SIMBAD references

There is little information concerning the azimuthal distribution of X-rays in dust-scattering halos. This paper describes a Chandra observation of the bright source Cyg X-2 designed specifically for this purpose. After measuring and subtracting ~10% instrument effects, we find the scattering halo to be rather uniform with possible fluctuations in the surface brightness of only 2%. Observations and data processing are discussed in detail. Some information about the dust distribution is derived.