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Date and Time of the Query: 2019-05-20 T07:40:14 PDT
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For refcode 2006ApJ...641...50W:
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Copyright by American Astronomical Society. Reproduced by permission
2006ApJ...641...50W Nonlinear Decline-Rate Dependence and Intrinsic Variation of Type Ia Supernova Luminosities Lifan Wang, Mark Strovink, Alexander Conley, Gerson Goldhaber, Marek Kowalski, Saul Perlmutter, and James Siegrist Abstract. Published B and V fluxes from nearby Type Ia supernovae (SNe) are fitted to light-curve templates with four to six adjustable parameters. Separately, B magnitudes from the same sample are fitted to a linear dependence on B-V color within a postmaximum time window prescribed by the CMAGIC method. These fits yield two independent SN magnitude estimates B_max_ and B_BV_. Their difference varies systematically with decline-rate {DELTA}m_15_ in a form that is compatible with a bilinear but not a linear dependence; a nonlinear form likely describes the decline-rate dependence of B_max_ itself. A Hubble fit to the average of B_max_ and B_BV_ requires a systematic correction for observed B-V color that can be described by a linear coefficient R=2.59+/-0.24, well below the coefficient R_B_~4.1 commonly used to characterize the effects of Milky Way dust. At 99.9% confidence the data reject a simple model in which no color correction is required for SNe that are clustered at the blue end of their observed color distribution. After systematic corrections are performed, B_max_ and B_BV_ exhibit mutual rms intrinsic variation equal to 0.074+/-0.019 mag, of which at least an equal share likely belongs to B_BV_. SN magnitudes measured using maximum luminosity or CMAGIC methods show comparable rms deviations of order ~0.14 mag from the Hubble line. The same fit also establishes a 95% confidence upper limit of 486 km s^-1^ on the rms peculiar velocity of nearby SNe relative to the Hubble flow. Key words: Cosmology: Observations, Cosmology: Distance Scale, Stars: Supernovae: General
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