Annu. Rev. Astron. Astrophys. 1997. 35: 309-355
Copyright © 1997 by . All rights reserved

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OPTICAL SPECTRA OF SUPERNOVAE

Alexei V. Filippenko


Department of Astronomy, University of California, Berkeley, California 94720-3411; e-mail: alex@astro.berkeley.edu


Key Words: spectroscopy, stellar evolution, supernovae


Abstract The temporal evolution of the optical spectra of various types of supernovae (SNe) is illustrated, in part to aid observers classifying supernova candidates. Type II SNe are defined by the presence of hydrogen, and they exhibit a very wide variety of photometric and spectroscopic properties. Among hydrogen-deficient SNe (Type I), three subclasses are now known: those whose early-time spectra show strong Si II (Ia), prominent He I (Ib), or neither Si II nor He I (Ic). The late-time spectra of SNe Ia consist of a multitude of blended emission lines of iron-group elements; in sharp contrast, those of SNe Ib and SNe Ic (which are similar to each other) are dominated by several relatively unblended lines of intermediate-mass elements. Although SNe Ia, which result from the thermonuclear runaway of white dwarfs, constitute a rather homogeneous subclass, important variations in their photometric and spectroscopic properties are undeniably present. SNe Ib/Ic probably result from core collapse in massive stars largely stripped of their hydrogen (Ib) and helium (Ic) envelopes, and hence they are physically related to SNe II. Indeed, the progenitors of some SNe II seem to have only a low-mass skin of hydrogen; their spectra gradually evolve to resemble those of SNe Ib. In addition to the two well-known photometric subclasses (linear and plateau) of SNe II, which may exhibit minor spectroscopic differences, there is a new subclass (SNe IIn) distinguished by relatively narrow emission lines with little or no P Cygni absorption component and slowly declining light curves. These objects probably have unusually dense circumstellar gas with which the ejecta interact.


Table of Contents

INTRODUCTION

GENERAL OVERVIEW OF SUPERNOVAE
Spectra
Light Curves
Environments and Progenitors

TYPE Ia SUPERNOVAE
Spectral Evolution
Homogeneity
Heterogeneity
Cosmological Uses of SNe Ia
Hydrogen in Spectra of SNe Ia

TYPE Ib AND Ic SUPERNOVAE
Historical Development
SNe Ib: Spectral Evolution
Type Ic Spectral Evolution
Is There Helium in SNe Ic?

TYPE II SUPERNOVAE
Type II-P Supernovae
Supernova 1987A
Type II-L Supernovae
Type IIn Supernovae
Links Between SNe II and SNe Ib/Ic

FINAL REMARKS

REFERENCES

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