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J. L. Mantini, R. J. Dukes (Coll. Charleston)
In this paper we report on a preliminary analysis of photometric observations of two interesting Cepheids. The first, EU Tauri, was originally reported to be a ``beat" Cepheid. That is, it was pulsating in both the fundamental and first overtone simultaneously. Later, this was shown to be apparently not true. The second, CO Aurigae, was also a beat Cepheid but was pulsating in the first and second overtones simultaneously. In order to verify the single mode nature of EU Tauri and to further analyze CO Aurigae which is the only such Cepheid known in our galaxy. We began observing them with the Four College Consortium Automatic Photometric Telescope located in southern Arizona. EU Tauri was observed in Johnson-Cousins UBVRI filters while CO Aurigae was observed in only UBV.
We found that EU Tauri was indeed a single mode Cepheid with a frequency of 0.47562 c/d and a V amplitude ratio of second harmonic to fundamental of 0.1624. On the other hand CO Aurigae is indeed a beat Cepheid. We found frequencies of 0.5608 c/d and 0.7004 which are essentially those found in previous studies. We also found in periodogram analysis evidence of several coupling terms including f1 + f2 and f1 - f2 with indications of the possible presence of other coupling terms.
We will also report on complete third, fourth, and fifth order expansions of the brightness variations and an analysis of the color variations of both stars. This research has made use of the SIMBAD database, operated at CDS, Strasbourg, France and has been funded by NSF Grants #AST86-16362, #AST91-15114, #AST95-28906, and #AST-0071260 all to the College of Charleston.
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The author(s) of this abstract have provided an email address for comments about the abstract: weasleywheeze@yahoo.com
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Bulletin of the American Astronomical Society, 35#5
© 2003. The American Astronomical Soceity.