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Broad-line reverberation in the Kepler-field Seyfert galaxy Zw 229-015

  • Author(s): Barth, AJ
  • Nguyen, ML
  • Malkan, MA
  • Filippenko, AV
  • Li, W
  • Gorjian, V
  • Joner, MD
  • Bennert, VN
  • Botyanszki, J
  • Cenko, SB
  • Childress, M
  • Choi, J
  • Comerford, JM
  • Cucciara, A
  • Da Silva, R
  • Duchêne, G
  • Fumagalli, M
  • Ganeshalingam, M
  • Gates, EL
  • Gerke, BF
  • Griffith, CV
  • Harris, C
  • Hintz, EG
  • Hsiao, E
  • Kandrashoff, MT
  • Keel, WC
  • Kirkman, D
  • Kleiser, IKW
  • Laney, CD
  • Lee, J
  • Lopez, L
  • Lowe, TB
  • Moody, JW
  • Morton, A
  • Nierenberg, AM
  • Nugent, P
  • Pancoast, A
  • Rex, J
  • Rich, RM
  • Silverman, JM
  • Smith, GH
  • Sonnenfeld, A
  • Suzuki, N
  • Tytler, D
  • Walsh, JL
  • Woo, JH
  • Yang, Y
  • Zeisse, C
  • et al.

The Seyfert 1 galaxy Zw 229-015 is among the brightest active galaxies being monitored by the Kepler mission. In order to determine the black hole mass in Zw 229-015 from Hβ reverberation mapping, we have carried out nightly observations with the Kast Spectrograph at the Lick 3 m telescope during the dark runs from 2010 June through December, obtaining 54 spectroscopic observations in total. We have also obtained nightly V-band imaging with the Katzman Automatic Imaging Telescope at Lick Observatory and with the 0.9 m telescope at the Brigham Young University West Mountain Observatory over the same period. We detect strong variability in the source, which exhibited more than a factor of two change in broad Hβ flux. From cross-correlation measurements, we find that the Hβ light curve has a rest-frame lag of 3.86+0.69-0.90 days with respect to the V-band continuum variations. We also measure reverberation lags for Hα and Hγ and find an upper limit to the Hδ lag. Combining the Hβ lag measurement with a broad Hβ width of σline = 1590 ± 47 km s-1 measured from the rms variability spectrum, we obtain a virial estimate of M BH = 1.00+0.19-0.24 × 107 M⊙ for the black hole in Zw 229-015. As a Kepler target, Zw 229-015 will eventually have one of the highest-quality optical light curves ever measured for any active galaxy, and the black hole mass determined from reverberation mapping will serve as a benchmark for testing relationships between black hole mass and continuum variability characteristics in active galactic nuclei. © 2011. The American Astronomical Society. All rights reserved.

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