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Millihertz quasi-periodic optical oscillations in 4U 0614+091

Authors

  • Y. Zhang,

    Corresponding author
    1. Department of Physics and Astronomy, Louisiana State University, Baton Rouge, LA 70803, USA
      E-mail: yzhang@phys.lsu.edu (YZ); rih@phys.lsu.edu (RIH); elr@astro.as.utexas.edu (ELR)
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  • R. I. Hynes,

    Corresponding author
    1. Department of Physics and Astronomy, Louisiana State University, Baton Rouge, LA 70803, USA
      E-mail: yzhang@phys.lsu.edu (YZ); rih@phys.lsu.edu (RIH); elr@astro.as.utexas.edu (ELR)
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  • E. L. Robinson

    Corresponding author
    1. Department of Astronomy, University of Texas at Austin, Austin, TX 78712, USA
      E-mail: yzhang@phys.lsu.edu (YZ); rih@phys.lsu.edu (RIH); elr@astro.as.utexas.edu (ELR)
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E-mail: yzhang@phys.lsu.edu (YZ); rih@phys.lsu.edu (RIH); elr@astro.as.utexas.edu (ELR)

ABSTRACT

We report the discovery of a 1-mHz optical quasi-periodic oscillation (QPO) in the candidate ultra-compact low-mass X-ray binary 4U 0614+091. The ultra-low-frequency QPO has no X-ray counterpart in contemporaneous RXTE/PCA data and is likely a signature of structure in the accretion disc. The QPO can be reasonably fitted with a single sine wave but with a phase jump part way through the observation, indicating that it is not coherent. We also identify a 48-min modulation, approximately consistent with the suggested orbital period of O’Brien and Shahbaz et al. If this is indeed orbital, it supports an identification of 4U 0614+091 as an ultra-compact source.

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