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Relativistic Astrophysics group: Research


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Magneto-thermal evolution and thermal radiation of neutron stars.



The thermal emission from isolated neutron stars is not well understood. The X-ray spectrum is very close to a blackbody but there is a systematic optical excess flux with   respect to the extrapolation to low energy of the   best blackbody fit. This fact, in combination with the observed pulsations in the X-ray flux, can be explained by anisotropies     in the surface temperature distribution. To explain the origin of this anis  otropy w  i study the thermal emission from neutron star s with strong crust magnetic fields, which   causes a senar-spherically symmetric temperature distribution. On the other hand,  the strong temperature dependence of the magnetic diffusivity and thermal conductivity, together with the heat generated by magnetic dissipation, couple the magnetic and thermal evolution of NSs, that cannot be formulated as separated one--dimensional problems.  We   are interested in the mutual influence of thermal and magnetic evolution in a neutron star's crust, and its observational effects.


Relativistic Magneto-Hydrodynamics Simulations.


We are engaged in numerical simulations of different astrophysical scenarios involving MHD processes (core collapse Supernovae, gravitational collapse of neutron stars). The possibility of metastable PNS (those that become unstable to collapse during the early evolution) has been suggested in the context of SN 1987A, for which no neutron star remnant has been observed. We are also interested in the study of the deleptonization driven collapse of metastable PNS. Modelling will be done with a general relativistic hydrodynamics code, including neutrino transport.  

  


Astrophysical Sources of Gravitational Waves.

  

According to General Relativity, the emission of gravitational waves is associated to a variety of  physical processes that range from astrophysical phenomena - such as the evolution and coalescence of binary systems, gravitational collapse, stellar oscillations and instabilities - to  cosmological processes that developed in the very early universe. Signals produced in these processes have different intensities, shapes and characteristic frequencies; some of them are emitted in short bursts, some are continuous, some superimpose to form stochastic backgrounds with spectral properties that depend on the generating phenomenon. The Rome group is concerned primarily with the study of the characteristic features of gravitational signals emitted by astrophysical sources, and of the spectral properties of stochastic backgrounds they generate. 

  


The Composition, Structure and Evolution of Newly Born Neutron Stars.

 
At birth, a neutron star has a large number of trapped neutrinos which will diffuse out of the star in about 10-15 seconds. As they leave, the composition and structure of the star changes. If exotic matter like quarks, a kaon or pion condensate, or hyperons ever exists in a neutron star, it probably appears only after most of the trapped neutrinos are gone. The appearance of this exotic component always softens the equation of state, and the possibility exists that the star collapses to a black hole at this time. This could explain why no neutron star has yet been seen in the remnant of SN 1987A, even though one certainly existed when the neutrinos detected on Feb 27, 1987 were observed.

  

Department of Applied Physics


Facultad de Ciencias, Fase II - Planta 2ª
Universidad de Alicante
Carretera de San Vicente del Raspeig s/n
03690 San Vicente del Raspeig
Alicante (Spain)

Tel: (+34) 96 590 3540

Fax: (+34) 96 590 9726

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Carretera San Vicente del Raspeig s/n - 03690 San Vicente del Raspeig - Alicante - Tel. 96 590 3400 - Fax 96 590 3464