A multiwavelength timing analysis of the eclipsing polar DP Leo

Abstract

Abstract.We present an analysis of the X-ray light curves of the magnetic cataclysmic variable DP Leo using recently performed XMM−Newton EPIC and archival published and unpublished ROSAT PSPC observations. We combine the timings of the X-ray eclipses with timings derived from archival HST-observations and new optical observations with the photon counting OPTIMA camera. We determine the eclipse length at X-ray wavelengths to be 235 ± 5 s, slightly longer than at ultra-violet wavelengths, where it lasts 225 s. A new orbital ephemeris is derived which connects the more than 120 000 binary cycles covered since 1979. It has a highly significant quadratic term, implying an orbital period change ofṖ = −4.4 × 10 −12 s s −1 , two orders of magnitude larger than being compatible with braking by gravitational radiation only. Over the last twenty years, the optical and X-ray bright phases display a continuous shift with respect to the eclipse center by ∼2.1• yr −1 . Over the last 8.5 years the shift of the X-ray bright phase is ∼2.5• yr −1 . We interpret this as evidence of an asynchronously rotating white dwarf although synchronization oscillations cannot be ruled out completely. If the observed phase shift continues, a fundamental rearrangement of the accretion geometry must occur on a time-scale of some ten years. Applying model atmosphere spectra to optical/UV eclipse light curves, we determine the temperature and mass of the white dwarf, the temperature and size of the optical/UV emitting spot and the distance to DP Leo to be T wd = 13 500 K, M wd 0.6 M , T spot = 32 000 K, A spot 0.1 A wd , and D = 400 pc, respectively. The implied inclination and mass ratio are i = 79.5• and Q = M wd /M 2 = 6.7. DP Leo is marginally detected at eclipse phase in X-rays. The upper limit eclipse flux is consistent with an origin on the late-type secondary, L X 2.5 × 10 29 ergs s −1 (0.20−7.55 keV), at a distance of 400 pc.

Planet formation from the ejecta of common envelopes

“…For the CVs, we find very good agreement in all three cases, with mass differences of less than a factor of 2. For the system DP Leo, we note that Schwope et al (2002) provide different stellar masses than Pandel et al (2002) and Beuermann et al (2011), but the resulting planetary masses are both comparable to the value derived by Zorotovic & Schreiber (2013).…”

“…For the system DP Leo, the index (1) refers to stellar masses as given by Pandel et al (2002) and Beuermann et al (2011), while (2) is based on the masses given by Schwope et al (2002). Beuermann et al (2011), as well as by Schwope et al (2002). We find that the theoretical predictions mark a narrow curve in the parameter space, and even 7 of our sources (8 data points due to DP Leo) are close to this curve.…”

“…We therefore give the value r P for our fiducial scenario (α L = 12.5) and a more conservative case r P,cons (α L = 4). For the system DP Leo, the index (1) refers to stellar masses as given by Pandel et al (2002) and Beuermann et al (2011), while (2) is based on the masses given by Schwope et al (2002). Beuermann et al (2011), as well as by Schwope et al (2002).…”

Origin of apparent period variations in eclipsing post-common-envelope binaries

“…DP Leo was the first eclipsing polar discovered (Biermann et al 1985). A decrease in the binary period was noticed by Schwope et al (2002) and Pandel et al (2002). Qian et al (2010a) find a reversal of this trend, suggesting a sinusoidal variation that may be related to the presence of a giant planet.…”

“…Qian et al (2010a) find a reversal of this trend, suggesting a sinusoidal variation that may be related to the presence of a giant planet. Beuermann et al (2011) Schwope et al (2002). The data spanning more than 30 years since 1979 suggest there is a third body orbiting the binary, most likely a giant planet.…”