Two-dimensional correlation analysis of periodicity in active galactic nuclei time series
The active galactic nuclei (AGN) are among the most powerful sources with an inherent, pronounced and random variation of brightness. The randomness of their time series is so subtle as to blur the border between aperiodic fluctuations and noisy oscillations. This poses challenges to analysing of su...
| Main Authors: | , , |
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| Format: | Article |
| Language: | English |
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De Gruyter
2020-07-01
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| Series: | Open Astronomy |
| Subjects: | |
| Online Access: | https://doi.org/10.1515/astro-2020-0007 |
| _version_ | 1818716407825694720 |
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| author | Kovačević Andjelka B. Popović Luka Č. Ilić Dragana |
| author_facet | Kovačević Andjelka B. Popović Luka Č. Ilić Dragana |
| author_sort | Kovačević Andjelka B. |
| collection | DOAJ |
| description | The active galactic nuclei (AGN) are among the most powerful sources with an inherent, pronounced and random variation of brightness. The randomness of their time series is so subtle as to blur the border between aperiodic fluctuations and noisy oscillations. This poses challenges to analysing of such time series because neither visual inspection nor pre-exisitng methods can identify well oscillatory signals in them. Thus, there is a need for an objective method for periodicity detection. Here we review our a new data analysis method that combines a two-dimensional correlation (2D) of time series with the powerful methods of Gaussian processes. To demonstrate the utility of this technique, we apply it to two example problems which were not exploited enough: damped rednoised artificial time series mimicking AGN time series and newly published observed time series of changing look AGN (CL AGN) NGC 3516. The method successfully detected periodicities in both types of time series. Identified periodicity of ~4 yr in NGC 3516 allows us to speculate that if the thermal instability formed in its accretion disc (AD) on a time scale resembling detected periodicity then AD radius could be ~0.0024 pc. |
| first_indexed | 2024-12-17T19:18:46Z |
| format | Article |
| id | doaj.art-857ab1e43772472da420af4c32d39c66 |
| institution | Directory Open Access Journal |
| issn | 2543-6376 |
| language | English |
| last_indexed | 2024-12-17T19:18:46Z |
| publishDate | 2020-07-01 |
| publisher | De Gruyter |
| record_format | Article |
| series | Open Astronomy |
| spelling | doaj.art-857ab1e43772472da420af4c32d39c662022-12-21T21:35:39ZengDe GruyterOpen Astronomy2543-63762020-07-01291515510.1515/astro-2020-0007astro-2020-0007Two-dimensional correlation analysis of periodicity in active galactic nuclei time seriesKovačević Andjelka B.0Popović Luka Č.1Ilić Dragana2Department of Astronomy, Faculty of Mathematics, University of Belgrade, Studentski trg 16,11000Belgrade, SerbiaAstronomical Observatory, Volgina 7, 11060Belgrade, Serbia; Department of Astronomy, Faculty of Mathematics, University of Belgrade, Studentski trg 16,11000Belgrade, SerbiaDepartment of Astronomy, Faculty of Mathematics, University of Belgrade, Studentski trg 16,11000Belgrade, SerbiaThe active galactic nuclei (AGN) are among the most powerful sources with an inherent, pronounced and random variation of brightness. The randomness of their time series is so subtle as to blur the border between aperiodic fluctuations and noisy oscillations. This poses challenges to analysing of such time series because neither visual inspection nor pre-exisitng methods can identify well oscillatory signals in them. Thus, there is a need for an objective method for periodicity detection. Here we review our a new data analysis method that combines a two-dimensional correlation (2D) of time series with the powerful methods of Gaussian processes. To demonstrate the utility of this technique, we apply it to two example problems which were not exploited enough: damped rednoised artificial time series mimicking AGN time series and newly published observed time series of changing look AGN (CL AGN) NGC 3516. The method successfully detected periodicities in both types of time series. Identified periodicity of ~4 yr in NGC 3516 allows us to speculate that if the thermal instability formed in its accretion disc (AD) on a time scale resembling detected periodicity then AD radius could be ~0.0024 pc.https://doi.org/10.1515/astro-2020-0007galaxies: activemethods: data analysismethods: statisticalgalaxies: individual (ngc 3516) |
| spellingShingle | Kovačević Andjelka B. Popović Luka Č. Ilić Dragana Two-dimensional correlation analysis of periodicity in active galactic nuclei time series Open Astronomy galaxies: active methods: data analysis methods: statistical galaxies: individual (ngc 3516) |
| title | Two-dimensional correlation analysis of periodicity in active galactic nuclei time series |
| title_full | Two-dimensional correlation analysis of periodicity in active galactic nuclei time series |
| title_fullStr | Two-dimensional correlation analysis of periodicity in active galactic nuclei time series |
| title_full_unstemmed | Two-dimensional correlation analysis of periodicity in active galactic nuclei time series |
| title_short | Two-dimensional correlation analysis of periodicity in active galactic nuclei time series |
| title_sort | two dimensional correlation analysis of periodicity in active galactic nuclei time series |
| topic | galaxies: active methods: data analysis methods: statistical galaxies: individual (ngc 3516) |
| url | https://doi.org/10.1515/astro-2020-0007 |
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