Evidence of a brown dwark in the eclipsing dwarf nova Z Chamaeleonis

Z. DAI; S.B. QIAN; E. FERNÁNDEZ LAJÚS

ASTROPHYSICAL JOURNAL

IOP Publishing

Lugar: Hamilton, Ontario, Canada; Año: 2009 vol. 703 p. 109 - 113

0004-637X

We presented three new CCD observations of light minima of Z Chamaeleonis. All 187 available times of light minimum including 37 photographic data are compiled, and a new orbital period analysis is made by means of the standard O – C technique. The O – C diagram of Z Chamaeleonis presents a cyclical periodic change of ~ 32.57 yr with a high significance level. We attempted to apply two plausible mechanisms (i.e., Applegate´s mechanism and light travel-time effect) to explain the cyclical variations of orbital period shown in the O-C diagram. Although the previous works suggested that solar-type magnetic cycles in the red dwarf are the best explanation, the analysis of Applegate´s mechanism in this paper presents a negative result. Accordingly, a light travel-time effect is proposed, and a brown dwarf as a tertiary component orbiting around dwarf nova Z Chamaeleonis is derived with a significance level of gsim81.6%, which may be a plausible explanation of the periodic variation in the systemic velocity of Z Chamaeleonis in superoutburst.