Evidence for a black hole in the X-ray transient XTE J1859+226

Authors

  • J. M. Corral-Santana,

    Corresponding author
    1. Instituto de Astrofísica de Canarias (IAC), Vía Láctea s/n, La Laguna E-38205, S/C de Tenerife, Spain
    2. Departamento de Astrofísica, Universidad de La Laguna, La Laguna E-38205, S/C de Tenerife, Spain
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  • J. Casares,

    Corresponding author
    1. Instituto de Astrofísica de Canarias (IAC), Vía Láctea s/n, La Laguna E-38205, S/C de Tenerife, Spain
    2. Departamento de Astrofísica, Universidad de La Laguna, La Laguna E-38205, S/C de Tenerife, Spain
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  • T. Shahbaz,

    Corresponding author
    1. Instituto de Astrofísica de Canarias (IAC), Vía Láctea s/n, La Laguna E-38205, S/C de Tenerife, Spain
    2. Departamento de Astrofísica, Universidad de La Laguna, La Laguna E-38205, S/C de Tenerife, Spain
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  • C. Zurita,

    Corresponding author
    1. Instituto de Astrofísica de Canarias (IAC), Vía Láctea s/n, La Laguna E-38205, S/C de Tenerife, Spain
    2. Departamento de Astrofísica, Universidad de La Laguna, La Laguna E-38205, S/C de Tenerife, Spain
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  • I. G. Martínez-Pais,

    Corresponding author
    1. Instituto de Astrofísica de Canarias (IAC), Vía Láctea s/n, La Laguna E-38205, S/C de Tenerife, Spain
    2. Departamento de Astrofísica, Universidad de La Laguna, La Laguna E-38205, S/C de Tenerife, Spain
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  • P. Rodríguez-Gil

    Corresponding author
    1. Instituto de Astrofísica de Canarias (IAC), Vía Láctea s/n, La Laguna E-38205, S/C de Tenerife, Spain
    2. Departamento de Astrofísica, Universidad de La Laguna, La Laguna E-38205, S/C de Tenerife, Spain
    3. Isaac Newton Group of Telescopes, Apartado de Correos 321, Santa Cruz de La Palma E-38700, Spain
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E-mail: jcorral@iac.es (JMC-S); jcv@iac.es (JC); tsh@iac.es (TS); czurita@iac.es (CZ); igm@iac.es (IGM-P); prguez@iac.es (PR-G)

ABSTRACT

We present the results of time-resolved optical photometry and spectroscopy of the X-ray transient XTE J1859+226 (V406 Vul). Photometric observations taken during 2000 and 2008 reveal the presence of the secondary star's ellipsoidal modulation. Further photometry obtained in 2010 shows the system ≃1 mag brighter than its quiescence level and the ellipsoidal modulation diluted by strong flaring activity. Spectroscopic data obtained with the 10.4-m GTC in 2010 reveal radial velocity variations of ∼500 km s−1 over 3 h. A simultaneous fit to the photometry and spectroscopy using sinusoids to represent the secondary star's ellipsoidal and radial velocity variations, yields an orbital period of 6.58 ± 0.05 h and a secondary star's radial velocity semi-amplitude of K2= 541 ± 70 km s−1. The implied mass function is f(M) = 4.5 ± 0.6 M, significantly lower than previously reported but consistent with the presence of a black hole in XTE J1859+226. The lack of eclipses sets an upper limit to the inclination of 70° which yields a lower limit to the black hole mass of 5.42 M.

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