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 ± 0.25 s. 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 ± 0.23 s. 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 6.385 keV with an equivalent width of 243 eV is required to account for fluorescent emission from neutral iron. The iron fluorescence (∼6.4 keV) and Fe XXVI lines (∼6.95 keV) 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.

Extensive photometry of the intermediate polar V2069 Cyg (RX J2123.7+4217)

“…Hence, these Xray periods and our shorter period conform to the spin period of the white dwarf. Although this spin period was already detected in optical light (Nasiroglu et al 2012), our measurement of the spin period should be considered as a new result because its precision is three orders of magnitude higher than the precisions of all other measurements of the spin period in V2069 Cyg. The longer period detected by us is the orbital sideband because it conforms to the formula: 1/P beat = 1/P spin − 1/P orb , where P orb is the orbital period found by Thorstensen and Taylor (2001).…”

“…8). Examining figure 6 in Nasiroglu et al (2012), we found out that in 2009 the spin pulse profile of V2069 Cyg was also double-peaked, where, in contrast with the spin pulse profile observed in 2014, two humps were equally pronounced. The reality of this pulse profile is confirmed by the power spectrum presented in figure 4 in Nasiroglu et al, which reveals the very strong first harmonic of the spin oscillation.…”

“…Only 14 years later de Martino et al (2009) proved that this assumption is correct due to detection of the oscillation with a period of 743.2 ± 0.4 s, which was observed both in X-rays and in optical light. Shortly afterwards this oscillation was independently confirmed both in X-rays (743.2 ± 0.9 s, Butters et al 2011;743.1 ± 0.6 s, Bernardini et al 2012) and in optical light (743.38 ± 0.25 s, Nasiroglu et al 2012). Thus, because all short periods measured by different authors are compatible with each other, the IP nature of V2069 Cyg seems undoubted.…”

The HU Aqr planetary system hypothesis revisited

“…Examples of results obtained with OPTIMA include e.g. pulsars (Słowikowska et al 2009), the first optical magnetar (Stefanescu et al 2008), intermediate polars (Nasiroglu et al 2012), polars (Słowikowska et al 2013) and a black hole candidate with optical variability (Kanbach et al 2001). Similar to previous years, we have conducted several observations of HU Aqr during our OPTIMA observing campaigns at the Skinakas Observatory (SKO) in 2011 and 2012 (Goździewski et al 2012;Słowikowska et al 2013).…”

XMM–Newtonobservations of the peculiar cataclysmic variable Lanning 386: X-ray evidence for a magnetic primary

“…Here, the first Tbabs component accounts for interstellar absorption, (PartCov*Tbabs) models the circumstellar absorption and Mekal is as before. As in Nasiroglu et al (2012), our first fit could not constrain the plasma temperature, but provided a lower limit of > 8 keV at the 3σ level. The resulting fit did not model the 6.7 keV Fe xxv line well, and had a χ 2 R = 1.04.…”