X-ray continuum with an iron emission line from the radio-quiet quasar PHL 909

Abstract

Results of the spectral analysis of the X-ray (0.1-10 keV) spectrum of the radio-quiet quasar, PHL 909, are presented. A spectrum of this quasar, which was observed on 1984/349, was obtained from the Exosat archives. Different models were used to fit the ME and LE + ME data. Fit parameters to the ME data show a steep spectral index for this quasar, typical of radio-quiet quasars. A weak 'soft excess' was detected in PHL 909. Two-power-law and broken-power-law models fitted well with the LE + ME data. A highly significant (greater than 99.9 percent) emission line was detected with line center energy being in the range 5.9-6.6 keV and the measured equivalent width between 300 and 1000 eV. A thermal bremsstrahlung model with a Gaussian line component also fits well with the data set (about 1.6 +0.4/-0.3 keV), suggesting a cluster origin from the known cluster around this quasar. Alternatively the detected line emission may be due to the fluorescence of cold matter around the central continuum source outside our line of sight