The effects of varying colour-luminosity relations on supernova science

Understand

The success of Type Ia supernova (SN Ia) distance standardisation for cosmology relies on a single global linear relationship between their peak luminosity and colour, the $\beta$ parameter.

• However, there are several pieces of evidence and physical reasons to believe that this relation is not universal and may change within different subgroups, or even among individual objects.
• In this work, we allow $\beta$ to vary among subpopulations with different observed properties in the cosmological fits.
• Although the inferred cosmological parameters are consistent with previous studies that assume a single colour-luminosity relation, we find that the SN data favour nonuniversal distributions of $\beta$ when split according to SN colour and/or host-galaxy mass.