[Mesa-users] stellar wind velocity

[Francis Timmes]

hi saul,

lines 542-549 in $MESA_DIR/star/defaults/history_columns.list
say how v_wind_Km_per_s is calculated. 

clearer?

fxt





> On Oct 6, 2021, at 2:17 PM, Saul A Rappaport <sar at mit.edu> wrote:
> 
> There is a column in the MESA output for the wind mass loss rate and another for the wind speed.  The wind mass loss rates make excellent sense, but I’m really confused about V_wind.  
> 
> The attached plot shows Log Rstar (in red), Log Vwind (blue), and Log Mdot (black).  It seems that as the star is starting to leave the MS, the wind mass loss rate approaches 10^(-6) Msun/year, and at the same time, V_wind goes up to ~50 km/sec (which is what I would expect).  This phase lasts for ~400,000 years.  Then, when the star really grows to huge proportions with a radius of ~1000 Rsun, the wind rate grows to ~10^(-5) Msun/year.  However, V_wind abruptly drops to 0.01 km/sec (10 meters/sec).  What does that mean when the escape speed is still 10’s of km/sec? 
> 
> I found this same issue in all models with masses between 10 and 20 Msun, so it’s not just this particular model that has a quirk.  
> 
> Can anyone enlighten me as to whether this is intended to be realistic, or if it is just an algorithm that is being misapplied? 
> 
> 
> Thanks,
> 
> 
> Saul Rappaport
> 
> <MESA_20_Msun_model.png>
> 
> 
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