Cepheid Calibration of the Peak Brightness of Type IA Supernovae: Calibration of SN 1990N in NGC 4639 Averaged with Six Earlier Type IA Supernova Calibrations to Give H 0 Directly
Abstract
Periods and light curves have been measured with the Hubble Space Telescope for 20 Cepheids in NGC 4639, parent galaxy to the Type Ia, prototypical supernova SN 1990N. The periods range from 17 to 69 days. The mean apparent magnitudes, averaged over the light curves, range from <V> = 25.6 to <V> = 27.3. Welldetermined periodluminosity relations exist in V and I. Corrected for differential extinction, these give a true modulus for NGC 4639 of (m  M)0 = 32.00 +/ 0.23. Combining the light curves for SN 1990N with this modulus gives MB(max) = 19.30 +/ 0.23 and MV(max) = 19.39 +/ 0.23. This, together with six previous calibrations of Type Ia supernovae, gives the mean calibrations of "Branch normal" supernovae to date as <MB(max)> = 19.47 +/ 0.07 and <MV(max)> = 19.48 +/ 0.07. The resulting Hubble constants, reading the Type Ia supernova Hubble diagrams at very large redshifts beyond any possible local velocity anomalies, give global values of the Hubble constant of H0(B) = 56 +/ 4 (internal) km s1 Mpc1 and H0(V) = 58 +/ 4 (internal) km s1 Mpc1.
 Publication:

The Astrophysical Journal
 Pub Date:
 March 1996
 DOI:
 10.1086/309973
 Bibcode:
 1996ApJ...460L..15S
 Keywords:

 STARS: VARIABLES: CEPHEIDS;
 GALAXIES: INDIVIDUAL NGC NUMBER: NGC 4639;
 COSMOLOGY: DISTANCE SCALE