The variable X-ray spectrum of Markarian 766 - I. Principal components analysis
Aims: We analyse a long XMM-Newton spectrum of the narrow-line Seyfert 1 galaxy Mrk 766, using the marked spectral variability on timescales >20ks to separate components in the X-ray spectrum. Methods: Principal components analysis is used to identify distinct emission components in the X-ray...
| Main Authors: | , , , , , |
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| Format: | Journal article |
| Language: | English |
| Published: |
2006
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| _version_ | 1797084685533184000 |
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| author | Miller, L Turner, T Reeves, J George, I Kraemer, S Wingert, B |
| author_facet | Miller, L Turner, T Reeves, J George, I Kraemer, S Wingert, B |
| author_sort | Miller, L |
| collection | OXFORD |
| description | Aims: We analyse a long XMM-Newton spectrum of the narrow-line Seyfert 1 galaxy Mrk 766, using the marked spectral variability on timescales >20ks to separate components in the X-ray spectrum. Methods: Principal components analysis is used to identify distinct emission components in the X-ray spectrum, possible alternative physical models for those components are then compared statistically. Results: The source spectral variability is well-explained by additive variations, with smaller extra contributions most likely arising from variable absorption. The principal varying component, eigenvector one, is found to have a steep (photon index 2.4) power-law shape, affected by a low column of ionised absorption that leads to the appearance of a soft excess. Eigenvector one varies by a factor 10 in amplitude on time-scales of days and appears to have broad ionised Fe K-alpha emission associated with it: the width of the ionised line is consistent with an origin at about 100 gravitational radii. There is also a strong component of near-constant emission that dominates in the low state, whose spectrum is extremely hard above 1 keV, with a soft excess at lower energies, and with a strong edge at Fe K but remarkably little Fe K-alpha emission. Although this component may be explained as relativistically-blurred reflection from the inner accretion disc, we suggest that its spectrum and lack of variability may alternatively be explained as either (i) ionised reflection from an extended region, possibly a disc wind, or (ii) a signature of absorption by a disc wind with a variable covering fraction. Absorption features in the low state may indicate the presence of an outflow. |
| first_indexed | 2024-03-07T01:58:29Z |
| format | Journal article |
| id | oxford-uuid:9c8d53b6-01dc-4baf-8057-01b693dd0704 |
| institution | University of Oxford |
| language | English |
| last_indexed | 2024-03-07T01:58:29Z |
| publishDate | 2006 |
| record_format | dspace |
| spelling | oxford-uuid:9c8d53b6-01dc-4baf-8057-01b693dd07042022-03-27T00:36:46ZThe variable X-ray spectrum of Markarian 766 - I. Principal components analysisJournal articlehttp://purl.org/coar/resource_type/c_dcae04bcuuid:9c8d53b6-01dc-4baf-8057-01b693dd0704EnglishSymplectic Elements at Oxford2006Miller, LTurner, TReeves, JGeorge, IKraemer, SWingert, BAims: We analyse a long XMM-Newton spectrum of the narrow-line Seyfert 1 galaxy Mrk 766, using the marked spectral variability on timescales >20ks to separate components in the X-ray spectrum. Methods: Principal components analysis is used to identify distinct emission components in the X-ray spectrum, possible alternative physical models for those components are then compared statistically. Results: The source spectral variability is well-explained by additive variations, with smaller extra contributions most likely arising from variable absorption. The principal varying component, eigenvector one, is found to have a steep (photon index 2.4) power-law shape, affected by a low column of ionised absorption that leads to the appearance of a soft excess. Eigenvector one varies by a factor 10 in amplitude on time-scales of days and appears to have broad ionised Fe K-alpha emission associated with it: the width of the ionised line is consistent with an origin at about 100 gravitational radii. There is also a strong component of near-constant emission that dominates in the low state, whose spectrum is extremely hard above 1 keV, with a soft excess at lower energies, and with a strong edge at Fe K but remarkably little Fe K-alpha emission. Although this component may be explained as relativistically-blurred reflection from the inner accretion disc, we suggest that its spectrum and lack of variability may alternatively be explained as either (i) ionised reflection from an extended region, possibly a disc wind, or (ii) a signature of absorption by a disc wind with a variable covering fraction. Absorption features in the low state may indicate the presence of an outflow. |
| spellingShingle | Miller, L Turner, T Reeves, J George, I Kraemer, S Wingert, B The variable X-ray spectrum of Markarian 766 - I. Principal components analysis |
| title | The variable X-ray spectrum of Markarian 766 - I. Principal components
analysis |
| title_full | The variable X-ray spectrum of Markarian 766 - I. Principal components
analysis |
| title_fullStr | The variable X-ray spectrum of Markarian 766 - I. Principal components
analysis |
| title_full_unstemmed | The variable X-ray spectrum of Markarian 766 - I. Principal components
analysis |
| title_short | The variable X-ray spectrum of Markarian 766 - I. Principal components
analysis |
| title_sort | variable x ray spectrum of markarian 766 i principal components analysis |
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