Light-Time Effect in the Eclipsing Binaries GO Cyg, GW Cep, AR Aur and V505 Sgr     

D. Chochol  T. Pribulla  M. Vaňko  P. Mayer  M. Wolf  P. G. Niarchos  K. D. Gazeas  V. N. Manimanis  L. Brát  M. Zejda 《Astrophysics and Space Science》2006,304(1-4):93-96

Orbital period changes of the eclipsing binaries GO Cyg and GW Cep are explained by the light-time effect for the first time. New minima of the eclipsing binary AR Aur improve the predicted light-time orbit. The light-time orbit with the quadratic ephemeris of the binary matches the new observations of V505 Sgr better than the linear one. As the light-time effect fits in corresponding O − C diagrams of all four systems have been reaching extreme values, the observations of minima times in forthcoming years are highly desirable.  相似文献   

Modelling of anisotropic damage in brittle rocks under compression dominated stresses     

Y.F. Lu  J.F. Shao 《国际地质力学数值与分析法杂志》2002,26(10):945-961

A new model for describing induced anisotropic damage in brittle rocks is proposed. Although phenomenological, the model is based on physical grounds of micromechanical analysis. Induced damage is represented by a second rank tensor, which is related to the density and orientation of microcracks. Damage evolution is related to the propagation condition of microcracks. The onset of microcrack coalescence leading to softening behaviour is also considered. The effective elastic compliance of the damaged material is obtained from a specific form of Gibbs potential. Irreversible damage‐related strains due to residual opening of microcracks after unloading are also captured. All the model's parameters could be determined from conventional triaxial compression tests. The proposed model is applied to a typical brittle rock. Comparison between test data and numerical simulations shows an overall good agreement. The proposed model is able to describe the main features related to induced microcracks in brittle geomaterials. Copyright © 2002 John Wiley & Sons, Ltd.  相似文献   

Multiple magnetic clouds in interplanetary space   总被引：7，自引：0，他引：7  

Wang  Y.M.  Wang  S.  Ye  P.Z. 《Solar physics》2002,211(1-2):333-344

An interplanetary magnetic cloud (MC) is usually considered the byproduct of a coronal mass ejection (CME). Due to the frequent occurrence of CMEs, multiple magnetic clouds (multi-MCs), in which one MC catches up with another, should be a relatively common phenomenon. A simple flux rope model is used to get the primary magnetic field features of multi-MCs. Results indicate that the magnetic field configuration of multi-MCs mainly depends on the magnetic field characteristics of each member of multi-MCs. It may be entirely different in another situation. Moreover, we fit the data from the Wind spacecraft by using this model. Comparing the model with the observations, we verify the existence of multi-MCs, and propose some suggestions for further work.  相似文献   

InFOCμS Hard X-ray Imaging Telescope     

J. Tueller  H. A. Krimm  T. Okajima  S. D. Barthelmy  S. M. Owens  P. J. Serlemitsos  Y. Soong  K.-W. Chan  Y. Ogasaka  R. Shibata  K. Tamura  A. Furuzawa  Y. Tawara  H. Kunieda  K. Yamashita 《Experimental Astronomy》2005,20(1-3):121-129

InFOCμS is a new generation balloon-borne hard X-ray telescope with focusing optics and spectroscopy. We had a successful 22.5-hour flight from Fort Sumner, NM on September 16,17, 2004. In this paper, we present the performance of the hard X-ray telescope, which consists of a depth-graded platinum/carbon multilayer mirror and a CdZnTe detector. The telescope has an effective area of 49 cm² at 30 keV, an angular resolution of 2.4 arcmin (HPD), and a field of view of 11 arcmin (FWHM) depending on energies. The CdZnTe detector is configured with a 12 × 12 segmented array of detector pixels. The pixels are 2 mm square, and are placed on 2.1 mm centers. An averaged energy resolution is 4.4 keV at 60 keV and its standard deviation is 0.36 keV over 128 pixels. The detector is surrounded by a 3-cm thick CsI anti coincidence shield to reduce background from particles and photons not incident along the mirror focal direction. The inflight background is 2.9 × 10⁻⁴ cts cm⁻² sec⁻¹ keV⁻¹ in the 20–50 keV band.  相似文献   

Near-infrared identification of the counterpart to X1908+075: a new OB-supergiant X-ray binary     

T. Morel  Y. Grosdidier 《Monthly notices of the Royal Astronomical Society》2005,356(2):665-670

We report the near-infrared (near-IR) identification of the likely counterpart to X1908+075, a highly absorbed Galactic X-ray source recently suspected to belong to the rare class of OB supergiant–neutron star binary systems. Our JHK_s -band imaging of the field reveals the existence within the X-ray error boxes of a near-IR source consistent with an early-type star lying at   d ∼ 7 kpc  and suffering   A_V ∼ 16 mag  of extinction, the latter value being in good agreement with the hydrogen column density derived from modelling of the X-ray spectrum. Our follow-up, near-IR spectroscopic observations confirm the nature of this candidate and lead to a late O-type supergiant classification, thereby supporting the identification of a new Galactic OB-supergiant X-ray binary.  相似文献   

Beaming Effects in GRBs and Orphan Afterglows     

Y. F. Huang  T. Lu  K. S. Cheng 《Astrophysics and Space Science》2005,297(1-4):53-61

The overall dynamical evolution and radiation mechanism of γ-ray burst (GRB) jets are briefly introduced. Various interesting topics concerning beaming in GRBs are discussed, including jet structures, orphan afterglows and cylindrical jets. The possible connection between GRBs and neutron stars is also addressed.  相似文献   

A model of Jupiter's magnetospheric magnetic field with variable magnetopause flaring     

E.S. Belenkaya  S.Y. Bobrovnikov  V.V. Kalegaev 《Planetary and Space Science》2005,53(9):863-872

We present a new model of the jovian magnetosphere in which the flaring of the magnetopause boundary can be varied. Magnetopause flaring is expected to vary due to changing conditions in the upstream interplanetary medium, related both to the dynamic pressure of the solar wind, and to changes in the direction of the interplanetary magnetic field. The model includes a tilted dipole field, which is screened by the magnetopause, a tail field current system, and the field of a screened equatorial current disc.  相似文献   

The iron Kα lines as a tool for magnetic field estimations in non-flat accretion flows     

A.F. Zakharov  Z. Ma  Y. Bao 《New Astronomy》2004,9(8):663-677

Observations of AGNs and microquasars by ASCA, RXTE, Chandra and XMM-Newton indicate the existence of broad X-ray emission lines of ionized heavy elements in their spectra. Such spectral lines were discovered also in X-ray spectra of neutron stars and X-ray afterglows of GRBs. Recently, Zakharov et al. [MNRAS 342 (2003) 1325] described a procedure to estimate an upper limit of the magnetic fields in regions from which X-ray photons are emitted. The authors simulated typical profiles of the iron Kα line in the presence of magnetic field and compared them with observational data in the framework of the widely accepted accretion disk model. Here we further consider typical Zeeman splitting in the framework of a model of non-flat accretion flows, which is a generalization of previous consideration into non-equatorial plane motion of particles emitting X-ray photons. Using perspective facilities of space borne instruments (e.g., Constellation-X mission) a better resolution of the blue peak structure of iron Kα line will allow to evaluate the magnetic fields with higher accuracy.  相似文献   

Infrared polarimetry of the stars in the inner galaxy     

Y. Kobayashi  J. Jugaku  H. Okuda  S. Sato  T. Nagata 《Astrophysics and Space Science》1986,119(1):135-139

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Green functions and associated sources in infinite and stratified poroelastic media     

C. Boutin  G. Bonnet  P. Y. Bard 《Geophysical Journal International》1987,90(3):521-550

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