Bibcode
                                    
                            DOI
                                    
                            Hynes, R. I.; Steeghs, D.; Casares, J.; Charles, P. A.; O'Brien, K.
    Bibliographical reference
                                    The Astrophysical Journal, Volume 609, Issue 1, pp. 317-324.
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                        7
            
                        2004
            
  Journal
                                    
                            Citations
                                    143
                            Refereed citations
                                    133
                            Description
                                    The distance to the black hole binary GX 339-4 remains a topic of
debate. We examine high-resolution optical spectra of the Na D lines
resolving the velocity structure along the line of sight. We find this
to be complex, with at least nine components, mostly blueshifted,
spanning a velocity range of nearly 200 km s-1. The presence
of components with a large blueshift rules out a nearby location and
requires that the binary be located at or beyond the tangent point,
implying a lower limit to the distance of ~6 kpc. The presence of a
significant redshifted component at +30 km s-1 is even more
intriguing, as GX 339-4 also has a slightly positive systemic velocity,
suggesting that the source, and this cloud, could be on the far side of
the Galaxy, where the radial velocities due to Galactic rotation become
positive again. If this is the case, we require a distance of ~15 kpc.
This is less secure than the 6 kpc lower limit, however. We discuss the
implications of these possible distances for the outburst and quiescent
luminosities, as well as the nature of the companion star, and argue
that a large distance explains these characteristics. In particular, it
would explain the nondetection of the companion star during the faintest
states.