2012/02/07 by L. Pilarčík, M. Wolf, P. A. Dubovský +3
Physics and Astronomy · #Astrophysical Phenomena and Observations #Stellar, planetary, and galactic studies #Gamma-ray bursts and supernovae
paper · pdf · doi:10.1051/0004-6361/201117972
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.