Speaker
Prof.
Rosario Iaria
(Univ. di Palermo - DSFC)
Description
The ultra-compact dipping source XB 1916-053 has an orbital period of
close to 50 min and a companion star with a very low mass (less
than 0.1 M$_{\odot}$). The known orbital period derivative
($1.5(3) \times 10^{-11}$ s/s) is extremely large and can be
explained by invoking an extreme, non-conservative mass transfer
rate that is not
easily justifiable. We extended the analysed data
from 1978 to 2014, by spanning 37 years, to verify whether a
larger sample of data can be fitted with a quadratic term or a
different scenario has to be considered. The 27 delays associated with the dip arrival times are well fitted using a sinusoidal term plus a quadratic function
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 with
mass between 0.10-0.14 M$_{\odot}$,
orbital period around the X-ray binary system of close to 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 $\ge 2.2$ 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$_{\odot}$. From the analysis of the delays,
we find that both in a conservative and non-conservative mass transfer
scenario we have to invoke the presence of a third
body to explain the observed sinusoidal modulation.
We propose that XB 1916-053
forms a hierarchical triple system.
Author
Prof.
Rosario Iaria
(Univ. di Palermo - DSFC)
Co-authors
Dr
Alessandro Riggio
(Univ. di Cagliari)
Dr
Andrea Sanna
(Univ. di Cagliari)
Mr
Angelo Francesco Gambino
(Univ. di Palermo)
Mrs
Fabiana Scarano
(Univ. di Cagliari)
Dr
Fabio Pintore
(Univ. di Cagliari)
Prof.
Luciano Burderi
(Univ. di Cagliari)
Prof.
Tiziana Di Salvo
(Univ. di Palermo - DSFC)
Dr
marco matranga
(Univ. di Palermo - DSFC)
