Space telescope and optical reverberation mapping project. II. Swift and HST reverberation mapping of the accretion disk of NGC 5548

R. Edelson, J.~M. Gelbord, K. Horne, I.~M. McHardy, B.~M. Peterson, P. Arévalo, A.~A. Breeveld, G. De Rosa, P.~A. Evans, M.~R. Goad, G.~A. Kriss, W.~N. Brandt, N. Gehrels, D. Grupe, J.~A. Kennea, C.~S. Kochanek, J.~A. Nousek, I. Papadakis, M. Siegel, D. Starkey & 30 others P. Uttley, S. Vaughan, S. Young, A.~J. Barth, M.~C. Bentz, B.~J. Brewer, D.~M. Crenshaw, E. Dalla Bontà, A. De Lorenzo-Cáceres, K.~D. Denney, M. Dietrich, J. Ely, M.~M. Fausnaugh, C.~J. Grier, P.~B. Hall, J. Kaastra, B.~C. Kelly, K.~T. Korista, P. Lira, S. Mathur, H. Netzer, A. Pancoast, L. Pei, R.~W. Pogge, J.~S. Schimoia, T. Treu, M. Vestergaard, C. Villforth, H. Yan, Y. Zu

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Abstract

Recent intensive Swift monitoring of the Seyfert 1 galaxy NGC 5548 yielded 282 usable epochs over 125 days across six UV/optical bands and the X-rays. This is the densest extended active galactic nucleus (AGN) UV/optical continuum sampling ever obtained, with a mean sampling rate <0.5 day. Approximately daily Hubble Space Telescope UV sampling was also obtained. The UV/optical light curves show strong correlations (${{r}_{{\rm max} }}=0.57-0.90$) and the clearest measurement to date of interband lags. These lags are well-fit by a $\tau \propto {{{\lambda }}^{4/3}}$ wavelength dependence, with a normalization that indicates an unexpectedly large disk radius of $\sim 0.35\pm 0.05$ lt-day at 1367 Å, assuming a simple face-on model. The U band shows a marginally larger lag than expected from the fit and surrounding bands, which could be due to Balmer continuum emission from the broad-line region as suggested by Korista and Goad. The UV/X-ray correlation is weaker (${{r}_{{\rm max} }}\lt 0.45$) and less consistent over time. This indicates that while Swift is beginning to measure UV/optical lags in general agreement with accretion disk theory (although the derived size is larger than predicted), the relationship with X-ray variability is less well understood. Combining this accretion disk size estimate with those from quasar microlensing studies suggests that AGN disk sizes scale approximately linearly with central black hole mass over a wide range of masses.
Original languageEnglish
Pages (from-to)129
Number of pages1
JournalAstrophysical Journal
Volume806
Issue number1
DOIs
Publication statusPublished - 12 Jun 2015

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reverberation
accretion disks
time lag
accretion
telescopes
sampling
active galactic nuclei
continuums
x rays
Hubble Space Telescope
quasars
light curve
wavelength
time measurement
monitoring
galaxies
radii
project
estimates
wavelengths

Keywords

  • galaxies: active, galaxies: individual: NGC 5548, galaxies: nuclei, galaxies: Seyfert

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Space telescope and optical reverberation mapping project. II. Swift and HST reverberation mapping of the accretion disk of NGC 5548. / Edelson, R.; Gelbord, J.~M.; Horne, K.; McHardy, I.~M.; Peterson, B.~M.; Arévalo, P.; Breeveld, A.~A.; De Rosa, G.; Evans, P.~A.; Goad, M.~R.; Kriss, G.~A.; Brandt, W.~N.; Gehrels, N.; Grupe, D.; Kennea, J.~A.; Kochanek, C.~S.; Nousek, J.~A.; Papadakis, I.; Siegel, M.; Starkey, D.; Uttley, P.; Vaughan, S.; Young, S.; Barth, A.~J.; Bentz, M.~C.; Brewer, B.~J.; Crenshaw, D.~M.; Dalla Bontà, E.; De Lorenzo-Cáceres, A.; Denney, K.~D.; Dietrich, M.; Ely, J.; Fausnaugh, M.~M.; Grier, C.~J.; Hall, P.~B.; Kaastra, J.; Kelly, B.~C.; Korista, K.~T.; Lira, P.; Mathur, S.; Netzer, H.; Pancoast, A.; Pei, L.; Pogge, R.~W.; Schimoia, J.~S.; Treu, T.; Vestergaard, M.; Villforth, C.; Yan, H.; Zu, Y.

In: Astrophysical Journal, Vol. 806, No. 1, 12.06.2015, p. 129.

Research output: Contribution to journalArticle

Edelson, R, Gelbord, JM, Horne, K, McHardy, IM, Peterson, BM, Arévalo, P, Breeveld, AA, De Rosa, G, Evans, PA, Goad, MR, Kriss, GA, Brandt, WN, Gehrels, N, Grupe, D, Kennea, JA, Kochanek, CS, Nousek, JA, Papadakis, I, Siegel, M, Starkey, D, Uttley, P, Vaughan, S, Young, S, Barth, AJ, Bentz, MC, Brewer, BJ, Crenshaw, DM, Dalla Bontà, E, De Lorenzo-Cáceres, A, Denney, KD, Dietrich, M, Ely, J, Fausnaugh, MM, Grier, CJ, Hall, PB, Kaastra, J, Kelly, BC, Korista, KT, Lira, P, Mathur, S, Netzer, H, Pancoast, A, Pei, L, Pogge, RW, Schimoia, JS, Treu, T, Vestergaard, M, Villforth, C, Yan, H & Zu, Y 2015, 'Space telescope and optical reverberation mapping project. II. Swift and HST reverberation mapping of the accretion disk of NGC 5548', Astrophysical Journal, vol. 806, no. 1, pp. 129. https://doi.org/10.1088/0004-637X/806/1/129
Edelson, R. ; Gelbord, J.~M. ; Horne, K. ; McHardy, I.~M. ; Peterson, B.~M. ; Arévalo, P. ; Breeveld, A.~A. ; De Rosa, G. ; Evans, P.~A. ; Goad, M.~R. ; Kriss, G.~A. ; Brandt, W.~N. ; Gehrels, N. ; Grupe, D. ; Kennea, J.~A. ; Kochanek, C.~S. ; Nousek, J.~A. ; Papadakis, I. ; Siegel, M. ; Starkey, D. ; Uttley, P. ; Vaughan, S. ; Young, S. ; Barth, A.~J. ; Bentz, M.~C. ; Brewer, B.~J. ; Crenshaw, D.~M. ; Dalla Bontà, E. ; De Lorenzo-Cáceres, A. ; Denney, K.~D. ; Dietrich, M. ; Ely, J. ; Fausnaugh, M.~M. ; Grier, C.~J. ; Hall, P.~B. ; Kaastra, J. ; Kelly, B.~C. ; Korista, K.~T. ; Lira, P. ; Mathur, S. ; Netzer, H. ; Pancoast, A. ; Pei, L. ; Pogge, R.~W. ; Schimoia, J.~S. ; Treu, T. ; Vestergaard, M. ; Villforth, C. ; Yan, H. ; Zu, Y. / Space telescope and optical reverberation mapping project. II. Swift and HST reverberation mapping of the accretion disk of NGC 5548. In: Astrophysical Journal. 2015 ; Vol. 806, No. 1. pp. 129.
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title = "Space telescope and optical reverberation mapping project. II. Swift and HST reverberation mapping of the accretion disk of NGC 5548",
abstract = "Recent intensive Swift monitoring of the Seyfert 1 galaxy NGC 5548 yielded 282 usable epochs over 125 days across six UV/optical bands and the X-rays. This is the densest extended active galactic nucleus (AGN) UV/optical continuum sampling ever obtained, with a mean sampling rate <0.5 day. Approximately daily Hubble Space Telescope UV sampling was also obtained. The UV/optical light curves show strong correlations (${{r}_{{\rm max} }}=0.57-0.90$) and the clearest measurement to date of interband lags. These lags are well-fit by a $\tau \propto {{{\lambda }}^{4/3}}$ wavelength dependence, with a normalization that indicates an unexpectedly large disk radius of $\sim 0.35\pm 0.05$ lt-day at 1367 {\AA}, assuming a simple face-on model. The U band shows a marginally larger lag than expected from the fit and surrounding bands, which could be due to Balmer continuum emission from the broad-line region as suggested by Korista and Goad. The UV/X-ray correlation is weaker (${{r}_{{\rm max} }}\lt 0.45$) and less consistent over time. This indicates that while Swift is beginning to measure UV/optical lags in general agreement with accretion disk theory (although the derived size is larger than predicted), the relationship with X-ray variability is less well understood. Combining this accretion disk size estimate with those from quasar microlensing studies suggests that AGN disk sizes scale approximately linearly with central black hole mass over a wide range of masses.",
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T1 - Space telescope and optical reverberation mapping project. II. Swift and HST reverberation mapping of the accretion disk of NGC 5548

AU - Edelson, R.

AU - Gelbord, J.~M.

AU - Horne, K.

AU - McHardy, I.~M.

AU - Peterson, B.~M.

AU - Arévalo, P.

AU - Breeveld, A.~A.

AU - De Rosa, G.

AU - Evans, P.~A.

AU - Goad, M.~R.

AU - Kriss, G.~A.

AU - Brandt, W.~N.

AU - Gehrels, N.

AU - Grupe, D.

AU - Kennea, J.~A.

AU - Kochanek, C.~S.

AU - Nousek, J.~A.

AU - Papadakis, I.

AU - Siegel, M.

AU - Starkey, D.

AU - Uttley, P.

AU - Vaughan, S.

AU - Young, S.

AU - Barth, A.~J.

AU - Bentz, M.~C.

AU - Brewer, B.~J.

AU - Crenshaw, D.~M.

AU - Dalla Bontà, E.

AU - De Lorenzo-Cáceres, A.

AU - Denney, K.~D.

AU - Dietrich, M.

AU - Ely, J.

AU - Fausnaugh, M.~M.

AU - Grier, C.~J.

AU - Hall, P.~B.

AU - Kaastra, J.

AU - Kelly, B.~C.

AU - Korista, K.~T.

AU - Lira, P.

AU - Mathur, S.

AU - Netzer, H.

AU - Pancoast, A.

AU - Pei, L.

AU - Pogge, R.~W.

AU - Schimoia, J.~S.

AU - Treu, T.

AU - Vestergaard, M.

AU - Villforth, C.

AU - Yan, H.

AU - Zu, Y.

PY - 2015/6/12

Y1 - 2015/6/12

N2 - Recent intensive Swift monitoring of the Seyfert 1 galaxy NGC 5548 yielded 282 usable epochs over 125 days across six UV/optical bands and the X-rays. This is the densest extended active galactic nucleus (AGN) UV/optical continuum sampling ever obtained, with a mean sampling rate <0.5 day. Approximately daily Hubble Space Telescope UV sampling was also obtained. The UV/optical light curves show strong correlations (${{r}_{{\rm max} }}=0.57-0.90$) and the clearest measurement to date of interband lags. These lags are well-fit by a $\tau \propto {{{\lambda }}^{4/3}}$ wavelength dependence, with a normalization that indicates an unexpectedly large disk radius of $\sim 0.35\pm 0.05$ lt-day at 1367 Å, assuming a simple face-on model. The U band shows a marginally larger lag than expected from the fit and surrounding bands, which could be due to Balmer continuum emission from the broad-line region as suggested by Korista and Goad. The UV/X-ray correlation is weaker (${{r}_{{\rm max} }}\lt 0.45$) and less consistent over time. This indicates that while Swift is beginning to measure UV/optical lags in general agreement with accretion disk theory (although the derived size is larger than predicted), the relationship with X-ray variability is less well understood. Combining this accretion disk size estimate with those from quasar microlensing studies suggests that AGN disk sizes scale approximately linearly with central black hole mass over a wide range of masses.

AB - Recent intensive Swift monitoring of the Seyfert 1 galaxy NGC 5548 yielded 282 usable epochs over 125 days across six UV/optical bands and the X-rays. This is the densest extended active galactic nucleus (AGN) UV/optical continuum sampling ever obtained, with a mean sampling rate <0.5 day. Approximately daily Hubble Space Telescope UV sampling was also obtained. The UV/optical light curves show strong correlations (${{r}_{{\rm max} }}=0.57-0.90$) and the clearest measurement to date of interband lags. These lags are well-fit by a $\tau \propto {{{\lambda }}^{4/3}}$ wavelength dependence, with a normalization that indicates an unexpectedly large disk radius of $\sim 0.35\pm 0.05$ lt-day at 1367 Å, assuming a simple face-on model. The U band shows a marginally larger lag than expected from the fit and surrounding bands, which could be due to Balmer continuum emission from the broad-line region as suggested by Korista and Goad. The UV/X-ray correlation is weaker (${{r}_{{\rm max} }}\lt 0.45$) and less consistent over time. This indicates that while Swift is beginning to measure UV/optical lags in general agreement with accretion disk theory (although the derived size is larger than predicted), the relationship with X-ray variability is less well understood. Combining this accretion disk size estimate with those from quasar microlensing studies suggests that AGN disk sizes scale approximately linearly with central black hole mass over a wide range of masses.

KW - galaxies: active, galaxies: individual: NGC 5548, galaxies: nuclei, galaxies: Seyfert

UR - http://dx.doi.org/10.1088/0004-637X/806/1/129

U2 - 10.1088/0004-637X/806/1/129

DO - 10.1088/0004-637X/806/1/129

M3 - Article

VL - 806

SP - 129

JO - Astrophysical Journal

JF - Astrophysical Journal

SN - 0004-637X

IS - 1

ER -