Annu. Rev. Astron. Astrophys. 1998. 36: 17-55 Copyright © 1998 by Annual Reviews. All rights reserved

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Abstract. The focus of this review is the work that has been done during the 1990s on using Type Ia supernovae (SNe Ia) to measure the Hubble constant (H₀). SNe Ia are well suited for measuring H₀. A straightforward maximum-light color criterion can weed out the minority of observed events that are either intrinsically subluminous or substantially extinguished by dust, leaving a majority subsample that has observational absolute-magnitude dispersions of less than _obs (M_B) _obs (M_V) 0.3 mag. Correlations between absolute magnitude and one or more distance-independent SN Ia or parent-galaxy observables can be used to further standardize the absolute magnitudes to better than 0.2 mag. The absolute magnitudes can be calibrated in two independent ways: empirically, using Cepheid-based distances to parent galaxies of SNe Ia, and physically, by light curve and spectrum fitting. At present the empirical and physical calibrations are in agreement at M_B M_V -19.4 or -19.5. Various ways that have been used to match Cepheid-calibrated SNe Ia or physical models to SNe Ia that have been observed out in the Hubble flow have given values of H₀ distributed throughout the range of 54-67 km s^-1 Mpc^-1. Astronomers who want a consensus value of H₀ from SNe Ia with conservative errors could, for now, use 60 ± 10 km s^-1 Mpc^-1.

Table of Contents

• INTRODUCTION
• OBSERVATIONAL PROPERTIES OF SNe Ia
• Homogeneity and Diversity
• Correlations
• Summary
• H₀ FROM CEPHEID CALIBRATIONS
• The Cepheid-Calibrated SNe Ia
• Matching the Calibrators to the Hubble Flow
• Summary
• PHYSICAL PROPERTIES
• Progenitors
• Explosion Models
• Light Curves
• Spectra
• Summary
• H₀ FROM PHYSICAL CONSIDERATIONS
• CONCLUSION
• REFERENCES