August 7-10, 2017

Abstract

On the photospheric sources of wind structures in hot luminous O-type stars

Tahina RAMIARAMANANTSOA (Université de Montréal)

Major advances in the characterization of hot star winds have been achieved during the era of the International Ultraviolet Explorer (IUE) space-based mission. Of paramount interest was the detection of the enigmatic Discrete Absorption Components (DACs): time-variable discrete absorption features propagating in the P Cygni absorption troughs of unsaturated UV resonance lines of O stars, best interpreted as spectroscopic manifestations of the presence of large-scale spiral-like Corotating Interaction Regions (CIRs) in the stellar wind. Additionally, ground-based optical spectroscopic observations have indicated the clumpy nature of the winds of O stars. Several theoretical investigations on the origins of these two distinct types of hot star wind structures have emerged over the past three decades. But on the observational side, now with the new generation of space-based missions delivering high-precision time-resolved optical photometric measurements, we are able to probe low-amplitude variability at the photosphere of O stars. This becomes even more powerful when complemented with high-quality intensive ground-based spectroscopic monitoring of wind-sensitive optical lines. In that regard, I will highlight the contribution of BRITE in bringing the first direct observational evidence for the photospheric drivers of both large and small-scale wind structures in a key O-type star, zeta Pup [O4I(n)fp], enlightening our perception of the behaviour at the photosphere-wind interface in O stars.

Mode of presentation need to be confirmed by the SOC