EDP Sciences
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Volume 392, Number 1, September II 2002
Page(s) 197 - 201
Section Formation, structure and evolution of stars
DOI http://dx.doi.org/10.1051/0004-6361:20020936

A&A 392, 197-201 (2002)
DOI: 10.1051/0004-6361:20020936

The secondary minimum in YY Herculis: Evidence for a tidally distorted giant

J. Mikolajewska1, E. A. Kolotilov2, S. Yu. Shugarov2, 3 and B. F. Yudin2, 3

1  N. Copernicus Astronomical Center, Bartycka 18, 00716 Warsaw, Poland
2  Sternberg Astronomical Institute, Universitetskii pr. 13, Moscow 119899, Russia
3  Isaac Newton Institute of Chile, Moscow Branch, Russia

(Received 28 March (2002) / Accepted 11 June (2002))

We present and analyze quiescent UBVRI light curves of the classical symbiotic binary YY Her. We show that the secondary minimum, which is clearly visible only in the quiescent VRI light curves, is due to ellipsoidal variability of the red giant component. Our simple light curve analysis, by fitting of the Fourier cosine series, resulted in a self-consistent phenomenological model of YY Her, in which the periodic changes can be described by a combination of the ellipsoidal changes and a sinusoidal changes of the nebular continuum and line emission.

Key words: stars: binaries: eclipsing -- binaries: symbiotic -- stars: fundamental parameters -- stars: individual: YY Her

Offprint request: J. Mikolajewska, mikolaj@camk.edu.pl

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