Pulsation-Initiated Mass Loss in Luminous Blue Variables: A Parameter Study

Abstract

AbstractLuminous blue variables (LBVs) are characterized by semi-periodic episodes of enhanced mass-loss, or outburst. The cause of these outbursts has thus far been a mystery. One explanation is that they are initiated by κ-effect pulsations in the atmosphere caused by a blocking of luminosity at temperatures near the so-called “iron bump” (T ~ 200,000 K), where the Fe opacity suddenly increases and blocks the luminosity. Due to a lag in the onset of convection, the luminosity can build until it exceeds the Eddington limit locally, seeding pulsations and possibly driving some mass from the star. We present preliminary results from a parameter study focusing on the conditions necessary to trigger normal S-Dor type (as opposed to extreme η-Car type) outbursts. We find that as Y increases or Z decreases, the pulsational amplitude decreases and outburst-like behavior, indicated by a large, sudden increase in photospheric velocity, becomes less likely.