Letter to the Editor

The bi-stability jump as the origin for multiple P-Cygni absorption components in luminous blue variables

¹ Max-Planck-Institut fuer Radioastronomie, Auf dem Huegel 69, 53121 Bonn, Germany
e-mail: jgroh@mpifr.de
² Armagh Observatory, College Hill, Armagh BT61 9DG, Northern Ireland
e-mail: jsv@arm.ac.uk

Received: 15 April 2011
Accepted: 23 May 2011

Abstract

Luminous blue variables (LBVs) oftentimes show double-troughed absorption in their strong Hα 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.