期刊
ASTRONOMY & ASTROPHYSICS
卷 592, 期 -, 页码 -出版社
EDP SCIENCES S A
DOI: 10.1051/0004-6361/201628464
关键词
galaxies: active; X-rays: galaxies; galaxies: individual: NGC 5548
资金
- ESA
- Italian Space Agency [ASI-INAF I/037/12/P1]
- EU Marie Curie Intra-European fellowship [FP-PEOPLE-2012-IEF-331095]
- ESA Member States
- USA (NASA)
- NASA [NAS5-26555]
- International Space Science Institute (ISSI) in Bern
- NWO, the Netherlands Organization for Scientific Research
- NWO
- UK STFC
- NASA through from the Space Telescope Science Institute [13184]
- ASI/INAF [I/037/12/0]
- PRIN INAF
- CNES
- CNRS/PICS
- Fondo Fortalecimiento de la Productividad Cientifica VRIDT
- EU Horizon 2020 research and innovation programme under the Marie Sklodowska-Curie grant [655324]
- iCORE program of the Planning and Budgeting Committee [1937/12]
- INAF/PICS
- US NSF [AST-1008882]
- Bundesministerium fur Wirtschaft und Technologie/Deutsches Zentrum fur Luft- und Raumfahrt [FKZ 50 OR 1408]
- VINCI program of the French-Italian University
- Direct For Mathematical & Physical Scien
- Division Of Astronomical Sciences [1008882] Funding Source: National Science Foundation
- STFC [ST/N000811/1] Funding Source: UKRI
- Marie Curie Actions (MSCA) [655324] Funding Source: Marie Curie Actions (MSCA)
In 2013, we conducted a large multi-wavelength campaign on the archetypical Seyfert 1 galaxy NGC 5548. Unexpectedly, this usually unobscured source appeared strongly absorbed in the soft X-rays during the entire campaign, and signatures of new and strong outflows were present in the almost simultaneous UV HST/COS data. Here we carry out a comprehensive spectral analysis of all available XMM-Newton observations of NGC 5548 (precisely 14 observations from our campaign plus three from the archive, for a total of similar to 763 ks) in combination with three simultaneous NuSTAR observations. We obtain a best-fit underlying continuum model composed by i) a weakly varying flat (Gamma similar to 1.5-1.7) power-law component; ii) a constant, cold reflection (FeK + continuum) component; iii) a soft excess, possibly owing to thermal Comptonization; and iv) a constant, ionized scattered emission-line dominated component. Our main findings are that, during the 2013 campaign, the first three of these components appear to be partially covered by a heavy and variable obscurer that is located along the line of sight (LOS), which is consistent with a multilayer of cold and mildly ionized gas. We characterize in detail the short timescale (mostly similar to ks-to-days) spectral variability of this new obscurer, and find it is mostly due to a combination of column density and covering factor variations, on top of intrinsic power-law (flux and slope) variations. In addition, our best-fit spectrum is left with several (but marginal) absorption features at rest-frame energies similar to 6.7-6.9 keV and similar to 8 keV, as well as a weak broad emission line feature redwards of the 6.4 keV emission line. These could indicate a more complex underlying model, e.g. a P-Cygni-type emission profile if we allow for a large velocity and wide-angle outflow. These findings are consistent with a picture where the obscurer represents the manifestation along the LOS of a multilayer of gas, which is also in multiphase, and which is likely outflowing at high speed, and simultaneously producing heavy obscuration and scattering in the X-rays, as well as broad absorption features in the UV.
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