An Empirical Fitting Method for Type Ia Supernova Light Curves: A Case Study of SN 2011fe

TL;DR

This paper introduces an empirical, analytically derived fitting method based on a broken-power-law function for modeling Type Ia supernova light curves, demonstrated on SN 2011fe, with potential for broad application.

Contribution

The paper presents a new empirical fitting function for Type Ia supernova light curves derived from physical assumptions, improving modeling accuracy and applicability.

Findings

Good fit to SN 2011fe light curves from first light to weeks after peak

Able to describe flux variations over 5 to 7 magnitudes in different bands

Potential to analyze large samples of SNe Ia with similar light-curve shapes

Abstract

We present a new empirical fitting method for the optical light curves of Type Ia supernovae (SNe~Ia). We find that a variant broken-power-law function provides a good fit, with the simple assumption that the optical emission is approximately the blackbody emission of the expanding fireball. This function is mathematically analytic and is derived directly from the photospheric velocity evolution. When deriving the function, we assume that both the blackbody temperature and photospheric velocity are constant, but the final function is able to accommodate these changes during the fitting procedure. Applying it to the case study of SN~2011fe gives a surprisingly good fit that can describe the light curves from the first-light time to a few weeks after peak brightness, as well as over a large range of fluxes ($\sim 5$\, mag, and even $\sim 7$\,mag in the $g$ band). Since SNe~Ia share similar light-curve shapes, this fitting method has the potential to fit most other SNe~Ia and characterize their properties in large statistical samples such as those already gathered and in the near future as new facilities become available.