The Foundation Supernova Survey: Photospheric Velocity Correlations in Type Ia Supernovae

Understand

The ejecta velocities of type-Ia supernovae (SNe Ia), as measured by the Si II $\lambda 6355$ line, have been shown to correlate with other supernova properties, including color and standardized luminosity.

• We investigate these results using the Foundation Supernova Survey, with a spectroscopic data release presented here, and photometry analyzed with the SALT2 light-curve fitter.
• We find that the Foundation data do not show significant evidence for an offset in color between SNe Ia with high and normal photospheric velocities, with $\Delta c = 0.005 \pm 0.014$.
• Our SALT2 analysis does show evidence for redder high-velocity SN Ia in other samples, including objects from the Carnegie Supernova Project, with a combined sample yielding $\Delta c = 0.017 \pm 0.007$.