1. Ladislav Hric Astronomical Institute Slovak Academy of Sciences Our team: V. Breus P. Dubovský R. Gális N. A. Katysheva E. Kundra S. Yu. Shugarov KOLOS

2. Schematic picture of CV – non magnetic system

3. Schematic picture of CV – the strong magnetic system - Polar

4. Schematic picture of CV – the moderately magnetic system - intermediate polar

5. V709 Cas was discovered as an optical counterpart of the ROSAT source RX J0028.8+5917 by Haberl & Motch (1995) The soft X-Ray flux was changing with a period of 312.8 s, which is the spin period of the white dwarf Radial velocity variations showed 2 possible orbital periods P = 5.4 h and 4.45 h which are one day aliases of each other (Motch 1996) Note to spin and orbital periods, the reprocessing of X-rays at some part of the system that revolves at the binary period gives rise to emission that varies with the beat period, where 1/Pbeat = 1/Pspin − 1/Porbit This synodic counterpart is often called the orbital sideband of the spin frequency.

6. Kozhevnikov (2001) reported the presence of strong optical oscillations at the spin period of 312.77 s and it’s orbital sideband of 317.94 s. Bonnet-Bidaud et al. (2001) studied radial velocities of the emission lines and published the ephemeris T0 = HJD 2451048.0575(2) + 0.2225(2) x E. Tamburini et al. (2009) studied the white-light flickering and reported that the light curve is strongly flickering dominated without any dominating frequency except the orbital motion. Thorstensen et al. (2010) found the value of the orbital period of the system using radial velocity spectroscopy P= 0d.2222033(7).

7. We obtained photometric CCD observations using different telescopes: 50cm AZT-5 (13 nights), 60cm Zeiss-Cassegrain (2 nights), 38cm K-380 (19 nights) at the Crimean Astrophysical Observatory (CrAO), and Crimean Laboratory of Sternberg Astronomical Institute, Nauchny, Crimea, Ukraine, and 1m Vihorlat National Telescope (VNT) (22 nights), Celestron 14 (1 night) at the Kolonica Observatory (KO), Slovakia mainly in V and R filters. 10 years of observations

8. Period analysis Periodograms near frequrency, that corresponds to the spin period of the white dwarf, exhibit the different highest peaks for different nights of observations in the range from 185 s to 330 s. Particulary, for data obtained 7. Oct 2010 at the 1m VNT we got highest peak that corresponds to the spin period of 311.7(4) s.

9. Results

10. Using all determined minima timings, we calculated (O - C) diagram with initial values of period P = 0.2222041 d (Thorstensen et al. 2010) and initial epoch T0 = 2454028.43349 determined for one night from the middle of our data. We chose the linear fit as the best approximation for the (O - C) data and the resulting orbital period was Porb = 0.2222123(6) d.

11. Results

12. The new period Periodograms in the range of 0.002 - 0.02 days exhibit strong peak around the period of 23 minutes (0.016 d). Different nights show different highest peaks in the range from 0.010 d to 0.019 d. We took the average value of Pnew = 0.01645 d, which corresponds to the frequency of 60.79 /day in the periodograms. Finally we took the set of 3 nights. The period analysis of these data reveals the highest peak at the frequency f = 61.15 /day which corresponds to the newly detected period of Pnew = 0.0163510(3) d. Periodogram

13. The new period

15. What about the conclusion It is worth to note that on the published by Norton (1999) and Kozhevnikov (2001) power spectra it is possible to identify the peaks corresponding to our new period. In the paper by Kozhevnikov (2001) the peak is more than two times higher than the spin period. Both authors did not notice this fact in their papers. These evidences support our opinion, that the period discovered by us is caused by real physical process. One of the possible explanations is the vibration of the accretion stream in the magnetic field of the white dwarf. The explanation of this new period is only speculative and for better understanding it is necessary to get spectroscopic data with higher time resolution.

16.  Our paper

17. The new data

20. Acknowledgements  Thank you very much for your attention 