Remarks on erratic period fluctuations of detached close binaries and the constancy of the orbital period of XY UMa |
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Authors: | E H Geyer |
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Institution: | 1. Observatorium Hoher List, Astronomische Institute der Universit?t Bonn, Germany
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Abstract: | It is shown that the erratic changes of the orbital period, which are observed in some detached eclipsing binary systems,
cannot be interpreted as real if their light curves show changing anomalies with asymmetric minimum profiles. In this case
the photometrically determined times of the minima do not coincide with the ideal geometric ones, which are unobservable.
This fact and the applied reduction methods for deriving the photometric times of minima cause systematic period errors of
cumulative character. The discussion of six photoelectrically-determined minima obtained within the last 20 yr, and earlier
photographic ones of the 0d.479 period eclipsing binary XY UMa yields a constant period. The long cyclic light curve variations due to starspot activity
of the larger and hotter component of this system are reflected in corresponding period oscillations.
Dedicated to Dr. Ida Noddack on the occasion of her eightieth birthday. |
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