The Man behind the Curtain: X-Rays Drive the UV through NIR Variability in the 2013 Active Galactic Nucleus Outburst in NGC 2617

June 2014 • 2014ApJ...788...48S

Authors • Shappee, B. J. • Prieto, J. L. • Grupe, D. • Kochanek, C. S. • Stanek, K. Z. • De Rosa, G. • Mathur, S. • Zu, Y. • Peterson, B. M. • Pogge, R. W. • Komossa, S. • Im, M. • Jencson, J. • Holoien, T. W. -S. • Basu, U. • Beacom, J. F. • Szczygieł, D. M. • Brimacombe, J. • Adams, S. • Campillay, A. • Choi, C. • Contreras, C. • Dietrich, M. • Dubberley, M. • Elphick, M. • Foale, S. • Giustini, M. • Gonzalez, C. • Hawkins, E. • Howell, D. A. • Hsiao, E. Y. • Koss, M. • Leighly, K. M. • Morrell, N. • Mudd, D. • Mullins, D. • Nugent, J. M. • Parrent, J. • Phillips, M. M. • Pojmanski, G. • Rosing, W. • Ross, R. • Sand, D. • Terndrup, D. M. • Valenti, S. • Walker, Z. • Yoon, Y.

Abstract • After the All-Sky Automated Survey for SuperNovae discovered a significant brightening of the inner region of NGC 2617, we began a ~70 day photometric and spectroscopic monitoring campaign from the X-ray through near-infrared (NIR) wavelengths. We report that NGC 2617 went through a dramatic outburst, during which its X-ray flux increased by over an order of magnitude followed by an increase of its optical/ultraviolet (UV) continuum flux by almost an order of magnitude. NGC 2617, classified as a Seyfert 1.8 galaxy in 2003, is now a Seyfert 1 due to the appearance of broad optical emission lines and a continuum blue bump. Such "changing look active galactic nuclei (AGNs)" are rare and provide us with important insights about AGN physics. Based on the Hβ line width and the radius-luminosity relation, we estimate the mass of central black hole (BH) to be (4 ± 1) × 10⁷ M _⊙. When we cross-correlate the light curves, we find that the disk emission lags the X-rays, with the lag becoming longer as we move from the UV (2-3 days) to the NIR (6-9 days). Also, the NIR is more heavily temporally smoothed than the UV. This can largely be explained by a simple model of a thermally emitting thin disk around a BH of the estimated mass that is illuminated by the observed, variable X-ray fluxes.

Links

• PREPRINT http://arxiv.org/abs/1310.2241
• NED https://ned.ipac.caltech.edu/uri/NED::InRefcode/2014ApJ...788...48S
• ELECTR https://doi.org/10.1088%2F0004-637X%2F788%2F1%2F48
• SIMBAD http://simbad.u-strasbg.fr/simbo.pl?bibcode=2014ApJ...788...48S
• PDF https://stacks.iop.org/0004-637X/788/48/pdf
• DATA http://cdsarc.cds.unistra.fr/viz-bin/cat/J/ApJ/788/48
• DATA http://heasarc.gsfc.nasa.gov/cgi-bin/W3Browse/biblink.pl?code=2014ApJ...788...48S
• DATA https://irsa.ipac.caltech.edu/bibdata/2014/S/2014ApJ...788...48S.html
• DATA https://nxsa.esac.esa.int/nxsa-web/#bibcode=2014ApJ...788...48S