H position determination of the binary Circinus X-1

Circinus X-1 was observed using the Anglo–Australian Telescope and RGO spectrograph on 1992 May 31 (approximate orbital phase 300°), with seeing conditions of ~ 1 arcsec. Hα emission was detected from an $${m}_{\upsilon } \sim 20.5$$, reddened star at a position 1.45 ± 0.15 arcsec south of star ‘L’. This Hα position for Circinus X-1 is in good agreement with an earlier VLBI measurement and a recent photometric and visual identification. The Doppler velocity of the Hα peak is found to be $$150 \pm 50\enspace \text {km}\enspace \text {s}^{ -1}$$, with the profile appearing skewed towards shorter wavelengths. The striking resemblance between this profile and the ‘stationary’ Hα profile of SS 433 may be further evidence for jet-like activity from Circinus X-1.