XMM–Newton observations of the eclipsing polar EP Dra     

Gavin Ramsay  C. M. Bridge  Mark Cropper  K. O. Mason  F. A. Córdova  W. Priedhorsky 《Monthly notices of the Royal Astronomical Society》2004,354(3):773-778

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I-band time-series observations of five bright ultracool dwarfs     

Chris Koen 《Monthly notices of the Royal Astronomical Society》2004,354(2):378-386

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Stokes imaging, Doppler mapping and Roche tomography of the AM Herculis system V834 Cen   总被引：1，自引：0，他引：1  

Stephen B. Potter  E. Romero-Colmenero  C. A. Watson  D. A. H. Buckley  A. Phillips 《Monthly notices of the Royal Astronomical Society》2004,348(1):316-324

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The R Coronae Borealis stars: carbon abundances from forbidden carbon lines     

Gajendra Pandey  David L. Lambert  N. Kameswara Rao  Bengt Gustafsson  Nils Ryde  David Yong 《Monthly notices of the Royal Astronomical Society》2004,353(1):143-152

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Short time-scale variability in the Faint Sky Variability Survey     

L. Morales-Rueda  P. J. Groot  T. Augusteijn  G. Nelemans  P. M. Vreeswijk  E. J. M. van den Besselaar 《Monthly notices of the Royal Astronomical Society》2006,371(4):1681-1692

We present the V -band variability analysis of the point sources in the Faint Sky Variability Survey on time-scales from 24 min to tens of days. We find that about one per cent of the point sources down to   V = 24  are variables. We discuss the variability-detection probabilities for each field depending on field sampling, amplitude and time-scale of the variability. The combination of colour and variability information allows us to explore the fraction of variable sources for different spectral types. We find that about 50 per cent of the variables show variability time-scales shorter than 6 h. The total number of variables is dominated by main-sequence sources. The distribution of variables with spectral type is fairly constant along the main sequence, with 1 per cent of the sources being variable, except at the blue end of the main sequence, between spectral types F0 and F5, where the fraction of variable sources increases to about 2 per cent. For bluer sources, above the main sequence, this percentage increases to about 3.5. We find that the combination of the sampling and the number of observations allows us to determine the variability time-scales and amplitudes for a maximum of 40 per cent of the variables found. About a third of the total number of short time-scale variables found in the survey were not detected in either B or/and I band. These show a similar variability time-scale distribution to that found for the variables detected in all three bands.  相似文献   

The investigation of nova-like variable MV Lyr during the 1999–2001 years     

N. A. Katysheva  S. Yu. Shugarov  E. P. Pavlenko  P. V. Abolmasov 《Journal of Astrophysics and Astronomy》2002,23(1-2):15-18

A peculiar nova-like MV Lyr was investigated. The CCD-observations of MV Lyr were continued in Crimea during the outbursts and quiescent states. Last year its behavior became non-typical for “anti-dwarf novae”. The length of its first deep minimum was 10 years. A modern state is characterized by very strong outbursts and very often changes of the stages. The periods 0. ^d 128 and 0. ^d 136 were obtained for 1998 and 1999 years accordingly. Possibly, a relation between the photometric period and the brightness exists.  相似文献   

Evolution of binary stars and the effect of tides on binary populations   总被引：1，自引：0，他引：1  

Jarrod R. Hurley †  Christopher A. Tout  Onno R. Pols ‡ 《Monthly notices of the Royal Astronomical Society》2002,329(4):897-928

We present a rapid binary-evolution algorithm that enables modelling of even the most complex binary systems. In addition to all aspects of single-star evolution, features such as mass transfer, mass accretion, common-envelope evolution, collisions, supernova kicks and angular momentum loss mechanisms are included. In particular, circularization and synchronization of the orbit by tidal interactions are calculated for convective, radiative and degenerate damping mechanisms. We use this algorithm to study the formation and evolution of various binary systems. We also investigate the effect that tidal friction has on the outcome of binary evolution. Using the rapid binary code, we generate a series of large binary populations and evaluate the formation rate of interesting individual species and events. By comparing the results for populations with and without tidal friction, we quantify the hitherto ignored systematic effect of tides and show that modelling of tidal evolution in binary systems is necessary in order to draw accurate conclusions from population synthesis work. Tidal synchronism is important but, because orbits generally circularize before Roche lobe overflow, the outcome of the interactions of systems with the same semilatus rectum is almost independent of eccentricity. It is not necessary to include a distribution of eccentricities in population synthesis of interacting binaries; however, the initial separations should be distributed according to the observed distribution of semilatera recta rather than periods or semimajor axes.  相似文献   

Trend-surface analysis     

G. S. Watson 《Mathematical Geology》1971,3(3):215-226

This paper is largely an exposition of the work of the French geostatistian G. Matheron and his school in English and at a simpler mathematical level. The probability theory on which it is based is essentially all contained in the references cited, most of which will be unfamiliar to mathematical geologists. The important method of universal kriging is explained intuitively. The genuine statistical problems, which have yet to be overcome, are pointed out.Research supported by the Office of Naval Research under contract NONR 4010(09) awarded to the Department of Statistics, The Johns Hopkins University. This paper in whole or in part may be reproduced for any purpose of the United States Government.  相似文献   

X-ray observations of 4 Draconis: symbiotic binary or cataclysmic triple?     

Peter J. Wheatley  Koji Mukai †  Domitilla de Martino 《Monthly notices of the Royal Astronomical Society》2003,346(3):855-860

We present the first X-ray observations of the 4 Draconis system, consisting of an M3 III giant with a hot ultraviolet companion. It has been claimed that the companion is itself an AM Her-type binary system, an identification that places strong constraints on the evolution of cataclysmic variables. We find that the X-ray properties of 4 Draconis are consistent with the presence of an accreting white dwarf, but not consistent with the presence of an AM Her system. We conclude that 4 Draconis is therefore most likely a symbiotic binary containing a white dwarf accreting material from the wind of the red giant.
The X-ray spectrum of 4 Draconis is sometimes dominated by partially ionized photoelectric absorption, presumably due to the wind of the red giant. We note that X-ray monitoring of such systems would provide a powerful probe of the wind and mass-loss rate of the giant, and would allow a detailed test of wind accretion models.  相似文献   

非保守弹性动力系统两类变量的广义拟变分原理及其应用     

宋海燕  梁立孚  刘殿魁 《地震工程与工程振动》2005,25(4):24-30

按照广义力和广义位移之间的对应关系,将弹性动力学的各基本方程分别乘上相应的虚量,然后在相应的体积域和面积域上积分,将积分式代数相加,再将代数和在时间域上积分,代入本构关系,并考虑到体积力和面积力均为伴生力,进而建立了非保守弹性动力系统的第1类两类变量的广义拟变分原理;再应用类似的方法,通过代入另一类本构关系,建立了非保守弹性动力系统的第2类两类变量广义拟变分原理.应用第1类两类变量广义拟余能原理给出同时求解1个典型的非保守弹性动力系统的固有频率、变形和内力的计算方法.最后,讨论了有关问题.  相似文献