Recently, general relations among the quadrupole moment (Q), the moment of inertia (I) and the tidal deformability (Love number) of a neutron star were shown to exist. They are nearly independent of the nuclear matter equation of state and would be of great aid in extracting parameters from observed gravitational waves and in testing general relativity. These relations, however, do not account for strong magnetic fields. We consider this problem by studying the effect of a strong magnetic field on slowly rotating relativistic neutron stars and show that, for simple magnetic field configurations that are purely poloidal or purely toroidal, the relation between Q and I is again nearly universal. However, different magnetic field geometries lead to different I-Q relations, and, in the case of a more realistic twisted-torus magnetic field configuration, the relation depends significantly on the equation of state, losing its universality. I-Love-Q relations must thus be used with very great care, since universality is lost for stars with long spin periods, i.e. P greater than or similar to 10 s, and strong magnetic fields, i.e. B greater than or similar to 10(12) G.
On the universality of I-Love-Q relations in magnetized neutron stars / Haskell, B.; Ciolfi, R.; Pannarale, F.; Rezzolla, L.. - In: MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY. LETTERS. - ISSN 1745-3925. - 438:1(2014), pp. L71-L75. [10.1093/mnrasl/slt161]
On the universality of I-Love-Q relations in magnetized neutron stars
Ciolfi R.;Pannarale F.;
2014
Abstract
Recently, general relations among the quadrupole moment (Q), the moment of inertia (I) and the tidal deformability (Love number) of a neutron star were shown to exist. They are nearly independent of the nuclear matter equation of state and would be of great aid in extracting parameters from observed gravitational waves and in testing general relativity. These relations, however, do not account for strong magnetic fields. We consider this problem by studying the effect of a strong magnetic field on slowly rotating relativistic neutron stars and show that, for simple magnetic field configurations that are purely poloidal or purely toroidal, the relation between Q and I is again nearly universal. However, different magnetic field geometries lead to different I-Q relations, and, in the case of a more realistic twisted-torus magnetic field configuration, the relation depends significantly on the equation of state, losing its universality. I-Love-Q relations must thus be used with very great care, since universality is lost for stars with long spin periods, i.e. P greater than or similar to 10 s, and strong magnetic fields, i.e. B greater than or similar to 10(12) G.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
