A Global Model of The Light Curves and Expansion Velocities of Type II-Plateau Supernovae

TL;DR

This paper introduces a new method to model the light curves and expansion velocities of Type II-Plateau supernovae, enabling accurate distance and physical parameter estimations without relying on complex atmosphere models.

Contribution

The authors develop a self-consistent, versatile model that fits supernova light curves and velocities across multiple bands, revealing how ejecta density profiles influence light curve shapes.

Findings

Model accurately fits 26 supernovae light curves and velocities.

Steeper ejecta density profiles lead to flatter light curve plateaus.

Good agreement with theoretical dilution factors in B and V bands.

Abstract

We present a new self-consistent and versatile method that derives photospheric radius and temperature variations of Type II-Plateau supernovae based on their expansion velocities and photometric measurements. We apply the method to a sample of 26 well-observed, nearby supernovae with published light curves and velocities. We simultaneously fit ~230 velocity and ~6800 magnitude measurements distributed over 21 photometric passbands spanning wavelengths from 0.19 to 2.2 microns. The light curve differences among the Type II-Plateau supernovae are well-modeled by assuming different rates of photospheric radius expansion, which we explain as different density profiles of the ejecta and we argue that steeper density profiles result in flatter plateaus, if everything else remains unchanged. The steep luminosity decline of Type II-Linear supernovae is due to fast evolution of the photospheric temperature, which we verify with a successful fit of SN1980K. Eliminating the need for theoretical supernova atmosphere models, we obtain self-consistent relative distances, reddenings, and nickel masses fully accounting for all internal model uncertainties and covariances. We use our global fit to estimate the time evolution of any missing band tailored specifically for each supernova and we construct spectral energy distributions and bolometric light curves. We produce bolometric corrections for all filter combinations in our sample. We compare our model to the theoretical dilution factors and find good agreement for the B and V filters. Our results differ from the theory when the I, J, H, or K bands are included. We investigate the reddening law towards our supernovae and find reasonable agreement with standard R_V ~ 3.1 reddening law in UBVRI bands. Results for other bands are inconclusive. We make our fitting code publicly available.