  Based on the periastron precession model to account for kHz QPO of the binary
X-ray neutron star, proposed by Stella and Vietri, we ascribe the 15-60 Hz
Quasi Periodic Oscillation (QPO) to the periastron precession frequency of the
orbiting accreted matter at the boundary of magnetosphere-disk of X-ray neutron
star (NS). The obtained conclusions include: all QPO frequencies increase with
increasing the accretion rate. The theoretical relations between 15-60 Hz QPO
(HBO) frequency and the twin kHz QPOs are similar to the measured empirical
formula. Further, the better fitted NS mass by the proposed model is about 1.9
solar masses for the detected LMXBs.
