摘要:

If a “young” supernova remnant is less than 1000 years old, then all of them have aged at least 10&percent; during the era of photographic astronomy. Nevertheless, historical investigations are, so far, probably telling us more about how astronomers behave than about how SNRs behave. The talk reviewed an assortment of firsts, lasts, and might-have-beens from roughly 5283 BCE to 2000 CE. ©2001 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.1377068

出版商:AIP    

年代:1901

数据来源: AIP

摘要:

The dynamical evolution of young supernova remnants (YSNRs) is governed by the density distribution in the ejecta and in the ambient medium. Analytic solutions are available for spherically symmetric expansion, including the transition from the ejecta-dominated stage to the Sedov-Taylor stage. YSNRs serve as valuable physics laboratories, in which we can study nucleosynthesis, the early evolution of compact objects, pulsar physics, particle acceleration, the formation and destruction of dust, hydrodynamics at high Reynolds numbers, shock physics at high Mach numbers, and the effects of thermal conduction in interstellar plasmas. There are several challenges in YSNR research: (1) Where are the very young remnants in the Galaxy? We expect 5–10 to have occurred since Cas A, but with the possible exception of a remnant reported at this conference, none have been seen. (2) Can very young SNRs produce gamma-ray bursts? The acceleration of a shock in the outer layers of a supernova, first suggested by Colgate, can account for gamma-ray bursts such as that believed to be associated with SN 1998bw, and more powerful explosions can account for the energies seen in many cosmological bursts. (3) The Connections Challenge: Can one infer the nature of the supernova and its progenitor star from observations of the YSNR? ©2001 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.1377069

出版商:AIP    

年代:1901

数据来源: AIP

摘要:

In this short review I suggest that recent developments support the conjecture that Type Ia supernovae (SNe Ia) are the complete disruptions of Chandrasekhar–mass carbon-oxygen white dwarfs in single–degenerate binary systems. The causes of the observational diversity of SNe Ia within the context of this standard model, and the implications of the model for young remnants of SNe Ia, are briefly discussed. ©2001 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.1377070

出版商:AIP    

年代:1901

数据来源: AIP

摘要:

I present an overview of optical observations (mostly spectra) of Type II, Ib, and Ic supernovae (SNe). SNe II are defined by the presence of hydrogen, and exhibit a very wide variety of properties. SNe II-L tend to show evidence of late-time interaction with circumstellar material. SNe IIn are distinguished by relatively narrow emission lines with little or no P-Cygni absorption component and (quite often) slowly declining light curves; they probably have unusually dense circumstellar gas with which the ejecta interact. Some SNe IIn, however, might not be genuine SNe, but rather are “impostors”—specifically, super-outbursts of luminous blue variables. SNe Ib do not exhibit the deep 6150 Å absorption characteristic of “classical” SNe Ia; instead, their early-time spectra have He I absorption lines. SNe Ic appear similar to SNe Ib, but lack the helium lines as well. Spectra of SNe IIb initially exhibit hydrogen, yet gradually evolve to resemble those of SNe Ib; their progenitors seem to contain only a low-mass skin of hydrogen. Spectropolarimetry thus far indicates large asymmetries in the ejecta of SNe IIn, but much smaller ones in SNe II-P. As one peers deeper into the ejecta of core-collapse SNe, the asymmetry (indicated by the amount of polarization) seems to increase. There is intriguing, but inconclusive, evidence that some peculiar SNe IIn might be associated with gamma-ray bursts. The rates of different kinds of SNe as a function of Hubble type are still relatively poorly known, although there are good prospects for future improvement. ©2001 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.1377071

出版商:AIP    

年代:1901

数据来源: AIP

摘要:

The structure and evolution of young supernova remnants are determined, to a large extent, by using the equations of ideal, compressible gas dynamics to evolve a hypersonically expanding ejecta propagating into an ambient gas. Even within this limited domain of ideal gas dynamics, this simple problem can become extremely complex. Here we review some of the hydrodynamic solutions describing young supernova remnants, from one-dimensional self-similar models to three-dimensional simulations incorporating nonuniform ejecta. An online version of the conference presentation is available at http://wonka.physics.ncsu.edu/∼blondin/october2000 ©2001 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.1377072

出版商:AIP    

年代:1901

数据来源: AIP

摘要:

We suggest that a parabolic emission feature observed in the optical spectra of several recent supernovae indicates the conical ejection of matter. ©2001 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.1377073

出版商:AIP    

年代:1901

数据来源: AIP

摘要:

We have started a study of the radio emission from supernovae (SNe) exploding in binary systems. Here, we present our results for the case of a Type II SN in a wide binary system, which is viewed pole–on, and in which the companion star is a massive Main Sequence star.At early timesthe light curves rise more slowly than in the single-star case and are sensitive functions of the separation of the two stars.At late timesthe light curves are strongly affected by the regions of highly compressed material and the fluxes are higher than in the single-star case. For a given mass loss rate of the SN progenitor star the radio emission of a binary system SNII mimicks the emission that would be produced by a single-star SNII with a higher mass loss rate. ©2001 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.1377074

出版商:AIP    

年代:1901

数据来源: AIP

摘要:

Using the Very Large Array (VLA), we have detected radio emission from the site of SN 1961V in the Sc galaxy NGC 1058. With a peak flux density of0.084±0.011&hthinsp;mJy/beamat 6 cm and0.145±0.028&hthinsp;mJy/beamat 18 cm, the source is nonthermal, with a spectral index of−0.51±0.21.Within errors, this index is the same value reported for previous VLA observations taken in 1984 and 1986. The radio emission at both wavelengths has decayed since the mid 1980’s observations with an averaged power-law index of&bgr;20cm&6cm=−0.98±0.13.We discuss the radio properties of this source and compare them with those of Type II radio supernovae and luminous blue variables. ©2001 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.1377075

出版商:AIP    

年代:1901

数据来源: AIP

摘要:

The interaction of a young supernova remnant and its surroundings can be described by a self-similar solution if the expanding supernova ejecta can be described by a power law density profile of&rgr;∝r−nwithn>5,and the surrounding ambient medium has a density power law of&rgr;∝r−swiths<3[1]. It has been shown in two dimensions that initializing a hydrodynamics code with the self-similar solution for the interaction region and perturbing the density randomly causes Rayleigh-Taylor instabilities [2]. We present hydrodynamic simulations of self-similar driven waves, with different parameters, for the purpose of comparing the growth and saturation of the convective instability in three dimensions compared to two dimensions. The contact discontinuity in all simulations produced Rayleigh-Taylor fingers with predictable morphologies; long, continually growing spikes fors=2,and shorter, mushroom capped blobs fors=0.A fourier spectrum was obtained and compared in both two and three dimensions to analyze the evolution of the instability’s growth. Turbulent energy density was measured and compared for different initial conditions. These simulations and diagnostics show how closely two-dimension codes can approximate three-dimensions and also provide information on expansion and mixing of young supernova remnants. ©2001 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.1377076

出版商:AIP    

年代:1901

数据来源: AIP

摘要:

We simulate experiments performed with the Falcon laser at Lawrence Livermore National Laboratory to generate strong blast waves expanding in cylindrical geometry of relevance to astrophysics. In particular, we are interested in producing and modeling radiative shocks. Our goal is to develop a laboratory setting for studying radiative shocks of relevance to supernova remnants (SNR). Although late-term supernovae are known for exhibiting radiative shocks, it is also likely that some young SNR are also radiative when they expand into a dense interstellar medium (ISM). In previous work we have demonstrated that it is possible to generate radiative shocks in the laboratory. In addition, we have shown how we can determine the energy-loss rate of the shock from the blast wave evolution using a simple analytic method that is independent of the details of radiative cooling, and is scalable to both the laboratory and astrophysical blast waves. Our future work deals with instabilities associated with radiative blast waves and their application to the laboratory and astrophysics. This paper examines some of the previous work done in the area of radiative instabilities and discusses the challenges in adapting this work to the laboratory setting. ©2001 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.1377077

出版商:AIP    

年代:1901

数据来源: AIP