BeppoSAX broad-band observations of low-redshift quasars: Spectral curvature and iron Kα lines

T. Mineo, F. Fiore, A. Laor, E. Costantini, William Nielsen Brandt, A. Comastri, R. Della Ceca, M. Elvis, T. Maccacaro, S. Molendi

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Abstract

We present results from BeppoSAX observations of 10 low redshift quasars. The quasars are part of the Laor et al. (1997) sample of 23 optically selected PG quasars with redshift < 0.4 and low Galactic absorption along the line of sight. Significant spectral curvature is detected for the 6 quasars with the highest signal to noise ratio in their low energy spectra. The average curvature can be parameterized as a flattening of the underlying power law by Δα ∼ 0.5 above ∼ 1 keV. We find that quasars with a steeper soft X-ray (0.1-2 keV) spectrum tend to be steeper also at higher (2-10keV) energies. The distribution of the best fit 2-10 keV slopes is similar to that found for other radio-quiet AGN and characterized by a large dispersion around the mean: αE ≃ 1.0 ± 0.3. Iron Kα lines are detected in 4 quasars. In the narrow-line quasar PG 1115+407, the rest frame line energy (6.69±0.11 keV) and equivalent width (580±280eV) are consistent with those found in a few low redshift narrow-line Seyfert 1 galaxies (NLSy1). This, together with the similarity of the 0.1-10 keV X-ray continuum, suggests that this quasar is the higher redshift and luminosity analog of a NLSy1. In the broad line quasar PG 0947+396, the rest-frame line energy suggests fluorescence from cold iron. The line equivalent width (> 400 eV) is however about 2-3 times higher than that usually found in Seyfert 1 galaxies. The high energy power-law slopes and the iron line emission properties seem to be unrelated to the X-ray luminosity.

Original languageEnglish (US)
Pages (from-to)471-482
Number of pages12
JournalAstronomy and Astrophysics
Volume359
Issue number2
StatePublished - Dec 1 2000

All Science Journal Classification (ASJC) codes

  • Astronomy and Astrophysics
  • Space and Planetary Science

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