Comprehensive Timing and X-ray Spectral Analysis of GX 1+4

M. M. Serim, S. Sahiner, D. Cerri-Serim, S. C. Inam, A. Baykal

Published 2017-01-16Version 1

We present analysis of RXTE--PCA observations of GX 1+4 between March 3, 2001 and January 31, 2003. We also look for episodic correlations and anti-correlations between torque and X-ray luminosity using CGRO--BATSE X-ray flux and frequency derivative time series between 1991 and 1999. From the timing analysis of RXTE-PCA observations, we are able to phase connect pulse arrival times of the source within two different time intervals and obtain corresponding timing solutions. Using these pulse arrival times, we contribute to long term pulse frequency history of the source. Using CGRO--BATSE time series, we find that correlation state of GX 1+4 seems to change on $\sim$ 100-200 days long intervals. We estimate torque noise of the source and observe flickering noise ($f^{-1}$). We achieve to measure the longest observed timescale for a noise process among accretion powered X-ray pulsars by extending the noise estimate for a time scale ranging from 31 days to 44 years. Spectral analysis of individual RXTE-PCA observations indicates a significant correlation between iron line flux and unabsorbed X-ray flux. Combining RXTE--PCA observations, we obtain four overall X-ray spectra. For these spectra, two different models are used for fitting: An absorbed power law with a high energy cut-off and an absorbed model based on Comptonization of soft photons in hot plasma. It is found that both models are equally successful to describe these four energy spectra. Pulse phase resolved spectra of the source are successfully modeled using both models.