Orbital parameters of the high-mass X-ray binary 4U 2206+54

TL;DR

This paper reports new radial velocity measurements of the high-mass X-ray binary 4U 2206+54, determining its orbital period and eccentricity, thereby resolving previous discrepancies in its orbital parameters.

Contribution

The study provides the first precise orbital parameters of 4U 2206+54 based on optical spectra, clarifying previous uncertainties.

Findings

Orbital period P_{orb} = 9.568 days

Eccentricity e = 0.3

Resolved previous orbital period disagreements

Abstract

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.