The Discovery of 3.9 Hour Periodic Dips in the X-Ray Intensity of XB 1254-690
Parmar, A. N.; Pakull, M.; Courvoisier, T. J. -L.; Peacock, A.
Germany, Netherlands
Abstract
The low-mass X-ray binary XB 1254 - 690 has been discovered to show irregular dips in X-ray intensity that recur with a period of 3.9 hr consistent with the optical period derived independently. The spectral changes observed during dipping are complex and can be successfully described using a two-component model. One of these components may be X-rays scattered into the line of sight by an accretion disk corona. In contrast to other X-ray dipping sources for which the metallicity has been measured, the abundance of the material responsible for the dips is close to that of cosmic material.