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The source X 1822-371 is an eclipsing compact binary system with a period close to 5.57 hr and an orbital period derivative $dot{P}_{rm orb}$ of 1.51(7)$times 10^{-10}$ s s$^{-1}$. The very large value of $dot{P}_{rm orb}$ is compatible with a super-Eddington mass transfer rate from the companion star, as suggested by X-ray and optical data. The XMM-Newton observation taken in 2017 allows us to update the orbital ephemeris and verify whether the orbital period derivative has been stable over the last 40 yr. We added to the X-ray eclipse arrival times from 1977 to 2008 two new values obtained from the RXTE and XMM-Newton observations performed in 2011 and 2017, respectively. We estimated the number of orbital cycles and the delays of our eclipse arrival times spanning 40 yr using as reference time the eclipse arrival time obtained from the Rossi-XTE observation taken in 1996. Fitting the delays with a quadratic model, we found an orbital period $P_{rm orb}=5.57062957(20)$ hr and a $dot{P}_{rm orb}$ value of $1.475(54) times 10^{-10}$ s s$^{-1}$. The addition of a cubic term to the model does not significantly improve the quality of the fit. We also determined a spin-period value of $P_{rm spin}=0.5915669(4)$ s and its first derivative $dot{P}_{rm spin}= -2.595(11) times 10^{-12}$ s s$^{-1}$. The obtained results confirm the scenario of a super-Eddington mass transfer rate; we also exclude a gravitational coupling between the orbit and the change in the oblateness of the companion star triggered by the nuclear luminosity of the companion star.
We report our measurements for orbital and spin parameters of X 1822-371 using its X-ray partial eclipsing profile and pulsar timing from data collected by the Rossi X-ray Timing Explorer (RXTE). Four more X-ray eclipse times obtained by the RXTE 201
The low mass X-ray binary 2A 1822-371 is an eclipsing system with an accretion disc corona and with an orbital period of 5.57 hr. The primary is an 0.59 s X-ray pulsar with a proposed strong magnetic field of 10^10-10^12 G. In this paper we study the
We have performed a comprehensive spectral and timing analysis of the first NuSTAR observation of the high-mass X-ray binary 4U 1538-522. The observation covers the X-ray eclipse of the source, plus the eclipse ingress and egress. We use the new meas
WASP-128 is a relatively bright (V= 12.37) G0-dwarf, known to host a transiting brown dwarf in a short-period orbit (Hodv{z}ic et al. 2018 arXiv:1807.07557 (H18)). Very few such objects are known, which makes WASP-128 a prime target for further obser
The X-ray source 4U 1822-371 is an eclipsing low-mass X-ray binary and X-ray pulsar, hosting a NS that shows periodic pulsations in the X-ray band. The inclination angle of the system is so high that in principle, it should be hard to observe both th