Accretion-disk reflection in the Seyfert 1 galaxy NGC 3783 as viewed by Chandra grating spectroscopy
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arXiv
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| Format: | Preprint |
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2025
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| _version_ | 1866917953140686848 |
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| author | Danehkar, A. Brandt, W. N. |
| author_facet | Danehkar, A. Brandt, W. N. |
| contents | In active galactic nuclei, X-ray illumination of the accretion disk around a supermassive black hole (SMBH) results in the production of the K$α$ fluorescent line of iron, which provides insights into accretion physics and SMBH spins. In this work, we studied X-ray reflection from the accretion disk in the Seyfert 1 galaxy NGC 3783 using all the data collected by the Chandra High Energy Transmission Grating Spectrometer. We used hardness-ratio diagrams to distinguish between different spectral states and conducted spectral analysis of all the multi-epoch datasets, as well as the source in the observed spectral states. Our hardness analysis indicates that the source gradually evolved into a harder state (2013-2016) compared to the previous epochs (2000-2001). Our spectral modeling implies that the relativistically broadened iron emission from the innermost accretion disk is associated with a near-maximal SMBH spin ($a=0.98^{+0.02}_{-0.12}$) in all the datasets, even though the hard state was present in 17% of them, and a consistent spin is also found in different spectral states. In addition, the narrow, bright Fe K$α$ line from distant regions has an excess velocity of $620^{+80}_{-70}$ km s$^{-1}$ relative to the rest frame, implying that some distant layers of the disk could be twisted. Our results suggest that, despite long-term changes in the X-ray brightness of NGC 3783, likely caused by eclipsing material, the relativistic reflection can be constrained thanks to the substantial counts provided by multi-epoch observations, while a warped disk structure may be present. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2502_05200 |
| institution | arXiv |
| publishDate | 2025 |
| record_format | arxiv |
| spellingShingle | Accretion-disk reflection in the Seyfert 1 galaxy NGC 3783 as viewed by Chandra grating spectroscopy Danehkar, A. Brandt, W. N. High Energy Astrophysical Phenomena Astrophysics of Galaxies In active galactic nuclei, X-ray illumination of the accretion disk around a supermassive black hole (SMBH) results in the production of the K$α$ fluorescent line of iron, which provides insights into accretion physics and SMBH spins. In this work, we studied X-ray reflection from the accretion disk in the Seyfert 1 galaxy NGC 3783 using all the data collected by the Chandra High Energy Transmission Grating Spectrometer. We used hardness-ratio diagrams to distinguish between different spectral states and conducted spectral analysis of all the multi-epoch datasets, as well as the source in the observed spectral states. Our hardness analysis indicates that the source gradually evolved into a harder state (2013-2016) compared to the previous epochs (2000-2001). Our spectral modeling implies that the relativistically broadened iron emission from the innermost accretion disk is associated with a near-maximal SMBH spin ($a=0.98^{+0.02}_{-0.12}$) in all the datasets, even though the hard state was present in 17% of them, and a consistent spin is also found in different spectral states. In addition, the narrow, bright Fe K$α$ line from distant regions has an excess velocity of $620^{+80}_{-70}$ km s$^{-1}$ relative to the rest frame, implying that some distant layers of the disk could be twisted. Our results suggest that, despite long-term changes in the X-ray brightness of NGC 3783, likely caused by eclipsing material, the relativistic reflection can be constrained thanks to the substantial counts provided by multi-epoch observations, while a warped disk structure may be present. |
| title | Accretion-disk reflection in the Seyfert 1 galaxy NGC 3783 as viewed by Chandra grating spectroscopy |
| topic | High Energy Astrophysical Phenomena Astrophysics of Galaxies |
| url | https://arxiv.org/abs/2502.05200 |