[vsnet-chat 7871] Paper: EX Hya, intermediate polar

[Ivan Andronov]

http://arxiv.org/abs/1308.1805 

Variability of the Spin Period of the White Dwarf 
in the Magnetic Cataclysmic Binary System 
EX Hya 

Ivan L. Andronov, Vitalii V. Breus 

Department «High and Applied mathematics»,
Odessa National Maritime University, Odessa, Ukraine;

 The observations of the two-periodic magnetic cataclysmic system EX Hya have 
been carried out, using the telescopes RC16 and TOA-150 of the Tzec Maun 
observatory. 6 nights of observations were obtained in 2010-2011 (alternatively 
changing filters VR). Also the databases of WASP, ASAS and AAVSO have been 
analyzed. Processing time series was carried out using the program MCV. We 
analyzed changes in the rotation period of the white dwarf, and based on our 
own and previously published moments of maximum. The ephemeris was determined 
for the maxima of the radiation flux associated with the rotation of the 
magnetic white dwarf: Tmax=2437699.89079(59) 
+0.0465464808(69).E-6.3(2)*10^{-13}E^2, which corresponds to the characteristic 
timescale of the rotation spin-up of 4.67(14)*10^6 years. This contradicts the 
estimated value of the mass of the white dwarf of 0.42M_\odot, based on X-ray 
observations made by Yuasa et al (2010), however, is consistent with estimates 
of the masses of 0.79 M_\odot (white dwarf) and 0.108 M_\odot (red dwarf) 
previously published Beuermann and Reinsch (2008), and the assumption that the 
capture of accreted plasma by magnetic field of the white dwarf is near the 
border of the Roche lobe. Analyzed moments do not support the assumption of 
Mauche et al (2009) for a statistically significant cubic term in the 
ephemeris. Despite the presence of outbursts in EX Hya, there are significant 
differences from the DO Dra, which supports the introduction to a detailed 
classification of the intermediate polars the groups of "outbursting 
intermediate polars" and "magnetic dwarf novae."