X-Rays from V723 Mon are due to Optical Loading in Swift XRT





Citation of Original Publication

Hare, Jeremy et al.; X-Rays from V723 Mon are due to Optical Loading in Swift XRT; Research Notes of the AAS, Volume 5, Number 11, November, 2021; https://doi.org/10.3847/2515-5172/ac35e5


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V723 Mon was recently reported to be hosting the nearest (d = 460 pc) candidate black hole by Jayasinghe et al. An X-ray detection was claimed based on deep Swift XRT observations with a luminosity of Lₓ ≈ 8 × 10²⁹ erg s⁻¹ or Lₓ/LEdd ≈ 10⁻⁹. Here we show that the X-ray photons detected by Swift XRT are due to optical loading from the bright (V = 8.3 mag) star. Using events in the 2–10 keV energy band, where optical loading does not strongly contribute, we find a 3σ upper-limit on the unabsorbed 2–10 keV X-ray flux of Fₓ < 2.8 × 10⁻¹⁴ erg cm⁻² s⁻¹, corresponding to a luminosity Lₓ < 7.2 × 10²⁹ erg s⁻¹ at a distance of 460 pc or Lₓ/LEdd ≲ 2 × 10⁻⁹ for a M ≈ 3M⊙ black hole.