Supernovae
Mostrando 13-24 de 25 artigos, teses e dissertações.
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13. Statefinder revisited
The quality of supernova data will dramatically increase in the next few years by new experiments that will add high-redshift supernova to the currently known ones. In order to use this new data to discriminate between different dark energy models, the statefinder diagnostic was suggested [1] and investigated by Alam et al.[3] in the light of the proposed Su
Brazilian Journal of Physics. Publicado em: 2005-12
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14. Gravitational waves: a 100-year tool applied to the dark energy problem
Recent observations from type Ia Supernovae and from cosmic microwave background (CMB) anisotropies have revealed that most of the matter of the Universe interacts in a repulsive manner, composing the so-called dark energy constituent of the Universe. Determining the properties of dark energy is one of the most important tasks of modern cosmology and this is
Brazilian Journal of Physics. Publicado em: 2005-12
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15. Studies in nuclear astrophysics using radioactive beams at the HRIBF
The availability of radioactive beams has produced great opportunities for advances in our understanding of the nucleosynthesis occurring in stellar explosions such as novae, X-ray bursts, and supernovae. At the HRIBF, we have used proton-rich beams such as 17;18F and neutron-rich beams such as 82Ge to study astrophysicallyimportant reaction rates. Large-are
Brazilian Journal of Physics. Publicado em: 2004-09
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16. Cosmological implications of old galaxies at high redshifts
Old high-z galaxies are important tools for understanding the structure formation problem and may become the key to determine the ultimate fate of the Universe. In this paper, the inferred ages of the three oldest galaxies at high redshifts reported in the literature are used to constrain the first epoch of galaxy formation and to reanalyse the high-z time s
Brazilian Journal of Physics. Publicado em: 2001-12
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17. Dark energy and the accelerated expansion of the Universe
Recent observations indicate that the expansion of the Universe is accelerating. This suggests the existence of some kind of exotic matter with negative pressure. The simplest possibility is a cosmological constant but there are alternatives, as for instance an evolving scalar field. In this paper we explore constraints from lensing statistics and high-z typ
Brazilian Journal of Physics. Publicado em: 2000-06
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18. An introduction to quintessence
There is a missing energy problem in cosmology: the total energy density of the Universe, based on a wide range of observations, is much greater than the energy density contributed by all baryons, neutrinos, photons, and dark matter. Deepening this mystery are the recent observations of type 1a supernovae which suggest that the expansion rate of the Universe
Brazilian Journal of Physics. Publicado em: 2000-06
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19. Loss Due to Missing Data in Efficiency of a Locally Optimal Test for Homogeneity with Respect to Very Rare Events*
With reference to observations of supernovae in galaxies, a locally optimal test for the hypothesis of homogeneity of the observational units with respect to occurrence of supernovae (treated as a very rare event) is obtained for the case where the data are available only for those galaxies where at least one supernova is observed. It is shown that the loss
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20. Is the velocity-distance relation for galaxies linear?
Diameters of ScI galaxies, the luminosities of supernovae of type Ia at maximum light, and the brightness of central galaxies in rich clusters are examined as potential yardsticks or standard candles for study of the velocity-distance relationship. Both supergiant ScI galaxies and supernovae Ia (which have luminosities that differ by up to a factor of approx
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21. Supernovae, an accelerating universe and the cosmological constant
Observations of supernova explosions halfway back to the Big Bang give plausible evidence that the expansion of the universe has been accelerating since that epoch, approximately 8 billion years ago and suggest that energy associated with the vacuum itself may be responsible for the acceleration.
The National Academy of Sciences.
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22. Afterglows from the largest explosions in the universe
The distinction of “largest explosions in the universe” has been bestowed on cosmic gamma-ray bursts. Their afterglows are brighter than supernovae and therefore are called hypernovae. Photometry and spectroscopy of these afterglows have provided major breakthroughs in our understanding of this mysterious phenomenon.
The National Academy of Sciences.
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23. The universe at z > 5: When and how did the “dark age” end?
This paper considers how the first subgalactic structures produced the UV radiation that ionized the intergalactic medium before z = 5 and the “feedback” effects of the UV radiation on structure formation. The first “pregalaxies” may eventually be detectable by their direct UV emission, with characteristic spectral features at Lyman α; high-z
National Academy of Sciences.
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24. On the possibility of dust condensation in the ejecta of supernova 1987a
We suggest that supernova 1987a may condense dust of substantial visual optical thickness as do many novae. The dust will act as a calorimeter of the photon luminosity of any central engine that is dominant at the time of dust formation. Observations of novae suggest that dust formation may occur when the expanding ejecta reach a temperature of 1000 K. The e