We present striking results from Rossi X-Ray Timing Explorer (RXTE) observa
tions of the 21 hr low-mass X-ray binary 4U 1624-49, showing five complex d
ips 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 similar to8 keV. Spectra selected by intensity during dip ep
isodes can be well fitted with a two-component model consisting of a pointl
ike blackbody from the neutron star and progressive covering of an extended
Comptonized region, presumably an accretion disk corona (ADC), corrected f
or 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 t
hat the envelope of material absorbing the ADC has smaller angular size tha
n the ADC itself and that the ADC is likely limited to a height-to-radius r
atio of 10% rather than being spherical in extent. In addition, we have ana
lyzed similar to4.5 yr of RXTE All-Sky Monitor (ASM) coverage to derive the
first accurate orbital ephemeris for 4U 1624-49, with phase zero (the time
of dip centers) well described by the relation 2,450,088.63918(69) + N + 0
. 869907(12) (JD).