  A nonlinear nature of the binary ephemeris of Cygnus X-3 indicates either a
change in the orbital period or an apsidal motion of the orbit. We have made
extended observations of Cygnus X-3 with the Pointed Proportional Counters
(PPCs) of the Indian X-ray Astronomy Experiment (IXAE) during 1999 July 3-13
and October 11-14. Using the data from these observations and the archival data
from ROSAT, ASCA, BeppoSAX and RXTE, we have extended the data base for this
source. Adding these new arrival time measurements to the published results, we
make a comparison between the various possibilities, (a) orbital decay due to
mass loss from the system, (b) mass transfer between the stars, and (c) apsidal
motion of the orbit due to gravitational interaction between the two
components. Orbital decay due to mass loss from the companion star seems to be
the most probable scenario.
