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

Abstract

The source X 1822-371 is an eclipsing compact binary system with a period close to 5.57 hr and an orbital period derivative ${\dot{P}}_{\mathrm{orb}}$ of 1.51(7)$\times 10^{-10}$ s s${}^{-1}$. The very large value of ${\dot{P}}_{\mathrm{orb}}$ 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 $P_{\mathrm{orb}}=5.57062957(20)$ hr and a ${\dot{P}}_{\mathrm{orb}}$ 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 $P_{\mathrm{spin}}=0.5915669(4)$ s and its first derivative ${\dot{P}}_{\mathrm{spin}}=-2.595(11)\times 10^{-12}$ 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.

5 pages, 3 figures, accepted for publication in A&A Letters

References in corpus (4)

• New ephemeris of the ADC source 2A 1822-371: a stable orbital-period derivative over 30 years
• On the timing properties of SAX J1808.4-3658 during its 2015 outburst
• A possible cyclotron resonance scattering feature near 0.7 keV in X1822-371
• Detailed study of the X-ray and Optical/UV orbital ephemeris of X1822-371

Cited by in corpus (6)

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• Anomalous orbital expansion of low-mass X-ray binary 2A 1822-371: the existence of a circumbinary disk?
• On the rapid orbital expansion in the compact low-mass X-ray binary 2A 1822$-$371
• Rapid orbital expansion in millisecond pulsar PSR J0636+5128: evaporation winds?
• Effect of tides on the orbital evolution of the redback system PSR 1723-2837