A short review of ultra-compact binaries, focused on ultra-compact X-ray binaries, is followed by a discussion of recent results of our VLT campaign to obtain optical spectra of (candidate) ultra-compact X-ray binaries. We find evidence for carbon/oxygen as well as helium/nitrogen discs and no evidence for (traces) of hydrogen. This suggests that the donors in the observed systems are white dwarfs. However, we also find large differences between the two C/O discs of which we have good spectra, which highlights the need for a better understanding of the optical spectra.
@article{arxiv.astro-ph/0605722,
title = {Ultra-compact (X-ray) binaries},
author = {G. Nelemans and P. G. Jonker},
journal= {arXiv preprint arXiv:astro-ph/0605722},
year = {2015}
}
Comments
To appear in proceedings of "A life with stars" a conference in honour of Ed van den Heuvel's 60th birthday, New Ast. Rev