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Nonthermal hard X-ray excess in the Coma cluster: resolving the discrepancy between the results of different PDS data analyses

Roberto Fusco-Femiano·Raffaella Landi·Mauro Orlandini
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Abstract

The detection of a nonthermal excess in the Coma cluster spectrum by two BeppoSAX observations analyzed with the XAS package (Fusco-Femiano et al.) has been disavowed by an analysis (Rossetti & Molendi) performed with a different software package (SAXDAS) for the extraction of the spectrum. To resolve this discrepancy we reanalyze the PDS data considering the same software used by Rossetti & Molendi. A correct selection of the data and the exclusion of contaminating sources in the background determination show that also the SAXDAS analysis reports a nonthermal excess with respect to the thermal emission at about the same confidence level of that obtained with the XAS package (~4.8sigma). Besides, we report the lack of the systematic errors investigated by Rossetti & Molendi and Nevalainen et al. taking into account the whole sample of the PDS observations off the Galactic plane, as already shown in our data analysis of Abell 2256 (Fusco-Femiano, Landi & Orlandini). All this eliminates any ambiguity and confirms the presence of a hard tail in the spectrum of the Coma cluster.

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Roberto Fusco-Femiano, Raffaella Landi, Mauro Orlandini. 2006-11-10. Nonthermal hard X-ray excess in the Coma cluster: resolving the discrepancy between the results of different PDS data analyses. https://doi.org/10.1086/510739

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