The orbital period analysis for two cataclysmic variables: UZ Fornacis and V348 Puppis inside Period Gap

Z. DAI; S.-B. QIAN; E. FERNÁNDEZ-LAJÚS; G.L. BAUME

MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY

WILEY-BLACKWELL PUBLISHING, INC

Lugar: Cambridge; Año: 2010 vol. 409 p. 1195 - 1202

0035-8711

 Four newest CCD eclipse timings of the white dwarf for polar UZ Fornacis and six  updated CCD mid-eclipse times for SW Sex type nova-like V348 Puppis are obtained. The detailed O-C analyses for both CVs inside period gap are made. Orbital period increases at a rate of 2.63 (±0.58) x 10^-11s s^-1 for UZ Fornacis and of 5.8 (±1.9) x  10 ^-12 s s^-1for V348 Puppis, respectively, are discovered in their new O-C diagrams. However, the conservative mass transfer from the secondary to the massive white dwarf cannot explain the observed orbital period increases for both CVs, which are regarded as part of modulations at longer periods. Moreover, the O-C diagram of UZ Fornacis shows a possible cyclical change witha period of 23.4 (±5.1) yr.For explaining the observed cyclical period changes in UZ Fornacis, both mechanisms of magnetic activity cycles in the late-type secondary and the light travel time effect are regarded as two probable causes. Not only does the modulation period 23.4 yr obey the empirical correlation derived by Lanza (1999), but also the estimated fractional period change DP/P ~ 7.3 x  10^-7 displays a behavior similar to that of the CVs below the period gap.On the other hand, a calculation for the light travel-time effect implies that the tertiary component in UZ Fornacis may be a brown dwarf with a high confidence level,when the orbital inclination of the third body is larger than 16º.