Wind accretion in HMXRB.

We present light curves and spectra of a ∼35ksec RXTE observation of Vela X-1 and a ∼300 ksec observation of Cen X-3. Both light curves show strong absorption which increases from no absorption at low orbital phases to large values at high orbital phases; in the case of Vela X-1 by a factor of almost 100. Superimposed are absorption dips which can be observed at any orbital phase, though mostly at high orbital phases. We study an unusually strong dip in Vela X-1 during which the flux is reduced by ∼90% and almost no pulses are detectable. The increase of N[sub H] and the scattered component show the in- and egress of material in the line of sight. A similar behaviour is observed in a pre-eclipse dip in Cen X-3. [ABSTRACT FROM AUTHOR]