We present striking results from Rossi X-ray Timing Explorer ( RXTE ) observations of the 21-hr low mass X-ray binary X1624 - 490 , showing five complex dips in unprecedented detail .
For the first time , dipping is detected up to 15 keV .
Prominent flares are also observed in the light curves , limited to energies above \sim 8 keV .
Spectra selected by intensity during dip episodes can be well fit with a two-component model consisting of a point-like blackbody from the neutron star and progressive covering of an extended Comptonized region , presumably an accretion disk corona ( ADC ) , corrected for photons scattered into and out of the X-ray beam by a interstellar dust halo .
We find that the outer regions of the absorber are highly ionized and that electron scattering is totally responsible for the X-ray attenuation during shallow dipping .
The timescales of dip ingress and egress indicate that the envelope of material absorbing the ADC has smaller angular size than the ADC itself , and that the ADC is likely limited to a height-to-radius ratio of 10 % , rather than being spherical in extent .
In addition , we have analyzed \sim 4.5 yrs of RXTE All Sky Monitor ( ASM ) coverage to derive the first accurate orbital ephemeris for X1624 - 490 , with phase zero ( the time of dip centers ) well-described by the relation 245 0088.63918 ( 69 ) + N \times 0.869907 ( 12 ) ( JD ) .