Periodic UV modulation of X1850 — 087: a double degenerate binary in the globular cluster NGC 6712?

Publisher Website
Google Scholar
Abstract
We report the discovery with the Hubble Space Telescope (HST) of a short-period (20.6 min) UV modulation in X1850 — 087, the luminous X-ray source in the globular cluster NGC 6712. The low-amplitude modulation (0.044 ± 0.007 mag) is not detected in archival X-ray observations with EXOSAT. We compare the properties of X1850 — 087 with the 11-min binary X1820 — 303 and identify the modulation as the orbital period, which requires the mass-losing companion to be degenerate and of low mass (0.04 M⊙).