共查询到20条相似文献，搜索用时 31 毫秒
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We have discussed the evolution of two pulsar types suggested by Huanget al. (1985). Starting from the formulae given by them, we find that these two types of pulsars follow different evolutionary tracks, different structures, different average ages; and they are going to different graveyards. From these differences we may infer that the two pulsar types may have different progenitors. 相似文献
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Among the terrestrial planets, Mercury's composition is characterized by two specific features: a high density and a low surface FeO content. Based on these two constraints, different geochemical models have been proposed, according to different formation scenarios. Here thermodynamical modeling is used to derive the mantle and crust mineralogy associated with these geochemical models. For each mineralogy, the electrical conductivity profile and associated electromagnetic data are computed. Due to the very different oxide/silicate ratios, most geochemical models proposed for Mercury's formation show very different electromagnetic signatures. As a result, future measurements with MESSENGER and BepiColombo missions will help differentiating between different interior models and different formation scenarios. 相似文献
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We review the methodology adopted in computing chemical evolution models of galaxies of different morphological type (ellipticals,
spirals and irregulars). We discuss the importance of the history of star formation in different galaxies in order to interpret
the observed abundances. In particular, we discuss the time-delay model which allows us to interpret the observed abundance
patterns in galaxies as due to the different contributions of supernovae II and Ia. We show that the time-delay model applied
to galaxies of different morphological type predicts different [X/Fe] versus [Fe/H] relations in different galaxies. As a
consequence of this, these relations can be used to infer the nature and to date high redshift objects. Finally, we show our
predictions for the cosmic star formation rate. 相似文献
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不同类型的射电望远镜阵的分辨率差异甚大，用它们的数据进行图像处理后所得到的源结构的尺度也不一样。为了得到中间尺度的结构信息，有时我们需要把不同类型的射电望远镜阵的观测数据结合起来再进行图像处理。本文阐述我们把不同类型阵的数据结合时所用的方法；也给出我们使用的方法所获得的结果的实际例子。 相似文献
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Rudolf A. Treumann 《Astrophysics and Space Science》1992,198(1):71-77
We examine the hypothesis of the connection between quasars and galaxies from the point of view of the theory of nonlinear dynamics of highly complex systems. It is found that complexity and nonlinearity of systems which are informationally disconnected may lead to different intrinsic time-scales of the systems. Systems with different intrinsic time-scales age at different rates. This kind of aging can be measured by observing their different redshifts. On interpreting strongly differing redshifts of astrophysically closely related objects as informational redshifts, we are in the position to determine their maturity ratios which are measures of the different nonlinear stages of the objects on the cosmological time-scale. 相似文献
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We study the large scale structure of galaxy distribution from the fractal point of view using the CfA survey data. Main results are as follows: 1. Within certain ranges, the galaxy distribution is fractal with fractal dimension about 2.0. This result is different fron the value 1.2 – 1.4, expected from the galaxy two-point correlation function. 2. Galaxies of different luminosities show somewhat different fractal dimensions. This result indicates that they may correspond to different perturbation ranges in the early universe, in apparent agreement with thepredictions of biased galaxy formation theory. 3. Scales smaller and greater than 10 Mpc seem to have different fractal dimensions. A preliminary analysis of these results is included. 相似文献
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Recent work on the PN classification scheme initially proposed by Peimbert has shown that type I and non-type I objects have
markedly different properties. Type I PN have He and N enrichments, lower heights relative to the galactic plane, and lower
peculiar velocities, while non-type I nebulae have normal abundances and increasing heights and peculiar velocities. This
implies some mass and age differences of the different types, which can be used in order to determine distances to disk PN.
In this work, the behaviour of PN of different types on the log g× log Teff plane is explored, in view of the fact that central stars of different masses have different paths on this diagram. As a
result, distances can be derived for some galactic PN, which can be compared with previous determinations. The possibility
is discussed of establishing a statistical distance scale based on the population segregation of PN of different Peimbert
types.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
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《天文和天体物理学研究(英文版)》2016,(12)
In large Solar Energetic Particle(SEP) events, ions can be accelerated at coronal mass ejection(CME)-driven shocks to very high energies. The spectra of heavy ions in many large SEP events show features such as roll-overs or spectral breaks. In some events when the spectra are plotted in terms of energy/nucleon, they can be shifted relative to each other to make the spectral breaks align. The amount of shift is charge to mass ratio(Q/A) dependent and varies from event to event. This can be understood if the spectra of heavy ions are organized by the diffusion coefficients(Cohen et al. 2005). In the work of Li et al.(2009), the Q/A dependence of the scaling is related to shock geometry when the CME-driven shock is close to the Sun. For events where multiple in-situ spacecraft observations exist, one may expect that different spacecraft are connected to different portions of the CME-driven shock that have different shock geometries, therefore yielding different Q/A dependence. In this work, we examine one SEP event which occurred on 2013 November 4. We study the Q/A dependence of the energy scaling for heavy ion spectra using helium, oxygen and iron ions. Observations from STEREO-A, STEREO-B and ACE are examined. We find that the scalings are different for different spacecraft. We suggest that this is because ACE, STEREOA and STEREO-B are connected to different parts of the shock that have different shock geometries. Our analysis indicates that studying the Q/A scaling of in-situ particle spectra can serve as a powerful tool to remotely examine the shock geometry for large SEP events. 相似文献
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It is confirmed that the penumbral bright grains are moving towards the sunspots umbra. We find different proper motions of 0.08 to 0.33 km s–1 for different penumbrae and different reduction methods. The lifetimes of these bright grains are about 1.5 to 3 hr depending on the position in the penumbra. 相似文献
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在提出的贫金属星中子俘获元素丰度的计算模型基础上研究1999年新发表的21颗贫金属星的中子俘获元素丰度分布。结果表明，对较重的中子俘获元素理论预测曲线与观测值符合得很好，而对较轻的中子俘获元素二者有所偏离。这表明在贫金属环境下，对较重的中子俘获元素各核合成过程产生的丰度分布与太阳系中相应过程的丰度分布相似，但贡献比例与太阳系不同；而对较轻的中子俘获元素丰度分布与太阳系的丰度分布有所偏离；这也说明较轻的和较重的中子俘获元素的核合成场所不同，即具有不同的核合成机制。同时还特别讨论了丰度观测误差对表征各核合成过程的分量系数的影响。 相似文献
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R. Gil-Hutton 《Planetary and Space Science》2002,50(1):57-62
A re-evaluation of the collisional resurfacing model based on up-to-date Kuiper belt objects size distribution and a more precise treatment of the cosmic-ray environment at the outer Solar System is presented. The result of the irradiation due to cosmic-rays with different energies altered in a different way the material of the objects, producing, under certain conditions, a thick irradiation mantle. Since the collisional resurfacing model is based in the competition between darkening by cosmic-rays and resurfacing due to impacts, the color of objects in different regions of the belt could vary if the projectile populations in those regions are truncated at a different radius. 相似文献
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由单脉冲星定义的脉冲星时受几种噪声源的影响,为削弱这些影响得到一种更稳定的时间尺度,采取将多颗脉冲星定义的单脉冲星时进行综合的分析方法得到综合脉冲星时．用两种方法:经典加权算法和小波分解算法,对PSRB1855 09和PSR B1937 21两颗脉冲星进行综合计算并做出比较,经典加权算法无法兼顾脉冲星不同频率上的稳定度,而用小波分析的方法对PSR B1855 09和PSR B1937 21两颗脉冲星进行综合,能够有效抑制不同频率上噪声的影响,达到更好的效果． 相似文献
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Coronal mass ejections (CMEs) are considered to be associated with large-scale, closed magnetic field structures in the corona. These structures change throughout the solar activity cycle following the evolution of the general solar magnetic field. To study the variation of CME characteristics with the evolution of coronal magnetic structures, we compute the 3-D coronal magnetic field at minimum and maximum of activity with a source-surface potential field model. In particular, we study the central latitude distribution of CMEs and the frequency of occurrence of the different CME types in these two periods. We find that most CMEs are indeed associated with large-scale, magnetically closed structures, and their latitudinal distribution follows the solar cycle latitudinal changes of the location of these structures. We also find that different CME types, which constitute different fractions of the total during the maximum and the minimum, are associated with different shapes and orientations of the closed structures at different times of the solar cycle. 相似文献
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By analyzing a canopy tube described by Athay, we point out the possibility that the different canopy heights given by different authors are caused by different definitions of canopy heights. For the same canopy tube, those heights where the magnetic field has horizontal components, where neighboring magnetic tubes meet each other and where the magnetic field becomes uniform or vertical range from near the solar photosphere to the solar corona. 相似文献
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A. W. Hotan M. Bailes S. M. Ord 《Monthly notices of the Royal Astronomical Society》2005,362(4):1267-1272
In the present paper, we investigate the distribution of the hardness ratio (HR) for short and long gamma-ray bursts (GRBs) in different time-scales for the first two seconds. After including and subtracting the background count, we performed a Kolmogorov–Smirnov (K–S) test on the HR distributions of the two classes of GRBs in each time interval. Our analysis shows that the probabilities of the K–S test to the distributions are very small, suggesting that the two classes of bursts are unlikely to arise from the same HR distributions. The result indicates that the two kinds of bursts probably originate from different mechanisms or have different central engines. In addition, we found that the HR of short bursts within the time interval 0–0.96 s changes from hard to soft; the HR of long bursts does not. The two kinds of bursts have different characteristics in the first two seconds, which might be associated with different physical mechanisms. 相似文献
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Cherki G. Mercier J. P. Raviart A. Treguer L. Maccagni D. Perotti F. Villa G. 《Solar physics》1974,34(1):223-229
Data on high energy electrons and protons in different energy windows are analyzed and compared for two solar flares which occurred at 37 W solar longitude on the 25th February 1969 and the 29th March 1970. While the data for the first of these flares can be interpreted in the framework of a diffusion model with suitable values of the parallel diffusion coefficient, in order to explain the time behaviour of the different particles after the second event, we are led to suppose that the coronal magnetic fields are such that particles of different rigidity are ejected at different longitudes and that there is no good magnetic connection of the Earth with the flare region. 相似文献