Improving the Calibration of Type Ia Supernovae Using Late-time Lightcurves

TL;DR

This paper investigates how late-time lightcurve slopes of Type Ia supernovae correlate with their peak luminosity, and demonstrates that correcting for this improves calibration accuracy, aiding dark energy research.

Contribution

It introduces a method to incorporate late-time lightcurve slope correlations into supernova calibration, reducing intrinsic dispersion in the Hubble diagram.

Findings

Tentative correlation between late-time lightcurve slope and luminosity.

Calibration correction reduces dispersion to 0.12 mag.

Implications for future dark energy surveys.

Abstract

The use of Type Ia supernovae (SNe Ia) as cosmological standard candles is a key to solving the mystery of dark energy. Improving the calibration of SNe Ia increases their power as cosmological standard candles. We find tentative evidence for a correlation between the late-time lightcurve slope and the peak luminosity of SNe Ia in the B band; brighter SNe Ia seem to have shallower lightcurve slopes between 100 and 150 days from maximum light. Using a Markov Chain Monte Carlo analysis in calibrating SNe Ia, we are able to simultaneously take into consideration the effect of dust extinction, the luminosity and lightcurve width correlation (parametrized by \Delta m_{15}), and the luminosity and late-time lightcurve slope correlation. For the available sample of 11 SNe Ia with well-measured late-time lightcurves, we find that correcting for the correlation between luminosity and late-time lightcurve slope of the SNe Ia leads to an intrinsic dispersion of 0.12 mag in the Hubble diagram. Our results have significant implications for future supernova surveys aimed to illuminate the nature of dark energy.