Astronomy and Astrophysics – Astronomy
Scientific paper
Jan 1998
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1998baas...30..760m&link_type=abstract
American Astronomical Society Meeting, 191, #125.04
Astronomy and Astrophysics
Astronomy
Scientific paper
The star alpha Cygni (HD 197345) is a bright A2 Ia-type supergiant. Its photometric and spectral variability are typical for early-type supergiants. As part of a campaign on spectral variability of BA-type supergiants, we have obtained high-resolution (R =~ 26,000) spectra of alpha \ Cyg in the region surrounding Hα . In early August 1997, the behavior of the Hα \ line suddenly changed. The line, which had shown a roughly constant P-Cygni profile from April through July, developed a cyclical pattern of variability near the center of the absorption component. This pattern has persisted through November 1997. Thanks to an unusually densely sampled set of observations (47 observations with a median separation between observations of only 1.93 days) and to the persistence of the phenomenon, its cyclical nature is evident. The timescale involved (about 40 days) and the cyclical nature of the variability suggest a corotating surface or wind feature as the source of this variability. The phenomenon may be related to the high-velocity absorption events reported in A-type supergiants by Kaufer et al. (1996, A&A, 305, 887). We will demonstrate the cyclical character of the recent variability using several forms of visual presentation. We will also present preliminary results from a time-series analysis of the Hα \ profile.
Morrison Nancy D.
Mulliss Christopher L.
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