Time-scales of Line-broadening Variability in OB Supergiants

TL;DR

This study investigates the time-scales of line-broadening variability in OB supergiants, exploring the hypothesis that oscillations cause macroturbulence, through high-quality spectral time series analysis.

Contribution

It provides observational constraints on the variability time-scales of line-broadening in OB supergiants, supporting the oscillation hypothesis for macroturbulence.

Findings

Initial results suggest variability consistent with oscillation timescales.

Spectral time series reveal patterns supporting the oscillation origin of macroturbulence.

Further analysis is ongoing to confirm these preliminary findings.

Abstract

Several works have recently shown that there is an important extra line-broadening (usually called $macroturbulence$) affecting the spectra of O and B Supergiants that adds to stellar rotation. So far, the only (very recent) physical explanation for the appearance of $macroturbulence$ relates to oscillations. This is a plausible explanation, but no direct evidence confirming its validity has been presented yet. We recently started an observational project to obtain constraints on the time-scales of variability associated to this extra line-broadening and its possible origin. Our observational strategy consists of the study of a well selected group of O and B stars, for which we obtain time series of high-quality spectra. We present some preliminary results from our first campaign with FIES@NOT2.5m.