Circumstellar Shells in Absorption in Type Ia Supernovae

TL;DR

This paper explores the potential for detecting circumstellar shells around Type Ia supernovae through Na I absorption lines, focusing on variability shortly after explosion to infer shell properties.

Contribution

It proposes a method to identify and analyze circumstellar shells in Type Ia SNe using variable Na I absorption lines during early phases.

Findings

Variable Na I absorption can indicate nearby circumstellar shells.

Shell distance can be estimated from line variability timescales.

Detection prospects depend on shell proximity and observational timing.

Abstract

Progenitors of Type Ia supernovae (SNe) have been predicted to modify their ambient circumstellar (CSM) and interstellar environments through the action of their powerful winds. While there is X-ray and optical evidence for circumstellar interaction in several remnants of Type Ia SNe, widespread evidence for such interaction in Type Ia SNe themselves has been lacking. We consider prospects for detection of CSM shells that have been predicted to be common around Type Ia SNe. Such shells are most easily detected in Na I absorption lines. Variable (declining) absorption is expected to occur soon after the explosion, primarily during the SN rise time, for shells located within 1 - 10 pc of a SN. The distance of the shell from the SN can be determined by measuring the time scale for line variability.