Light curves of five type Ia supernovae at intermediate redshift

TL;DR

This study presents multi-band light curves and distance measurements for five intermediate-redshift type Ia supernovae, confirming cosmological models and revealing unexpected reddening in one supernova.

Contribution

It provides new observational data and analysis methods for intermediate-redshift supernovae, enhancing understanding of their properties and cosmological implications.

Findings

Light curve peak luminosities align with LambdaCDM predictions

One supernova shows unexpectedly large reddening

Distances are consistent with cosmological models

Abstract

We present multi-band light curves and distances for five type Ia supernovae at intermediate redshifts, 0.18<z<0.27. Three telescopes on the Canary Island of La Palma, INT, NOT and JKT, were used for discovery and follow-up of type Ia supernovae in the g' and r' filters. Supernova fluxes were measured by simultaneously fitting a supernova and host galaxy model to the data, and then calibrated using star catalogues from the Sloan Digital Sky Survey. The light curve peak luminosities, corrected for light curve shape and colour, are consistent with the expectations for a flat LambdaCDM universe at the 1.5-sigma level. One supernova in the sample, SN1999dr, shows surprisingly large reddening, considering that it is both located at a significant distance from the core of its host (~4 times the fitted exponential radius) and that the galaxy can be spectroscopically classified as early-type with no signs of ongoing star formation.