High-frequency oscillations from CIR X-1.

Abstract

The author reports results from an EXOSAT observation of Cir X-1 during which strong, low-frequency (5-20 Hz) quasi-periodic oscillations (QPO) were detected. QPO were also detected at much higher frequencies (100-200 Hz). These high frequencies are consistent with rotation periods in the inner accretion disc region. High-frequency QPO lend weight to the idea that the low-frequency QPO peak is due to a beating between a pulsar and disc rotation frequencies. Coherent pulsations from the neutron star have not been observed.