Study of the Cir X--1 Broad Band Spectrum at Orbital Phases Close to the Apoastron

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 broad band spectrum: a blackbody component, at a temperature of $\sim 0.6$ keV, a Comptonized component, with a seed-photon temperature of $\sim 1.2$ keV, electron temperature of $\sim 6$ keV and optical depth of $\sim 1.7$, 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 (Iaria et al. 2001a) because of the presence of the blackbody component. We discuss the implications of this difference and the presence of the power-law component.

15 pages, 6 figures, accepted by ApJ

References in corpus (2)

• Detection of a Hard Tail in the X-ray Spectrum of the Z Source GX 349+2
• Spectral Evolution of Circinus X-1 Along its Orbit

Cited by in corpus (13)

• On the Soft Excess in the X-ray Spectrum of Cir X-1: Revisitation of the Distance to Cir X-1
• On the nature of the first transient Z-source XTE J1701-462: its accretion disk structure, neutron star magnetic field strength, and hard tail
• Disc-Jet coupling in the LMXB 4U1636-53 from INTEGRAL
• X-Ray Polarized View on the Accretion Geometry in the X-Ray Binary Circinus X-1
• A re-analysis of the NuSTAR and XMM-Newton broad-band spectrum of Ser~X-1
• The hard X-ray tails in neutron star low mass X-ray binaries: BeppoSAX observations and possible theoretical explanation of the GX 17+2 case
• A complete X-ray spectral coverage of the 2010 May-June outbursts of Circinus X-1
• Evolution of Hard X-Ray Spectra Along the Branches in Cir X-1
• X-ray spectral variations of Circinus X-1 observed with NICER throughout an entire orbital cycle
• High Resolution and Broad Band Spectra of Low Mass X-ray Binaries: A Comparison between Black Holes and Neutron Stars
• The hard X-ray emission along the "Z" track in GX 17+2
• Insight-HXMT Detections of Hard X-ray Tails in Scorpius X-1
• Long Term Studies of Z sources with HEXTE/RXTE