[Users] Determination of the final spin of the remnant of a binary neutron star merger

Erik Schnetter schnetter at gmail.com
Thu Mar 5 09:42:54 CST 2020


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.


On Wed, Mar 4, 2020 at 11:22 AM Beyhan Karakaş <beyhannkarakas at gmail.com> 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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Erik Schnetter <schnetter at gmail.com>

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