Detection of an unidentified soft X-ray emission feature in NGC 5548
| Autor: | Liyi Gu, Junjie Mao, Jelle S. Kaastra, Missagh Mehdipour, Ciro Pinto, Sam Grafton-Waters, Stefano Bianchi, Hermine Landt, Graziella Branduardi-Raymont, Elisa Costantini, Jacobo Ebrero, Pierre-Olivier Petrucci, Ehud Behar, Laura di Gesu, Barbara De Marco, Giorgio Matt, Jake A. J. Mitchell, Uria Peretz, Francesco Ursini, Martin Ward |
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| Přispěvatelé: | Universitat Politècnica de Catalunya. Departament de Física, Universitat Politècnica de Catalunya. GAA - Grup d'Astronomia i Astrofísica, Gu, Liyi, Mao, Junjie, Kaastra, Jelle S., Mehdipour, Missagh, Pinto, Ciro, Grafton-Waters, Sam, Bianchi, Stefano, Landt, Hermine, Branduardi-Raymont, Graziella, Costantini, Elisa, Ebrero, Jacobo, Petrucci, PIERRE-OLIVIER, Behar, Ehud, di Gesu, Laura, De Marco, Barbara, Matt, Giorgio, Mitchell, Jake A. J., Peretz, Uria, Ursini, Francesco, Ward, Martin |
| Jazyk: | angličtina |
| Rok vydání: | 2022 |
| Předmět: |
Seyfert [Galaxies]
active [Galaxies] Atomic Physics (physics.atom-ph) FOS: Physical sciences active Galaxies individual NGC 5548 Physics - Atomic Physics X-ray X-rays galaxies Galaxies Seyfert individual individual: NGC 5548 [Galaxies] High Energy Astrophysical Phenomena (astro-ph.HE) galaxie X-Rays Astronomy and Astrophysics Atomic processes Astrophysics - Astrophysics of Galaxies galaxies [X-rays] Galaxies active Space and Planetary Science NGC 5548 Astrophysics of Galaxies (astro-ph.GA) Física::Astronomia i astrofísica [Àrees temàtiques de la UPC] Seyfert Raigs X Astrophysics - High Energy Astrophysical Phenomena |
| Zdroj: | Astronomy & Astrophysics, 665:A93 Astronomy & Astrophysics, 2022, Vol.665 [Peer Reviewed Journal] |
| Popis: | NGC~5548 is an X-ray bright Seyfert 1 active galaxy. It exhibits a variety of spectroscopic features in the soft X-ray band, including in particular the absorption by the AGN outflows of a broad range of ionization states, with column densities up to 1E27 /m^2, and having speeds up to several thousand kilometers per second. The known emission features are in broad agreement with photoionized X-ray narrow and broad emission line models. We report on an X-ray spectroscopic study using 1.1 Ms XMM-Newton and 0.9 Ms Chandra grating observations of NGC 5548 spanning two decades. The aim is to search and characterize any potential spectroscopic features in addition to the known primary spectral components that are already modeled in high precision. We detect a weak unidentified excess emission feature at 18.4 Angstrom (18.1 Angstrom in the restframe). The feature is seen at >5 sigma statistical significance taking into account the look elsewhere effect. No known instrumental issues, atomic transitions, and astrophysical effects can explain this excess. The observed intensity of the possible feature seems to anti-correlate in time with the hardness ratio of the source. However, the variability might not be intrinsic, it might be caused by the time-variable obscuration by the outflows. An intriguing possibility is the line emission from charge exchange between a partially ionized outflow and a neutral layer in the same outflow, or in the close environment. Other possibilities, such as emission from a highly-ionized component with high outflowing speed, cannot be fully ruled out. 14 pages, 8 figures, accepted for publication in Astronomy & Astrophysics |
| Databáze: | OpenAIRE |
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