期刊
ASTROPHYSICAL JOURNAL
卷 602, 期 2, 页码 L73-L76出版社
IOP PUBLISHING LTD
DOI: 10.1086/382695
关键词
BL Lacertae objects : individual (1ES 1255+244); cosmic microwave background; galaxies : clusters : individual (Coma); magnetic fields; radiation mechanisms : nonthermal; X-rays : galaxies
We report the hard X- ray spectrum of the Coma Cluster obtained using the Phoswich Detection System data of two independent BeppoSAX observations performed with a time interval of about 3 yr. In both the spectra a nonthermal excess with respect to the thermal emission is present at a confidence level of similar to 3.4 sigma. The combined spectrum obtained by adding up the two spectra allows a measurement of the excess at the level of similar to 4.8 sigma at energies above 20 keV. The analysis of the full BeppoSAX data set provides a revised nonthermal X- ray flux that is slightly lower than that previously estimated ( Fusco- Femiano et al.) and in agreement with that measured by two Rossi X- Ray Timing Explorer observations. The analysis of the offset fields in our Coma observations provides a possible flux determination of the BL Lac object 1ES 1255 + 244.
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