排序方式： 共有84条查询结果，搜索用时 15 毫秒
11.
Ge-Ying Xie Bo ZhangHong-Jie Li Jin-Jiang HuChen-Pu Li 《Chinese Astronomy and Astrophysics》2011,35(1):29
Based on a large amount of observed data of element abundances in metal-poor stars, taking the abundance distribution of heavy elements in the solar system as a standard, and selecting Sr, Ba and Eu as the typical elements of the three nucleosynthetic processes in metal-poor stars, namely the weak sprocess, main s-process and r-process, we have studied the contributions of the three kinds of neutron-capture processes to the abundance distribution of heavy elements in metal-poor stars, with the parameterization method. It is found that the higher the metal abundance, the greater the contributions of the weak s-process and the chief s-process to the abundances of lighter neutron-capture elements. The heavier neutron-capture elements are mainly produced by the r-process and the chief s-process; and that at low metallicity, the abundances of heavy neutron-capture elements are mainly produced by the r-process. In the early Galaxy, the weak s-process has almost no contribution to the element abundance. 相似文献
12.
S.L. Martell 《Astronomische Nachrichten》2011,332(5):467-474
Star‐to‐star variations in abundances of the light elements carbon, nitrogen, oxygen, and sodium have been observed in stars of all evolutionary phases in all Galactic globular clusters that have been thoroughly studied. The data available for studying this phenomenon, and the hypotheses as to its origin, have both co‐evolved with observing technology; once high‐resolution spectra were available even for main‐sequence stars in globular clusters, scenarios involving multiple closely spaced stellar generations enriched by feedback from moderate‐ and high‐mass stars began to gain traction in the literature. This paper briefly reviews the observational history of globular cluster abundance inhomogeneities, discusses the presently favored models of their origin, and considers several aspects of this problem that require further study (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
13.
Jordi Gómez-Gomar Margarita Hernanz Jordi José & Jordi Isern 《Monthly notices of the Royal Astronomical Society》1998,296(4):913-920
Classical novae are important producers of radioactive nuclei, such as 7 Be, 13 N, 18 F, 22 Na and 26 Al. The disintegration of these nuclei produces positrons (except for 7 Be) that through annihilation with electrons produce photons of energies 511 keV and below. Furthermore, 7 Be and 22 Na decay producing photons with energies of 478 and 1275 keV, respectively, well in the γ-ray domain. Therefore, novae are potential sources of γ-ray emission. We have developed two codes in order to analyse carefully the γ-ray emission of individual classical novae: a hydrodynamical one, which follows both the accretion and the explosion stages, and a Monte Carlo one, able to treat both production and transfer of γ-ray photons. Both codes have been coupled in order to simulate realistic explosions. The properties of γ-ray spectra and γ-ray light curves (for the continuum and for the lines at 511, 478 and 1275 keV) have been analysed, with a special emphasis on the difference between carbon–oxygen and oxygen–neon novae. Predictions of detectability of individual novae by the future SPI spectrometer on board the INTEGRAL satellite are made. Concerning 26 Al, its decay produces photons of 1809 keV but this occurs on a time-scale much longer than the typical time interval between nova outbursts in the Galaxy, making it undetectable in individual novae. The accumulated emission of 26 Al from many Galactic novae has not been modelled in this paper. 相似文献
14.
Wolfgang Hillebrandt 《Astrophysics and Space Science》2002,281(1-2):173-182
Recent developments in theoretical model-calculations for the synthesis of the chemical elements during late stages of stellar
evolution are reviewed. Special emphasis is put on a discussion of various astrophysical sites, including core-collapse and
thermonuclear supernovae, and the physics of turbulent reactive fluids. Results of numerical simulations are presented and
discussed, together with new results concerning solar-system abundances as well as abundances observed in very metal-poor
stars, in the context of searches for constraints on the still rather uncertain nuclear physics data and astrophysical models.
This revised version was published online in September 2006 with corrections to the Cover Date. 相似文献
15.
V. N. Kondratyev I. M. Kadenko 《Monthly notices of the Royal Astronomical Society》2005,359(3):927-929
The atomic mass distribution of nuclides in an ultramagnetized astrophysical plasma is considered by employing a model of nuclear statistical equilibrium. The magnetization of atomic nuclei is shown to enhance the portion of light nuclear species in the iron region. 相似文献
16.
综述了近扯为ＡＧＢ星核合成的理论研究情况，包括轻，重核素核合成理论，ＡＧＢ星的分类，ＡＧＢ星的演化特征，ＡＧＢ星内的元素核合成理论的研究及外赋ＭＳ，Ｓ 双星吸积机制的研究情况。 相似文献
17.
18.
Keiichi Maeda Nozomu Tominaga 《Monthly notices of the Royal Astronomical Society》2009,394(3):1317-1324
Theoretically expected natures of a supernova (SN) driven by a wind/jet are discussed. Approximate analytical formulations are derived to clarify basic physical processes involved in the wind/jet-driven explosions, and it is shown that the explosion properties are characterized by the energy injection rate and the mass injection rate . To explain observations of Supernova 1998bw associated with gamma-ray burst (GRB) 980425, the following conditions are required: and (if the wind Lorentz factor Γw ∼ 1 ) or (if Γw ≫ 1 ). In Supernova 1998bw, 56 Ni (∼0.4 M⊙ ) is probably produced in the shocked stellar mantle, not in the wind. The expected natures of SNe, e.g. ejected 56 Ni mass and ejecta mass, vary depending on and . The sequence of the SN properties from high and to low and is as follows: Supernova 1998bw-like – intermediate case – low mass ejecta (≲1 M⊙ ) where 56 Ni is from the wind – whole collapse. This diversity may explain the diversity of SNe associated with GRBs. Our result can be used to constrain natures of the wind/jet, which are linked to the central engine of GRBs, by studying properties of the associated SNe. 相似文献
19.
20.
The velocity profiles and properties of proto-magnetar winds are investigated.It is found that the corotation of wind matter with magnetic field lines significantly affects r-process nucleosynthesis and could lead to long duration γ-ray bursts and hyper-energetic supernovae. 相似文献