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The Dichotomy of Seyfert Galaxies at Hardest X-rays

Volker Beckmann ISDC Data Centre for Astrophysics & Observatoire de Genève & UMBC T. J.-L. Courvoisier, N. Gehrels, S. Soldi, J. Tueller, J. Wendt, et al. The Dichotomy of Seyfert Galaxies at Hardest X-rays. The X-ray Universe 2008, May 29, 2008. Overview.

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The Dichotomy of Seyfert Galaxies at Hardest X-rays

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  1. Volker Beckmann ISDC Data Centre for Astrophysics & Observatoire de Genève & UMBC T. J.-L. Courvoisier, N. Gehrels, S. Soldi, J. Tueller, J. Wendt, et al. The Dichotomy of Seyfert Galaxies at Hardest X-rays The X-ray Universe 2008, May 29, 2008

  2. Overview • Differences of Seyfert type AGN ? • Variability of AGN at hardest X-rays • Swift/BAT detected AGN in the 9 month survey • Variability analysis • Maximum Likelihood approach • variability as function of Lx and Eddington ratio • other parameters as a function of the hard X-ray spectrum? • Future work V. Beckmann, ISDC

  3. Scientific goals • On what time scales do AGN show variability above 15 keV ? • Does variability depend on source type, on intrinsic absorption, or on spectral shape ? • What processes drive the hard X-ray variability? NGC 2992; Beckmann, Gehrels & Tueller (2007)

  4. Swift/BAT 9 month survey • First 9 months of survey, starting December 2004 • 15 - 195 keV count rates • 408 sources with significance >5 • 160 AGN (w/o unid. sources) • 44 AGN with significance >10 • Swift/BAT AGN paper by Jack Tueller et al. 2008, arXiv:0711.4130

  5. Variability 2test - only for correct errors (systematic error?) Crab lightcurve from Swift/BAT 9 month survey V. Beckmann, ISDC

  6. Maximum Likelihood estimator • Variance has two components: noise and intrinsic variability Q • Assume that the intrinsic variability is constant • For Gaussian statistics we can determine the probability density for obtaining the N measurements (xi, i) • This can be solved in a simple least2form (see Almaini et al. 2000, MNRAS, 315, 325, for details): • this becomes the excess variance for constant i V. Beckmann, ISDC

  7. The variability is not a function of source flux Maximum Likelihood estimator Blazars in red V. Beckmann, ISDC

  8. Variability Variability seems to be a function of intrinsic absorption NH Blazars excluded Redsquares: variable according to structure function analysis Black triangles: three lowest flux objects, excluded from analysis V. Beckmann, ISDC

  9. Variability vs. Luminosity NGC 4151 NGC 4945 NGC 2110 IGR J21247+5058 Cen A Blazars excluded Redsquares: variable according to structure function analysis NGC 4051 V. Beckmann, ISDC

  10. Photon index vs. variability Photon indices from INTEGRAL IBIS/ISGRI V. Beckmann, ISDC

  11. Variability vs. black hole mass Blazars in red Black hole masses from Woo & Urry and references therein V. Beckmann, ISDC

  12. Variability vs. Eddington ratio NGC 2992 3C 273 Blue: sources showing a cut-off in INTEGRAL IBIS/ISGRI spectra V. Beckmann, ISDC

  13. Results • 44 brightest Swift/BAT AGN • 30% of Seyfert type AGN exhibit variability • strong variability seen in blazars • 15% show >20% variability in maximum likelihood estimator • type 1 objects seem to be less variable than type 2 • probably a function of luminosity / Eddington ratio: • variable objects are the ones with Lx < 1044 erg sec-1 and with Eddington ratio < 1% • seen previously at soft X-rays, optical, UV (for recent XMM-Newton results see Papadakis et al. 2008) • Beckmann et al. 2007, A&A 475, 827, astro-ph/0709.2230

  14. Future Work • underlying physical process • are absorbed/unabsorbed sources intrinsically different? • what role does the mass / Eddington ratio play ? • use of INTEGRAL combined JEM-X, IBIS ISGRI/PICsIT and SPI spectra for the brightest ~100 AGN V. Beckmann, ISDC

  15. Dichotomy ? Seyfert 1/Seyfert 2 galaxies show no differences so far in hardest X-rays (except for spectral slope?) V. Beckmann, ISDC

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