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

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

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

Mathur, S.; Gupta, A.; Page, K.; Pogge, R.W.; Krongold, Y.; Goad, M.R.; Adams, S.M.; Anderson, M.D.; Arévalo, 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.; Breeveld, A.A.; Brown, J.E.; Brown, J.S.; Cackett, E.M.; Canalizo, G.; Carini, M.T.; Clubb, K.I.; Comerford, J.M.; Coker, C.T.; Corsini, E.M.; Crenshaw, D.M.; Croft, S.; Croxall, K.V.; Dalla Bontà, E.; Deason, A.J.; Denney, K.D.; De Lorenzo-Cáceres, A.; De Rosa, G.; Dietrich, M.; Edelson, R.; Ely, J.; Eracleous, M.; Evans, P.A.; Fausnaugh, M.M.; Ferland, G.J.; Filippenko, A.V.; Flatland, K.; Fox, O.D.; Gates, E.L.; Gehrels, N.; Geier, S.; Gelbord, J.M.; Gorjian, V.; Greene, J.E.; Grier, C.J.; Grupe, D.; Hall, P.B.; Henderson, C.B.; Hicks, S.; Holmbeck, E.; Holoien, T.W.-S.; Horenstein, D.; Horne, Keith; Hutchison, T.; Im, M.; Jensen, J.J.; Johnson, C.A.; Joner, M.D.; Jones, J.; Kaastra, J.; Kaspi, S.; Kelly, B.C.; Kelly, P.L.; Kennea, J.A.;...

Authors

S. Mathur

A. Gupta

K. Page

R.W. Pogge

Y. Krongold

M.R. Goad

S.M. Adams

M.D. Anderson

P. Arévalo

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 Bontà

Dr Alis Deason alis.j.deason@durham.ac.uk
Associate Professor

K.D. Denney

A. De Lorenzo-Cáceres

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

Keith 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. Villanueva Jr.

C. Villforth

Y. Weiss

J.-H. Woo

H. Yan

S. Young

H. Yuk

W. Zheng

W. Zhu

Y. Zu

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.

Citation

Mathur, S., Gupta, A., Page, K., Pogge, R., Krongold, Y., Goad, M., …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

Journal Article Type	Article
Acceptance Date	Jul 29, 2017
Online Publication Date	Aug 31, 2017
Publication Date	Aug 31, 2017
Deposit Date	Oct 10, 2017
Publicly Available Date	Oct 10, 2017
Journal	Astrophysical Journal
Print ISSN	0004-637X
Publisher	American Astronomical Society
Peer Reviewed	Peer Reviewed
Volume	846
Issue	1
Article Number	55
DOI	https://doi.org/10.3847/1538-4357/aa832b