Do pulsating stars reveal inhibited convection?

Jun 3, 2022 09:34 · 326 words · 2 minute read astronomy science research

I sometimes have research ideas that I think are cool, but that don’t make sense for me to pursue. I generally just make a note of them and move on. This is the eighth post in a series describing some of the ideas I’ve accumulated.

Do pulsating stars reveal inhibited convection?

What’s the idea?

Many A/B stars have pulsations driven by the $\kappa$-mechanism. In these stars, the pulsation often interacts with near-surface convective layers, motivating tools like time-dependent convection theories.

At the same time, magnetic fields can inhibit convection, and we know of A/B stars with strong enough fields to do this in near-surface layers. Unfortunately this has been hard to detect directly because these near-surface convection zones have a very small effect on stellar structure.

So the question is: Can we tell which A/B stars have near-surface convection zones and which don’t by looking at the properties of their pulsations?

Why is this interesting?

This would be a pretty direct test of the theory that magnetic fields can inhibit convection. It could also tell us that some stars lack near-surface convection zones, which we’ve suspected but has been hard to prove.

How can I get started?

One approach is to start from the theory and calculate the properties of pulsating A/B stars with strong magnetic fields and no subsurface convection, then go looking in the data for signatures of that in observations.

The reverse approach would be to plot pulsation properties of A/B stars as a function of measured magnetic field strength. My guess is that there will be some effect of the magnetic field but (without theory) it’ll be hard to tell if what you’re seeing is the magnetic field interacting with the pulsations, or the pulsations happening against a non-convective background.

$\gamma$ Doradus and SPB stars are good candidates to look at. In particular the SPB star “o Lup” has $B \sim 5300,\rm G$, which could be enough to inhibit subsurface convection zones.

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