X-ray observation of SS 433 with RXTE

Apart from regular monitoring with the All Sky Monitor, the compact object SS 433 was observed with RXTE several times over the last 2 or 3 yr. We present the first analysis of these observations. We also include the results of the recent exciting Target of Opportunity campaign made during donor inferior ( orbital phase phi = 0) and superior (phi = 0.5) conjunctions which took place on 2003 October 2 and 2004 March 13, respectively, when the jet was directly pointing towards us (i.e. precessional phase psi similar to 0). Generally, we found that two distinct lines fit the spectra taken on these days. We present some of the light curves and the X-ray spectra, and show that the Doppler shifts of the emitted lines roughly match those predicted by the kinematic model for the jets. We find that the line with a higher energy can be best identified with a Fe XXVI Lyman-alpha transition while the line with lower energy can be identified with a Fe XXV (1s2p-1s(2)) transition. We observe that the X-ray flux on 2004 March 13 ( when the base of the jet was exposed) is more than twice that on 2003 October 2 ( when the base is covered by the companion). We find that the flux continues to remain high at least until another orbital period. We believe that this is because SS 433 was undergoing a weak flaring activity during the recent observation.