Very fast photometric and X-ray observations of the intermediate polar V2069 Cygni (RX J2123.7+4217)

Abstract

We present fast timing photometric observations of the intermediate polar V2069 Cygni (RX J2123.7+4217) using the Optical Timing Analyzer (OPTIMA) at the 1.3-m telescope of Skinakas Observatory. The optical (450-950 nm) light curve of V2069 Cygni was measured with sub-second resolution for the first time during 2009 July and revealed a double-peaked pulsation with a period of 743.38 ± 0.25s. A similar double-peaked modulation was found in the simultaneous Swift satellite observations. We suggest that this period represents the spin of the white dwarf accretor. Moreover, we present results from a detailed analysis of the XMM-Newton observation, which also shows a double-peaked modulation, however shifted in phase, with a period of 742.35 ± 0.23s. The X-ray spectra obtained from the XMM-Newton European Photon Imaging Camera (EPIC) instruments were modelled by a plasma emission and a soft blackbody component with a partial covering photoelectric absorption model with a covering fraction of 0.65. An additional Gaussian emission line at 6.385keV with an equivalent width of 243eV is required to account for fluorescent emission from neutral iron. The iron fluorescence (~6.4keV) and Fexxvi lines (~6.95keV) are clearly resolved in the EPIC spectra. In the P orb-P spin diagram of intermediate polars, V2069 Cyg shows a low spin-to-orbit ratio of ~0.0276 in comparison with ~0.1 for other intermediate polars. © 2012 The Authors Monthly Notices of the Royal Astronomical Society © 2012 RAS.