2003ApJ...592..486B

Rossi X-Ray Timing Explorer (RXTE) observations of Sco X-1 during 1997-1999 have been analyzed for spectral characteristics. All the X-ray branches of Sco X-1 were observed during these epochs. On the basis of our observations, we present a simple model for the behavior of Sco X-1 as a function of accretion rate and angle of the observer's line of sight that explains quantitatively the results of VLBA and RXTE observations. Our model presents a unified view of bright low-mass X-ray binaries as an accretion-driven system in which, at the Eddington accretion rate, material overflows the magnetosphere of the neutron star and quenches the jets of Sco X-1. We present supporting evidence of absorption as a function of X-ray branch. The model explains the two distinct color diagrams of observed Z source horizontal branches as variations in the observed line of sight to the accretion disk. The model also applies to the recently discovered Z traces in atoll sources.