Periodic mass loss episodes due to an oscillation mode with variable amplitude in the hot supergiant HD50064

TL;DR

This study investigates the variability of the luminous blue supergiant HD 50064, revealing a 37-day oscillation with amplitude changes and episodic mass loss, interpreted as a strange mode oscillation.

Contribution

It provides the first combined photometric and spectroscopic analysis of HD 50064, identifying a variable oscillation mode and episodic mass loss in a luminous blue supergiant.

Findings

Detected a 37-day pulsation period with amplitude variation.

Observed episodic mass loss episodes correlated with variability.

Identified spectral line velocity differences indicating complex stellar dynamics.

Abstract

We aim to interpret the photometric and spectroscopic variability of the luminous blue variable supergiant HD\,50064 ($V=8.21$).CoRoT space photometry and follow-up high-resolution spectroscopy, with a time base of 137\,d and 169\,d, respectively, was gathered, analysed and interpreted using standard time series analysis and light curve modelling methods as well as spectral line diagnostics.The space photometry reveals one period of 37\,d, which undergoes a sudden amplitude change with a factor 1.6. The pulsation period is confirmed in the spectroscopy, which additionally reveals metal line radial velocity values differing by $\sim 30\,$km\,s$^{-1}$ depending on the spectral line and on the epoch. We estimate \teff$\sim$13\,500\,K, \logg$\sim$1.5 from the equivalent width of Si lines. The Balmer lines reveal that the star undergoes episodes of changing mass loss on a time scale similar to the changes in the photometric and spectroscopic variability, with an average value of $\log\dot{\rm M}\simeq-5$ (in M$_\odot$\,yr$^{-1}$). We tentatively interpret the 37\,d period as due to a strange mode oscillation.