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Issue A&A
Volume 420, Number 2, June III 2004
Page(s) 595 - 604
Section Stellar structure and evolution
DOI http://dx.doi.org/10.1051/0004-6361:20040115



A&A 420, 595-604 (2004)
DOI: 10.1051/0004-6361:20040115

Long-term luminosity variations and period changes in CG Cygni

M. Afsar1, P. A. Heckert2 and C. Ibanoglu1

1  Ege University, Science Faculty, Department of Astronomy and Space Sciences, Bornava, Izmir 35100, Turkey
    e-mail: ibanoglu@astronomy.sci.ege.edu.tr
2  Western Carolina University, Department of Chemistry and Physics, Cullowhee, NC 28723, USA
    e-mail: heckert@email.wcu.edu

(Received 27 August 2003 / Accepted 16 February 2004 )

Abstract
We report new photometry of CG Cyg from 1998-2002. We also analyze published photometry collected since 1965. An O-C analysis reveals evidence of a third body in the system having a 51 year orbital period. After removing the effects of the third body, we note a remaining 22.5 year cyclic variation in the O-C curve that is similar to the period of the luminosity variations. Modeling the spot activity for 28  V band light curves obtained between 1965 and 2002 confirms the presence of two active longitude belts (ALBs) at approximately $90^{\circ}$ and  $270^{\circ}$. Most of the spots occur at mid latitudes with a few at low latitudes. We note no spots at latitudes greater than  $60^{\circ}$.


Key words: stars: activity -- stars: binaries: eclipsing -- stars: individual: CG Cyg -- stars: starspots

Offprint request: M. Afsar, afsar@astronomy.sci.ege.edu.tr

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