New highdispersion radialvelocity curves of W Sagittarii.
Abstract
Radialvelocity curves of W Sgr for 1969 and 1973 have been constructed from the author's definitive measurements of 20 highdispersion spectrograms taken by Wallerstein with the coude' spectrographs at Mount Wilson, Kitt Peak, and Cerro Tololo. The curves were compared with the author's highdispersion curves constructed from his Mills threeprism spectrograms of 1923 and 1925. From an intercomparison of the various curves the following results emerge: (1) To a first approximation the systemic velocity varies in an estimated period of 80 years in a manner well described by Keplerian orbital elements. (2) The shape of the curve representing the shortperiod pulsation of 7.59+ days is definitely variable with time. There is definite evidence of a 51year separation between two similar shapes. A comparison with curves of lower dispersion by Curtiss, Stibbs, and Evans suggest the possibility of a 17year periodicity in the changing shapes. (3) The average spectroscopic pulsation period between 1923 and 1973 is derived. Comparison of this value with the four bestdetermined photometric periods reveals an increase in period between 1872 and about 1917 at the average rate of 1.364s per year, and a linearly decreasing period at the rate of 0.1345 per year after about 1917. The apparent spectroscopic pulsation period for y = 27.58 km 1 should be given by 7.594875  0.00000155(t  1938.6) mean solar days. (4) The spectra show interstellar Dlines of Na I at a constant velocity of 4.20km 5 Subject headings: binaries  Cepheids and W Virginis stars  stars, individual
 Publication:

The Astrophysical Journal
 Pub Date:
 August 1974
 DOI:
 10.1086/153010
 Bibcode:
 1974ApJ...191..691J