Accretion Disks in Magnetized Kerr's Spacetimes

IGNACIO FRANCISCO RANEA SANDOVAL; GARCÍA FEDERICO

Buenos Aires

Congreso; Gravitation, Astrophysics, and Cosmology II Argentinian-Brazilian Meeting; 2014

Observations of X-ray binary systems provide strong evidences of the existence of compact objects too massive for theoretical models of neutron stars to explain. When this systems are in the thermal (high/soft) state their emission spectra in the $0.1-5}$~keV range can be explained by means of the thermal radiation emitted by an accretion disk formed around super-compact objects. In this work we present some of the results obtained from numerically calculated observed thermal energy spectra of thin accretion disk formed on a Kerr spacetime of arbitrary value of its rotational parameter, $a$, that is, our model includes not only black holes but also naked singularities as the central compact object. Our numerical code includes ray tracking from the source to the observer taking into account relativistic effects such us light bending, relativistic Doppler effect and gravitational redshift. Moreover, we analyze the effects on this observed energy spectra of the presence of external magnetic fields. We study in detail two different magnetic field configurations: a) the uniform and b) a dioplar one. We show that observational data from X-ray binary systems discard models of accretion disks formed around naked singularities (that are described by a Kerr metric when $a>1$). This results can be used to reinforce the paradigm of black hole formation as the result of the astrophysical collapse of a high mass star, in accordance to Penrose´s weak cosmic censorship conjecture.