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We report our measurements for orbital and spin parameters of X 1822-371using its X-ray partial eclipsing profile and pulsar timing from data collectedby the Rossi X-ray Timing Explorer (RXTE). Four more X-ray eclipse timesobtained by the RXTE 2011 observations were combined with historical records totrace evolution of orbital period. We found that a cubic ephemeris likelybetter describes evolution of the X-ray eclipse times during a time span ofabout 34 years with a marginal second order derivative of$\ddot{P}_{orb}=(-1.05 \pm 0.59) \times 10^{-19}$ s$^{-1}$. Using the pulsearrival time delay technique, the orbital and spin parameters were obtainedfrom RXTE observations from 1998 to 2011. The detected pulse periods show thatthe neutron star in X 1822-371 is continuously spun-up with a rate of$\dot{P}_{s}=(-2.6288 \pm 0.0095) \times 10^{-12}$ s s$^{-1}$. Evolution of theepoch of the mean longitude $l=\pi /2$ (i.e. $T_{\pi / 2}$) gives an orbitalperiod derivative value consistent with that obtained from the quadraticephemeris evaluated by the X-ray eclipse but the detected $T_{\pi / 2}$ valuesare significantly and systematically earlier than the corresponding expectedX-ray eclipse times by $90 \pm 11$ s. This deviation is probably caused byasymmetric X-ray emissions. We also attempted to constrain the mass and radiusof the neutron star using the spin period change rate and concluded that theintrinsic luminosity of X 1822-371 is likely more than $10^{38}$ ergs s$^{-1}$.

Orbital and Spin Parameter Variations of Partial Eclipsing Low Mass X-ray Binary X 1822-371