title: Interaction in Abell 2256: The BeppoSAX View.
abstract: We present results from a spatially resolved spectral analysis of the merging cluster Abell 2256. The long integration time (135 ks) and the good spatial resolution of the Medium-Energy Concentrator/Spectrometer on board BeppoSAX allow us to derive a new and substantially improved measurement of the temperature structure. We find that, within a central region of the cluster, where the effects of the merger are visible in the ROSAT surface brightness image, the azimuthally averaged projected temperature is remarkably flat; outside this region, the projected temperature rapidly declines. The BeppoSAX data also show clear evidence of an azimuthal temperature gradient in the 4&arcmin;-8&arcmin; (0.4-0.8 Mpc) radial bin, oriented in the same direction as the merger itself. Our metal abundance profile shows, for the first time, firm evidence of an abundance gradient in a rich merging cluster. Intriguingly, the abundance map shows, in the southeast sector, i.e., the one farthest away from the merger, a sharp factor of 2 drop in abundance at a radius comparable to the core radius of the cluster. A possible interpretation is that prior to the merger event, a cooling flow had already developed in the core of the infalling subgroup, as suggested by Fabian & Daines. The interaction between the substructures would have disrupted the cooling flow, thereby reheating and remixing the gas. Since the merger in A2256 is still in a relatively early stage, the gas located on the side opposite the merger event would still retain the low abundances associated with the intracluster medium prior to the cooling flow disruption.
authors.initials: S
authors.lastname: Molendi
authors.lastname: De Grandi S
authors.initials: R
authors.lastname: Fusco-Femiano