Browsing by Author "Fabian, A."

Now showing 1 - 4 of 4
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    Nustar and suzaku X-Ray spectroscopy of NGC 4151: evidence for reflection from the inner accretion disk
    (2015) Keck, M.; Brenneman, L.; Ballantyne, D.; Bauer, Franz Erik; Boggs, S.; Christensen, F.; Craig, W.; Dauser, T.; Elvis, M.; Fabian, A.; Fuerst, F.; García, J.; Grefenstette, B.; Hailey, C.; Harrison, F.; Madejski, G.; Marinucci, A.; Matt, G.; Reynolds, C.; Stern, D.; Walton, D.; Zoghbi, A.
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    NuSTAR and XMM-Newton observations of NGC 1365 : Extreme absorption variability and a constant inner accretion disk
    (2014) Walton, D.; Risaliti, G.; Harrison, F.; Fabian, A.; Miller, J.; Arévalo, Patricia; Ballantyne, D.; Boggs, S.
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    The NuSTAR X-ray spectrum of the low-luminosity active galactic nucleus in NGC 7213
    (2015) Ursini, F.; Marinucci, A.; Matt, G.; Bianchi, S.; Tortosa, A.; Stern, D.; Arévalo, P.; Ballantyne, D.; Bauer, Franz Erik; Fabian, A.; Harrison, F.; Lohfink, A.; Reynolds, C.; Walton, D.
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    X-Ray Unveiling Events in a z ≈ 1.6 Active Galactic Nucleus in the 7 Ms Chandra Deep Field-South
    (2023) Yu, Li-Ming; Luo, Bin; Brandt, W. N.; Bauer, Franz E.; De Cicco, D.; Fabian, A.; Gilli, R.; Koekemoer, A.; Paolillo, M.; Schneider, D. P.; Shemmer, O.; Tozzi, P.; Trump, Jonathan R.; Vignali, C.; Vito, F.; Wang, J. -x.; Xue, Y. Q.
    We investigate the extreme X-ray variability of a z = 1.608 active galactic nucleus in the 7 Ms Chandra Deep Field-South (XID 403), which showed two significant X-ray brightening events. In the first event, XID 403 brightened by a factor of >2.5 in less than or similar to 6.1 rest-frame days in the observed-frame 0.5-5 keV band. The event lasted for approximate to 5.0-7.3 days, and then XID 403 dimmed by a factor of >6.0 in less than or similar to 6.1 days. After approximate to 1.1-2.5 yr in the rest frame (including long observational gaps), it brightened again, with the 0.5-5 keV flux increasing by a factor of >12.6. The second event lasted over 251 days, and the source remained bright until the end of the 7 Ms exposure. The spectrum is a steep power law (photon index Gamma = 2.8 +/- 0.3) without obscuration during the second outburst, and the rest-frame 2-10 keV luminosity reaches 1.5(-0.5)(+0.8) x 10(43) erg s(-1); there is no significant spectral evolution within this epoch. The infrared-to-UV spectral energy distribution of XID 403 is dominated by the host galaxy. There is no significant optical/UV variability and R-band (rest-frame approximate to 2500 angstrom) brightening contemporaneous with the X-ray brightening. The extreme X-ray variability is likely due to two X-ray unveiling events, where the line of sight to the corona is no longer shielded by high-density gas clumps in a small-scale dust-free absorber. XID 403 is probably a high-redshift analog of local narrow-line Seyfert 1 galaxies, and the X-ray absorber is a powerful accretion disk wind. On the other hand, we cannot exclude the possibility that XID 403 is an unusual candidate for tidal disruption events.