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AGN X-ray Variability in the XMM-COSMOS Survey

AGN X-ray Variability in the XMM-COSMOS Survey. Authors: G.Lanzuisi ; G.Ponti et al. 2013 Speaker: Xuechen Zheng. Outlines. 1. Introduction 2. V parameter 3. Excess variance 4. vs. AGN parameters 5. Conclusions. Introduction. Variability of AGN. Previous:

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AGN X-ray Variability in the XMM-COSMOS Survey

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  1. AGN X-ray Variability in the XMM-COSMOS Survey Authors: G.Lanzuisi; G.Ponti et al. 2013 Speaker: Xuechen Zheng

  2. Outlines • 1. Introduction • 2. V parameter • 3. Excess variance • 4. vs. AGN parameters • 5. Conclusions

  3. Introduction

  4. Variability of AGN • Previous: • EXOSAT and RXTE: variability vs. X-ray luminosity; PSD • Break frequency in PSD vs. black hole mass • Excess variance • Samples: local, short term • In this paper: • XMM-Newton : 2 field of COSMOS, Dec. 2003 to May 2007 • Spectroscopic redshifts or reliable photometric redshifts available

  5. V parameter

  6. Definition of V parameter • Variability index V = - • V = 1, P = 90%; V = 1.3, P=95%; V = 2, P=99%

  7. V vs. counts • V parameter strongly dependent on counts

  8. V vs. counts

  9. V vs. • Decreasing density toward low L: • Small volume at low z • Typical exposure time • The fraction of variable sources is constant

  10. V vs. z • Lack of high z and high counts sources: • Constant exposure time • Fraction of variables decrease • Indicate: hard to detect variables at high z

  11. V vs. type Type I has the highest fraction of variable sources: due to typical higher number of counts of type I

  12. Excess variance

  13. Calculate the normalize excess variance Problem: 1. err()> 2. <

  14. vs. counts • Anti correlation between and counts : bias • Difference between and V parameter

  15. vs. AGN parameters

  16. vs. and z • L: • z: no correlation

  17. From z<0.7 to 1.5<z<3.5  slope from −0.40±0.07 to −0.65±0.10 Bias from selection!

  18. The constraint V>1.3 lead to overestimated average Use all 638 sources without selection or use sources that counts>700

  19. vs. BHMs and Eddington ratios • vs. BHMs: a slope of −0.42 ± 0.11 (BHMs from BL or scaling relation) • vs. Eddington ratios: no correlation (from SED)

  20. -L relation might be the byproduct of -BHM relation

  21. Optical and X-ray variability • No clear correlation between optical and X-ray variability found

  22. Conclusions

  23. 1. variability is prevalent in AGN • 2. Type I and Type II sources has similar variability distribution • 3. There is anti-correlation between and • 4. No evolution in z of the - if only the sources with good statistics considered • 5. Strong anti-correlation between and observed; no correlation between and Eddington ratios is found • 6. No clear correlation is found between optical and X-ray variability

  24. Thanks!

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