Steps toward determination of the size and structure of the broad-line region in active galactic nuclei. XVI. A 13 year study of spectral variability in NGC 5548

B. M. Peterson*, P. Berlind, R. Bertram, K. Bischoff, N. G. Bochkarev, N. Borisov, A. N. Burenkov, M. Calkins, L. Carrasco, V. H. Chavushyan, R. Chornock, M. Dietrich, V. T. Doroshenko, O. V. Ezhkova, A. V. Filippenko, A. M. Gilbert, J. P. Huchra, W. Kollatschny, D. C. Leonard, W. LiV. M. Lyuty, Yu F. Malkov, T. Matheson, N. I. Merkulova, V. P. Mikhailov, M. Modjaz, C. A. Onken, R. W. Pogge, V. I. Pronik, B. Qian, P. Romano, S. G. Sergeev, E. A. Sergeeva, A. I. Shapovalova, O. I. Spiridonova, J. Tao, S. Tokarz, J. R. Valdes, V. V. Vlasiuk, R. M. Wagner, B. J. Wilkes

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

142 Scopus citations

Abstract

We present the final installment of an intensive 13 year study of variations of the optical continuum and broad Hβ emission line in the Seyfert 1 galaxy NGC 5548. The database consists of 1530 optical continuum measurements and 1248 Hβ measurements. The Hβ variations follow the continuum variations closely, with a typical time delay of about 20 days. However, a year-by-year analysis shows that the magnitude of emission-line time delay is correlated with the mean continuum flux. We argue that the data are consistent with the simple model prediction between the size of the broad-line region and the ionizing luminosity, r ∝ Lion1/2. Moreover, the apparently linear nature of the correlation between the Hβ response time and the nonstellar optical continuum Fopt arises as a consequence of the changing shape of the continuum as it varies, specifically Fopt ∝ FUV0.56.

Original languageEnglish (US)
Pages (from-to)197-204
Number of pages8
JournalAstrophysical Journal
Volume581
Issue number1 I
DOIs
StatePublished - Dec 10 2002
Externally publishedYes

Keywords

  • Galaxies: Seyfert
  • Galaxies: active
  • Galaxies: individual (NGC 5548)
  • Galaxies: nuclei

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science

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