| Autor: |
Simm, T, Buchner, J, Merloni, A, Nandra, K, Shen, Y, Erben, T, Coil, A L, Willmer, C N A, Schneider, D P |
| Předmět: |
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| Zdroj: |
Monthly Notices of the Royal Astronomical Society; Nov2018, Vol. 480 Issue 4, p4912-4917, 6p |
| Abstrakt: |
We report on the discovery of a dramatic X-ray spectral variability event observed in a |$z$| ∼ 1 broad line type-1 QSO. The XMM - Newton spectrum from the year 2000 is characterized by an unobscured power-law spectrum with photon index of Γ ∼ 2, a column density of |$N_{\mathrm{H}}\sim 5\times 10^{20}\, \mathrm{cm^{-2}}$|, and no prominent reflection component. Five years later, Chandra captured the source in a heavily-obscured, reflection-dominated state. The observed X-ray spectral variability could be caused by a Compton-thick cloud with |$N_{\mathrm{H}}\sim 2\times 10^{24}\, \mathrm{cm^{-2}}$| eclipsing the direct emission of the hot corona, implying an extreme N H variation never before observed in a type-1 QSO. An alternative scenario is a corona that switched off in between the observations. In addition, both explanations require a significant change of the X-ray luminosity prior to the obscuration or fading of the corona and/or a change of the relative geometry of the source/reflector system. Dramatic X-ray spectral variability of this kind could be quite common in type-1 QSOs, considering the relatively few data sets in which such an event could have been identified. Our analysis implies that there may be a population of type-1 QSOs which are Compton-thick in the X-rays when observed at any given time. [ABSTRACT FROM AUTHOR] |
| Databáze: |
Complementary Index |
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