Astronomy and Astrophysics – Astrophysics
Scientific paper
Aug 1981
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1981pasp...93..481j&link_type=abstract
Astronomical Society of the Pacific, Publications, vol. 93, Aug.-Sept. 1981, p. 481-485.
Astronomy and Astrophysics
Astrophysics
20
Cepheid Variables, Radial Velocity, Stellar Motions, Stellar Spectrophotometry, H Alpha Line, Velocity Distribution
Scientific paper
A new radial velocity curve is presented for the bright Cepheid Eta Aquilae. The curve was derived from 21 red spectrograms taken with the 1.2-m coude spectrograph at the Dominion Astrophysical Observatory at a dispersion of 10 A/mm. The shape of the curve is found to be unchanged since 1923, with a possible small increase in amplitude since 1898 and an apparent 0.74 km/sec decrease in systematic velocity, possibly associated with orbital motion about a recently discovered companion. The previously noted increase in period since 1825 is also confirmed. Comparison of the behavior of the H-alpha curve with that of the metallic line curves indicates the H-alpha to be formed at an optical depth of 0.01 if the metallic lines are assumed to be formed at a depth of 0.10, and the presence of infalling material high in the atmosphere at the time when the velocity of the metallic absorbing layer has been reversed.
Jacobsen Theodor S.
Wallerstein George
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