Periodic mass-loss episodes due to an oscillation mode with variable amplitude in the hot supergiant HD 50064

Abstract

<i>Aims. <i/>We aim to interpret the photometric and spectroscopic variability of the luminous blue variable supergiant HD 50064 (<i>V<i/> = 8.21).<i>Methods. <i/>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.<i>Results. <i/>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 ~30 km s<sup>-1<sup/> depending on the spectral line and on the epoch. We estimate <i>T<i/><sub>eff<sub/> ~ 13 500 K, log <i>g<i/> ~ 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 -5 (in M yr<sup>-1<sup/>). We tentatively interpret the 37 d period as the result of a strange mode oscillation.