SF-magnetic-stars · The impact of superfluidity and superconductivity on the magneto-thermal evolution and X-ray observations of neutron stars.

The impact of superfluidity and superconductivity on the magneto-thermal evolution and X-ray observations of neutron stars.

Neutron stars are astrophysical objects where matter is in very extreme physical conditions, impossible to reproduce in terrestrial laboratories. More than 2000 neutron stars have been so far observed in different electromagnetic bands with quite different characteristics. In the last decades, X-ray astronomy provided a wealth of information about their thermal history and surface magnetic field. In order to interpret these data, we need to understand many aspects of the neutron star physics and, in particular, the influence of the magnetic field on the emission properties. The main purpose of this research project was to study the evolution of the magnetic field in the core of neutron stars by including the relevant mechanisms and microphysical conditions of a realistic system. The magnetic field evolution in the core is still not well understood, in particular after neutrons and protons, undergo a transition to a superfluid and superconducting state, respectively. Such a transition is predicted by nuclear theory and is expected when the star temperature drops below a giga-Kelvin. One of the most controversial mechanisms driving the evolution of magnetic fields in the core is ambipolar diffusion, suggested to be very efficient in magnetars, which are neutron stars with a magnetic field larger than ten giga-Tesla. Strongly magnetized neutron stars also show a very rich X-ray activity which include outbursts and flares. In the tail of two giant flares (SGR 1806-20 and SGR 1900+14), which are rare and very powerful events, the power spectra revealed a series of quasi-periodic oscillations (QPOs). The detection of QPOs was very important, because has opened the possibility to use Asteroseismology to study the physics of neutron stars, i.e. to infer the properties of the system by studying its seismic wave propagation. This very powerful and well-established technique has been successfully used to study the interior of the Sun and other variable stars. With this research project we have studied the seismic vibrations of magnetars by introducing important physical ingredients in the stellar model. To exploit the potentiality of Astereoseismology, we need in fact sophisticated theoretical models and accurate templates to compare with observations. The objectives of this research project were to provide a more detailed description of the neutron star dynamics in order to have better theoretical models for the analysis of X-ray observations. The project mainly focused on the study of the magnetic field evolution in the core of neutron stars, and on the seismology of magnetars. The combined information available from thermal history and magnetar QPOs can in fact be potentially used to determine the physical properties of highly magnetized neutron stars as well as to constrain the equation of state of dense matter.

Текст от CORDIS, на английски · Данни: CORDIS, © Европейски съюз