The lowest neutron star masses currently measured are in the range 1.0 - 1.1 ~ { } M _ { \odot } , but these measurement have either large uncertainties or refer to isolated neutron stars .
The recent claim of a precisely measured mass M / M _ { \odot } = 1.174 \pm 0.004 \citep Martinez:2015mya in a double neutron star system suggests that low-mass neutron stars may be an interesting target for gravitational-wave detectors .
Furthermore , [ \citeauthoryear Sotani , Iida , Oyamatsu & OhnishiSotani et al.2014 ] recently found empirical formulas relating the mass and surface redshift of nonrotating neutron stars to the star ’ s central density and to the parameter \eta \equiv ( K _ { 0 } L ^ { 2 } ) ^ { 1 / 3 } , where K _ { 0 } is the incompressibility of symmetric nuclear matter and L is the slope of the symmetry energy at saturation density .
Motivated by these considerations , we extend the work by [ \citeauthoryear Sotani , Iida , Oyamatsu & OhnishiSotani et al.2014 ] to slowly rotating and tidally deformed neutron stars .
We compute the moment of inertia , quadrupole moment , quadrupole ellipticity , tidal and rotational Love number and apsidal constant of slowly rotating neutron stars by integrating the Hartle-Thorne equations at second order in rotation , and we fit all of these quantities as functions of \eta and of the central density .
These fits may be used to constrain \eta , either via observations of binary pulsars in the electromagnetic spectrum , or via near-future observations of inspiralling compact binaries in the gravitational-wave spectrum .