# Can accretion push RGB stars onto the Main-Sequence?

## Jun 7, 2022 09:17 · 226 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 thirteenth post in a series describing some of the ideas I’ve accumulated.

## Can accretion push RGB stars onto the Main-Sequence?

### What’s the idea?

Stars enter the Red Giant Branch (RGB) when they exhaust hydrogen in their cores. Mixing hydrogen-rich material into their cores should reverse this transition, pushing them back onto the main-sequence.

Accretion may be able to cause such a mixing event, either directly (as in a stellar merger) or by causing the formation of a core convection zone. I think the latter requires that the mass become large enough that hydrogen burning is no longer confined to a thin burning shell around the helium core.

### Why is this interesting?

It just seems like a cool idea. This should be quite rare and I am not sure how to detect it from looking at the resulting massive star, so it may be of more theoretical interest. It also seems possible that this could happen to Red Giants embedded in AGN disks, as the high density environment supports great accretion rates.

### How can I get started?

I’d just run models of accreting RGB stars in MESA with different $\dot{M}$’s and see what happens.

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