Dwarf Nova Oscillations and Quasi-Periodic Oscillations in Cataclysmic Variables: III. A New Kind of Dwarf Nova Oscillation, and Further Examples of the Similarities to X-Ray Binaries

摘要

We present measurements of the periods of Dwarf Nova Oscillations (DNOs) andQuasi-Periodic Oscillations (QPOs) in Cataclysmic Variable stars (CVs), manyculled from published literature, but also others newly observed (in VZ Pyx, CRBoo, OY Car, Z Cha, AQ Eri, TU Men, HX Peg, CN Ori, V893 Sco, WX Hyi andEC2117-54). These provide data for 26 systems. We show that in general P_QPO ~15 P_DNO and that the correlation for CVs extends by three orders of magnitudelower in frequency the similar relationship found for X-Ray binaries. Inaddition, we have found that there is a second type of DNO, previouslyoverlooked, which have periods ~ 4 times those of the regular DNOs (As well asthose mined from publications, we have observed them in VW Hyi, OY Car, AQ Eri,V803 Cen, CR Boo, VZ Pyx, HX Peg and EC2117-54). Often both types of DNOcoexist. Unlike the standard DNOs, the periods of the new type, which we referto as longer period DNOs (lpDNOs), are relatively insensitive to accretionluminosity and can even appear in quiescence of dwarf novae. We interpret themas magnetically channelled accretion onto the differentially rotating main bodyof the white dwarf primary, rather than onto a rapidly slipping equatorial beltas in the case of the standard DNOs. This is supported by publishedmeasurements of v sin(i) for some of the primaries. Some similarities of theDNOs, lpDNOs and QPOs in CVs to the three types of QPO in X-Ray binaries (burstpulsation, high and low frequency QPOs) are noted.