Edelson, R;
Gelbord, J;
Cackett, E;
Connolly, S;
Done, C;
Fausnaugh, M;
Gardner, E;
... Zheng, W; + view all
(2017)
Swift Monitoring of NGC 4151: Evidence for a Second X-Ray/UV Reprocessing.
Astrophysical Journal
, 840
, Article 41. 10.3847/1538-4357/aa6890.
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Abstract
Swift monitoring of NGC 4151 with an ∼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 Å). 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 ∼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 ∼0.5-1 days. This combination of ≳3 day lags between the X-rays and UV and ≲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.
| Type: | Article |
|---|---|
| Title: | Swift Monitoring of NGC 4151: Evidence for a Second X-Ray/UV Reprocessing |
| Open access status: | An open access version is available from UCL Discovery |
| DOI: | 10.3847/1538-4357/aa6890 |
| Publisher version: | http://doi.org/10.3847/1538-4357/aa6890 |
| Language: | English |
| Additional information: | © 2017. The American Astronomical Society. All rights reserved. This version is the version of record. For information on re-use, please refer to the publisher’s terms and conditions. |
| Keywords: | Galaxies: active; galaxies: individual (NGC 4151); galaxies: nuclei; galaxies: Seyfert |
| UCL classification: | UCL UCL > Provost and Vice Provost Offices > UCL BEAMS UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences > Dept of Space and Climate Physics |
| URI: | https://discovery-pp.ucl.ac.uk/id/eprint/1552346 |
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