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The source X 1822-371 is an eclipsing compact binary system with a periodclose to 5.57 hr and an orbital period derivative $\dot{P}_{\rm orb}$ of1.51(7)$\times 10^{-10}$ s s$^{-1}$. The very large value of $\dot{P}_{\rmorb}$ is compatible with a super-Eddington mass transfer rate from thecompanion star, as suggested by X-ray and optical data. The XMM-Newtonobservation taken in 2017 allows us to update the orbital ephemeris and verifywhether the orbital period derivative has been stable over the last 40 yr. Weadded to the X-ray eclipse arrival times from 1977 to 2008 two new valuesobtained from the RXTE and XMM-Newton observations performed in 2011 and 2017,respectively. We estimated the number of orbital cycles and the delays of oureclipse arrival times spanning 40 yr using as reference time the eclipsearrival time obtained from the Rossi-XTE observation taken in 1996. Fitting thedelays with a quadratic model, we found an orbital period $P_{\rmorb}=5.57062957(20)$ hr and a $\dot{P}_{\rm orb}$ value of $1.475(54) \times10^{-10}$ s s$^{-1}$. The addition of a cubic term to the model does notsignificantly improve the quality of the fit. We also determined a spin-periodvalue of $P_{\rm spin}=0.5915669(4)$ s and its first derivative $\dot{P}_{\rmspin}= -2.595(11) \times 10^{-12}$ s s$^{-1}$. The obtained results confirm thescenario of a super-Eddington mass transfer rate; we also exclude agravitational coupling between the orbit and the change in the oblateness ofthe companion star triggered by the nuclear luminosity of the companion star.

Updated orbital ephemeris of the ADC source X 1822-371: a stable orbital expansion over 40 years