Open AccessVLT spectroscopy of XTE J2123−058 during quiescence: the masses of the two components
Author(s) -
Casares J.,
Dubus G.,
Shahbaz T.,
Zurita C.,
Charles P.A.
Publication year - 2002
Publication title -
monthly notices of the royal astronomical society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.058
H-Index - 383
eISSN - 1365-2966
pISSN - 0035-8711
DOI - 10.1046/j.1365-8711.2002.04964.x
Subject(s) - physics , astrophysics , neutron star , halo , spectroscopy , very large telescope , telescope , accretion (finance) , flux (metallurgy) , position angle , stars , light curve , astronomy , galactic halo , emission spectrum , spectral line , galaxy , materials science , metallurgy
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 λ 6300 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 . M 2 agrees well with the observed spectral type. Doppler tomography of the H α 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.