Hello Chia-Hui, I am very sorry for the late response.
There are (at least) two notions of mass that are relevant for neutron
stars
1. the baryon mass which is the integral \int \sqrt{\gamma} \rho W d^3x
2. the ADM mass (or a similar object) which is the mass measured by an
observer far away
the former can be computed as the integral of the "dens" variable of
GRHydro for example by requesting "sum" scalar output for it:
CarpetIOScalar::outScalar_vars = "GRHydro::dens"
CarpetIOScalar::outScalar_every = 1
and then multiplying the numbers in there by the volume of a cell on
the coarsest grid (ie the product of the values of CoordBase::dx,
CoordBase::dy, and CoordBase::dz in the parameter file).
The later can be computed using the QuasiLocalMeasures thorn on a
spherical surface or using the ADMMass thorn
(https://www.einsteintoolkit.org/thornguide/EinsteinAnalysis/ADMMass/documentation.html
see the example parfile here:
https://bitbucket.org/einsteintoolkit/einsteinanalysis/raw/39b8ae09c3b55d842e19ed5e89a716d3534883d0/ADMMass/test/tov_carpet.par).
Yours,
Roland
> Dear whom it may concern,
>
> I simulated the binary neutron star merger as in gallery
> code(https://einsteintoolkit.org/gallery/bns/index.html). I tried to find out
> the mass of the merged neutron star. For test, I calculated the initial mass
> of each neutron star from the file rho.xy.h5 which is the rest mass density.
> What I computed is about 0.9 solar mass , however it supposed to be much
> larger because the baryonic mass of the initial data of each neutron star is
> about 1.45 solar mass. I also calculated magnetic energy which corresponds to
> about 1e-6 solar mass which is not a possible reason of the discrepancy. I
> also considered velocity which may increase mass due to the relativity but
> the maximum of the initial velocity is only about 0.1c which also does not
> raise the mass too much. What is the possible reason that the total rest mass
> is so much smaller than the baryonic mass ?
>
> Thank you.
>
>
> Best regards,
>
> Chia-Hui
--
My email is as private as my paper mail. I therefore support encrypting
and signing email messages. Get my PGP key from http://pgp.mit.edu .
pgpEZwXNSN6S4.pgp
Description: OpenPGP digital signature
_______________________________________________ Users mailing list [email protected] http://lists.einsteintoolkit.org/mailman/listinfo/users
