Far-ultraviolet observations of Cygnus X-2.
Maraschi, L.; Tanzi, E. G.; Treves, A.
Italy
Abstract
Two far-ultraviolet (1150-1950 A) spectra of V 1341 Cyg identical with Cyg X-2, taken with the International Ultraviolet Explorer, at orbital phase 0.3 and 0.6 show an intensity variation of a factor of 2. Strong emission lines (N V, Si IV, and He II) are apparent on a poorly defined continuum. The observations can be interpreted in terms of UV emission by the X-ray heated atmosphere of the noncollapsed star in the binary system. A neutron star rather than a white dwarf is indicated as the compact companion.