the Ca H&K feature is caused by calcium, with implications for our understanding of SN Ia progenitors, explosions, and cosmology.'
author:
- |
    Ryan J. Foley$^{1}$[^1]\
    $^{1}$Harvard–Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138, USA
bibliography:
- '../astro\_refs.bib'
date: 'Accepted . Received ; in original form '
title: On Spectral Line Profiles in Type I Supernova Spectra
---

\[firstpage\]

[line: identification – line: profile – supernovae: general – supernovae: individual: SN 2010ae – supernovae: individual: SN 2011fe]{}

Introduction {#s:intro}
============

The spectral-energy distribution (SED) of a Type Ia supernova (SN Ia) near maximum brightness is relatively similar to that of a hot star. An SN SED is predominantly a black body with line blanketing in the ultraviolet. There are also prominent spectral features associated with absorption and emission from elements primarily generated in the SN explosion. These features typically have broad P-Cygni profiles, although overlapping lines can produce larger and more complicated profiles.

The exact SED of a SN Ia depends on the velocity and density structure of the SN ejecta [e.g., @Branch85]. Since broad-band filters sample portions of the SED, and measurements in such filters are used to determine SN distances to ultimately measure cosmological parameters [e.g., 