Supernova Type Ia Luminosities, Their Dependence on Second Parameters, and the Value ofH₀

Abstract

A sample of 35 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 also peak magnitudes in I are known. The SNe Ia have uniform colors at maximum, i.e. <B-V >=−0 m . 012 (σ=0.051) and <V -I>=−0 m . 276 (σ=0.078). In the Hubble diagram they define a Hubble line with a scatter of σ M =0 m . 21-0 m . 16, decreasing with wavelength. The scatter is further reduced if the SNe Ia are corrected for differences in decline rate ∆m 15 or color (B−V ). A combined correction reduces the scatter to σ < ∼ 0 m . 13. After the correction no significant dependence remains on Hubble type or galactocentric distance. The Hubble line suggests some curvature which can be differently interpreted. A consistent solution is obtained for a cosmological model with Ω M =0.3, Ω Λ =0.7, which is indicated also 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 ∆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 finally adopted value at the 90-percent 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.

Slow-Roll Inflation and Cosmic Microwave Background Anisotropy Data

“…In particular, we take to be in agreement with the most important Q p 1 0 prediction of inflation, , which is consistent with Type h p 0.60 Ia supernovae measurements ( at 90% conh p 0.585 ‫ע‬ 0.063 fidence level [Parodi et al 2000 In this Letter, we recall the basic predictions of slow-roll inflation ( § 2) and correct errors and misconceptions that have recently been made in the literature on this issue ( § 3). In § 4, we compare for the first time the predictions of slow-roll inflation with the recent data of BOOMERanG and MAXIMA-1 (without any elaborated statistical technique; we remind that only 5% of the BOOMERanG data have been analyzed so far).…”

On the contribution of microlensing to X-ray variability of high-redshifted QSOs

“…However, Parodi et al (2000); Tammann & Reindl (2002a,b) give lower limits for h = 0.585 ± 0.063. Therefore, using for example the estimate by Freedman et al (2001) one could obtain for the cosmic baryon density (Turner 2002)…”

Not Color‐Blind: Using Multiband Photometry to Classify Supernovae

“…SNe Ia are excellent distance indicators, and their Hubble diagram has been used to determine the local value of the Hubble constant (e.g., Parodi et al 2000 and references therein). The extension of the Hubble diagram to higher redshifts ( ) probes the geometry z ≈ 1 and matter-energy content of the universe (e.g., Goobar & Perlmutter 1995).…”