ZTF SN Ia DR2. Secondary maximum in Type Ia SN

The secondary maximum is relatively weak in the r band, but holds the advantage that it is accessible, even at high redshift. We used Gaussian Process fitting to parameterise the light curves of 893 SNe Ia from the Zwicky Transient Facility's (ZTF) second data release (DR2), and we were able to extract information about the timing and strength of the secondary maximum.

We found >5{sigma} correlations between the light curve decline rate ({DELTA}m15(g)) and the timing and strength of the secondary maximum in the r band. Whilst the timing of the secondary maximum in the i band also correlates with {DELTA}m15(g), the strength of the secondary maximum in the i band shows significant scatter as a function of {DELTA}m15(g). We found that the transparency timescales of 97 per cent of our sample are consistent with double detonation models, and that SNe Ia with small transparency timescales (<32d) reside predominantly in locally red environments.