[Mesa-users] stellar wind velocity

[Saul A Rappaport]

Hi Frank:

> ok. well, at least my message pointed out to the larger community
> what the output quantity is and how it is being calculated. 
> 
> in some regimes the formula being used seems to makes some sense:
> 
>> 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).  
> 
> but in other regimes it does not seem to make sense:
> 
>> 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 don't know what your model looks like, but its possible that 
> the atmosphere is not resolved enough to give a consistent 
> optical depth at the base of the envelope. or maybe the atmosphere
> is sufficiently resolved and the solution lies elsewhere, up to 
> and including using a different formula.
> 
> i know there are several mass loss wind speed experts lurking 
> on this mailing list. perhaps one of them can chime in.

	Thanks very much for this additional feedback. 

> p.s. - always cc mesa-users on replies. its how we track resolving issues.

	Fair enough - let’s see if any of the stellar wind pundits out there
can shed some more light on what I find to be very peculiar wind speeds.

	To reiterate, I’m simply trying to understand why, when a massive 
star (5-20 Msun) reaches the giant branch, the stellar wind abruptly 
drops from 50 km/sec to 10 m/sec.


				Saul