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

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 and 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.

Authors:
 [1];  [2];  [3]; ;  [4]; ;  [5]; ;  [6];  [7]; ;  [8];  [9];  [10];  [11];  [12];  [13];  [14];  [15];  [16] more »; « less
  1. University of Maryland, Department of Astronomy, College Park, MD 20742-2421 (United States)
  2. Spectral Sciences Inc., 4 Fourth Avenue, Burlington, MA 01803 (United States)
  3. Department of Physics and Astronomy, Wayne State University, 666 W. Hancock Street, Detroit, MI 48201 (United States)
  4. University of Southampton, Highfield, Southampton, SO17 1BJ (United Kingdom)
  5. University of Durham, Center for Extragalactic Astronomy, Department of Physics, South Road, Durham, DH1 3LE (United Kingdom)
  6. The Ohio State University, Department of Astronomy, 140 W 18th Avenue, Columbus, OH 43210 (United States)
  7. Astrophysics Science Division, NASA Goddard Space Flight Center, Greenbelt, MD 20771 (United States)
  8. University of Leicester, Department of Physics and Astronomy, Leicester, LE1 7RH (United Kingdom)
  9. SUPA Physics and Astronomy, University of St. Andrews, Fife, KY16 9SS Scotland (United Kingdom)
  10. Dark Cosmology Centre, Niels Bohr Institute, University of Copenhagen, Juliane Maries Vej 30, DK-2100 Copenhagen (Denmark)
  11. Mullard Space Science Laboratory, University College London, Holmbury St. Mary, Dorking, Surrey RH5 6NT (United Kingdom)
  12. Department of Physics and Astronomy, 4129 Frederick Reines Hall, University of California, Irvine, CA 92697 (United States)
  13. Department of Physics and Astronomy, Georgia State University, 25 Park Place, Suite 605, Atlanta, GA 30303 (United States)
  14. Physics Department, Southwestern University, Georgetown, TX 78626 (United States)
  15. Department of Astronomy and Astrophysics, Eberly College of Science, 525 Davey Laboratory, The Pennsylvania State University, University Park, PA 16802 (United States)
  16. South African Astronomical Observatory, P.O. Box 9, Observatory 7935, Cape Town (South Africa)
Publication Date:
OSTI Identifier:
22663652
Resource Type:
Journal Article
Resource Relation:
Journal Name: Astrophysical Journal; Journal Volume: 840; Journal Issue: 1; Other Information: Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; ACCRETION DISKS; CORRELATIONS; EMISSION; GALAXIES; GALAXY CLUSTERS; GALAXY NUCLEI; HARD X RADIATION; HEAT; KEV RANGE; REPROCESSING; ULTRAVIOLET RADIATION; VISIBLE RADIATION

Citation Formats

Edelson, R., Gelbord, J., Cackett, E., Connolly, S., McHardy, I., Done, C., Gardner, E., Fausnaugh, M., Peterson, B. M., Gehrels, N., Goad, M., Vaughan, S., Horne, K., Vestergaard, M., Breeveld, A., Barth, A. J., Bentz, M., Bottorff, M., Brandt, W. N., Crawford, S. M., and and others. Swift Monitoring of NGC 4151: Evidence for a Second X-Ray/UV Reprocessing. United States: N. p., 2017. Web. doi:10.3847/1538-4357/AA6890.
Edelson, R., Gelbord, J., Cackett, E., Connolly, S., McHardy, I., Done, C., Gardner, E., Fausnaugh, M., Peterson, B. M., Gehrels, N., Goad, M., Vaughan, S., Horne, K., Vestergaard, M., Breeveld, A., Barth, A. J., Bentz, M., Bottorff, M., Brandt, W. N., Crawford, S. M., & and others. Swift Monitoring of NGC 4151: Evidence for a Second X-Ray/UV Reprocessing. United States. doi:10.3847/1538-4357/AA6890.
Edelson, R., Gelbord, J., Cackett, E., Connolly, S., McHardy, I., Done, C., Gardner, E., Fausnaugh, M., Peterson, B. M., Gehrels, N., Goad, M., Vaughan, S., Horne, K., Vestergaard, M., Breeveld, A., Barth, A. J., Bentz, M., Bottorff, M., Brandt, W. N., Crawford, S. M., and and others. Mon . "Swift Monitoring of NGC 4151: Evidence for a Second X-Ray/UV Reprocessing". United States. doi:10.3847/1538-4357/AA6890.
@article{osti_22663652,
title = {Swift Monitoring of NGC 4151: Evidence for a Second X-Ray/UV Reprocessing},
author = {Edelson, R. and Gelbord, J. and Cackett, E. and Connolly, S. and McHardy, I. and Done, C. and Gardner, E. and Fausnaugh, M. and Peterson, B. M. and Gehrels, N. and Goad, M. and Vaughan, S. and Horne, K. and Vestergaard, M. and Breeveld, A. and Barth, A. J. and Bentz, M. and Bottorff, M. and Brandt, W. N. and Crawford, S. M. and and others},
abstractNote = {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 and 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.},
doi = {10.3847/1538-4357/AA6890},
journal = {Astrophysical Journal},
number = 1,
volume = 840,
place = {United States},
year = {Mon May 01 00:00:00 EDT 2017},
month = {Mon May 01 00:00:00 EDT 2017}
}