Microturbulence across the HR Diagram

Our findings indicate that photospheric micro-turbulence is a genuine physical phenomenon, rather than a modelling artefact. A direct comparison between observed vmic velocities and corresponding theoretical predictions for the turbulent pressure fraction strongly suggests that this phenomenon most likely arises from photospheric motions driven (directly or indirectly) by envelope convection zones, with an additional pulsational component likely operating in main sequence B stars.

We show that neglecting micro-turbulence in Fourier transform analyses can partly (but not solely) explain the dearth of slow rotators and the scarcity of stars with extremely low vmac. We argue that including micro-turbulent pressure in atmospheric modelling can significantly mitigate (and even resolve) the mass discrepancy for less massive O stars. We provide new observational insights into the nature and origin of micro-turbulence across the HRD.

Our database offers a valuable resource for testing and refining theoretical scenarios, particularly those addressing a range of puzzling phenomena in hot, massive stars.