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Title: Space Telescope and Optical Reverberation Mapping Project. VII. Understanding the Ultraviolet Anomaly in NGC 5548 with X-Ray Spectroscopy

Abstract

During the Space Telescope and Optical Reverberation Mapping Project observations of NGC 5548, the continuum and emission-line variability became decorrelated during the second half of the six-month-long observing campaign. Here we present Swift and Chandra X-ray spectra of NGC 5548 obtained as part of the campaign. The Swift spectra show that excess flux (relative to a power-law continuum) in the soft X-ray band appears before the start of the anomalous emission-line behavior, peaks during the period of the anomaly, and then declines. This is a model-independent result suggesting that the soft excess is related to the anomaly. We divide the Swift data into on- and off-anomaly spectra to characterize the soft excess via spectral fitting. The cause of the spectral differences is likely due to a change in the intrinsic spectrum rather than to variable obscuration or partial covering. The Chandra spectra have lower signal-to-noise ratios, but are consistent with the Swift data. Our preferred model of the soft excess is emission from an optically thick, warm Comptonizing corona, the effective optical depth of which increases during the anomaly. This model simultaneously explains all three observations: the UV emission-line flux decrease, the soft-excess increase, and the emission-line anomaly.

Authors:
; ; ; ;  [1];  [2]; ;  [3];  [4]; ; ;  [5];  [6];  [7];  [8];  [9];  [10];  [11];  [12];  [13] more »; « less
  1. Department of Astronomy, The Ohio State University, 140 West 18th Avenue, Columbus, OH 43210 (United States)
  2. Center for Cosmology and AstroParticle Physics, The Ohio State University, 191 West Woodruff Avenue, Columbus, OH 43210 (United States)
  3. Department of Physics and Astronomy, University of Leicester, Leicester, LE1 7RH (United Kingdom)
  4. Instituto de Astronomia, Universidad Nacional Autonoma de Mexico, Cuidad de Mexico (Mexico)
  5. Department of Physics and Astronomy, Georgia State University, 25 Park Place, Suite 605, Atlanta, GA 30303 (United States)
  6. Instituto de Física y Astronomía, Facultad de Ciencias, Universidad de Valparaíso, Gran Bretana N 1111, Playa Ancha, Valparaíso (Chile)
  7. Department of Physics and Astronomy, 4129 Frederick Reines Hall, University of California, Irvine, CA 92697 (United States)
  8. Department of Astronomy, University of California, Berkeley, CA 94720-3411 (United States)
  9. Crimean Astrophysical Observatory, P/O Nauchny, Crimea 298409 (Russian Federation)
  10. Las Cumbres Observatory Global Telescope Network, 6740 Cortona Drive, Suite 102, Goleta, CA 93117 (United States)
  11. Fountainwood Observatory, Department of Physics FJS 149, Southwestern University, 1011 East University Avenue, Georgetown, TX 78626 (United States)
  12. Department of Astronomy and Astrophysics, Eberly College of Science, The Pennsylvania State University, 525 Davey Laboratory, University Park, PA 16802 (United States)
  13. Mullard Space Science Laboratory, University College London, Holmbury St. Mary, Dorking, Surrey RH5 6NT (United Kingdom)
Publication Date:
OSTI Identifier:
22663172
Resource Type:
Journal Article
Journal Name:
Astrophysical Journal
Additional Journal Information:
Journal Volume: 846; Journal Issue: 1; Other Information: Country of input: International Atomic Energy Agency (IAEA); Journal ID: ISSN 0004-637X
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; EMISSION; NOISE; SIGNAL-TO-NOISE RATIO; SOFT X RADIATION; SPACE; TELESCOPES; ULTRAVIOLET RADIATION; X-RAY GALAXIES; X-RAY SPECTRA; X-RAY SPECTROSCOPY

Citation Formats

Mathur, S., Pogge, R. W., Adams, S. M., Beatty, T. G., Bisogni, S., Gupta, A., Page, K., Goad, M. R., Krongold, Y., Anderson, M. D., Bazhaw, C., Bentz, M. C., Arévalo, P., Barth, A. J., Bigley, A., Borman, G. A., Boroson, T. A., Bottorff, M. C., Brandt, W. N., Breeveld, A. A., and others, and. Space Telescope and Optical Reverberation Mapping Project. VII. Understanding the Ultraviolet Anomaly in NGC 5548 with X-Ray Spectroscopy. United States: N. p., 2017. Web. doi:10.3847/1538-4357/AA832B.
Mathur, S., Pogge, R. W., Adams, S. M., Beatty, T. G., Bisogni, S., Gupta, A., Page, K., Goad, M. R., Krongold, Y., Anderson, M. D., Bazhaw, C., Bentz, M. C., Arévalo, P., Barth, A. J., Bigley, A., Borman, G. A., Boroson, T. A., Bottorff, M. C., Brandt, W. N., Breeveld, A. A., & others, and. Space Telescope and Optical Reverberation Mapping Project. VII. Understanding the Ultraviolet Anomaly in NGC 5548 with X-Ray Spectroscopy. United States. doi:10.3847/1538-4357/AA832B.
Mathur, S., Pogge, R. W., Adams, S. M., Beatty, T. G., Bisogni, S., Gupta, A., Page, K., Goad, M. R., Krongold, Y., Anderson, M. D., Bazhaw, C., Bentz, M. C., Arévalo, P., Barth, A. J., Bigley, A., Borman, G. A., Boroson, T. A., Bottorff, M. C., Brandt, W. N., Breeveld, A. A., and others, and. Fri . "Space Telescope and Optical Reverberation Mapping Project. VII. Understanding the Ultraviolet Anomaly in NGC 5548 with X-Ray Spectroscopy". United States. doi:10.3847/1538-4357/AA832B.
@article{osti_22663172,
title = {Space Telescope and Optical Reverberation Mapping Project. VII. Understanding the Ultraviolet Anomaly in NGC 5548 with X-Ray Spectroscopy},
author = {Mathur, S. and Pogge, R. W. and Adams, S. M. and Beatty, T. G. and Bisogni, S. and Gupta, A. and Page, K. and Goad, M. R. and Krongold, Y. and Anderson, M. D. and Bazhaw, C. and Bentz, M. C. and Arévalo, P. and Barth, A. J. and Bigley, A. and Borman, G. A. and Boroson, T. A. and Bottorff, M. C. and Brandt, W. N. and Breeveld, A. A. and others, and},
abstractNote = {During the Space Telescope and Optical Reverberation Mapping Project observations of NGC 5548, the continuum and emission-line variability became decorrelated during the second half of the six-month-long observing campaign. Here we present Swift and Chandra X-ray spectra of NGC 5548 obtained as part of the campaign. The Swift spectra show that excess flux (relative to a power-law continuum) in the soft X-ray band appears before the start of the anomalous emission-line behavior, peaks during the period of the anomaly, and then declines. This is a model-independent result suggesting that the soft excess is related to the anomaly. We divide the Swift data into on- and off-anomaly spectra to characterize the soft excess via spectral fitting. The cause of the spectral differences is likely due to a change in the intrinsic spectrum rather than to variable obscuration or partial covering. The Chandra spectra have lower signal-to-noise ratios, but are consistent with the Swift data. Our preferred model of the soft excess is emission from an optically thick, warm Comptonizing corona, the effective optical depth of which increases during the anomaly. This model simultaneously explains all three observations: the UV emission-line flux decrease, the soft-excess increase, and the emission-line anomaly.},
doi = {10.3847/1538-4357/AA832B},
journal = {Astrophysical Journal},
issn = {0004-637X},
number = 1,
volume = 846,
place = {United States},
year = {2017},
month = {9}
}

Works referencing / citing this record:

A Falling Corona Model for the Anomalous Behavior of the Broad Emission Lines in NGC 5548
journal, April 2018


A Novel Approach to Study the Variability of NGC 5548
journal, July 2019

  • Belete, A. Bewketu; Goicoechea, L. J.; Leão, I. C.
  • The Astrophysical Journal, Vol. 879, Issue 2
  • DOI: 10.3847/1538-4357/ab2457

A Hard Look at Thermal Reverberation and Optical/Ultraviolet Lags in NGC 5548
journal, July 2019

  • Kammoun, E. S.; Papadakis, I. E.; Dovčiak, M.
  • The Astrophysical Journal, Vol. 879, Issue 2
  • DOI: 10.3847/2041-8213/ab2a72