An investigation on the FWHM of absorption features of type Ia supernovae

TL;DR

This study analyzes the FWHM of absorption features in Type Ia supernovae, revealing how it correlates with wavelength, velocity, temperature, and supernova subtype, and proposing FWHM-related metrics as luminosity indicators.

Contribution

It provides a detailed analysis of factors influencing FWHM in SNe Ia and introduces FWHM-based parameters as potential luminosity estimators.

Findings

FWHM correlates with rest wavelength and velocity.

1991T/1999aa-like objects have larger FWHMs and faster FWHM decrease.

A/{b3} of Si II b59792 strongly correlates with b415, serving as a luminosity indicator.

Abstract

We present an investigation of the full width at half maximum (FWHM, or {\gamma}) of absorption features of Type Ia supernova (SNe Ia). We found that, the average value of FWHM can be well predicted with the rest wavelength ({\lambda}). The velocity also plays an important role, as objects with a higher velocity tend to have a larger FWHM. Temperature may be the third factor, as we found that, at the same velocity (but different phases), a normal-velocity (NV) object tends to have a larger FWHM than high-velocity (HV) object. Also, 1991T/1999aa-like objects that are believed to have relatively high temperatures show the largest FWHMs if compared at the same velocity. Generally speaking, FWHM evolves very slowly with time and shows no correlation with {\Delta}m15, but 1991T/1999aa-like objects are characterized by relatively fast decreasing FWHM. On the other hand, we found that, objects with relatively small FWHMs shows a tighter correlation between absorption depth (A) and {\Delta}m15, possibly a sign of higher degree of homogeneity. We also found that A/{\gamma} of Si II {\lambda}5972 has a strong correlation with {\Delta}m15, and more importantly, a relatively slow time evolution, making it a useful luminosity estimator even in the absence of phase information.