Temporal delay characteristics of photometric maxima in the \(i\)-band of type Ia supernovae

Abstract

To investigate the physical origin of the secondary maximum in the \(i\)-band of Type Ia Supernovae (SNe Ia) and assess its application value in supernova physics research, a sample of 33 nearby SNe Ia with well-sampled \(i\)-band light curves from the LSQ/LCO collaboration and recent low-redshift follow-up data were selected. A comprehensive method combining SNooPy2 light curve fitting, Continuous Wavelet Transform (CWT) for objective peak identification, and Bayesian multi-Gaussian decomposition for peak parameter quantification was adopted to systematically analyze the temporal characteristics of the secondary maximum and its correlation with key physical parameters of SNe Ia. The results show that the temporal parameters of the secondary maximum have a significant negative correlation with the light curve decline rate \(\Delta m_{15}\), among which the time interval between the primary and secondary maxima (\(\mu _{3}\)-\(\mu _{1}\)) has the strongest correlation (\(R^{2} \approx 0.98\), slope \({\approx} -13.61 \pm 0.37\text{ days/magnitude}\)). The epoch of the secondary maximum is found to track both the \(B-V\) and \(g-i\) colour-peak epochs (Pearson \(r\approx 0.77\) and \(r\approx 0.92\), respectively), supporting the interpretation that these colour turnovers and \(\mu _{3}\) trace related phases of the post-maximum thermal evolution. These quantitative relationships provide a new perspective for investigating the thermal evolution and explosion physics of SNe Ia, and may offer a potential avenue for refining their use as standardizable candles in future cosmological studies.