Paper detail

X-ray Spectral Evolution of Her X-1 in a Low State and the Following Short High State

We analyzed spectral variations of $\sim 8.5$ days long RXTE monitoring observations of Her X-1 in December 2001. This set of observations enables, for the first time, frequent continuous monitoring (111 pointings in $\sim 8.5$ days) of the source with RXTE including $\sim 1.7$ days long low state part and the following $\sim 6.8$ days long short high state part. We used absorbed power law model with iron line energy complex modeled as a Gaussian to fit both the 3-60 keV PCA-HEXTE overall short high state spectrum and 3-20 keV individual PCA spectra. Additional partial cold absorber model was used for both cases. Using 3-20 keV individual PCA spectra, absorption in anomalous dips and preeclipse dips in short high state were compared. Decreasing ratio of unabsorbed flux to absorbed flux with increasing unabsorbed flux in anomalous and preeclipse dips was interpreted as an evidence of the fact that the regions causing opaque obscuration and soft absorption are not geometrically far away from each other. Higher iron line peak energies in low state and short high state ($\sim 6.6-6.9$ keV) were interpreted as a clue of the presence of iron line components other than K$α$ emission line.