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Session 45 - New Insights on X-ray Binaries.
Display session, Wednesday, June 11
South Main Hall,

[45.03] RXTE Observations of the Cataclysmic Variable RX J1940.1+1025: Evidence for Energy Dependent Absorption.

R. D. Geckeler, R. Staubert (IAAT-Astronomie, Univ. Tuebingen, Germany)

The magnetic Cataclysmic Variable RX\,J1940.1-1025 belongs to the three-member subclass of polars with a slight non-synchronism (<2%) between the spin of the white dwarf and the orbital rotation.

New RXTE X-ray as well as optical CCD observations confirm a synchronization of the the WD with a refined value for the timescale of the order of 100\,yrs, which is the smallest synchronization timescale for a nearly-synchronous polar when compared to 170\,yrs for V1500 Cyg and 1600\,yrs for BY Cam, the other two members of this group.

We present RXTE X-ray data showing time dependent absorption in this roche-lobe overflowing binary caused by the magnetically funneled accreting matter. The accretion flow reveals itself by broad (2000-3000\,s FWHM) absorption troughs and by absorption dips of shorter duration (approx. 700\,s FWHM). These features are due to absorption by the accretion funnel near the WD surface and by parts of the more distant accretion stream, respectively. RXTE data show a correlated increase of the X-ray hardness for both of these absorption features.

In addition we give a refined ephemeris and parameters for the accretion geometry in RX\,J1940.

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