排序方式： 共有84条查询结果，搜索用时 15 毫秒
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Ph. Podsiadlowski 《Astronomische Nachrichten》2010,331(2):218-222
Supersoft X‐ray sources have been proposed as one of the major channels to produce Type Ia supernovae (SNe Ia). However, the true nature of the progenitors has remained an unsolved problem. In this review I summarize the present status of our understanding of SN Ia progenitors, the main classes of progenitor models and recent observational constraints. At present, neither the single‐degenerate nor the double‐degenerate model can be ruled out, and indeed more than one channel may be required to explain the observed SN Ia diversity. Finally, I discuss the origin of the lightcurve peak – lightcurve width relation (the ‘Phillips relation’) and show that it is expected to depend on metallicity; this needs to be taken into account in high‐precision cosmological applications (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
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I. V. Panov 《Astronomy Letters》2003,29(3):163-169
The concept of the r-process path is considered from the standpoint of a dynamic model. Rapid nucleosynthesis is shown to proceed not along certain preferential lines called the r-process paths but in the region of nuclei bounded on the one side by the existing nuclei and on the other side by nuclei upon reaching which the r-process enters a cooling phase. This view is shown to account for the main heavy-element abundance patterns. 相似文献
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The most recent fission-barrier calculations based on improved mass formulas indicate that the adopted values are underestimated. We analyze the dependence of the fission rates on the fission barrier and show that an increase in the fission barriers leads not so much to a decrease in the importance of fission as to the possible synthesis of heavier elements in the r-process. The rates of induced fission of most isotopes with Z>80 at astrophysical energies have been calculated for the first time for fission barriers obtained from different theoretical models. 相似文献
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F.-K. Thielemann D. Argast F. Brachwitz G. Martinez-Pinedo T. Rauscher M. Liebendörfer A. Mezzacappa P. Höflich K. Nomoto 《Astrophysics and Space Science》2002,281(1-2):25-37
Two of the basic building blocks of galaxies are stars and the interstellar medium. The evolution of the abundance composition
in the latter and especially the enrichment of heavy elements as a function of space and time reflects in turn the history
of star formation and the lifetimes of the diverse contributing stellar objects. Therefore, the understanding of stellar evolution
and its endpoints (mainly planetary nebulae, supernovae of type Ia and type II/Ib/Ic) is essential. Despite many efforts,
a full and self-consistent understanding of supernovae (the main contributors to nucleosynthesis in galaxies) is not existing,
yet. However, they leave fingerprints, seen either in spectra, lightcurves, radioactivities/decay gamma-rays or in galactic
evolution. Here we want to address the composition of ejecta, their model uncertainties and relate them to constraints from
abundance observations in galactic evolution.
This revised version was published online in September 2006 with corrections to the Cover Date. 相似文献
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We study the nucleosynthesis and the induced mixing during the merging of massive stars inside a common envelope. The systems
of interest are close binaries, initially consisting of a massive red supergiant and a main-sequence companion of a few solar
masses. We apply parameterized results based on hydrodynamical simulations to model the stream-core interaction and the response
of the star in a standard stellar-evolution code. Preliminary results are presented illustrating the possibility of unusual
nucleosynthesis and post-merging dredge-up which can cause composition anomalies in the supergiant's envelope.
This revised version was published online in September 2006 with corrections to the Cover Date. 相似文献
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C. Travaglio S. Randich D. Galli C. Abia J. Lattanzio 《Astrophysics and Space Science》2002,281(1-2):219-220
Different stellar sources may have contributed to the 7Li enrichmentof the Galaxy: type-II supernovae, novae, and AGB stars. In the latter case, the interplay between the Hot Bottom
Burning (HBB) process (via the Cameron-Fowler mechanism) and a very high mass-loss rate before the evolution off the AGB (the
so-called ‘superwind’ phase), can lead to a significant production of 7Li from low- and intermediate-mass AGB stars (Travaglio et al., 2001). We have now undertaken an observational campaign aimed
at constraining our stellar and Galactic models, with a twofold goal: (i) to assemble a compilation of high-resolution spectra of Galactic, unevolved (i.e. dwarfs), warm(spectral type F) stars,
in a selected metallicity range (-1.0 ≤>[Fe/H] ≤ -0.3), using the ESO 1.5m telescope and the FEROS spectrograph; (ii) to carry out a Li survey among a sample of selected AGB stars, to investigate the possible correlation between7Li abundance (when detected) and mass-loss rate.
This revised version was published online in September 2006 with corrections to the Cover Date. 相似文献
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Ken’ichi Nomoto Keiichi Maeda Nozomu Tominaga Takuya Ohkubo Jinsong Deng Paolo A. Mazzali 《Astrophysics and Space Science》2005,298(1-2):81-86
The nature of very energetic supernovae (hypernovae) is discussed. They are the explosive death of stars more massive than
~20–25M
⊙, probably linked to the enigmatic Gamma-Ray Bursts. The optical properties of hypernovae indicate that they are significantly
aspherical. Synthetic light curves and late-phase spectra of aspherical supernova/hypernova models are presented. These models
can account for the optical observations of SNe 1998bw and 2002ap. The abundance patterns of hypernovae are characterized
by large ratios (Zn, Co)/Fe and small ratios (Mn, Cr)/Fe, indicating a significant contribution of hypernovae to the early
Galactic chemical evolution. 相似文献