Time-dependent scattering and transmission function in an anisotropic two-layered atmosphere     

T. K. Deb  S. Karanjai  G. Biswas 《Astrophysics and Space Science》1992,189(1):95-117

In this paper we consider the time-dependent diffuse reflection and transmission problems for a homogeneous anisotropically-scattering atmosphere of finite optical depth and solve it by the principle of invariance. Also we consider the time-dependent diffuse reflection and transmission of parallel rays by a slab consisting of two anisotropic homogeneous layers, whose scattering and transmission properties are known. It is shown how to express the time-dependent reflected and transmitted intensities in terms of their components. In a manner similar to that given by Tsujita (1968), we assumed that the upward-directed intensities of radiation at the boundary of the two layers are expressed by the sum of products of some auxiliary functions depending on only one argument. Then, after some analytical manipulations, three groups of systems of simultaneous integral equations governing the auxiliary functions are obtained.  相似文献   

XMM–Newton confirmation of a warm absorber in the z = 4.4 blazar PMN J0525−3343     

M. A. Worsley  A. C. Fabian  A. K. Turner  A. Celotti  K. Iwasawa 《Monthly notices of the Royal Astronomical Society》2004,350(1):207-212

  相似文献   

Polar fields for AB Doradus     

T. McIvor  M. Jardine  A. Collier Cameron  K. Wood  J.-F. Donati 《Monthly notices of the Royal Astronomical Society》2003,345(2):601-608

  相似文献   

Exchange and correlation interactions in electron-positron plasma     

A. V. Yudin  D. K. Nadyozhin 《Astronomy Letters》2003,29(3):158-162

The effect of particle-particle interaction on the adiabatic index γ for an electron-positron plasma is considered. An improved method for numerically calculating the Hartree-Fock exchange integral is presented and its relativistic asymptotics is determined. An approximation formula is derived for the correlation part of the interaction in the low-density limit. This formula includes degeneracy and the positron component.  相似文献   

A high-velocity ionized outflow and XUV photosphere in the narrow emission line quasar PG1211+143   总被引：1，自引：0，他引：1  

K. A. Pounds  J. N. Reeves  A. R. King  K. L. Page  P. T. O'Brien  M. J. L. Turner 《Monthly notices of the Royal Astronomical Society》2003,345(3):705-713

We report on the analysis of a ∼60-ks XMM–Newton observation of the bright, narrow emission line quasar PG1211+143. Absorption lines are seen in both European Photon Imaging Camera and Reflection Grating Spectrometer spectra corresponding to H- and He-like ions of Fe, S, Mg, Ne, O, N and C. The observed line energies indicate an ionized outflow velocity of ∼24 000 km s⁻¹. The highest energy lines require a column density of   N _H∼ 5 × 10²³ cm⁻²  , at an ionization parameter of  log ξ∼ 3.4  . If the origin of this high-velocity outflow lies in matter being driven from the inner disc, then the flow is likely to be optically thick within a radius of ∼130 Schwarzschild radii, providing a natural explanation for the big blue bump (and strong soft X-ray) emission in PG1211+143.  相似文献   

Hα Photometry of Two Contact Binaries     

Szilárd Csizmadia  Zsolt Kővári  Péter Klagyivik 《Astrophysics and Space Science》2006,304(1-4):355-357

We carried out optical and Hα photometry of two contact binaries (V861 Herculis, EQ Tauri). The light curve modeling revealed stellar spots in both contact systems and strong Hα excess in the position of the observed stellar spots. A correlation was found between the V−R and R−H_α colour indices of V861 Her.  相似文献   

B0850+054: a new gravitational lens system from CLASS     

A. D. Biggs  D. Rusin  I. W. A. Browne  A. G. de Bruyn  N. J. Jackson  L. V. E. Koopmans  J. P. McKean  S. T. Myers  R. D. Blandford  K.-H. Chae  C. D. Fassnacht  M. A. Norbury  T. J. Pearson  P. M. Phillips  A. C. S. Readhead  P. N. Wilkinson 《Monthly notices of the Royal Astronomical Society》2003,338(4):1084-1088

  相似文献   

FUSE and HST ultraviolet observations of the disc wind of RW Sextantis     

R. K. Prinja  K. S. Long  C. S. Froning  C. Knigge  D. K. Witherick  J. S. Clark  F. A. Ringwald 《Monthly notices of the Royal Astronomical Society》2003,340(2):551-561

  相似文献   

North European last glacial–interglacial transition (LGIT; 15–9 ka) tephrochronology: extended limits and new events     

C. S. M. Turney  K. Van Den Burg  S. Wastegrd  S. M. Davies  N. J. Whitehouse  J. R. Pilcher  C. Callaghan 《第四纪科学杂志》2006,21(4):335-345

High‐precision correlation of palaeoclimatic and palaeoenvironmental records is crucial for testing hypotheses of synchronous change. Although radiocarbon is the traditional method for dating late Quaternary sedimentary sequences, particularly during the last glacial–interglacial transition (LGIT; 15–9 ka), there are inherent problems with the method, particularly during periods of climate change which are often accompanied by major perturbations in atmospheric radiocarbon content. An alternative method is the use of tephras that act as time‐parallel marker horizons. Within Europe, numerous volcanic centres are known to have erupted during the LGIT, providing considerable potential for high‐precision correlation independent of past radiocarbon fluctuations. Here we report the first identification of the Vedde Ash and Askja Tephra in Ireland, significantly extending the known provenance of these events. We have also identified two new horizons (the Roddans Port Tephras A and B) and tentatively recognise an additional horizon from Vallensgård Mose (Denmark) that provide crucial additional chronological control for the LGIT. Two phases of the Laacher See Tephra (LST) are reported, the lower Laacher See Tephra (LLST) and probably the C2 phase of the Middle Laacher See Tephra (MLST‐C2) indicating a more northeasterly distribution of this fan than reported previously. Copyright © 2006 John Wiley & Sons, Ltd.  相似文献   

Observational Test of an Accretion Model of Star Formation in Galactic Clusters     

J. N. Pramanik  S. K. Bhattacharjee 《Astrophysics and Space Science》2006,306(4):241-248

Theoretical predictions of an accretion model of star formation in galactic clusters, published quite long ago, which is found to have some relevance with the current picture of star formation have been tested with observation of seven clusters of young and intermediate ages. It is found that the agreement between the theory and observation is very good.  相似文献