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

S. Mathur; A. Gupta; K. Page; R.~W. Pogge; Y. Krongold; M.~R. Goad; S.~M. Adams; M.~D. Anderson; P. Arevalo; A.~J. Barth; C. Bazhaw; T.~G. Beatty; M.~C. Bentz; A. Bigley; S. Bisogni; G.~A. Borman; T.~A. Boroson; M.~C. Bottorff; W.~N. Brandt; A.~A. Breeveld; J.~E. Brown; J.~S. Brown; E.~M. Cackett; G. Canalizo; M.~T. Carini; K.~I. Clubb; J.~M. Comerford; C.~T. Coker; E.~M. Corsini; D.~M. Crenshaw; S. Croft; K.~V. Croxall; E. Dalla Bonta; A.~J. Deason; K.~D. Denney; A. De Lorenzo-Caceres; G. De Rosa; M. Dietrich; R. Edelson; J. Ely; M. Eracleous; P.~A. Evans; M.~M. Fausnaugh; G.~J. Ferland; A.~V. Filippenko; K. Flatland; O.~D. Fox; E.~L. Gates; N. Gehrels; S. Geier; J.~M. Gelbord; V. Gorjian; J.~E. Greene; C.~J. Grier; D. Grupe; P.~B. Hall; C.~B. Henderson; S. Hicks; E. Holmbeck; T.~W.-S. Holoien; D. Horenstein; K. Horne; T. Hutchison; M. Im; J.~J. Jensen; C.~A. Johnson; M.~D. Joner; J. Jones; J. Kaastra; S. Kaspi; B.~C. Kelly; P.~L. Kelly; J.~A. Kennea; M. Kim; S. Kim; S.~C. Kim; A. King; S.~A. Klimanov; C.~S. Kochanek; K.~T. Korista; G.~A. Kriss; M.~W. Lau; J.~C. Lee; D.~C. Leonard; M. Li; P. Lira; Z. Ma; F. MacInnis; E.~R. Manne-Nicholas; M.~A. Malkan; J.~C. Mauerhan; R. McGurk; I.~M. McHardy; C. Montouri; L. Morelli; A. Mosquera; D. Mudd; F. Muller-Sanchez; R. Musso; S.~V. Nazarov; H. Netzer; M.~L. Nguyen; R.~P. Norris; J.~A. Nousek; P. Ochner; D.~N. Okhmat; B. Ou-Yang; A. Pancoast; I. Papadakis; J.~R. Parks; L. Pei; B.~M. Peterson; A. Pizzella; R. Poleski; J.-U. Pott; S.~E. Rafter; H.-W. Rix; J. Runnoe; D.~A. Saylor; J.~S. Schimoia; K. Schnülle; S.~G. Sergeev; B.~J. Shappee; I. Shivvers; M. Siegel; G.~V. Simonian; A. Siviero; A. Skielboe; G. Somers; M. Spencer; D. Starkey; D.~J. Stevens; H.-I. Sung; J. Tayar; N. Tejos; C.~S. Turner; P. Uttley; J. Van Saders; M. Vestergaard; L. Vican; S. VillanuevaJr.; C. Villforth; Y. Weiss; J.-H. Woo; H. Yan; S. Young; H. Yuk; W. Zheng; W. Zhu; Y. Zu

doi:10.3847/1538-4357/aa832b

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

S. Mathur, A. Gupta, K. Page, R.~W. Pogge, Y. Krongold, M.~R. Goad, S.~M. Adams, M.~D. Anderson, P. Arevalo, A.~J. Barth, C. Bazhaw, T.~G. Beatty, M.~C. Bentz, A. Bigley, S. Bisogni, G.~A. Borman, T.~A. Boroson, M.~C. Bottorff, W.~N. Brandt, A.~A. BreeveldJ.~E. Brown, J.~S. Brown, E.~M. Cackett, G. Canalizo, M.~T. Carini, K.~I. Clubb, J.~M. Comerford, C.~T. Coker, E.~M. Corsini, D.~M. Crenshaw, S. Croft, K.~V. Croxall, E. Dalla Bonta, A.~J. Deason, K.~D. Denney, A. De Lorenzo-Caceres, G. De Rosa, M. Dietrich, R. Edelson, J. Ely, M. Eracleous, P.~A. Evans, M.~M. Fausnaugh, G.~J. Ferland, A.~V. Filippenko, K. Flatland, O.~D. Fox, E.~L. Gates, N. Gehrels, S. Geier, J.~M. Gelbord, V. Gorjian, J.~E. Greene, C.~J. Grier, D. Grupe, P.~B. Hall, C.~B. Henderson, S. Hicks, E. Holmbeck, T.~W.-S. Holoien, D. Horenstein, K. Horne, T. Hutchison, M. Im, J.~J. Jensen, C.~A. Johnson, M.~D. Joner, J. Jones, J. Kaastra, S. Kaspi, B.~C. Kelly, P.~L. Kelly, J.~A. Kennea, M. Kim, S. Kim, S.~C. Kim, A. King, S.~A. Klimanov, C.~S. Kochanek, K.~T. Korista, G.~A. Kriss, M.~W. Lau, J.~C. Lee, D.~C. Leonard, M. Li, P. Lira, Z. Ma, F. MacInnis, E.~R. Manne-Nicholas, M.~A. Malkan, J.~C. Mauerhan, R. McGurk, I.~M. McHardy, C. Montouri, L. Morelli, A. Mosquera, D. Mudd, F. Muller-Sanchez, R. Musso, S.~V. Nazarov, H. Netzer, M.~L. Nguyen, R.~P. Norris, J.~A. Nousek, P. Ochner, D.~N. Okhmat, B. Ou-Yang, A. Pancoast, I. Papadakis, J.~R. Parks, L. Pei, B.~M. Peterson, A. Pizzella, R. Poleski, J.-U. Pott, S.~E. Rafter, H.-W. Rix, J. Runnoe, D.~A. Saylor, J.~S. Schimoia, K. Schnülle, S.~G. Sergeev, B.~J. Shappee, I. Shivvers, M. Siegel, G.~V. Simonian, A. Siviero, A. Skielboe, G. Somers, M. Spencer, D. Starkey, D.~J. Stevens, H.-I. Sung, J. Tayar, N. Tejos, C.~S. Turner, P. Uttley, J. Van Saders, M. Vestergaard, L. Vican, S. VillanuevaJr., C. Villforth, Y. Weiss, J.-H. Woo, H. Yan, S. Young, H. Yuk, W. Zheng, W. Zhu, Y. Zu

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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.

Original language	English
Article number	55
Number of pages	9
Journal	Astrophysical Journal
Volume	846
Issue number	1
DOIs	https://doi.org/10.3847/1538-4357/aa832b
Publication status	Published - 31 Aug 2017

Keywords

Astrophysics - Astrophysics of Galaxies

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10.3847/1538-4357/aa832b

1704.06345
The final version is © 2018 The American Astronomical Society, and is available at AAS/IOP via https://doi.org/10.3847/1538-4357/aa832b.
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Mathur, S., Gupta, A., Page, K., Pogge, R. W., Krongold, Y., Goad, M. R., Adams, S. M., Anderson, M. D., Arevalo, P., Barth, A. J., Bazhaw, C., Beatty, T. G., Bentz, M. C., Bigley, A., Bisogni, S., Borman, G. A., Boroson, T. A., Bottorff, M. C., Brandt, W. N., ... Zu, Y. (2017). Space Telescope and Optical Reverberation Mapping Project. VII. Understanding the Ultraviolet anomaly in NGC 5548 with X-Ray Spectroscopy. Astrophysical Journal, 846(1), Article 55. https://doi.org/10.3847/1538-4357/aa832b

Mathur, S, Gupta, A, Page, K, Pogge, RW, Krongold, Y, Goad, MR, Adams, SM, Anderson, MD, Arevalo, P, Barth, AJ, Bazhaw, C, Beatty, TG, Bentz, MC, Bigley, A, Bisogni, S, Borman, GA, Boroson, TA, Bottorff, MC, Brandt, WN, Breeveld, AA, Brown, JE, Brown, JS, Cackett, EM, Canalizo, G, Carini, MT, Clubb, KI, Comerford, JM, Coker, CT, Corsini, EM, Crenshaw, DM, Croft, S, Croxall, KV, Dalla Bonta, E, Deason, AJ, Denney, KD, De Lorenzo-Caceres, A, De Rosa, G, Dietrich, M, Edelson, R, Ely, J, Eracleous, M, Evans, PA, Fausnaugh, MM, Ferland, GJ, Filippenko, AV, Flatland, K, Fox, OD, Gates, EL, Gehrels, N, Geier, S, Gelbord, JM, Gorjian, V, Greene, JE, Grier, CJ, Grupe, D, Hall, PB, Henderson, CB, Hicks, S, Holmbeck, E, Holoien, TW-S, Horenstein, D, Horne, K, Hutchison, T, Im, M, Jensen, JJ, Johnson, CA, Joner, MD, Jones, J, Kaastra, J, Kaspi, S, Kelly, BC, Kelly, PL, Kennea, JA, Kim, M, Kim, S, Kim, SC, King, A, Klimanov, SA, Kochanek, CS, Korista, KT, Kriss, GA, Lau, MW, Lee, JC, Leonard, DC, Li, M, Lira, P, Ma, Z, MacInnis, F, Manne-Nicholas, ER, Malkan, MA, Mauerhan, JC, McGurk, R, McHardy, IM, Montouri, C, Morelli, L, Mosquera, A, Mudd, D, Muller-Sanchez, F, Musso, R, Nazarov, SV, Netzer, H, Nguyen, ML, Norris, RP, Nousek, JA, Ochner, P, Okhmat, DN, Ou-Yang, B, Pancoast, A, Papadakis, I, Parks, JR, Pei, L, Peterson, BM, Pizzella, A, Poleski, R, Pott, J-U, Rafter, SE, Rix, H-W, Runnoe, J, Saylor, DA, Schimoia, JS, Schnülle, K, Sergeev, SG, Shappee, BJ, Shivvers, I, Siegel, M, Simonian, GV, Siviero, A, Skielboe, A, Somers, G, Spencer, M, Starkey, D, Stevens, DJ, Sung, H-I, Tayar, J, Tejos, N, Turner, CS, Uttley, P, Van Saders, J, Vestergaard, M, Vican, L, VillanuevaJr., S, Villforth, C, Weiss, Y, Woo, J-H, Yan, H, Young, S, Yuk, H, Zheng, W, Zhu, W & Zu, Y 2017, 'Space Telescope and Optical Reverberation Mapping Project. VII. Understanding the Ultraviolet anomaly in NGC 5548 with X-Ray Spectroscopy', Astrophysical Journal, vol. 846, no. 1, 55. https://doi.org/10.3847/1538-4357/aa832b

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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.",

keywords = "Astrophysics - Astrophysics of Galaxies",

author = "S. Mathur and A. Gupta and K. Page and R.~W. Pogge and Y. Krongold and M.~R. Goad and S.~M. Adams and M.~D. Anderson and P. Arevalo and A.~J. Barth and C. Bazhaw and T.~G. Beatty and M.~C. Bentz and A. Bigley and S. Bisogni and G.~A. Borman and T.~A. Boroson and M.~C. Bottorff and W.~N. Brandt and A.~A. Breeveld and J.~E. Brown and J.~S. Brown and E.~M. Cackett and G. Canalizo and M.~T. Carini and K.~I. Clubb and J.~M. Comerford and C.~T. Coker and E.~M. Corsini and D.~M. Crenshaw and S. Croft and K.~V. Croxall and {Dalla Bonta}, E. and A.~J. Deason and K.~D. Denney and {De Lorenzo-Caceres}, A. and {De Rosa}, G. and M. Dietrich and R. Edelson and J. Ely and M. Eracleous and P.~A. Evans and M.~M. Fausnaugh and G.~J. Ferland and A.~V. Filippenko and K. Flatland and O.~D. Fox and E.~L. Gates and N. Gehrels and S. Geier and J.~M. Gelbord and V. Gorjian and J.~E. Greene and C.~J. Grier and D. Grupe and P.~B. Hall and C.~B. Henderson and S. Hicks and E. Holmbeck and T.~W.-S. Holoien and D. Horenstein and K. Horne and T. Hutchison and M. Im and J.~J. Jensen and C.~A. Johnson and M.~D. Joner and J. Jones and J. Kaastra and S. Kaspi and B.~C. Kelly and P.~L. Kelly and J.~A. Kennea and M. Kim and S. Kim and S.~C. Kim and A. King and S.~A. Klimanov and C.~S. Kochanek and K.~T. Korista and G.~A. Kriss and M.~W. Lau and J.~C. Lee and D.~C. Leonard and M. Li and P. Lira and Z. Ma and F. MacInnis and E.~R. Manne-Nicholas and M.~A. Malkan and J.~C. Mauerhan and R. McGurk and I.~M. McHardy and C. Montouri and L. Morelli and A. Mosquera and D. Mudd and F. Muller-Sanchez and R. Musso and S.~V. Nazarov and H. Netzer and M.~L. Nguyen and R.~P. Norris and J.~A. Nousek and P. Ochner and D.~N. Okhmat and B. Ou-Yang and A. Pancoast and I. Papadakis and J.~R. Parks and L. Pei and B.~M. Peterson and A. Pizzella and R. Poleski and J.-U. Pott and S.~E. Rafter and H.-W. Rix and J. Runnoe and D.~A. Saylor and J.~S. Schimoia and K. Schn{\"u}lle and S.~G. Sergeev and B.~J. Shappee and I. Shivvers and M. Siegel and G.~V. Simonian and A. Siviero and A. Skielboe and G. Somers and M. Spencer and D. Starkey and D.~J. Stevens and H.-I. Sung and J. Tayar and N. Tejos and C.~S. Turner and P. Uttley and {Van Saders}, J. and M. Vestergaard and L. Vican and S. VillanuevaJr. and C. Villforth and Y. Weiss and J.-H. Woo and H. Yan and S. Young and H. Yuk and W. Zheng and W. Zhu and Y. Zu",

year = "2017",

month = aug,

day = "31",

doi = "10.3847/1538-4357/aa832b",

language = "English",

volume = "846",

journal = "Astrophysical Journal",

issn = "0004-637X",

publisher = "IOP Publishing",

number = "1",

}

TY - JOUR

T1 - Space Telescope and Optical Reverberation Mapping Project. VII. Understanding the Ultraviolet anomaly in NGC 5548 with X-Ray Spectroscopy

AU - Mathur, S.

AU - Gupta, A.

AU - Page, K.

AU - Pogge, R.~W.

AU - Krongold, Y.

AU - Goad, M.~R.

AU - Adams, S.~M.

AU - Anderson, M.~D.

AU - Arevalo, P.

AU - Barth, A.~J.

AU - Bazhaw, C.

AU - Beatty, T.~G.

AU - Bentz, M.~C.

AU - Bigley, A.

AU - Bisogni, S.

AU - Borman, G.~A.

AU - Boroson, T.~A.

AU - Bottorff, M.~C.

AU - Brandt, W.~N.

AU - Breeveld, A.~A.

AU - Brown, J.~E.

AU - Brown, J.~S.

AU - Cackett, E.~M.

AU - Canalizo, G.

AU - Carini, M.~T.

AU - Clubb, K.~I.

AU - Comerford, J.~M.

AU - Coker, C.~T.

AU - Corsini, E.~M.

AU - Crenshaw, D.~M.

AU - Croft, S.

AU - Croxall, K.~V.

AU - Dalla Bonta, E.

AU - Deason, A.~J.

AU - Denney, K.~D.

AU - De Lorenzo-Caceres, A.

AU - De Rosa, G.

AU - Dietrich, M.

AU - Edelson, R.

AU - Ely, J.

AU - Eracleous, M.

AU - Evans, P.~A.

AU - Fausnaugh, M.~M.

AU - Ferland, G.~J.

AU - Filippenko, A.~V.

AU - Flatland, K.

AU - Fox, O.~D.

AU - Gates, E.~L.

AU - Gehrels, N.

AU - Geier, S.

AU - Gelbord, J.~M.

AU - Gorjian, V.

AU - Greene, J.~E.

AU - Grier, C.~J.

AU - Grupe, D.

AU - Hall, P.~B.

AU - Henderson, C.~B.

AU - Hicks, S.

AU - Holmbeck, E.

AU - Holoien, T.~W.-S.

AU - Horenstein, D.

AU - Horne, K.

AU - Hutchison, T.

AU - Im, M.

AU - Jensen, J.~J.

AU - Johnson, C.~A.

AU - Joner, M.~D.

AU - Jones, J.

AU - Kaastra, J.

AU - Kaspi, S.

AU - Kelly, B.~C.

AU - Kelly, P.~L.

AU - Kennea, J.~A.

AU - Kim, M.

AU - Kim, S.

AU - Kim, S.~C.

AU - King, A.

AU - Klimanov, S.~A.

AU - Kochanek, C.~S.

AU - Korista, K.~T.

AU - Kriss, G.~A.

AU - Lau, M.~W.

AU - Lee, J.~C.

AU - Leonard, D.~C.

AU - Li, M.

AU - Lira, P.

AU - Ma, Z.

AU - MacInnis, F.

AU - Manne-Nicholas, E.~R.

AU - Malkan, M.~A.

AU - Mauerhan, J.~C.

AU - McGurk, R.

AU - McHardy, I.~M.

AU - Montouri, C.

AU - Morelli, L.

AU - Mosquera, A.

AU - Mudd, D.

AU - Muller-Sanchez, F.

AU - Musso, R.

AU - Nazarov, S.~V.

AU - Netzer, H.

AU - Nguyen, M.~L.

AU - Norris, R.~P.

AU - Nousek, J.~A.

AU - Ochner, P.

AU - Okhmat, D.~N.

AU - Ou-Yang, B.

AU - Pancoast, A.

AU - Papadakis, I.

AU - Parks, J.~R.

AU - Pei, L.

AU - Peterson, B.~M.

AU - Pizzella, A.

AU - Poleski, R.

AU - Pott, J.-U.

AU - Rafter, S.~E.

AU - Rix, H.-W.

AU - Runnoe, J.

AU - Saylor, D.~A.

AU - Schimoia, J.~S.

AU - Schnülle, K.

AU - Sergeev, S.~G.

AU - Shappee, B.~J.

AU - Shivvers, I.

AU - Siegel, M.

AU - Simonian, G.~V.

AU - Siviero, A.

AU - Skielboe, A.

AU - Somers, G.

AU - Spencer, M.

AU - Starkey, D.

AU - Stevens, D.~J.

AU - Sung, H.-I.

AU - Tayar, J.

AU - Tejos, N.

AU - Turner, C.~S.

AU - Uttley, P.

AU - Van Saders, J.

AU - Vestergaard, M.

AU - Vican, L.

AU - VillanuevaJr., S.

AU - Villforth, C.

AU - Weiss, Y.

AU - Woo, J.-H.

AU - Yan, H.

AU - Young, S.

AU - Yuk, H.

AU - Zheng, W.

AU - Zhu, W.

AU - Zu, Y.

PY - 2017/8/31

Y1 - 2017/8/31

N2 - 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.

AB - 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.

KW - Astrophysics - Astrophysics of Galaxies

UR - https://doi.org/10.3847/1538-4357/aa832b

U2 - 10.3847/1538-4357/aa832b

DO - 10.3847/1538-4357/aa832b

M3 - Article

SN - 0004-637X

VL - 846

JO - Astrophysical Journal

JF - Astrophysical Journal

IS - 1

M1 - 55

ER -

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

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