Orbital parameters of the high-mass X-ray binary 4U 2206+54
  We present new radial velocities of the high-mass X-ray binary star 4U 2206+54 based on optical spectra obtained with the Coude spectrograph at the 2m RCC telescope at the Rozhen National Astronomical Observatory, Bulgaria in the period November 2011 -- July 2013. The radial velocity curve of the HeI $\lambda$6678 \AA\ line is modeled with an orbital period P$_{orb}$ = 9.568~d and an eccentricity of $e$ = 0.3. These new measurements of the radial velocity resolve the disagreements of the orbital period discussions. 
K. A. Stoyanov, R. K. Zamanov, G. Y. Latev, A. Y. Abedin, N. A. Tomov
astro-ph.SR astro-ph.HE