THE QUASI-PERIODIC OSCILLATIONS AND VERY-LOW FREQUENCY NOISE OF SCORPIUS X-1 AS TRANSIENT CHAOS - A DRIPPING HANDRAIL

We present evidence that the quasi-periodic oscillations (QPO) and ver y low frequency noise (VLFN) characteristic of many accretion sources are different aspects of the same physical process. We analyzed a long , high time resolution EXOSAT observation of the low-mass X-ray binary (LMXB) Sco X-1. The X-ray luminosity varies stochastically on time sc ales from milliseconds to hours. The nature of this variability-as qua ntified with both power spectrum analysis and a new wavelet technique, the scalegram-agrees well with the dripping handrail accretion model, a simple dynamical system which exhibits transient chaos. In this mod el both the QPO and VLFN are produced by radiation from blobs with a w ide size distribution, resulting from accretion and subsequent diffusi on of hot gas, the density of which is limited by an unspecified insta bility to lie below a threshold.