On magnetic inhibition of photospheric macroturbulence generated in the iron-bump opacity zone of O-stars

We use these observational results to test the hypothesis that the field can stabilize the atmosphere and suppress the generation of macroturbulence down to stellar layers where the magnetic pressure P-B and the gas pressure P-g are comparable. Using a simple grey atmosphere to estimate the temperature T-0 at which P-B = P-g, we find that T-0 > T-eff for all investigated magnetic stars, but that T-0 reaches the similar to 160 000 K layers associated with the iron opacity bump in hot stars only for NGC 1624-2. This is consistent with the view that the responsible physical mechanism for photospheric O-star macroturbulence may be stellar gravity-mode oscillations excited by sub-surface convection zones, and it suggests that a sufficiently strong magnetic field can suppress such iron-bump generated convection and associated pulsational excitation.