IPTF Discovery of the Rapid "turn-on" of a Luminous Quasar

S. Gezari, T. Hung, S. B. Cenko, N. Blagorodnova, Lin Yan, S. R. Kulkarni, K. Mooley, A. K.H. Kong, T. M. Cantwell, P. C. Yu, Y. Cao, C. Fremling, J. D. Neill, C. C. Ngeow, P. E. Nugent, P. Wozniak

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Abstract

We present a radio-quiet quasar at z = 0.237 discovered "turning on" by the intermediate Palomar Transient Factory (iPTF). The transient, iPTF 16bco, was detected by iPTF in the nucleus of a galaxy with an archival Sloan Digital Sky Survey spectrum with weak narrow-line emission characteristic of a low-ionization nuclear emission-line region (LINER). Our follow-up spectra show the dramatic appearance of broad Balmer lines and a power-law continuum characteristic of a luminous ( Lbol ≈ 1045 erg s-1) type 1 quasar 12 yr later. Our photometric monitoring with PTF from 2009-2012 and serendipitous X-ray observations from the XMM-Newton Slew Survey in 2011 and 2015 constrain the change of state to have occurred less than 500 days before the iPTF detection. An enhanced broad Hα/[O iii] λ5007 line ratio in the type 1 state relative to other changing-look quasars also is suggestive of the most rapid change of state yet observed in a quasar. We argue that the >10 increase in Eddington ratio inferred from the brightening in UV and X-ray continuum flux is more likely due to an intrinsic change in the accretion rate of a preexisting accretion disk than an external mechanism such as variable obscuration, microlensing, or the tidal disruption of a star. However, further monitoring will be helpful in better constraining the mechanism driving this change of state. The rapid "turn-on" of the quasar is much shorter than the viscous infall timescale of an accretion disk and requires a disk instability that can develop around a ∼ 108 M black hole on timescales less than 1 yr.

Original languageEnglish
Article number144
JournalAstrophysical Journal
Volume835
Issue number2
DOIs
StatePublished - 1 Feb 2017

Keywords

  • accretion, accretion disks
  • black hole physics
  • galaxies: active surveys

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