An Empirical Fitting Method for Type Ia Supernova Light Curves. II. Estimating the First-Light Time and Rise Time

TL;DR

This paper introduces an empirical fitting method to estimate the first-light time of Type Ia supernovae from optical light curves, enabling more accurate rise time measurements even when early discovery is missed.

Contribution

It presents a new empirical fitting approach for SNe Ia light curves that accurately estimates first-light times and computes rise times for a sizable sample.

Findings

Rise times range from 10.5 to 20.5 days with a mean of 16.0 days.

Rise time correlates with decline rate but shows large scatter.

Method improves early light curve analysis for SNe Ia.

Abstract

We investigate a new empirical fitting method for the optical light curves of Type Ia supernovae (SNe~Ia) that is able to estimate the first-light time of SNe~Ia, even when they are not discovered extremely early. With an improved ability to estimate the time of first light for SNe Ia, we compute the rise times for a sample of 56 well-observed SNe~Ia. We find rise times ranging from 10.5 to 20.5 days, with a mean of 16.0 days, and confirm that the rise time is generally correlated with the decline rate $\Delta m_{15}(B)$, but with large scatter. The rise time could be an additional parameter to help classify SN~Ia subtypes.