[mesa-users] Building stars via accretion with MESA

[Sergei Nayakshin]

Hi Richard,

I agree that this is a very interesting problem, but I doubt that this can be done. Having said that, I’m only an occasional MESA user so far, so perhaps somebody could correct me if I’m wrong.

1) My understanding is that MESA EOS does not sample the appropriately low gas temperatures and densities for this. As Larson (1969) shows, first cores start off with T ~ 100 K and densities of order ~ 10^-13 g/cm^3. 

2) The second problem might be that the first core goes through a dynamical collapse when H_2 molecules dissociate (once the central T reaches ~ 2000 K). Most stellar evolution codes would fail at that point.

3) You would clearly need to come up with a new initial condition routine to initialise the first core. 

Or perhaps you were thinking of starting from the second core (after H_2 dissociation)? But that phase usually happen at much later time, when the core reached a higher mass, say ~ 0.03 Msun (see Masunaga and Inutsuka 2000, for example).

Cheers,
Sergei.




> On 8 Sep 2015, at 08:14, Richard Townsend <rhtownsend at icloud.com> wrote:
> 
> Hi folks —
> 
> I’d like to see if I can use MESA to build up a star by accretion — basically, start with an adiabatic core with mass ~ Mjupiter, and then accrete mass (following some prescription) until it reaches its final mass and then contracts onto the main sequence.
> 
> Does anyone have any words of wisdom about this — things to watch out for with MESA, previous experiences with MESA or other codes, pointers?
> 
> Many thanks,
> 
> Rich
> 
> 
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