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High frequency (millisecond) quasi-periodic oscillations (HF QPOs) areobserved in the X-ray power-density spectra of several microquasars and lowmass X-ray binaries. Two distinct QPO peaks, so-called twin peak QPOs, areoften detected simultaneously exhibiting their frequency ratio close or equalto 3/2. Following the analytic theory and previous studies of observablespectral signatures, we aim to model the twin peak QPOs as a spectral imprintof specific dual oscillation regime defined by a combination of the lowestradial and vertical oscillation mode of optically thick slender tori withconstant specific angular momentum. We examined power spectra and fluorescentK$\alpha$ iron line profiles for two different simulation setups with the modefrequency relations corresponding to the epicyclic resonance HF QPOs model andmodified relativistic precession QPOs model. We use relativistic ray-tracingimplemented in parallel simulation code LSDplus. In the background of the Kerrspacetime geometry, we analyze the influence of the distant observerinclination and the spin of the central compact object. Relativistic opticalprojection of the oscillating slender torus is illustrated by images in falsecolours related to the frequency shift. We show that performed simulationsyield power spectra with the pair of dominant peaks corresponding to thefrequencies of radial and vertical oscillation modes with the proper ratioequal to 3/2 on a wide range of inclinations and spin values. We also discussexceptional cases of a very small and very high inclination as well as unstablehigh spin relativistic precession-like configuration predicting constantfrequency ratio equal to 1/2. We demonstrate signifiant dependency of broadenedK$\alpha$ iron line profiles on the inclination of the distant observer.

Twin peak HF QPOs as a spectral imprint of dual oscillation modes of accretion tori