The ultracompact nature of the black hole candidate X-ray binary 47 Tuc X9

Understand

47 Tuc X9 is a low mass X-ray binary (LMXB) in the globular cluster 47 Tucanae, and was previously thought to be a cataclysmic variable.

• However, Miller-Jones et al.
• (2015) recently identified a radio counterpart to X9 (inferring a radio/X-ray luminosity ratio consistent with black hole LMXBs), and suggested that the donor star might be a white dwarf.
• We report simultaneous observations of X9 performed by Chandra, Nustar and Australia Telescope Compact Array.