A Vertical Resonance of g-Mode Oscillations in Warped Disks and QPOs in Low-Mass X-Ray Binaries

Resonant oscillations in warped disks are examined in order to explainhigh-frequency QPOs and horizontal-branch QPOs in low-mass X-ray binaries.Different from our previous work, addressed to the same subjects, we relax inthis paper the assumption that the disks are isothermal in the verticaldirection. That is, the pressure, density, and temperature are assumed to bedistributed in the vertical direction with a polytropic relation, and thepolytropic index changes as the disk state changes. By this generalization andby some subsidiaries we can qualitatively explain, within the framework of ourresonance model, observed large frequency variations in neutron-star QPOs andlittle variations in black-hole QPOs. We consider vertical resonances of g-modeoscillations, since they are most appropriate to explain observations.Comment: 11 pages, 3 figures, to be published in PASJ 57, Vol.