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Dirk Pandel France A. Cordova Robert E. Shirey Gavin Ramsay Mark Cropper Keith O. Mason Rudi Much Dave Kilkenny 《Monthly notices of the Royal Astronomical Society》2002,332(1):116-126
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. 相似文献
994.
A. Olech J. Kaluzny I. B. Thompson A. Schwarzenberg-Czerny 《Monthly notices of the Royal Astronomical Society》2003,345(1):86-96
New photometry of RRab and RRc stars in ω Centauri is used to calibrate their absolute magnitudes MV as a function of (a) metallicity and (b) the Fourier parameters of light curves in the V band. The zero point of both calibrations relies on the distance modulus to the cluster derived earlier by the Cluster AgeS Experiment (CASE) project based on observations of the detached eclipsing binary OGLE GC17. For RRab variables, we obtained a relation of MV = (0.26 ± 0.08)[ Fe/H ] + (0.91 ± 0.13) . A dereddened distance modulus to the Large Magellanic Cloud (LMC) based on that formula is μ0 = 18.56 ± 0.14 mag . The second calibration of MV , which is based on Fourier coefficients of decomposed light curves, results in the LMC distance of μ0 = 18.51 ± 0.07 mag . 相似文献
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From optical photometry the cataclysmic variable RX J0944.5+0357 is shown to have a double-peaked pulse profile with a period
∼ 2160 s. The two peaks vary rapidly in relative amplitude. Often most of the optical power is concentrated in the first harmonic
of the 2160 s modulation; RX J0944.5+0357therefore probably belongs to the relatively rare class of two-pole accreting intermediate
polars exemplified by YY Dra and V405 Aur.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
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Michael W. Feast Patricia A. Whitelock Freddy Marang 《Monthly notices of the Royal Astronomical Society》2003,346(3):878-884
JHKL observations of the mass-losing carbon Mira variable IRAS 15194–5115 (II Lup) extending over about 18 yr are presented and discussed. The pulsation period is 575 d and has remained essentially constant over this time span. The star has undergone an extensive obscuration minimum during this time. This is complex and, like such minima in similar objects (e.g. R For), does not fit the model predictions of a simple long-term periodicity. Together with the high-resolution observations of Lopez et al., the results suggest that the obscuration changes are caused by the formation of dust clouds of limited extent in the line of sight. This is an R Coronae Borealis-type (RCB-type) model. The effective reddening law at J and H is similar to that found for R For. 相似文献