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Register a new userAn XMM-Newton timing analysis of the eclipsing polar DP Leo
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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 ROSAT PSPC observations. We determine the eclipse length at X-ray wavelengths to be 235 +-5 s, slightly longer than at ultra-violet wavelengths, where it lasts 225s. The implied inclination and mass ratio for an assumed 0.6 M(sun) white dwarf are i=79.7 degrees and Q = M(wd)/M2 = 6.7. We determine a new linear X-ray eclipse and orbital ephemeris which connects the more than 120000 binary cycles covered since 1979. 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 degr/yr. Over the last 8.5 years the shift of the X-ray bright phase is ~2.5 degr/yr. 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. DP Leo is marginally detected at eclipse phase. The upper limit eclipse flux is consistent with an origin on the late-type secondary, L_X ~ 2.5 x 10**(29) ergs/s (0.20-7.55 keV}), at a distance of 400 pc.
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XMM-Newton was used to observe two eclipsing, magnetic cataclysmic variables, DP Leo and WW Hor, continuously for three orbital cycles each. Both systems were in an intermediate state of accretion. For WW Hor we also obtained optical light curves with the XMM-Newton Optical Monitor and from ground-based observations. Our analysis of the X-ray and optical light curves allows us to constrain physical and geometrical parameters of the accretion regions and derive orbital parameters and eclipse ephemerides of the systems. For WW Hor we directly measure horizontal and vertical temperature variations in the accretion column. From comparisons with previous observations we find that changes in the accretion spot longitude are correlated with the accretion rate. For DP Leo the shape of the hard X-ray light curve is not as expected for optically thin emission, showing the importance of optical depth effects in the post-shock region. We find that the spin period of the white dwarf is slightly shorter than the orbital period and that the orbital period is decreasing faster than expected for energy loss by gravitational radiation alone.
We present XMM-Newton observations of the eclipsing polar EP Dra which cover nearly 3 binary orbital cycles. The X-ray and UV data show evidence for a prominent dip before the eclipse which is due to the accretion stream obscuring the accretion region. The dip ingress is rapid in hard X-rays suggesting there is a highly collimated core of absorption. We find that a different level of absorption column density is required to match the observed count rates in different energy bands. We propose that this is due to the fact that different absorption components should be used to model the reprocessed X-rays, the shocked X-ray component and the UV emission and explore the affect that this has on the resulting fits to the spectrum. Further, there is evidence that absorption starts to obscure the softer X-rays shortly after the onset of the bright phase. This suggests that material is threaded by an unusually wide range of magnetic field lines, consistent with the suggestion of Bridge et al. We find that the period is slightly greater than that determined by Schwope & Mengel.
We present an analysis of the X-ray spectra of two strongly magnetic cataclysmic variables, DP Leo and WW Hor, made using XMM-Newton. Both systems were in intermediate levels of accretion. Hard optically thin X-ray emission from the shocked accreting gas was detected from both systems, while a soft blackbody X-ray component from the heated surface was detected only in DP Leo. We suggest that the lack of a soft X-ray component in WW Hor is due to the fact that the accretion area is larger than in previous observations with a resulting lower temperature for the re-processed hard X-rays. Using a multi-temperature model of the post-shock flow, we estimate that the white dwarf in both systems has a mass greater than 1 Msun. The implications of this result are discussed. We demonstrate that the `soft X-ray excess observed in many magnetic cataclysmic variables can be partially attributed to using an inappropriate model for the hard X-ray emission.
We present an {sl XMM-Newton} observation of the eclipsing binary Algol which contains an X-ray dark B8V primary and an X-ray bright K2IV secondary. The observation covered the optical secondary eclipse and captured an X-ray flare that was eclipsed by the B star. The EPIC and RGS spectra of Algol in its quiescent state are described by a two-temperature plasma model. The cool component has a temperature around 6.4$times 10^{6}$ K while that of the hot component ranges from 2 to 4.0$times 10^{7}$ K. Coronal abundances of C, N, O, Ne, Mg, Si and Fe were obtained for each component for both the quiescent and the flare phases, with generally upper limits for S and Ar, and C, N, and O for the hot component. F-tests show that the abundances need not to be different between the cool and the hot component and between the quiescent and the flare phase with the exception of Fe. Whereas the Fe abundance of the cool component remains constant at $sim$0.14, the hot component shows an Fe abundance of $sim$0.28, which increases to $sim$0.44 during the flare. This increase is expected from the chromospheric evaporation model. The absorbing column density $N_H$ of the quiescent emission is 2.5$times10^{20}$ cm$^{-2}$, while that of the flare-only emission is significantly lower and consistent with the column density of the interstellar medium. This observation substantiates earlier suggestions of the presence of X-ray absorbing material in the Algol system.
We present results of a timing analysis of various isolated pulsars using ESAs emph{XMM-Newton} observatory. Isolated pulsars are useful for calibration purposes because of their stable emission. We have analyzed six pulsars with different pulse profiles in a range of periods between 15 and 200 ms. All observations were made using the emph{EPIC-pn camera} in its faster modes (Small window, Timing and Burst modes). We investigate the relative timing accuracy of the camera by comparing the pulse periods determined from the emph{EPIC-pn camera} observations with those from radio observations. As a result of our analysis we conclude that the relative timing accuracy of the emph{EPIC-pn camera} is of the order of $1times 10^{-8}$.
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