DOI: 10.1051/0004-6361:20011357
The light and period changes of RT Andromedae
A. Erdem, O. Demircan and M. GüreÇanakkale Onsekiz Mart University, Faculty of Arts and Sciences, Department of Physics, 17100 Çanakkale, Turkey
(Received 11 June 2001 / Accepted 5 September 2001 )
Abstract
The nature of the long-term orbital period variation and the light
level variation of RT And was studied based on all available
photometric observations. The (O-C) diagram formed by all
available times of eclipse minima could be either of a
quasi-sinusoidal form superimposed on a parabolic form, or a long
period sinusoidal form. The quasi-sinusoidal form with an
amplitude of ~0.002 days and a period of ~65 years could
be due to a cyclic magnetic activity modulation on the orbital
period of the system. Applegate's theory (Applegate 1992), in
this case, predicts an ~3 kG mean subsurface magnetic field
for the primary component of the system. The parabolic form
corresponds to a secular period decrease of about
caused by mass loss from the system, and
the long-period sinusoidal form with an amplitude of ~0.02 days
and a period of ~105 years corresponds to a secular period
change caused by the light-time effect due to an unseen third star
in the system. It was estimated that the unseen third star should
be a low mass (lower than
) and faint
(
fainter than the system RT And) star, whose detection
is almost impossible. Future data will add information on the
nature of the secular (O-C) variation. Secular light level
variation of the system was found to be irregular and no
correlation was detected with the orbital period variation.
Key words: stars: binaries: eclipsing -- stars: individual: RT And
Offprint request: A. Erdem, aerdem@bornova.ege.edu.tr
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