Item

Abstract

We provide accurate universal relations that allow to estimate the moment of
inertia $I$ and the ratio of kinetic to gravitational binding energy $T/W$ of
uniformly rotating neutron stars from the knowledge of mass, radius, and moment
of inertia of an associated non-rotating neutron star. Based on these, several
other fluid quantities can be estimated as well. Astrophysical neutron stars
rotate to varying degrees and although rotational effects may be neglected in
some cases, not modeling them will inevitably introduce bias when performing
parameter estimation. This is especially important for future, high-precision
measurements coming from electromagnetic and gravitational wave observations.
The proposed universal relations facilitate computationally cheap EOS inference
codes that permit the inclusion of observations of rotating neutron stars. To
demonstrate this, we deploy them into a recent Bayesian framework for equation
of state parameter estimation that is now valid for arbitrary, uniform
rotation. Our inference results are robust up to around percent level precision
for the generated neutron star observations, consisting of the mass, equatorial
radius, rotation rate, as well as co- and counter-rotating $f$-mode
frequencies, that enter the framework as data.