Exploring the spreading layer of GX 9+9 using RXTE and INTEGRAL

Abstract

We have fitted ~200 RXTE and INTEGRAL spectra of the neutron star LMXB GX 9+9 from 2002-2007 with a model consisting of a disc blackbody and another blackbody representing the spreading layer (SL), i.e. an extended accretion zone on the NS surface as opposed to the more traditional disc-like boundary layer. Contrary to theory, the SL temperature was seen to increase towards low SL luminosities, while the approximate angular extent had a nearly linear luminosity dependency. Comptonization was not required to adequately fit these spectra. Together with the ~70 degree upper bound of inclination implied by the lack of eclipses, the best-fitting normalization of the accretion disc blackbody component implies a distance of ~10 kpc, instead of the usually quoted 5 kpc.

14 pages, 10 figures, accepted for publication in MNRAS

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Cited by in corpus (10)

• Black hole-like hysteresis and accretion states in neutron star low mass X-ray binaries
• Spread of Matter over a Neutron-Star Surface During Disk Accretion: Deceleration of Rapid Rotation
• A new radio census of neutron star X-ray binaries
• X-ray polarimetry and spectroscopy of the neutron star low-mass X-ray binary GX 9+9: an in-depth study with IXPE and NuSTAR
• The Galactic LMXB Population and the Galactic Centre Region
• Spectro-polarimetric view of bright atoll source GX 9+9 using IXPE and AstroSat
• On the Origin of Highly Ionized X-ray Absorbers Detected in the Galactic X-ray Binaries
• Suzaku Observation of the High-Inclination Binary EXO 0748-676 in the Hard State
• Reflection component in the Bright Atoll Source GX 9+9
• XMM-Newton Survey of Local OVII Absorption Lines in the Spectra of Galactic X-ray Sources