Study of the Circinus X‐1 Broadband Spectrum at Orbital Phases Close to the Apoastron

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Abstract
We report on the results of a BeppoSAX (1.8-200 keV) observation of the peculiar X-ray binary source Circinus X-1 (Cir X-1) at the orbital phases between 0.61 and 0.63. We find that three components are needed to fit the broadband spectrum: a blackbody component at a temperature of ~0.6 keV; a Comptonized component with a seed-photon temperature of ~1.2 keV, electron temperature of ~6 keV, and optical depth of ~1.7; and a power-law component dominating the spectrum at energies higher than 20 keV. We interpret the blackbody as the emission from the accretion disk, while the Comptonized component probably comes from a corona surrounding the inner part of the system. This spectrum is different from that observed at the periastron (in our previous work) because of the presence of the blackbody component. We discuss the implications of this difference and the presence of the power-law component.
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