Analysis of RXTE-PCA Observations of SMC X-1

We present timing and spectral analysis of Rossi X-ray Timing Explorer-Proportional Counter Array observations of SMC X-1 between 1996 January and 2003 December. From observations around 1996 August 30 with a time-span of ∼6 d, we obtain a precise timing solution for the source and resolve the eccentricity as 0.00089(6). We find an orbital decay rate of ˙Porb/Porb = −3.402(7) × 10−6 yr−1 which is close to the previous results. Using our timing analysis and the previous studies, we construct a ∼30 yr long pulse period history of the source. We show that frequency derivative shows long- (i.e. more than a few years) and short-term (i.e. order of days) fluctuations. From the spectral analysis, we found that all spectral parameters except Hydrogen column density showed no significant variation with time and X-ray flux. Hydrogen column density is found to be higher as X-ray flux gets lower. This may be due to the increase in soft absorption when the pulsar is partially obscured as in Her X-1 or may just be an artefact of the tail of a soft excess in energy spectrum