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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

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

Edelson, 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. 03 May 2017 (has links)
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.

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