087099

An ultra-compact X-ray binary openParUCXBclosePar candidate with potentially the shortest known orbital period of 10.2 minutes was serendipitously discovered in the Galactic Bulge. Its only available X-ray spectra from XMM comma and radio-IR observations suggest that the source may be the first direct impact NS binary with no accretion disk or openParless likelyclosePar an intermediate polar. The proposed NuSTAR+XMM observations will confirm the period for a NS spin comma and identify the source by a combination of broad-band X-ray spectroscopy and Fe line diagnostics. Given its short orbital period comma the source may be one of the few UCXBs detectable by the future LISA GW observatory.