On the spectrum and nature of the peculiar Type Ia supernova 1991T
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A parameterized supernova synthetic-spectrum code is used to study line identifications in the photospheric-phase spectra of the peculiar Type Ia SN 1991T, and to extract some constraints on the composition structure of the ejected matter. The inferred composition structure is not like that of any hydrodynamical model for Type Ia supernovae. Evidence that SN 1991T was overluminous for an SN Ia is presented, and it is suggested that this peculiar event probably was a substantially super-Chandrasekhar explosion that resulted from the merger of two white dwarfs.An extremely luminous Type Ic SN 2007bi is considered to produce 56Ni of 3 – 10M⊙ and two possibilities of the explosion mechanism are proposed: pair-instability supernova and corecollapse supernova. We investigate the evolution of very massive stars with MMS = 100 – 500M⊙ and Z = 0.004 to discuss the explosion mechanism of SN 2007bi. From the evolution of the very massive stars, the stellar masses at the main-sequence appropriate for pair-instability and corecollapse explosions of SN 2007bi are 515 – 575M⊙ and 110 – 280M⊙, respectively. Core-collapse supernova would be more adequate for the explosion of SN 2007bi.
Type II supernova
Pair-instability supernova
Near-Earth supernova
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Radioactive decay
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We consider here the nebular phase spectra of supernovae whose late time luminosity is provided by the radioactive decay of 56 Ni and 56 Co synthesized in the explosion. A broad variety of supernovae are known or suspected to fall in this category. This includes all SNIa and SNIb, and at least some SNII, in particular SN1987a. At sufflciendy late times the expanding supernova becomes basically nebular in character due to its decreasing optical depth. The spectra produced during this stage contain information on the density and abundance structure of the entire supernova, as opposed to spectra near maximum light which are affected only by the outermost layers. A numerical model for nebular spectrum formation is therefore potentially very valuable for answering currently outstanding questions about the post-explosion supernova structure. As an example, we can hope to determine the degree of mixing which occurs between the layers of the “onion-skin” abundance structure predicted by current one dimensional explosion calculations.
Radioactive decay
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This report discusses supernova light simulations. A brief review of supernovae, basics of supernova light curves, simulation tools used at LANL, and supernova results are included. Further, it happens that many of the same methods used to generate simulated supernova light curves can also be used to model the emission from fireballs generated by explosions in the earth's atmosphere.
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Supernova 1993J in the spiral galaxy M81 is the brightest supernova since SN 1987A and, like the latter, appears to be another peculiar type II supernova. Its early light curve is characterized by a very sharp initial peak (lasting for less than ten days) followed by a less rapid secondary brightening, which was qualitatively similar to the secondary brightening observed in SN 1987A.
Pair-instability supernova
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Summary X-ray spectra of young supernovae (SNe) can provide information on the progenitor star and the interaction of the supernova ejecta and the circumstellar material. I will discuss some examples, with particular emphasis on SN 1998S, whose X-ray spectrum revealed for the first time in a young supernova a wealth of heavy element emission features (Ne, Al, Si, S, Ar, and Fe). By comparison with detailed calculations of supernova explosion elemental yields, these data can be used to constrain the progenitor mass. With increasingly sophisticated models and additional high quality data, application of this technique could result in many more reliable progenitor mass determinations. In addition, high resolution X-ray spectra allow us to measure the temperature evolution of a supernova and can give us a detailed picture of the progenitor’s pre-supernova evolution. As we build up additional examples from the great diversity of core collapse supernovae, we hope to come to a better understanding of the last stages of massive star evolution.
Near-Earth supernova
Type II supernova
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The author presents new measurements of the type Ia SN rate from the SDSS-II Supernova Survey. The SDSS-II Supernova Survey was carried out during the Fall months (Sept.-Nov.) of 2005-2007 and discovered ~ 500 spectroscopically confirmed SNe Ia with densely sampled (once every ~ 4 days), multi-color light curves. Additionally, the SDSS-II Supernova Survey has discovered several hundred SNe Ia candidates with well-measured light curves, but without spectroscopic confirmation of type. This total, achieved in 9 months of observing, represents ~ 15-20% of the total SNe Ia discovered worldwide since 1885. The author describes some technical details of the SN Survey observations and SN search algorithms that contributed to the extremely high-yield of discovered SNe and that are important as context for the SDSS-II Supernova Survey SN Ia rate measurements.
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One promising method to test progenitor models for Type Ia supernovae is to identify surviving companion stars in historical supernova remnants. A surviving companion will have been strongly affected by its interaction with the supernova ejecta. Here we systematically explore the evolution and appearance of a typical companion star that has been stripped and heated by the supernova interaction during the post-impact re-equilibration phase. We show that, depending on the amount of heating and the amount of mass stripped by the impact or the previous binary mass transfer, such a star may be significantly overluminous or underluminous 10^3 - 10^4 yr after the supernova relative to its pre-supernova luminosity (by up to two orders of magnitude) and discuss the implications of these results for the strategies to be employed in searches for such companions.
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This article first introduces the supernova survey and the classification of supernovae, then discusses the SN 1006 after one millennium.Subsequently,the physics of the core collapse supernovae(C-C SNe) and some well-observed events(such s SN 1987A 20 years,SN 2006gy,and SN 2008D) as well as the connection of some C-C SNe with Gamma-ray Burst are described.The type Ia supernovae(SNe Ia) and cosmology are addressed,while the applications of SNe Ia in cosmology and determining the Hubble constant are highlighted.Finally,the challenges and the major issues in current supernova researches are prospected.
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