The bi-stability jump as the origin for multiple P-Cygni absorption components in Luminous Blue Variables

TL;DR

This paper demonstrates that the bi-stability jump causes the double-troughed P-Cygni absorption features in LBVs by modeling wind velocity changes, linking LBV variability to supernova progenitors and offering a new detection method.

Contribution

It provides the first detailed radiative transfer modeling linking wind velocity jumps to double absorption features in LBVs, supporting their connection to supernova progenitors.

Findings

Double-troughed absorption profiles are explained by wind velocity changes due to the bi-stability jump.

Wind variability from the bi-stability jump can be used to identify LBVs in other galaxies.

Spectral analysis at a single epoch can reveal LBV mass-loss history.

Abstract

Luminous Blue Variables (LBVs) oftentimes show double-troughed absorption in their strong Halpha lines, which are as yet not understood. Intriguingly, the feature has also been seen in the interacting supernova SN 2005gj, which was for this reason suggested to have an LBV progenitor. Our aims are to understand the double-troughed absorption feature in LBVs and investigate whether this phenomenon is related to wind variability. To this purpose, we perform time-dependent radiative transfer modeling using CMFGEN. We find that abrupt changes in the wind-terminal velocity - as expected from the bi-stability jump - are required to explain the double-troughed absorption profiles in LBVs. This strengthens scenarios that discuss the link between LBVs and SNe utilizing the progenitor's wind variability resulting from the bi-stability jump. We also discuss why the presence of double-troughed P-Cygni components may become an efficient tool to detect extra-galactic LBVs and how to analyze their mass-loss history on the basis of just one single epoch of spectral observations.