Timescale Stretch Parameterization of Type Ia SupernovaB‐Band Light Curves

Abstract

R-band intensity measurements along the light curve of Type Ia supernovae discovered by the Supernova Cosmology Project (SCP) are fitted in brightness to templates allowing a free parameter the time-axis width factor w ≡ s × (1 + 2 z). The data points are then individually aligned in the time-axis, normalized and K-corrected back to the rest frame, after which the nearly 1300 normalized intensity measurements are found to lie on a well-determined common rest-frame B-band curve which we call the "composite curve". The same procedure is applied to 18 low-redshift Calán/Tololo SNe with z < 0.11; these nearly 300 B-band photometry points are found to lie on the composite curve equally well. The SCP search technique produces several measurements before maximum light for each supernova. We demonstrate that the linear stretch factor, s, which parameterizes the light-curve timescale appears independent of z, and applies equally well to the declining and rising parts of the light curve. In fact, the B band template that best fits this composite curve fits the individual supernova photometry data when stretched by a factor s with χ 2 /DoF ≈ 1, thus as well as any parameterization can, given the current data sets. The measurement of the date of explosion, however, is model dependent and not tightly constrained by the current data. We also demonstrate the 1 + z light-curve time-axis broadening expected from cosmological expansion. This argues strongly against alternative explanations, such as tired light, for the redshift of distant objects.

The Nearby Supernova Factory

“…We use a V-band lightcurve template from Goldhaber et al (2001) to model the rise and fall of SNe Ia. 1 The simulator calculates the amount of time a supernova would be visible at a given redshift assuming a normal (stretch = 1) SN Ia.…”

Photometric properties of intermediate-redshift Type Ia supernovae observed by the Sloan Digital Sky Survey-II Supernova Survey

“…This method is a revised Stretch method (cf. Perlmutter et al 1997;Goldhaber et al 2001) extended to five bands. There are several methods for parameterizing light curve shapes of SN Ia.…”

Non-minimal derivative coupling gravity in cosmology

“…Amongst these are supernova type Ia (SNIa) [1][2][3][4][5][6][7][8][9][10], large-scale structure surveys [11,12], cosmic microwave background (CMB) anisotropies [13][14][15][16] and X-ray luminosity from galaxy clusters [15,17,18]. The acceleration is responsible by an unknown energy form called dark energy [19][20][21] which is typically in form of either cosmological constant or scalar field [19][20][21][22].…”