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http://hdl.handle.net/20.500.12386/34542
Titolo: | X-Ray Unveiling Events in a z ≈ 1.6 Active Galactic Nucleus in the 7 Ms Chandra Deep Field-South | Autori: | Yu, Li Ming Luo, Bin Brandt, W. N. Bauer, Franz E. De Cicco, D. Fabian, A. GILLI, Roberto Koekemoer, A. PAOLILLO, Maurizio Schneider, D. P. Shemmer, O. TOZZI, Paolo Trump, Jonathan R. VIGNALI, CRISTIAN VITO, Fabio Wang, J. X. Xue, Y. Q. |
Data pubblicazione: | 2023 | Rivista: | THE ASTROPHYSICAL JOURNAL | Numero: | 949 | Fascicolo: | 1 | Da pagina:: | 6 | Abstract: | 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 ≲6.1 rest-frame days in the observed-frame 0.5-5 keV band. The event lasted for ≈5.0-7.3 days, and then XID 403 dimmed by a factor of >6.0 in ≲6.1 days. After ≈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 Γ = 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 × 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 ≈2500 Å) 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. | URI: | http://hdl.handle.net/20.500.12386/34542 | URL: | https://iopscience.iop.org/article/10.3847/1538-4357/acc17e https://ui.adsabs.harvard.edu/abs/2023ApJ...949....6Y/abstract https://api.elsevier.com/content/abstract/scopus_id/85159802301 |
ISSN: | 0004-637X | DOI: | 10.3847/1538-4357/acc17e | Bibcode ADS: | 2023ApJ...949....6Y | Fulltext: | open |
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