Volume 539, March 2012
|Number of page(s)||5|
|Section||Stellar structure and evolution|
|Published online||12 March 2012|
Period changes of the long-period cataclysmic binary EX Draconis
1 Astronomical Institute, Faculty of Mathematics and Physics, Charles University Prague, 180 00 Praha 8, V Holešovičkách 2, Czech Republic
2 Vihorlat Observatory, Mierova 4, 066 01 Humenné, Slovakia
3 Astronomical Institute, Academy of Sciences, Fričova 298, 251 65 Ondřejov, Czech Republic
Received: 30 August 2011
Accepted: 22 January 2012
The cataclysmic variable star EX Dra is a relatively faint but frequently investigated eclipsing dwarf nova. In total 35 new eclipses were measured photometrically as part of our long-term monitoring of interesting eclipsing systems. Using published and new mid-eclipse times obtained between 2004 and 2011 we constructed the observed-minus-calculated diagram. The current data present 21 years of period modulation with a semi-amplitude of 2.5 min. The eclipse timings show significant deviations from the best sinusoidal fit, which indicates that this ephemeris is not a complete description of the data. The fractional period change is roughly ΔP/P = 3 × 10-6.
Key words: binaries: close / binaries: eclipsing / stars: dwarf novae / stars: individual: EX Draconis / novae, cataclysmic variables
© ESO, 2012
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