X-ray studies of cross-correlation function and its link to radio emission in Sco X-1

The formation and origin of jets in Z sources are not clearly understood though a strong X-ray-radio correlation has been noticed. We analyzed seventeen observations of Sco X-1 observed by RXTE where radio jet emissions were detected. In five observations, we report the detection of asymmetric cross-correlation functions (CCF) with delays of a few tens of seconds between soft and hard energy bands in the horizontal branch associated with a flat-topped noise in the power density spectrum (PDS). Interestingly, these five observations were connected to the ballistic-type radio emission. In the remaining twelve observations, the CCF was highly symmetric exhibiting NBO or NBO+HBO (Normal Branch Oscillations, Horizontal Branch Oscillations) in PDS. During these X-ray observations, the radio observations were found to be associated with ultra-relativistic flow (URF) radio emission. We found that during the lags, the spectral parameters did not vary and marginal variations in flux were noted in a few observations. I will discuss the possible scenario associating the CCF, PDS and radio jet in Sco X-1