Relativistic reflection modeling in AGN and related variability from PCA: a brief review
X-ray observations of active galactic nuclei (AGNs) reveal relativistic reflections from the innermost regions of accretion disks, which contain general-relativistic footprints caused by spinning supermassive black holes (SMBH). We anticipate the spin of a SMBH to be stable over the human timeframe,...
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Frontiers Media S.A.
2024-10-01
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| Series: | Frontiers in Astronomy and Space Sciences |
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| Online Access: | https://www.frontiersin.org/articles/10.3389/fspas.2024.1479301/full |
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| author | A. Danehkar |
| author_facet | A. Danehkar |
| author_sort | A. Danehkar |
| collection | DOAJ |
| description | X-ray observations of active galactic nuclei (AGNs) reveal relativistic reflections from the innermost regions of accretion disks, which contain general-relativistic footprints caused by spinning supermassive black holes (SMBH). We anticipate the spin of a SMBH to be stable over the human timeframe, so brightness changes in the high-energy corona above the SMBH should slightly alter relativistic reflection. In this brief review, we discuss the latest developments in modeling relativistic reflection, as well as the rapid small variation in relativistic emission disclosed by the principal component analysis (PCA) of X-ray variability in AGN. PCA studies of X-ray spectra from AGNs have shown that relativistically blurred reflection has negligible fluctuations over the course of observations, which could originate from rapid (intrahour) intrinsic variations in near-horizon accretion flows and photon rings. The PCA technique is an effective way to disclose relativistic reflection from X-ray observations of AGNs, simplifying the complexity of largely variable X-ray data for automated spectral analysis with machine learning algorithms. |
| format | Article |
| id | doaj-art-e380c1f3f50248c6b425245010490fbf |
| institution | OA Journals |
| issn | 2296-987X |
| language | English |
| publishDate | 2024-10-01 |
| publisher | Frontiers Media S.A. |
| record_format | Article |
| series | Frontiers in Astronomy and Space Sciences |
| spelling | doaj-art-e380c1f3f50248c6b425245010490fbf2025-08-20T02:11:37ZengFrontiers Media S.A.Frontiers in Astronomy and Space Sciences2296-987X2024-10-011110.3389/fspas.2024.14793011479301Relativistic reflection modeling in AGN and related variability from PCA: a brief reviewA. DanehkarX-ray observations of active galactic nuclei (AGNs) reveal relativistic reflections from the innermost regions of accretion disks, which contain general-relativistic footprints caused by spinning supermassive black holes (SMBH). We anticipate the spin of a SMBH to be stable over the human timeframe, so brightness changes in the high-energy corona above the SMBH should slightly alter relativistic reflection. In this brief review, we discuss the latest developments in modeling relativistic reflection, as well as the rapid small variation in relativistic emission disclosed by the principal component analysis (PCA) of X-ray variability in AGN. PCA studies of X-ray spectra from AGNs have shown that relativistically blurred reflection has negligible fluctuations over the course of observations, which could originate from rapid (intrahour) intrinsic variations in near-horizon accretion flows and photon rings. The PCA technique is an effective way to disclose relativistic reflection from X-ray observations of AGNs, simplifying the complexity of largely variable X-ray data for automated spectral analysis with machine learning algorithms.https://www.frontiersin.org/articles/10.3389/fspas.2024.1479301/fullactive galactic nucleirelativistic disksblack hole spinreflectionX-ray sourcesprincipal component analysis |
| spellingShingle | A. Danehkar Relativistic reflection modeling in AGN and related variability from PCA: a brief review Frontiers in Astronomy and Space Sciences active galactic nuclei relativistic disks black hole spin reflection X-ray sources principal component analysis |
| title | Relativistic reflection modeling in AGN and related variability from PCA: a brief review |
| title_full | Relativistic reflection modeling in AGN and related variability from PCA: a brief review |
| title_fullStr | Relativistic reflection modeling in AGN and related variability from PCA: a brief review |
| title_full_unstemmed | Relativistic reflection modeling in AGN and related variability from PCA: a brief review |
| title_short | Relativistic reflection modeling in AGN and related variability from PCA: a brief review |
| title_sort | relativistic reflection modeling in agn and related variability from pca a brief review |
| topic | active galactic nuclei relativistic disks black hole spin reflection X-ray sources principal component analysis |
| url | https://www.frontiersin.org/articles/10.3389/fspas.2024.1479301/full |
| work_keys_str_mv | AT adanehkar relativisticreflectionmodelinginagnandrelatedvariabilityfrompcaabriefreview |