A Study of the Long-Term Evolution of Quasi-Periodic Oscillations in the Accretion-Powered X-Ray Pulsar 4U 1626–67

摘要: We report here a study of the long-term properties quasiperiodic oscillations (QPOs) in an unusual accreting X-ray pulsar, 4U 1626–67. This is unique accretion-powered pulsar which we have found QPOs to be present during all sufficiently long observations with wide range observatories. In spin-down era this source, QPO central frequency decreasing. earlier spin-up there are only two reports detections, 1983 EXOSAT and 1988 Ginga increasing trend. The evolution 1626–67 last 22 years changed from positive negative trend, somewhat coincident torque reversal source. pulsars, directly related inner radius accretion disk, as per Keplerian model (KFM) beat mdel (BFM). A gradual depletion disk reported spectral, flux, pulse profile measurements. shows that flux mass rate may not change by same factor; hence simple KFM BFM able explain show persistent also first history for timescale relating it disk.