Distance determination to 12 Type II-P Supernovae using the Expanding Photosphere Method

TL;DR

This study applies the expanding photosphere method to 12 Type II-P supernovae using various models and filters, revealing systematic differences and estimating the Hubble constant with a focus on minimizing dispersion.

Contribution

It provides a comprehensive analysis of distance measurements to Type II-P supernovae using multiple models and methods, highlighting systematic uncertainties and optimizing filter choices.

Findings

Systematic differences in models cause ~50% variation in distances.

Lowest dispersion achieved with the VI filter subset (${\sigma_{\mu} = 0.32}$ mag).

Hubble constant estimated between 52 and 101 km s^{-1} Mpc^{-1}.

Abstract

We use early-time photometry and spectroscopy of 12 Type II plateau supernovae (SNe IIP) to derive their distances using the expanding photosphere method (EPM). We perform this study using two sets of Type II supernova (SN II) atmosphere models, three filter subsets ($\{BV\}$, $\{BVI\}$, $\{VI\}$), and two methods for the host-galaxy extinction, which leads to 12 Hubble diagrams. We find that systematic differences in the atmosphere models lead to $\sim $50% differences in the EPM distances and to a value of ${\rm H_0}$ between 52 and 101 ${\rm km s^{-1} Mpc^{-1}}$. Using the $\{VI\}$ filter subset we obtain the lowest dispersion in the Hubble diagram, {${\rm \sigma_{\mu} = 0.32}$ mag}. We also apply the EPM analysis to the well-observed SN IIP 1999em. With the $\{VI\}$ filter subset we derive a distance ranging from 9.3 $\pm$ 0.5 Mpc to 13.9 $\pm$ 1.4 Mpc depending on the atmosphere model employed.