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Register a new userA cyclical period variation detected in the updated orbital period analysis of TV Columbae
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The two CCD photometries of the intermediate polar TV Columbae are made for obtaining the two updated eclipse timings with high precision. There is an interval time sim 17yr since the last mid-eclipse time observed in 1991. Thus, the new mid-eclipse times can offer an opportunity to check the previous orbital ephemerides. A calculation indicates that the orbital ephemeris derived by Augusteijn et al. (1994) should be corrected. Based on the proper linear ephemeris (Hellier, 1993), the new orbital period analysis suggests a cyclical period variation in the O-C diagram of TV Columbae. Using Applegates mechanism to explain the periodic oscillation in O-C diagram, the required energy is larger than that a M0-type star can afford over a complete variation period sim 31.0(pm 3.0)yr. Thus, the light travel-time effect indicates that the tertiary component in TV Columbae may be a dwarf with a low mass, which is near the mass lower limit sim 0.08Msun as long as the inclination of the third body high enough.
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We report a long-term (1961-2017) study of the eclipse times in the dwarf nova WZ Sagittae, in an effort to learn its rate of orbital-period change. Some wiggles with a time scale of 20-50 years are apparent, and a connection with the 23-year interval between dwarf-nova eruptions is possible. These back-and-forth wiggles dominate the O-C diagram, and prevent a secure measurement of the steady rate of orbital-period change. The line, it is drawn, the curse, it is cast. The slow one now will later be fast... For the times, they are a-changin. - Dylan (1963)
We report a long-term study of the eclipse times in the 10-minute helium binary ES Ceti. The binary period increases rapidly, with P/P-dot = 6.2x10^6 yr. This is consistent with the assumption that gravitational radiation (GR) drives the mass transfer, and appears to be the first dynamical evidence that GR is indeed the driver of evolution in this class of very old cataclysmic variables -- the AM Canum Venaticorum stars.
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