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Observations of Variable Stars with the R-Coronae Phenomenon and Other Unique Objects
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| UBV Photometry of the R Coronae Borealis Star RY Sgr - 1984 to 1986
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| The S201 far-ultraviolet imaging survey. III - A field in Sagittarius
Far-ultraviolet imagery of a 20 deg diameter field in Sagittarius,centered near (1950) R.A. 18 h 34 m, decl. -30 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, 1034 star images are detectable, with a limiting ultravioletmagnitude of about 10. Most of these objects are identified withearly-type stars listed in the Smithsonian Astrophysical ObservatoryStar Catalog, the Catalog of Stellar Identifications, or both, but 203objects remain unidentified or are identified with late-type stars. Thephotometric measurements appear to be in reasonable agreement with thoseof the International Ultraviolet Explorer for stars in common, and withexpectations for A0 stars. A detailed photometric study was made of theMessier 8 region, and it is concluded that dust-scattered starlightcontributes about half of the total radiation observed from the centralregion of M8.
| Spectra of RY SGR near minimum light
Spectra of RY Sgr were obtained near minimum light in the blue and greenranges, using the electronic camera. These spectra show a few absorptionlines and bands: the (0-0) and (1-1) Swan bands in the green wereobserved for the first time. The spectra show, moreover, two kinds ofemission lines: numerous 'narrow bright lines' and a few 'broad brightlines'. High excitation absorption lines show that at least a part ofthe photosphere remains with an essentially unchanged temperature. Thenarrow bright lines, observed in R Cr B and in the 1967 light drop of RYSgr, were ascribed by Payne-Gaposchkin (1963) to a chromosphericspectrum. The broad bright lines are slightly red-shifted lines of He Iand Ca II. An additional yellow-red photographic spectrum shows complexemission D line structures, easily separated into conspicuous narrowbright lines superposed on redshifted broad bright lines. The broadbright lines seem to be linked to the minimum phase but neither to theamplitude nor to the duration of the light drop. In a preceding lightdrop of RY Sgr in 1967, the broad bright lines are reported to be blueshifted. This behavior could be explained by some asymmetry in theejection of material.
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