For refcode 2000ApJ...540..634P: Retrieve 142 NED objects in this reference. Please click here for ADS abstract
NED Abstract
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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 Branchnormal. For 29 of the SNe Ia, peak magnitudes in
I are also known. The SNe Ia have uniform colors at maximum, i.e.,<BV> = 
0.012 mag ({sigma} = 0.051) and <VI> = 0.276 mag ({sigma} = 0.078). In
the Hubble diagram, they define a Hubble line with a scatter of {sigma}_M_
= 0.210.16 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 (BV). 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 (Branchnormal) SNe Ia in spirals whose
Cepheid distances are known. If their welldefined 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 (BV), 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 lightcurve
parameter and/or on an unwarranted reduction of the Cepheid distances of
the calibrating SNe Ia.
Subject headings: distance scalegalaxies: distances and redshifts 
supernovae: general
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