Precision Ephemerides For Gravitational Wave Searches: II. Cyg X-2

Understand

Accreting neutron stars in low-mass X-ray binaries (LMXBs) are candidate high-frequency persistent gravitational wave sources.

• These may be detectable with next generation interferometers such as Advanced LIGO/VIRGO within this decade.
• However, the search sensitivity is expected to be limited principally by the uncertainty in the binary system parameters.
• We combine new optical spectroscopy of Cyg X-2 obtained with the Liverpool Telescope (LT) with available historical radial velocity data, which gives us improved orbital parameter uncertainties based on a 44-year baseline.