Hello all, for a (somewhat recent, likely not the first nor the latest) study of how well this particular way of measuring spin of a neutron star works, you may want to consult sections III.C (in particular figure 9) of https://arxiv.org/abs/1508.06986 which deals with both initial data construction and evolution (though not in the context of the Einstein Toolkit). The method used is the one Erik suggested.
Yours,
Roland
> Beyhan
>
> The QuasiLocalMeasures thorn can examine not only horizons, but also
> other 2-surfaces. You can set up a surface that is large and which
> encloses both the remnant and surrounding matter, but which is still
> inside the emitted gravitational wave train. QuasiLocalMeasures can
> then calculate the angular momentum contained inside that sphere.
>
> As Zach mentioned, the details of setting up a parameter file to do so
> are difficult to explain over email. The example parameter file
> "Cactus/par/qc0-mclachlan.par" contains such a setup; surface #3
> ("horizon" #4, although this surface is of course not a horizon) is a
> sphere with areal radius R=50 where such quantities are calculated.
>
> -erik
>
> On Wed, Mar 4, 2020 at 11:22 AM Beyhan Karakaş <[email protected]>
> wrote:
> >
> > Dear to whom it may concern,
> >
> > I am interested in determining the spin of the remnant which are resulted
> > from binary neutron star (initially are in irrotational configuration)
> > merger . How could the method to determine the final spin differ (if it
> > does) in case of remnant is a black hole or a neutron star. For the former
> > case, I suppose QuasiLocalMeasures parameter "begin_qlm_calculations_after"
> > along with AHFinderDirect parameter "find_after_individual" should be set
> > to the time/iteration that the black hole formed. If this is not the case,
> > please clarify how could it be determined? In addition, is there a way to
> > find the evolution of the spin and orbital eccentricity of the binary?
> >
> > Best regards,
> >
> > Beyhan.
> > _______________________________________________
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>
>
>
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