Updating the orbital ephemeris of the dipping source XB 1254690 and the distance to the source
Abstract
XB 1254690 is a dipping low mass Xray binary system hosting a neutron star and showing type I Xray bursts. We aim at obtaining a more accurate orbital ephemeris and at constraining the orbital period derivative of the system for the first time. In addition, we want to better constrain the distance to the source in order to locate the system in a well defined evolutive scenario. We apply, for the first time, an orbital timing technique to XB 1254690, using the arrival times of the dips present in the light curves that have been collected during 26 yr of Xray pointed observations acquired from different space missions. We estimate the dip arrival times using a statistical method that weights the countrate inside the dip with respect to the level of persistent emission outside the dip. We fit the obtained delays as a function of the orbital cycles both with a linear and a quadratic function. We infer the orbital ephemeris of XB 1254690, improving the accuracy of the orbital period with respect to previous estimates. We infer a mass of M _{2} = 0.42 ± 0.04 M _{ʘ} for the donor star, in agreement with estimations already present in literature, assuming that the star is in thermal equilibrium while it transfers part of its mass via the inner Lagrangian point, and assuming a neutron star mass of 1.4 M _{ʘ}. Using these assumptions, we also constrain the distance to the source, finding a value of 7.6 ± 0.8 kpc. Finally, we discuss the evolution of the system, suggesting that it is compatible with a conservative mass transfer driven by magnetic braking.
 Publication:

Research in Astronomy and Astrophysics
 Pub Date:
 September 2017
 DOI:
 10.1088/16744527/17/10/108
 arXiv:
 arXiv:1707.03161
 Bibcode:
 2017RAA....17..108G
 Keywords:

 Astrophysics  High Energy Astrophysical Phenomena
 EPrint:
 13 pages, 5 figures, accepted for publication in Research in Astronomy and Astrophysics (RAA)