Swift-XRT and NuSTAR Monitoring of Obscuration Variability in Mrk 477
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arXiv
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2025
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| author | Torres-Albà, N. Hu, Z. Cox, I. Marchesi, S. Ajello, M. Pizzetti, A. Pal, I. Silver, R. Zhao, X. |
| author_facet | Torres-Albà, N. Hu, Z. Cox, I. Marchesi, S. Ajello, M. Pizzetti, A. Pal, I. Silver, R. Zhao, X. |
| contents | We present the analysis of 15 X-ray observations of Mrk 477, a nearby Seyfert 2 active galactic nucleus, with the objective to monitor its obscuring column density variability. The full dataset consists of five archival observations, split into two XMM-Newton, two NuSTAR and one Chandra observation, plus two dedicated monitoring campaigns. The monitoring campaigns were performed with Swift-XRT and NuSTAR, containing five observations each. We performed a simultaneous analysis using self-consistent torus models, deriving geometric properties of the torus as well as the obscuration along the line of sight. Mrk 477 is best modeled with a torus with large covering factor yet low column density (on average). Its line of sight column density oscillates between $1.5-7\times10^{23}$~cm$^{-2}$. Mrk~477 presents frequent obscuring column density variability, on timescales as short as $\sim2$~weeks. The probability of drawing a pair of obscuration-variable observations for Mrk~477 when having 2, 3, and 4 observations is 40\%, 78\% and 95\%, respectively. Adding the results of this work to those of another 26 sources, we find a trend of increasing obscuration variability with time (from $\sim20$\% at $Δt<10$~days, to $\sim60-70$\% at timescales larger than 5 years). We discuss whether this is compatible with the majority of obscuration variability coming from broad line region clouds. |
| format | Preprint |
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arxiv_https___arxiv_org_abs_2502_09759 |
| institution | arXiv |
| publishDate | 2025 |
| record_format | arxiv |
| spellingShingle | Swift-XRT and NuSTAR Monitoring of Obscuration Variability in Mrk 477 Torres-Albà, N. Hu, Z. Cox, I. Marchesi, S. Ajello, M. Pizzetti, A. Pal, I. Silver, R. Zhao, X. High Energy Astrophysical Phenomena Astrophysics of Galaxies We present the analysis of 15 X-ray observations of Mrk 477, a nearby Seyfert 2 active galactic nucleus, with the objective to monitor its obscuring column density variability. The full dataset consists of five archival observations, split into two XMM-Newton, two NuSTAR and one Chandra observation, plus two dedicated monitoring campaigns. The monitoring campaigns were performed with Swift-XRT and NuSTAR, containing five observations each. We performed a simultaneous analysis using self-consistent torus models, deriving geometric properties of the torus as well as the obscuration along the line of sight. Mrk 477 is best modeled with a torus with large covering factor yet low column density (on average). Its line of sight column density oscillates between $1.5-7\times10^{23}$~cm$^{-2}$. Mrk~477 presents frequent obscuring column density variability, on timescales as short as $\sim2$~weeks. The probability of drawing a pair of obscuration-variable observations for Mrk~477 when having 2, 3, and 4 observations is 40\%, 78\% and 95\%, respectively. Adding the results of this work to those of another 26 sources, we find a trend of increasing obscuration variability with time (from $\sim20$\% at $Δt<10$~days, to $\sim60-70$\% at timescales larger than 5 years). We discuss whether this is compatible with the majority of obscuration variability coming from broad line region clouds. |
| title | Swift-XRT and NuSTAR Monitoring of Obscuration Variability in Mrk 477 |
| topic | High Energy Astrophysical Phenomena Astrophysics of Galaxies |
| url | https://arxiv.org/abs/2502.09759 |