Speaker
Description
Following the previous research on epicyclic oscillations of accretion disks around black holes (BHs) and neutron stars (NSs), a new model of high-frequency quasi-periodic oscillations (QPOs) considering radial precession of accretion flow, has been proposed (CT model). Within the model the configuration of accreted fluid is approximated by marginally overflowing accretion tori predicted by general relativity (tori terminated by cusps).} According to preliminary investigations based on Kerr spacetimes, the model provides overall better fits of the NS QPO data compared to the relativistic precession (RP) model often considered in the context of NS and BH parameters estimations. It also implies a significantly higher upper limit on the Galactic microquasars BH spin. A short analytic formula has been noticed to well reproduce the model's predictions on the QPO frequencies in Schwarzschild spacetimes. We derive an extended version of this formula that applies to rotating compact objects and include effects given by NS oblateness. For a particular choice of a single parameter, our relation with high accuracy provides frequencies predicted by the CT model. For another value, it provides frequencies predicted by the RP model. Considering this relation along with the data of several atoll sources we find that the CT model is compatible with realistic values of the NS mass and provides better fits of data than the RP model.
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