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Spectral absolute magnitudes of 312 stars of the B5-A3 spectral classes in the region of the association Cygnus OB4
Observations of the region of the association Cygnus OB4 were made witha 70-cm meniscus telescope with an 8 deg objective prism and adispersion of 166 A/mm at H-gamma. The equivalent widths of the H-gammaand H-delta lines were measured and a reduction was performed withKopylov's system of equivalent widths using a number of standard stars.The absolute magnitudes of 312 stars of the B5-A3 spectral classes arederived. The positions of these stars in the H-R diagram are discussed.A table of the absolute magnitudes, spectral types, and luminosityclasses is given.
| The S201 far-ultraviolet imaging survey. II - A field in Cygnus
Far-ultraviolet imagery of a region in Cygnus, a 20 deg diameter fieldcentered near (1950) R. A. 21 h 31.2 m decl. +37 deg 25 arcmin, wasobtained by the S201 far-ultraviolet camera during the Apollo 16mission. In a 10 minute exposure covering the 1250-1600 A wavelengthrange (effective wavelength 1400 A), 730 star images can be detected,corresponding to a limiting ultraviolet magnitude of about m (1400) =10. Assuming nominal interstellar extinction values in this region nearthe galactic plane, this result corresponds to the detection of A0 Vstars to a distance of 300 pc and of B0 V stars to 1500 pc.Uncertainties in spectral classification and interstellar extinction forindividual objects are probably more significant than calibration ormeasurement errors. Most of the objects detected are identified withstars in the Smithsonian Astrophysical Observatory Star Catalog (1966),or the Catalog of Stellar Identifications (1979) or both, but 87 objectsremain unidentified (or are identified with late-type stars).
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