Volume 625, May 2019
|Number of page(s)||5|
|Section||Letters to the Editor|
|Published online||20 May 2019|
Letter to the Editor
Updated orbital ephemeris of the ADC source X 1822-371: a stable orbital expansion over 40 years
Dipartimento di Fisica e Chimica – Emilio Segrè, Università di Palermo, via Archirafi 36, 90123 Palermo, Italy
2 Dipartimento di Fisica, Università degli Studi di Cagliari, SP Monserrato-Sestu, KM 0.7, Monserrato 09042, Italy
3 Istituto Nazionale di Astrofisica, IASF Palermo, Via U. La Malfa 153, 90146 Palermo, Italy
4 IRAP, Université de Toulouse, CNRS, UPS, CNES, Toulouse, France
5 Dipartimento di Fisica e Astronomia “Galileo Galilei”, Università di Padova, Vicolo dell’Osservatorio 3, Padova 35122, Italy
Accepted: 8 May 2019
Aims. Source X 1822-371 is an eclipsing compact binary system with a period close to 5.57 h and an orbital period derivative Ṗorb of 1.51(7)×10−10 s s−1. The very high value of Ṗorb 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 past 40 yr.
Methods. We added two new values obtained from the Rossi-XTE (RXTE) and XMM-Newton observations performed in 2011 and 2017, respectively, to the X-ray eclipse arrival times from 1977 to 2008. 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 RXTE observation taken in 1996.
Results. Fitting the delays with a quadratic model, we found an orbital period Porb = 5.57062957(20) h and a Ṗorb value of 1.475(54)×10−10 s s−1. The addition of a cubic term to the model does not significantly improve the fit quality. We also determined a spin-period value of Pspin = 0.5915669(4) s and its first derivative Ṗspin = − 2.595(11) × 10−12 s s−1.
Conclusions. Our 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.
Key words: stars: neutron / stars: individual: X 1822-371 / X-rays: binaries / eclipses / ephemerides
© ESO 2019
Current usage metrics show cumulative count of Article Views (full-text article views including HTML views, PDF and ePub downloads, according to the available data) and Abstracts Views on Vision4Press platform.
Data correspond to usage on the plateform after 2015. The current usage metrics is available 48-96 hours after online publication and is updated daily on week days.
Initial download of the metrics may take a while.