Mj. Henriksen, X-RAY SPECTRAL OBSERVATIONS OF CLUSTERS OF GALAXIES UNDERGOING MERGEREVENTS, The Astrophysical journal, 414(1), 1993, pp. 120000005-120000008
We have analyzed the HEAO 1 A2 observations of two clusters whose opti
cal and X-ray isophotes are suggestive of merging subclusters, A119 an
d A754, and find evidence of nonisothermal X-ray emission from both cl
usters. The X-ray spectrum of both clusters, when fitted with a single
isothermal model, shows residual soft X-ray emission. There is a stat
istically significant reduction in chi2 (98% probability based on the
F-test) when a second temperature component is added. If the asymmetri
c isophotes seen in the soft X-ray image are indicative of merging sub
clusters, then our analysis of the Einstein Imaging Proportional Count
er (IPC) spectra and Solid State Spectrometer (SSS) observations of A7
54, which provide some spatial and spectral resolution, suggests that
the two temperature components seen in the HEAO 1 A2 spectra are assoc
iated with gas trapped in the subcluster potential wells. The implied
subcluster isothermal masses suggest that a more massive cluster is ac
creting a less massive companion in A754. The present observations can
not rule out the alternative possibility that the cooler gas is associ
ated with the outer cluster atmosphere rather than individual subclust
ers, as appears to be the case for A119. Astro D observations will be
necessary to distinguish between these two possibilities for both clus
ters.