The bright X ray transient GS2023+338 (=V404 Cyg) in optical outburst and decline

P. A. Charles, J. Casares, D. H. P. Jones, T. Broadhurst, P. J. Callanan, D. Carter, P. Hacking, B. J. M. Hassall, A. Lawrence, T. Naylor, R. G. M. Rutten, K. C. Sahu, A. Taylor

Research output: Contribution to conferencePaperpeer-review


The results of optical spectroscopy and photometry from La Palma (Canary Islands) of V404 Cyg are presented. They correspond to the optical counterpart of the new X-ray transient GS2023+338 discovered by Ginga. The overall light curve is similar to that of the previous optical outburst of this object, recorded as Nova Cyg 1938 and classified as a classical nova. It is not a classical or recurrent nova. The large range in optical brightness and intense X-ray emission at maximum indicate that the system must be a low-mass X-ray binary. The optical spectrum is unlike any known LMXB or X-ray transient in that it displays strong, broad, variable and complex emission lines of H, He I and He II. The reddened spectrum and interstellar absorption features indicate a problable distance in the range 1 to 3 kpc. Charged coupled device photometry reveals that the source is variable, but gives no indication of the orbital period, there being no eclipse or regular modulation.
Original languageEnglish
Publication statusPublished - 1 Nov 1989


  • Light Curve
  • Stellar Radiation
  • Stellar Spectra
  • Stellar Spectrophotometry
  • Transient Oscillations
  • X Ray Binaries
  • Bursts
  • Light (Visible Radiation)
  • Spectrum Analysis
  • Stellar Luminosity
  • X Ray Spectroscopy


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