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| - VLT spectroscopy of XTE J2123−058 during quiescence: the masses of the two components
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| - Abstract. We present Very Large Telescope (VLT) low-resolution spectroscopy of the neutron star X-ray transient XTE J2123−058 during its quiescent state. Our data reveal the presence of a K7V companion which contributes 77 per cent to the total flux at λ6300 and orbits the neutron star at . Contrary to other soft X-ray transients (SXTs), the H emission is almost exactly in antiphase with the velocity curve of the optical companion. Using the light-centre technique we obtain and hence This, combined with a previous determination of the inclination angle yields and . M2 agrees well with the observed spectral type. Doppler tomography of the Hα emission shows a non-symmetric accretion disc distribution mimicking that seen in SW Sex stars. Although we find a large systemic velocity of − this value is consistent with the galactic rotation velocity at the position of J2123−058, and hence a halo origin. The formation scenario of J2123−058 is still unresolved.
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