Simultaneous observations of a pair of kilohertz QPOs and a plausible 1860Hz QPO from an accreting neutron star system     

Sudip Bhattacharyya 《中国天文和天体物理学报》2010,10(3)

We report an indication(3.22 σ)of ≈ 1860Hz quasi-periodic oscillations from a neutron star low-mass X-ray binary 4U 1636-536.If confirmed,this will be by far the highest frequency feature observed from an accreting neutron star system,and hence could be very useful in understanding such systems.This plausible timing feature was observed simultaneously with lower(≈ 585Hz)and upper(≈ 904Hz)kilohertz quasi-periodic oscillations.The two kilohertz quasi-periodic oscillation frequencies had a ratio of ≈ 1.5,and t...  相似文献   

Alfvén polar oscillations of relativistic stars     

Hajime Sotani  Kostas D. Kokkotas 《Monthly notices of the Royal Astronomical Society》2009,395(2):1163-1172

We study polar Alfvén oscillations of relativistic stars endowed with a strong global poloidal dipole magnetic field. Here, we focus only on the axisymmetric oscillations which are studied by numerically evolving the two-dimensional perturbation equations. Our study shows that the spectrum of the polar Alfvén oscillations is discrete in contrast to the spectrum of axial Alfvén oscillations which is continuous. We also show that the typical fluid modes, such as the f and p modes, are not significantly affected by the presence of the strong magnetic field.  相似文献   

The bending of light and lensing in modified gravity     

J. W. Moffat  V. T. Toth 《Monthly notices of the Royal Astronomical Society》2009,397(4):1885-1892

Our modified gravity theory (MOG) was used successfully in the past to explain a range of astronomical and cosmological observations, including galaxy rotation curves, the cosmic microwave background acoustic peaks, and the galaxy mass power spectrum. MOG was also used successfully to explain the unusual features of the Bullet Cluster  1E0657−558  without exotic dark matter. In the present work, we derive the relativistic equations of motion in the spherically symmetric field of a point source in MOG and, in particular, we derive equations for light bending and lensing. Our results also have broader applications in the case of extended distributions of matter, and they can be used to validate the Bullet Cluster results and provide a possible explanation for the merging clusters in Abell 520.  相似文献   

Matter wave explorer of gravity (MWXG)     

《Experimental Astronomy》2009,23(2):611-649

In response to ESA’s Call for proposals of 5 March 2007 of the COSMIC VISION 2015–2025 plan of the ESA science programme, we propose a M-class satellite mission to test of the Equivalence Principle in the quantum domain by investigating the extended free fall of matter waves instead of macroscopic bodies as in the case of GAUGE, MICROSCOPE or STEP. The satellite, called Matter Wave Explorer of Gravity, will carry an experiment to test gravity, namely the measurement of the equal rate of free fall with various isotopes of distinct atomic species with precision cold atom interferometry in the vicinity of the earth. This will allow for a first quantum test the Equivalence Principle with spin polarised particles and with pure fermionic and bosonic atomic ensembles. Due to the space conditions, the free fall of Rubidium and Potassium isotopes will be compared with a maximum accelerational sensitivity of 5·10^− 16 m/s² corresponding to an accuracy of the test of the Equivalence Principle of 1 part in 10¹⁶. Besides the primary scientific goal, the quantum test of the Equivalence Principle, the mission can be extended to provide additional information about the gravitational field of the earth or for testing theories of fundamental processes of decoherence which are investigated by various theory groups in the context of quantum gravity phenomenology. In this proposal we present in detail the mission objectives and the technical aspects of the proposed mission.  相似文献   

2004年南宁市空气质量回顾     

陆甲  董蕙青  谢宏斌 《气象研究与应用》2005,26(1):38-40

对2004年南宁市的空气质量进行分析,结果表明:南宁市各种污染物(SO2、NO2、PM10)的变化有着明显季节性,SO2、NO2、PM10之间以及它们与气象要素有着密切的相关性,不同的监测点污染物的排放情况不同,清洁对照点需要重新选择。  相似文献   

New upper limit on the cosmological constant from solar system dynamics     

Shuang Liang  Yi Xie 《天文和天体物理学研究(英文版)》2014,(5):527-532

The cosmological constantΛis the simplest model for explaining the dark energy which supposedly drives the observed accelerated expansion rate of the Universe.Together with the concept of cold dark matter,it satisfactorily accommodates a wealth of observations related to cosmology.Due to its assumed constancy throughout the Universe,Λmight also affect the dynamics of the planets in the solar system,although with extremely small effects.However,modern high-precision ephemerides provide a promising tool for constraining it.Using the supplementary advances in the perihelia provided by current INPOP10a and EPM2011 ephemerides,we obtain a new upper limit onΛin the solar system when the Lense-Thirring effect due to the Sun’s angular momentum and the uncertainty of the Sun’s quadrupole moment are properly taken into account.These two factors were mostly absent in previous works dealing withΛ.We find that INPOP10a yields an upper limit ofΛ=(0.26±1.45)×10-43m-2and EPM2011 givesΛ=(-0.44±8.93)×10-43m-2.Such bounds are about 10 times less than previously estimated results.  相似文献   

太原地震台短水准受水位影响分析及异常识别     

孟彩菊 《地震地磁观测与研究》2010,31(1):77-83

水位是影响水准高差变化最为显著和普遍的因素,本文研究了晋7-1~#井水位变化对太原地震台水准高差的影响,分析了两者的相关性及年最大变化量的异同情况。结果显示,相关性、年最大变化量比值异常与山西地震带地震有较好对应。  相似文献   

Gravitational Faraday rotation in binary pulsar systems     

M. L. Ruggiero  A. Tartaglia 《Monthly notices of the Royal Astronomical Society》2007,374(3):847-851

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The first high-amplitude δ Scuti star in an eclipsing binary system     

J. L. Christiansen  A. Derekas  M. C. B. Ashley  J. K. Webb  M. G. Hidas  D. W. Hamacher  L. L. Kiss 《Monthly notices of the Royal Astronomical Society》2007,382(1):239-244

Consider radar ranging of a distant galaxy in a Friedman–Lemaître cosmological model. In this model the comoving coordinate of the galaxy is constant; hence, the equations of null geodesics for photons travelling to the distant galaxy and back imply Here, τ_e, τ_r and τ_o are, respectively, the times of emission, reflection and observation of the reflected photons, and a (τ) is the scalefactor. Since the Universe is expanding, a (τ) is a monotonically increasing function, so the return traveltime, τ_o−τ_r, must be greater than the forward traveltime, τ_r−τ_e. Clearly, space expands, and on their way back, the photons must travel a longer distance! This paper explains why this argument for the Expansion of Space (EoS) is wrong. We argue that, unlike the expansion of the cosmic substratum, the EoS is unobservable. We therefore propose to apply to it – just like to the ether – Ockham's razor.  相似文献   

Exact general relativistic discs and the advance of perihelion     

D. Vogt  P. S. Letelier 《Monthly notices of the Royal Astronomical Society》2008,384(2):834-842

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