Ariel 1118 - 61: A Very Close Binary System?

The hypothesis is considered that the 6·75-min periodicity observed in the transient X-ray source Ariel 1118 – 61 is due to orbital motion. Such a binary system would consist of a white dwarf transferring matter on to a compact object. The average mass transfer rate is $$\sim 10^{-7} \,M_{\odot} \,\text{yr}^{-1}$$ and is driven almost entirely by gravitational radiation. This rate of mass transfer obscures the X-ray source for most of the time and a transient X-ray source is seen when the mass transfer temporarily drops below this level.