On the Optical Identification of Cygnus X-1 (original) (raw)
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Abstract
We believe that the bright star at the location of the radio source near Cyg X-1 may not be associated with the X-ray source because its distance is greater than the upper limit for the distance to Cyg X-1, and because its spectrum and energy distribution are those of a normal BO supergiant, with no peculiarities seen. Analysis of presently incomplete data suggests possible peculiarity of a very red faint star, which is the only other object in the radio error box brighter than V 19. Available data indicate that Cyg X-1, whether or not it is the radio source, must be intrinsically several magnitudes fainter than, or have much redder colors than, either Sco X-1 or Cyg X-2.
Publication:
The Astrophysical Journal
Pub Date:
September 1971
DOI:
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