Gravitational wave signatures of highly magnetized neutron stars

Abstract

Motivated by the recent gravitational wave detection by the LIGO–VIRGO observatories, we study the Love number and dimensionless tidal polarizability of highly magnetized stars. We also investigate the fundamental quasi-normal mode of neutron stars subject to high magnetic fields. To perform our calculations we use the chaotic field approximation and consider both nucleonic and hyperonic stars. As far as the fundamental mode is concerned, we conclude that the role played by the constitution of the stars is far more relevant than the intensity of the magnetic field, and if massive stars are considered, the ones constituted by nucleons only present frequencies somewhat lower than the ones with hyperonic cores. This feature that can be used to point out the real internal structure of neutron stars. Moreover, our studies clearly indicate that strong magnetic fields play a crucial role in the deformability of low mass neutron stars, with possible consequences on the interpretation of the detected gravitational waves signatures.

A Neutron Star Is Born

“…As different neutron star EOS and related composition have different responses to the tidal field, the tidal polarizability can be used to discriminate between different equations of state. A complete overview on the theory of Love numbers in both Newtonian and General Relativity theories can be found in [81]. Here, I show next only the main equations for the understanding of the constraints on NS.…”

“…From the theoretical point of view, there is no reason to believe that the structure of the magnetars differs from the ones I have mentioned in this article. Thus, they can also be described as hadronic objects [81,[154][155][156][157][158], as quark stars [138,139,[157][158][159][160] or as hybrid stars [155,157].…”

“…In this case, the perturbations on the metric can couple to the fluid through the field equations [164,165]. For a comprehensive discussion of the equations involved, please refer to [81]. The gravitational wave frequency of the fundamental mode is expected to be detected in the near future by detectors such as the Einstein Telescope.…”

“…The gravitational wave frequency of the fundamental mode is expected to be detected in the near future by detectors such as the Einstein Telescope. In [81], the effect of strong magnetic fields on the fundamental mode was investigated. From the results presented in that paper, one can clearly see that magnetars with masses below 1.8 M present practically the same frequencies.…”

Hypermassive quark cores

“…Therefore, it is out of the scope of the present work. We refer the interested reader to [18,[46][47][48] and to the references therein. We plot the tidal dimensionless parameter for three different values of G V , as well as for the pure hadronic model with hyperons (QHD) in Fig.…”