THE MINIMUM EJECTION VELOCITY OF CALCIUM IN TYPE Ia SUPERNOVAE AND THE VALUE OF THE HUBBLE CONSTANT

摘要

Evidence is presented for a relation between the visual absolute magnitudes of Type Ia supernovae (SN Ia's) and their minimum ejection velocities of calcium as indicated by the red edge of the Ca II H and K absorption blend in moderately late-time spectra. Independent calibrations of the relation by means of (1) the Cepheid-based distance to NGC 5253, the parent galaxy of SN 1972E, and (2) light-curve calculations based on hydrodynamic models of SN Ia's, give low H_0, near 60 km s~(-1) Mpc~(-1).