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N. D. Richardson, N. D. Morrison (U. Toledo), S. J. Adelman (The Citadel), E. E. Allgaier (U. Toledo)
The prototype A-type supergiant is Deneb (A2Iae). Lucy's (1976, ApJ 206, 499) harmonic analysis of radial velocities revealed 16 different pulsation modes and a binary period (approximately 850 days). Kaufer et al. (1996, A&A 305, 887) found evanescent periodicity in BA type supergiants. We analyzed 339 red-yellow echelle spectra (R=26,000) from Ritter Observatory, as well as 370 differential Stromgren photometric observations from the Four College Automated Photoelectric Telescope, all obtained during the years 1997-2001. Long-term variability studies such as the present one may elucidate physical processes in supergiant stars.
H alpha shows a P Cygni morphology, with a variable emission component and a blue-shifted absorption component. We measured the net equivalent width of H alpha as well as that of its emission component. We used the radial velocities of the red Si II lines for analysis of photospheric variations.
In each data set, we searched for periodicities with the CLEAN algorithm (Roberts et al. 1987, AJ 93, 968), both by observing season and globally. Noteworthy among our results is that some periods were found to persist, while others were present in only one observing season. Furthermore, the predominant period of the net H alpha equivalent width varied with each observing season. The binary period proposed by Lucy is not found in our data set.
Research at Ritter Observatory is supported by The University of Toledo, the Fund for Astrophysical Research, and the American Astronomical Society Small Grants Program (NASA funds). Community access to the facility is supported by NSF-PREST. E.E. Allgaier's participation was supported by the NSF-REU program. S.J. Adelman's participation in this work was supported by NSF grant AST-0507381.
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Bulletin of the American Astronomical Society, 37 #4
© 2005. The American Astronomical Soceity.