We perform long-term (≈15 years, observed-frame) X-ray variability analyses of the 68 brightest radio-quiet active galactic nuclei (AGNs) in the 6 Ms Chandra Deep Field-South survey; the majority are in the redshift range of 0.6-3.1, providing access to penetrating rest-frame X-rays up to ≈10-30 keV. Of the 68 sources, 24 are optical spectral type I AGNs, and the rest (44) are type II AGNs. The timescales probed in this work are among the longest for X-ray variability studies of distant AGNs. Photometric analyses reveal widespread photon flux variability: 90% of AGNs are variable above a 95% confidence level, including many X-ray obscured AGNs and several optically classified type II quasars. We characterize the intrinsic X-ray luminosity () and absorption () variability via spectral fitting. Most (74%) sources show variability; the variability amplitudes are generally smaller for quasars. A Compton-thick candidate AGN shows variability of its high-energy X-ray flux, indicating the size of reflecting material to be ≲0.3 pc. variability is also detected in a broad absorption line quasar. The variability amplitude for our sample appears to rise as time separation increases. About 16% of sources show variability. One source transitions from an X-ray unobscured to obscured state, while its optical classification remains type I; this behavior indicates the X-ray eclipsing material is not large enough to obscure the whole broad-line region.

Long-term X-ray variability of typical active galactic nuclei in the distant universe / Yang, G.; Brandt, W.N.; Luo, B.; Xue, Y.Q.; Bauer, F.E.; Sun, M.Y.; Kim, S.; Schulze, S.; Zheng, X.C.; Paolillo, M.; Shemmer, O.; Liu, T.; Schneider, D.P.; Vignali, C.; Vito, F.; Wang, J.-X.. - In: THE ASTROPHYSICAL JOURNAL. - ISSN 0004-637X. - STAMPA. - 831:2(2016), pp. 145.145-145.164. [10.3847/0004-637X/831/2/145]

Long-term X-ray variability of typical active galactic nuclei in the distant universe

VIGNALI, CRISTIAN;VITO, FABIO;
2016

Abstract

We perform long-term (≈15 years, observed-frame) X-ray variability analyses of the 68 brightest radio-quiet active galactic nuclei (AGNs) in the 6 Ms Chandra Deep Field-South survey; the majority are in the redshift range of 0.6-3.1, providing access to penetrating rest-frame X-rays up to ≈10-30 keV. Of the 68 sources, 24 are optical spectral type I AGNs, and the rest (44) are type II AGNs. The timescales probed in this work are among the longest for X-ray variability studies of distant AGNs. Photometric analyses reveal widespread photon flux variability: 90% of AGNs are variable above a 95% confidence level, including many X-ray obscured AGNs and several optically classified type II quasars. We characterize the intrinsic X-ray luminosity () and absorption () variability via spectral fitting. Most (74%) sources show variability; the variability amplitudes are generally smaller for quasars. A Compton-thick candidate AGN shows variability of its high-energy X-ray flux, indicating the size of reflecting material to be ≲0.3 pc. variability is also detected in a broad absorption line quasar. The variability amplitude for our sample appears to rise as time separation increases. About 16% of sources show variability. One source transitions from an X-ray unobscured to obscured state, while its optical classification remains type I; this behavior indicates the X-ray eclipsing material is not large enough to obscure the whole broad-line region.
2016
Long-term X-ray variability of typical active galactic nuclei in the distant universe / Yang, G.; Brandt, W.N.; Luo, B.; Xue, Y.Q.; Bauer, F.E.; Sun, M.Y.; Kim, S.; Schulze, S.; Zheng, X.C.; Paolillo, M.; Shemmer, O.; Liu, T.; Schneider, D.P.; Vignali, C.; Vito, F.; Wang, J.-X.. - In: THE ASTROPHYSICAL JOURNAL. - ISSN 0004-637X. - STAMPA. - 831:2(2016), pp. 145.145-145.164. [10.3847/0004-637X/831/2/145]
Yang, G.; Brandt, W.N.; Luo, B.; Xue, Y.Q.; Bauer, F.E.; Sun, M.Y.; Kim, S.; Schulze, S.; Zheng, X.C.; Paolillo, M.; Shemmer, O.; Liu, T.; Schneider, D.P.; Vignali, C.; Vito, F.; Wang, J.-X.
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11585/597521
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