The strength and width of Fe Kα lines in Seyferts and their correlations with the X-ray slope

We study properties of Fe K lines of a large sample of Seyfert 1s observed by ASCA. Fits with power laws and Gaussian lines yield the average linewidth and equivalent width of 0.22±0.03 keV and 0.13±0.01 keV, respectively. Thus, the typical lines are weak and narrow. We then obtain the average line profile of all our spectra, and find it to consist of a narrow core and blue and red wings, with the red wing being much weaker than that of e.g. MCG −6-30-15. We obtain three average spectra of Seyferts grouped according to the hardness, and find the equivalent width of the core (originating in a remote medium) to be ≃50 eV in all three cases. The wings are well fitted by a broad line from a disc with strong relativistic effects. Its equivalent width correlates with the slope, increasing from ∼70 eV for the hardest spectrum to ∼120 eV for the softest one. The inner disc radius decreases correspondingly from ∼40 to ∼10 gravitational radii, and the fitted disc inclination is ∼45°. The obtained correlation between the slope and the strength of the broad Fe K line is found to be consistent with the previously found correlation of the slope and Compton reflection.

[1]  T. J. Turner,et al.  The Properties of the Relativistic Iron K-Line in NGC 3516 , 1999, astro-ph/9907193.

[2]  R. Narayan,et al.  Advection dominated accretion: Underfed black holes and neutron stars , 1994, astro-ph/9411059.

[3]  G. Matt,et al.  Iron Kα lines from X-ray photoionized accretion discs , 1993 .

[4]  K. O. Mason,et al.  The Physics of Accretion onto Compact Objects , 1986 .

[5]  Chris Biemesderfer,et al.  Astronomical Data Analysis Software and Systems X , 2001 .

[6]  David A. Smith,et al.  Unified theories of active galactic nuclei: a hard X-ray sample of Seyfert 2 galaxies , 1996 .

[7]  Nicholas E. White,et al.  X-ray fluorescence from the inner disc in Cygnus X-1 , 1989 .

[8]  T. Joseph W. Lazio,et al.  The Gaussian Plasma Lens in Astrophysics: Refraction , 1998 .

[9]  D. Smith,et al.  Correlation between Compton reflection and X-ray slope in Seyferts and X-ray binaries , 1998, astro-ph/9812215.

[10]  J. Chiang,et al.  Simultaneous EUVE/ASCA/RXTE Observations of NGC 5548 , 1999, astro-ph/9907114.

[11]  Andrew C. Fabian,et al.  X-ray reflection from cold matter in Active Galactic Nuclei and X-ray binaries , 1991 .

[12]  A. M. Beloborodov.  Plasma Ejection from Magnetic Flares and the X-Ray Spectrum of Cygnus X-1 , 1999 .

[13]  B. Czerny,et al.  The iron ${\rm K}\alpha$ line from a partially ionized reflecting medium in an active galactic nucleus , 1994 .

[14]  P. Grandi,et al.  The Broadband Spectrum of 3C 120 Observed by BeppoSAX , 2000, astro-ph/0011543.

[15]  K. Nandra,et al.  ASCA Observations of Seyfert 1 Galaxies. II. Relativistic Iron Kα Emission , 1996, astro-ph/9606169.

[16]  K. Nandra,et al.  GINGA observations of the X-ray spectra of Seyfert galaxies. , 1994 .

[17]  C. Done,et al.  Evolution of the Accretion Flow in Nova Muscae 1991 , 1998, astro-ph/9801232.

[18]  K. Nandra,et al.  X-ray reflection from cold matter in the nuclei of active galaxies , 1990, Nature.

[19]  B. M. Peterson,et al.  The Origin of the X-Ray and Ultraviolet Emission in NGC 7469 , 2000, astro-ph/0006339.

[20]  J. Nousek,et al.  Iron Kα Evidence for Two X-Ray Reprocessors in MCG –5-23-16 , 1997 .

[21]  A. Fabian,et al.  Special relativistic effects on the strength of the fluorescent Kα iron line from black hole accretion discs , 1997 .

[22]  Mitsuru Ebihara,et al.  Solar-system abundances of the elements , 1982 .

[23]  A. Zdziarski,et al.  Angle-dependent Compton reflection of X-rays and gamma-rays , 1995 .

[24]  H. Kunieda,et al.  Gravitationally redshifted emission implying an accretion disk and massive black hole in the active galaxy MCG–6–30–15 , 1995, Nature.

[25]  Hans-Peter Schertl,et al.  Geochim. cosmochim. acta , 1989 .

[26]  W. N. Johnson,et al.  Broad-band γ-ray and X-ray spectra of NGC 4151 and their implications for physical processes and geometry , 1996 .

[27]  K. Nandra,et al.  The variable iron K emission line in MCG-6-30-15 , 1996 .

[28]  Ucla,et al.  Evidence for Rapid Iron Kα Line Flux Variability in MCG –6-30-15 , 2000, astro-ph/0010274.

[29]  G. Matt,et al.  Iron Kα line intensity from accretion discs around rotating black holes , 1996 .