Ⅰ. INTRODUCTION There was a great dust storm on Mars when Mariner 9 flew past it in November 1971. The spectra of sun light, scattered by the dust clouds, was recorded by a UV spectrometer attached to Mariner 9. Pang... 详细信息

关键词： spectrometer attached anatase processed rutile scattered storm evaporation tungsten amorphous

Optical and X-Ray Observations of MAXI J1820+070 During the Early Outburst Phase in 2018:Zooming in the Low Frequency QPOs

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Research in Astronomy and Astrophysics 2022年第4期22卷 106-113页

作者： Dong-Ming Mao Wen-Fei Yu Ju-Jia Zhang Zhen Yan Stefano Rapisarda Xiao-Feng Wang Jin-Ming Bai Shanghai Astronomical Observatory Chinese Academy of SciencesShanghai 200030China University of Chinese Academy of Sciences Beijing 100049China Yunnan Observatories Chinese Academy of SciencesKunming 650011China Key Laboratory for the Structure and Evolution of Celestial Objects CASKunming 650216China Physics Department Tsinghua UniversityBeijing 100084China beijing planetarium Beijing Academy of Sciences and TechnologyBeijing 100044China

We report a further investigation of the optical low frequency quasi periodic oscillations(LF QPOs)detected in the black hole transient MAXI J1820+070 in the 2018 observations with the YFOSC mounted on Lijiang 2.4 m telescope(LJT).In addition,we make use of the Insight-HXMT/HE observations to measure the properties of the quasi-simultaneous X-ray LF QPOs of MAXI J1820+070 on the same *** compared the centroid frequency,the full width at half maximum(FWHM)and the fractional rms of the LF QPOs in both wavelength *** found that the centroid frequency of the optical QPO is at a frequency of 51.58 m Hz,which is consistent with that of the X-ray LF QPO detected on the same day within 1 m *** also found that the FWHM of the optical LF QPO is significantly smaller than that of the X-ray LF QPO,indicating that the optical QPO has a higher *** quasi-simultaneous optical and the X-ray LF QPO at a centroid frequency of about 52 m Hz suggests that the actual mechanisms of these LF QPOs as the Lense-Thirring precession should work in the vicinity of a radius of about 80-117 gravitational radii(R_(g)=GM/c^(2),M is the mass of the black hole)from the black hole if the QPO frequency is related to a proxy of the orbital frequency in the accretion fiow as the Lense-Thirring precession model ***,the apparent higher coherence of the optical QPO favors that it is a more original signal as compared with the X-ray QPO.

关键词： X-ray stars Low mass binary stars X-ray transient sources

Forecasting supernova observations with the CSST:*** samples

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Science China(Physics,Mechanics & Astronomy) 2024年第11期67卷 164-177页

作者： Chengqi Liu Youhua Xu Xianmin Meng Xin Zhang Shi-Yu Li Yuming Fu Xiaofeng Wang Shufei Liu Zun Luo Guanghuan Wang Hu Zhan Department of Astronomy School of PhysicsPeking UniversityBeijing 100871China Kavli Institute for Astronomy and Astrophysics Peking UniversityBeijing 100871China Key Laboratory of Space Astronomy and Technology National Astronomical ObservatoriesChinese Academy of SciencesBeijing 100101China beijing planetarium Beijing Academy of Science and TechnologyBeijing 100044China Leiden Observatory Leiden UniversityNL-2300 RA LeidenThe Netherlands Kapteyn Astronomical Institute University of GroningenNL-9700 AV GroningenThe Netherlands Physics Department Tsinghua UniversityBeijing 100084China School of Astronomy and Space Science University of ChineseAcademy of SciencesBeijing 100049China

The China Space Station Telescope(CSST,also known as Xuntian)is a serviceable two-meter-aperture wide-field telescope operating in the same orbit as the China Space *** CSST plans to survey a sky area of 17,500 deg^(2)of the medium-to-high Galactic latitude to a depth of 25-26 AB mag in at least 6 photometric bands over 255-1,000 *** such a large sky area,slitless spectra will also be taken over the same wavelength range as the imaging *** though the CSST survey is not dedicated to time-domain studies,it would still detect a large number of transients,such as supernovae(SNe).In this paper,we simulate photometric SN observations based on a strawman survey plan using the Sncosmo *** its 10-year survey,the CSST is expected to observe about 5 million SNe of various *** quality cuts,we obtain a“gold”sample that comprises roughly 7,400 SNe Ia,2,200 SNe Ibc,and 6,500 SNeⅡcandidates with correctly classified percentages reaching 91%,63%,and 93%(formally defined as classification precision),*** same survey can also trigger alerts for the detection of about 15,500 SNe Ia(precision 61%)and 2,100 SNeⅡ(precision 49%)candidates at least two days before the light ***,the near-ultraviolet observations of the CSST will be able to catch hundreds of shock-cooling events serendipitously every *** results demonstrate that the CSST can make a potentially significant contribution to SN studies.

关键词： space-based ultraviolet optical and infrared telescopes supernovae data analysis

The dusty and extremely red progenitor of the typeⅡsupernova 2023ixf in Messier 101

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Science China(Physics,Mechanics & Astronomy) 2024年第1期67卷 160-172页

作者： Danfeng Xiang Jun Mo Lingzhi Wang Xiaofeng Wang Jujia Zhang Han Lin Lifan Wang Department of Physics Tsinghua UniversityBeijing 100084China South America Center for Astronomy National Astronomical ObservatoriesChinese Academy of SciencesBeijing 100101China beijing planetarium Beijing Academy of Sciences and TechnologyBeijing 100044China Yunnan Observatories Chinese Academy of SciencesKunming 650216China Key Laboratory for the Structure and Evolution of Celestial Objects Chinese Academy of SciencesKunming 650216China International Centre of Supernovae Yunnan Key LaboratoryKunming 650216China Mitchell Institute for Fundamental Physics and Astronomy Texas A&M UniversityCollege StationTX 77843USA

Stars with initial masses in the range of 8-25 solar masses are thought to end their lives as hydrogen-rich supernovae(SNeⅡ).Based on the pre-explosion images of Hubble space telescope(HST)and Spitzer space telescope,we place tight constraints on the progenitor candidate of type IIP SN 2023ixf in Messier *** of the spectral energy distribution(SED)of its progenitor with dusty stellar spectral models results in an estimation of the effective temperature as 3091+*** luminosity is estimated as lg(L/L⊙)~4.83,consistent with a red supergiant(RSG)star with an initial mass of 12-1+2M⊙.The derived mass loss rate(6×10^(-6)-9×10^(-6)M⊙yr^(-1))is much lower than that inferred from the flash spectroscopy of the SN,suggesting that the progenitor experienced a sudden increase in mass loss when approaching the final *** the infrared bands,significant deviation from the range of regular RSGs in the color-magnitude diagram and period-luminosity space of the progenitor star indicates enhanced mass loss and dust *** with new evidence of polarization at the early phases of SN 2023ixf,such a violent mass loss is likely a result of binary interaction.

关键词： stellar evolution mass loss red supergiants infrared emission supernovae

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