riassunto2

Speaker	Torok, Gabriel
Co-autors	*Pavel Bakala, Eva Sramkova, Zdenek Stuchlik, Martin Urbanec, Petr Cech*
Talk Title	Neutron star mass and angular-momentum based on twin peak QPO models
Abstract	Comparing two very different neutron star (NS) candidates 4U 1636-53 and Circinus X-1 we make an analysis of the compact object properties based on models of kHz QPOs. We take into account five kinematic and disc-seismology QPO models. Our analysis involves consideration of the frame-dragging effects associated with rotating spacetimes providing thus constrainst on both NS mass M and angular momentum j. We show that the data could be described for a certain M-j relation which is specific for each of the considered models. There are in principle testable differences. For instance the relativistic precession model predicts the mass which is about twice of those predicted by the model assuming a resonance between radial and vertical epicyclic frequency. We also include calculations with NS equations of state.
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