Unconfirmed/Unpublished Planets Catalogue

We have measured the orbital light curve of dwarf nova OY Carinae on 8 separate occasions between 1997 September and 2005 December. The measurements were made in white light using CCD photometers on the Mt Canopus 1 m telescope. The time of eclipse in 2005 December was 168 +- 5 s earlier than that predicted by the Wood et al.(1989) ephemeris. Using the times of eclipse from our measurements and the compilation of published measurements by Pratt et al (1999) we find that the observational data are inconsistent with a constant period and indicate that the orbital period is decreasing by 5+-1 X 10^-12 s/s. This is too fast to be explained by gravitational radiation emission. It is possible that the change is cyclic with a period greater than about 80 years. This is much longer than typical magnetic activity cycles and may be due to the presence of a third object in the system. Preliminary estimates suggest that this is a brown dwarf with mass about 0.016 Msun and orbital radius >= 17 AU.

For Z Cha the period of the reflex orbit would be greater than 25 yrs and its projected semimajor axis would be greater than 40 light seconds or 1.2x10¹² cm. A third body with a mass as small as 0.01 M_Sun at a distance greater than 8 AUs would be enough to account for the eclipse ephemeris. Such an object would be undetectable by other means. At present there is no way to choose among these possible interpretations of the eclipse ephemeris

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.

Having analyzed the light curve for the Herbig Ae star BF Ori, we justify the hypothesis of a giant protocomet, GPC I BF Ori, with a period of 6.3 years and semimajor axis a = 10 +/- 3 AU. Passing through periastron, such a giant protocomet partially breaks up. During each passage through periastron, the protocomet and the fragments that follow it supply dust to circumstellar space for a certain period of time. This hypothesis can account for the entire complex of observable phenomena of cyclic Algol-like activity in Herbig Ae/Be and T Tauri stars. Conditions in a protoplanetary disk after cocoon breakup are discussed. We adduce arguments for the absence of a dust disk and for the weak effect of objects other than comets on cyclic large-scale variability.

The O-C curve of the Algol-type semi-detached binary V505 Sgr has been analyzed using a new method proposed by Kalimeris et al. (1994). It is shown that the orbital period oscillates with an amplitude of 0.453×10^-5days and a period of aobut 41.5 years that differs from the previous period of 105 years. The physical mechanisms explaining the orbital period behaviour have been studied. It is indicated that the present period change may not be caused by the existence of the third body proposed previously. The presence of a fourth body with mass 0.013 M_sun and orbit semimajor axis 17.35 AU or the magnetic activity cycle of the secondary component may be used to explain the present period change.

As an alternative origin the cyclic period changes could also be caused by an unseen third body in which case the variation should be strictly periodic. Taking the elementsof the quadratic plus sinusoidal ephemeris we compute the minimum mass of such a body assuming that its inclination is 90◦. The observed mass function (Borkovits & Hegedues1996) is 1.1 × 10−7M⊙ implying a minimum mass of the third body of 0.0047M⊙ (5 Jupiter masses) for an assumed total mass of the system of 1.0 M⊙. On the other hand, athird body more massive than an object at the hydrogen burning limit would require an inclination < 3◦ and istherefore not very likely.

The cyclicalvariation has a period of 6.9 yr and an semi-amplitude of∼ 9 sec.