# [mesa-users] Rotation velocity problem

Aaron Dotter aaron.dotter at gmail.com
Mon Dec 17 20:20:39 EST 2012

```Hi Roberto,

The radius column is in units of Rsun (see profiles_column.list).  If you
multiply radius by omega, and convert Rsun to km, you will get the same
value as in the v_rot column.

(8.082E1 Rsun) * (Rsun=6.96e5 km) * (3.074E-8 Hz)=1.729 km/s

Aaron

On Tue, Dec 18, 2012 at 12:09 PM, trobolo dinni <
trobolo.trobolo.dinni5 at gmail.com> 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:
>
>              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:
>
>
> 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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