Asteroseismic theory of rapidly oscillating Ap stars     

Margarida S. Cunha 《Journal of Astrophysics and Astronomy》2005,26(2-3):213-221

This paper reviews some of the important advances made over the last decade concerning theory of roAp stars.  相似文献   

Transition probabilities and lifetimes in singly ionized rhenium     

P. Palmeri  P. Quinet  É. Biémont  H. L. Xu  S. Svanberg 《Monthly notices of the Royal Astronomical Society》2005,362(4):1348-1352

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The λ Bootis phenomenon: interaction between a star and a diffuse interstellar cloud     

Inga Kamp  Ernst Paunzen 《Monthly notices of the Royal Astronomical Society》2002,335(2):L45-L49

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The 5200-Å flux depression of chemically peculiar stars – I. Synthetic Δa photometry: the normality line     

F. Kupka  E. Paunzen †  H. M. Maitzen 《Monthly notices of the Royal Astronomical Society》2003,341(3):849-854

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Giant CP Stars?     

L. O. Lodén  A. Sundman 《Journal of Astrophysics and Astronomy》1989,10(2):183-196

This study is part of an investigation of the possibility of using chemically peculiar (CP) stars to map local galactic structure. Correct luminosities of these stars are therefore crucial. CP stars are generally regarded as main-sequence or near-main-sequence objects. However, some CP stars have been classified as giants. A selection of stars, classified in literature as CP giants, are compared to normal stars in the same effective temperature interval and to ordinary ‘non giant’ CP stars. We find no clear confirmation of a higher luminosity for ‘CP giants’, than for CP stars in general. In addition, CP characteristics seem to be individual properties not repeated in a component star or other cluster members.  相似文献   

Radial pulsations of helium stars with masses from 10 to 50<Emphasis Type="Italic">M</Emphasis><Subscript>⊙</Subscript>     

Yu. A. Fadeyev  M. F. Novikova 《Astronomy Letters》2004,30(10):707-714

We have performed hydrodynamic calculations of the radial pulsations of helium stars with masses 10M_⊙ ≤ M ≤ 50M_⊙, luminosity-to-mass ratios 5 × 10³L_⊙/M_⊙ ≤ L/M ≤ 2.5 × 10⁴L_⊙/M_⊙, and effective temperatures 2 × 10⁴ K ≤ T_eff ≤ 10⁵ K for helium and heavy-element mass fractions of Y=0.98 and Z=0.02, respectively. We show that the high-temperature boundary of the instability region for radial pulsations at L/M ? 10⁴L_⊙/M_⊙ extends to T_eff≈10⁵ K. The amplitude of the velocity variations for outer layers is several hundred km s^?1, while the brightness variations in the B band of the UBV photometric system are within the range from several hundredths to half a magnitude. At constant luminosity-to-mass ratio, the radial pulsation period is determined only by the effective temperature of the star. In the ranges of luminosity-to-mass ratios 10⁴L_⊙/M_⊙ ≤ L/M ≤ 2 × 10⁴L_⊙/M_⊙ and effective temperatures 5 × 10⁴ K ≤ T_eff ≤ 9 × 10⁴ K, the periods of the radial modes are within 6 min ?Π?10³ min.  相似文献   

UGC 5119: A galaxy with a stellar polar ring?     

V. A. Yakovleva  G. M. Karataeva 《Astronomy Letters》2004,30(8):519-526

We present our photometric BV R_c observations of UGC 5119, a candidate polar-ring galaxy. We have determined its absolute magnitude, \(M_{0,B} = - 20\mathop m\limits_. 3\), and total color indices, \((B - V)_t^0 = + 0\mathop m\limits_. 73 \pm 0\mathop m\limits_. 10\) and \((V - R_c )_t^0 = + 0\mathop m\limits_. 54 \pm 0\mathop m\limits_. 10\). A Fourier analysis of the shape of its isophotes shows that UGC 5119 is most likely an elliptical galaxy with a disk component in the central part and a “boxy” feature on the periphery. At distances larger than 8″, the galaxy exhibits a turn of its major axis and a change in the phase of the fourth harmonic. Assuming the position angle of the major axis to be constant, a stellar ringlike structure is distinguished in the galaxy. The age of the ring stars is the same as that of the stars in the host galaxy. The distinguished ringlike structure cannot be attributed to typical polar rings rich in gas and in young stars.  相似文献   

GIS专题数据库中多层注记重叠问题的解决与自动配置   总被引：1，自引：0，他引：1  

祁洪霞  杨敏华  杨文亮 《测绘科学》2012,(1):201-202

GIS专题数据库中面状对象的注记一般会自动配置在图形的重心位置。当同一个面状对象在多个数据层中被赋予不同的属性定义时,注记符号和文字将会重叠在同一个位置。当使用的GIS建库软件存在这方面的缺陷时,解决多层注记重叠、自动重新配置注记符号这一命题就显得至关重要。本文以张家界市武陵源城镇地籍数据为例,从多边形形状度量入手,给出基于Delaunay三角网法的骨架线提取算法,较好地解决了多数据层注记重叠和注记符号自动配置问题,提高了工作效率。  相似文献   

Correlations among the properties of galaxies found in a blind H i survey, which also have SDSS optical data     

D. A. Garcia-Appadoo  A. A. West  J. J. Dalcanton  L. Cortese  M. J. Disney 《Monthly notices of the Royal Astronomical Society》2009,394(1):340-356

We have used the Parkes Multibeam system and the Sloan Digital Sky Survey to assemble a sample of 195 galaxies selected originally from their H  i signature to avoid biases against unevolved or low surface brightness objects. For each source nine intrinsic properties are measured homogeneously, as well as inclination and an optical spectrum. The sample, which should be almost entirely free of either misidentification or confusion, includes a wide diversity of galaxies ranging from inchoate, low surface brightness dwarfs to giant spirals. Despite this diversity there are five clear correlations among their properties. They include a common dynamical mass-to-light ratio within their optical radii, a correlation between surface brightness and luminosity and a common H  i surface density. Such correlation should provide strong constrains on models of galaxy formation and evolution.  相似文献   

Abundance analysis of Barium stars     

Guo-Qing Liu Yan-Chun Liang Li-Cai Deng 《中国天文和天体物理学报》2009,9(4)

We obtain the chemical abundances of six barium stars and two CH subgiant stars based on the high signal-to-noise ratio and high resolution Echelle spectra. The neu- tron capture process elements Y, Zr, Ba, La and Eu show obvious overabundances relative to the Sun, for example, their [Ba/Fe] values are from 0.45 to 1.27. Other elements, in- cluding Na, Mg, A1, Si, Ca, Sc, Ti, V, Cr, Mn and Ni, show comparable abundances to the Solar ones, and their [Fe/H] covers a range from -0.40 to 0.21, which means they belong to the Galactic disk. The predictions of the theoretical model of wind accretion for bi- nary systems can explain the observed abundance patterns of the neutron capture process elements in these stars, which means that their overabundant heavy-elements could be caused by accreting the ejecta of AGB stars, the progenitors of present-day white dwarf companions in binary systems.  相似文献