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|Title:||Anatomy of the AGN in NGC 5548. IV. The short-term variability of the outflows||Authors:||Di Gesu, L.
Kaastra, J. S.
Petrucci, P. O.
Kriss, G. A.
De Marco, B.
DE ROSA, ALESSANDRA
Steenbrugge, K. C.
|Issue Date:||2015||Journal:||ASTRONOMY & ASTROPHYSICS||Number:||579||First Page:||A42||Abstract:||During an extensive multiwavelength campaign that we performed in 2013-2014, we found the prototypical Seyfert 1 galaxy NGC 5548 in an unusual condition of heavy and persistent obscuration. The newly discovered "obscurer" absorbs most of the soft X-ray continuum along our line of sight and lowers the ionizing luminosity received by the classical warm absorber. We present the analysis of the high resolution X-ray spectra collected with XMM-Newton and Chandra throughout the campaign, which are suitable to investigate the variability of both the obscurer and classical warm absorber. The time separation between these X-ray observations range from two days to eight months. On these timescales the obscurer is variable both in column density and in covering fraction. This is consistent with the picture of a patchy wind. The most significant variation occurred in September 2013 when the source brightened for two weeks. A higher and steeper intrinsic continuum and a lower obscurer covering fraction are both required to explain the spectral shape during the flare. We suggest that a geometrical change of the soft X-ray source behind the obscurer causes the observed drop in the covering fraction. Because of the higher soft X-ray continuum level, the September 2013 Chandra spectrum is the only X ray spectrum of the campaign in which individual features of the warm absorber could be detected. The spectrum shows absorption from Fe-UTA, O iv, and O v, consistent with belonging to the lower-ionization counterpart of the historical NGC 5548 warm absorber. Hence, we confirm that the warm absorber has responded to the drop in the ionizing luminosity caused by the obscurer.||Acknowledgments:||This work is based on observations obtained with XMM-Newton an ESA science mission with instruments and contributions directly funded by ESA Member States and the USA (NASA). This research has made use of data obtained with the NuSTAR mission, a project led by the California Institute of Technology (Caltech), managed by the Jet Propulsion Laboratory (JPL) and funded by NASA. This work made use of data supplied by the UK Swift Science Data Centre at the University of Leicester. We thank the Chandra team for allocating the LETGS triggered observations. We thank the International Space Science Institute (ISSI) in Bern for their support and hospitality. SRON is supported financially by NWO, the Netherlands Organization for Scientific Research. M.M. acknowledges support from NWO and the UK STFC. This work was supported by NASA through grants for HST program number 13184 from the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Incorporated, under NASA contract NAS5-26555. M.C. acknowledges financial support from contracts ASI/INAF n.I/037/12/0 and PRIN INAF 2011 and 2012. P.O.P and F.U. acknowledge funding support from the CNES and the French-Italian International Project of Scientific Collaboration: PICS-INAF project n181542 S.B. and A.D.R. acknowledge INAF/PICS financial support and financial support from the Italian Space Agency under grant ASI/INAF I/037/12. A.D.R acknowledge financial support from contract PRIN INAF 2011. G.P. acknowledges support via an EU Marie Curie Intra-European fellowship under contract no. FP-PEOPLE-2012-IEF-331095 and Bundesministerium für Wirtschaft und Technologie/Deutsches Zentrum für Luft- und Raumfahrt (BMWI/DLR, FKZ 50 OR 1408). FU acknowledges support from Université Franco-Italienne (Vinci Ph.D. fellowship). M.W. acknowledges the support of a PhD studentship awarded by the UK STFC.||URI:||http://hdl.handle.net/20.500.12386/26411||URL:||https://www.aanda.org/articles/aa/abs/2015/07/aa25934-15/aa25934-15.html||ISSN:||0004-6361||DOI:||10.1051/0004-6361/201525934||Bibcode ADS:||2015A&A...579A..42D||Fulltext:||open|
|Appears in Collections:||1.01 Articoli in rivista|
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