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Swift Monitoring of NGC 4151: Evidence for a Second X-Ray/UV Reprocessing

Swift monitoring of NGC 4151 with an similar to 6 hr sampling over a total of 69 days in early 2016 is used to construct light curves covering five bands in the X-rays (0.3-50 keV) and six in the ultraviolet (UV)/optical (1900-5500 angstrom). The three hardest X-ray bands (> 2.5 keV) are all strongly correlated with no measurable interband lag, while the two softer bands show lower variability and weaker correlations. The UV/optical bands are significantly correlated with the X-rays, lagging similar to 3-4 days behind the hard X-rays. The variability within the UV/optical bands is also strongly correlated, with the UV appearing to lead the optical by similar to 0.5-1 days. This combination of greater than or similar to 3 day lags between the X-rays and UV and less than or similar to 1 day lags within the UV/optical appears to rule out the "lamp-post" reprocessing model in which a hot, X-ray emitting corona directly illuminates the accretion disk, which then reprocesses the energy in the UV/optical. Instead, these results appear consistent with the Gardner & Done picture in which two separate reprocessings occur: first, emission from the corona illuminates an extreme-UV-emitting toroidal component that shields the disk from the corona; this then heats the extreme-UV component, which illuminates the disk and drives its variability.

Identiferoai:union.ndltd.org:arizona.edu/oai:arizona.openrepository.com:10150/624341
Date03 May 2017
CreatorsEdelson, R., Gelbord, J., Cackett, E., Connolly, S., Done, C., Fausnaugh, M., Gardner, E., Gehrels, N., Goad, M., Horne, K., McHardy, I., Peterson, B. M., Vaughan, S., Vestergaard, M., Breeveld, A., Barth, A. J., Bentz, M., Bottorff, M., Brandt, W. N., Crawford, S. M., Bonta, E. Dalla, Emmanoulopoulos, D., Evans, P., Jaimes, R. Figuera, Filippenko, A. V., Ferland, G., Grupe, D., Joner, M., Kennea, J., Korista, K. T., Krimm, H. A., Kriss, G., Leonard, D. C., Mathur, S., Netzer, H., Nousek, J., Page, K., Romero-Colmenero, E., Siegel, M., Starkey, D. A., Treu, T., Vogler, H. A., Winkler, H., Zheng, W.
ContributorsUniv Arizona, Steward Observ
PublisherIOP PUBLISHING LTD
Source SetsUniversity of Arizona
LanguageEnglish
Detected LanguageEnglish
TypeArticle
Rights© 2017. The American Astronomical Society. All rights reserved.
Relationhttp://stacks.iop.org/0004-637X/840/i=1/a=41?key=crossref.4593b5fd47ed97abb254e75023ef72f1

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