Study the X-ray Dust Scattering Halos with Chandra Observations of Cygnus X-3 and Cygnus X-1

摘要

We improve the method proposed by Yao \emph{et al} (2003) to resolve theX-ray dust scattering halos of point sources. Using this method we re-analyzethe Cygnus X-1 data observed with {\it Chandra} (ObsID 1511) and derive thehalo radial profile in different energy bands and the fractional halo intensity(FHI) as $I(E)=0.402\times E_{{\rm keV}}^{-2}$. We also apply the method to theCygnus X-3 data ({\it Chandra} ObsID 425) and derive the halo radial profilefrom the first order data with the {\it Chandra} ACIS+HETG. It is found thatthe halo radial profile could be fit by the halo model MRN (Mathis, Rumpl $&$Nordsieck, 1977) and WD01 (Weingartner $&$ Draine, 2001); the dust cloudsshould be located at between 1/2 to 1 of the distance to Cygnus X-1 and between1/6 to 3/4 (from MRN model) or 1/6 to 2/3 (from WD01 model) of the distance toCygnus X-3, respectively.