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Changing Look AGN: An X-ray Lookстатья
- Авторы: Titarchuk Lev, Seifina Elena, Mishin Yegor
- Сборник: ArXiV.org.e-Print
- Серия: astro-ph.GA
- Год издания: 2024
- Издательство: Cornell University Press
- Местоположение издательства: United States
- Первая страница: 1
- Последняя страница: 60
- Номер статьи: 2411.09781
- DOI: 10.48550/arXiv.2411.09781
- Аннотация: To date, a number of changing-look (CL) active galactic nuclei (AGNs) are known. We studied, in detail what happens to the X-ray spectrum during the CL events using the example of the nearby CL Seyfert NGC 1566, which was observed by Swift, NuSTAR, XMM-Newton, and Suzaku. We applied the Comptonization model to describe an evolution of NGC 1566 X-ray spectra during outbursts and compared these results with a typical behavior for other AGNs to identify some differences and common properties that can ultimately help us to better understand the physics of the CL phenomenon. We found that changes in the X-ray properties of NGC 1566 are characterized by a different combination of Sy1 (using 1H 0707–495 as a representative) and Sy2 properties (using NGC 7679 and Mrk 3 as their representatives). At high X-ray luminosities NGC 1566 exhibits the behavior typical for Sy1, and at low luminosities we see a transition of NGC 1566 from the Sy1 behavior to the Sy2 pattern. We revealed the saturation of the spectral indices, α for these four AGNs during outbursts (α_1566∼1.1, α_0707∼2, α_7679∼0.9 and α_mrk3∼0.9) and determined the masses of the black holes (BHs) in the centers of these AGNs namely, M_0707∼6.8×10^7 M⊙, M_7679∼8.4×10^6 M⊙, Mmrk_3∼2.2×10^8 M⊙ and M_1566 ∼2×10^5 M⊙, applying the scaling method. Our spectral analysis shows that the changing-look of NGC1566 from Sy1.2 to Sy1.9 in 2019 was accompanied by the transition of NGC 1566 to an accretion regime which is typical for the intermediate and highly soft spectral states of other BHs. We also find that when going from Sy2 to Sy1, the spectrum of NGC 1566 shows an increase in the soft excess accompanied by a decrease in the Comptonized fraction (0.1<f<0.5), which is consistent with the typical behavior of BH sources during X-ray outburst decay. Our results strongly suggest that the large diversity in its behavior observed among CL, Sy1, and Sy2 AGNs with different X-ray luminosities can be explained by changes in a single variable parameter, such as the ratio of the AGN’s X-ray luminosity to its Eddington luminosity, without any need for additional differences in Sy AGN parameters, such as its inclination, thereby blurring the distinction between the Sy1, Sy2 and CL-AGN subclasses.
- Добавил в систему: Сейфина Елена Викторовна