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Date and Time of the Query: 2019-05-22 T03:56:48 PDT
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For refcode 2000ApJ...540..634P:
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2000ApJ...540..634P Supernova Type Ia Luminosities, Their Dependence on Second Parameters, and the Value of H_0_ B. R. Parodi, A. Saha, A. Sandage, and G. A. Tammann Received 2000 February 29; accepted 2000 April 7 ABSTRACT A sample of 35 Type Ia supernovae (SNe Ia) with good to excellent photometry in B and V, minimum internal absorption, and 1200 < v <~ 30,000 km s^-1^ is compiled from the literature. As far as their spectra are known, they are all Branch-normal. For 29 of the SNe Ia, peak magnitudes in I are also known. The SNe Ia have uniform colors at maximum, i.e.,<B-V> = - 0.012 mag ({sigma} = 0.051) and <V-I> = -0.276 mag ({sigma} = 0.078). In the Hubble diagram, they define a Hubble line with a scatter of {sigma}_M_ = 0.21-0.16 mag, decreasing with wavelength. The scatter is further reduced if the SNe Ia are corrected for differences in decline rate, {DELTA}m_15_, or color (B-V). A combined correction reduces the scatter to {sigma} <~ 0.13 mag. After the correction, no significant dependence remains on Hubble type or Galactocentric distance. The Hubble line suggests some curvature that can be differently interpreted. A consistent solution is obtained for a cosmological model with {OMEGA}_M_ = 0.3, {OMEGA}_{LAMBDA}_ = 0.7, which is also indicated by much more distant SNe Ia. Absolute magnitudes are available for eight equally blue (Branch-normal) SNe Ia in spirals whose Cepheid distances are known. If their well-defined mean values of M_B_, M_V_, and M_I_ are used to fit the Hubble line to the above sample of SNe Ia, one obtains H_0_ = 58.3 km s^-1^ Mpc^-1^, or, after adjusting all SNe Ia to the average values of {DELTA}m_15_ and (B-V), H_0_ = 60.9 km s^-1^ Mpc^-1^. Various systematic errors are discussed whose elimination tends to decrease H_0_. The value finally adopted at the 90% level, including random and systematic errors, is H_0_ = 58.5 +/- 6.3 km s^-1^ Mpc^-1^. Several higher values of H_0_ from SNe Ia, as suggested in the literature, are found to depend on large corrections for variations of the light-curve parameter and/or on an unwarranted reduction of the Cepheid distances of the calibrating SNe Ia. Subject headings: distance scale-galaxies: distances and redshifts - supernovae: general
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