Poster abstract details

We report the updated X-ray ephemeris of the dipping source XB 1916-053. We collected 37 years of data to obtain the dips arrival times. The known orbital period derivative is extremely large and could be explained invoking an extreme non-conservative mass transfer rate. The obtained delays are well fitted using a quadratic function containing a sinusoidal term or, alternatively, with a series of sinusoidal terms that can be associated with a modulation of the dip arrival times due to the presence of a third body that has an elliptical orbit. We infer that for a conservative mass transfer scenario the modulation of the delays can be explained by invoking the presence of a third body having a mass between 0.10–0.14 M$_{\odot}$, an orbital period around the X-ray binary system of about 51 yr and an eccentricity of 0.28 $\pm$ 0.15. In a non-conservative mass transfer scenario we estimate that the fraction of matter yielded by the degenerate companion star and accreted onto the neutron star is $\beta$=0.08, the neutron star mass is $\geq$ 2.2 M$_{\odot}$, and the companion star mass is 0.028 M$_{\odot}$. In this case, we explain the sinusoidal modulation of the delays by invoking the presence of a third body with orbital period of 26 yr and mass of 0.055 M$_{\odot}$.