WZ CYGNI: A MARGINAL CONTACT BINARY IN A TRIPLE SYSTEM?
We present new multiband CCD photometry for WZ Cyg made on 22 nights in two observing seasons of 2007 and 2008. Our light-curve synthesis indicates that the system is in poor thermal contact with a fill-out factor of 4.8% and a temperature difference of 1447 K. Including our 40 timing measurements, a total of 371 times of minimum light spanning more than 112 yr were used for a period study. Detailed analysis of the O-C diagram showed that the orbital period has varied by a combination of an upward parabola and a sinusoid. The upward parabola means continuous period increase and indicates that some stellar masses are thermally transferred to the more massive primary star at a rate of about 5.80 x 10{sup -8} M{sub sun} yr{sup -1}. The sinusoidal variation with a period of 47.9 yr and a semi-amplitude of 0.008 days can most likely be interpreted as the light-travel-time effect due to the existence of a low-mass M-type tertiary companion with a projected mass of M{sub 3}sin i{sub 3} = 0.26 M{sub sun}. We examined the evolutionary status of WZ Cyg from the absolute dimensions of the eclipsing pair. It belongs to the marginal contact binary systems before the broken contact phase, consisting of a massive primary star with spectral type F4 and a secondary star with type K1.
- OSTI ID:
- 21583064
- Journal Information:
- Astronomical Journal (New York, N.Y. Online), Vol. 142, Issue 1; Other Information: DOI: 10.1088/0004-6256/142/1/12; ISSN 1538-3881
- Country of Publication:
- United States
- Language:
- English
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