Discovery of new quasi-periodic oscillations in the X-ray transient source V0332+53

We report the discovery of a new quasi-periodic oscillation (QPO) at 0.22 Hz, centered on the source spin frequency of the high-mass X-ray binary system V0332 + 53 when the source was observed during its 2004 November/2005 March outburst by RXTE. In addition to this new QPO, we also detected the known 0.05 Hz QPO. Both the 0.22 and 0.05 Hz QPOs stand out clearly at a midflux level of the outburst during 2005 January 15 - 19, and later at an even lower flux level as the width of the 0.22 Hz QPO drops. No evolution of the centroid frequency with the flux is seen in either QPO. The rms value below 10 keV is around 4% - 6% for both QPOs and decreases at higher energies. We discuss our results in the context of current QPO models.