2006MNRAS.368..781K -
Mon. Not. R. Astron. Soc., 368, 781-795 (2006/May-2)
Simultaneous X-ray/optical observations of GX9+9 (4U1728-16).
KONG A.K.H., CHARLES P.A., HOMER L., KUULKERS E. and O'DONOGHUE D.
Abstract (from CDS):
We report on the results of the first simultaneous X-ray (RXTE) and optical [South African Astronomical Observatory (SAAO)] observations of the luminous low-mass X-ray binary (LMXB) GX9+9 in 1999 August. The high-speed optical photometry revealed an orbital period of 4.1958 h and confirmed previous observations, but with greater precision. No X-ray modulation was found at the orbital period. On shorter time-scales, a possible 1.4-h variability was found in the optical light curves which might be related to the MHz quasi-periodic oscillations seen in other LMXBs. We do not find any significant X-ray/optical correlation in the light curves. In X-rays, the colour-colour and hardness-intensity diagrams indicate that the source shows characteristics of an atoll source in the upper banana state, with a correlation between intensity and spectral hardness. Time-resolved X-ray spectroscopy suggests that two-component spectral models give a reasonable fit to the X-ray emission. Such models consist of a blackbody component which can be interpreted as the emission from an optically thick accretion disc or an optically thick boundary layer, and a hard Comptonized component for an extended corona.
Abstract Copyright:
2006 The Authors. Journal compilation © 2006 RAS
Journal keyword(s):
accretion, accretion discs - binaries: close - stars: individual: GX 9+9 - X-rays: stars
Simbad objects:
15
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