[mesa-users] Rotation velocity problem

Josiah Schwab jwschwab at berkeley.edu
Mon Dec 17 20:29:30 EST 2012

```Hi Roberto,

Remember, omega is an angular frequency, so v_rot = radius * omega.  There is no "2*pi".

Josiah

PS.  I see Aaron just demonstrated that the numbers to indeed work.

On Dec 17, 2012, at 5:09 PM, trobolo dinni wrote:

> Dear MESA users,
>
> I would like to ask a suggestion to understand the MESA outputs from a rotating star.
> I simply launched a basic 1Msun from preMS to WD simulation by using the default inlist file, but I added a solid-body rotation beginning from ZAMS. Now, what I want to check is the surface rotation velocity during RGB so I set up my profile_column.list file to show me the rotational parameters, in particular omega (expressed in Hz) and v_rot (which, as said in the profile_column.list file is expressed in Km/s).
>
> My doubt is now the following, when I went read the numbers on the surface of the star in a profile file, what I read is:
>
> r_div_R                                  radius                                        omega                                     v_rot
>
> 1.0000000000000000E+000     8.0820064813736806E+001         3.0743441369562425E-008       1.7292924054249237E+000
>
> which should mean that the rotation velocity on the surface is ~1.73 Km/s.
> Then I tried to do a rough estimation of v_rot from omega by simply using the relation:
>
> v_rot = 2pi*radius*omega
>
> and what I get is
>
> v_rot ~ 10.9 Km/s
>
> which is completely different from what the output in the profile tells me. Also, from the final plot of the simulation (attached) the v_rot seems to be at least greater of ~8 (I supposed that the scale in the plot is in Km/s).
>
> I would like to ask if in your opinion my reasoning is correct or how I should interpret the v_rot parameter in the profile file.
>
> Thanks,
>                     Roberto
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```

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