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Title:
A new physical interpretation of optical and infrared variability in quasars
Authors:
Ross, Nicholas P.; Ford, K. E. Saavik; Graham, Matthew; McKernan, Barry; Stern, Daniel; Meisner, Aaron M.; Assef, Roberto J.; Dey, Arjun; Drake, Andrew J.; Jun, Hyunsung D.; Lang, Dustin
Affiliation:
AA(Institute for Astronomy, University of Edinburgh, Royal Observatory, Blackford Hill, Edinburgh EH9 3HJ, UK 0000-0003-1830-6473), AB(Department of Science, BMCC, City University of New York, New York, NY 10007, USA; Department of Astrophysics, Rose Center for Earth and Space, American Museum of Natural History, Central Park West at 79th Street, NY 10024, USA; Graduate Center, City University of New York, 365 5th Avenue, New York, NY 10016, USA), AC(Cahill Center for Astronomy and Astrophysics, California Institute of Technology, Mail Code 249/17, 1200 E California Blvd, Pasadena, CA 91125, USA 0000-0002-3168-0139), AD(Department of Science, BMCC, City University of New York, New York, NY 10007, USA; Department of Astrophysics, Rose Center for Earth and Space, American Museum of Natural History, Central Park West at 79th Street, NY 10024, USA; Graduate Center, City University of New York, 365 5th Avenue, New York, NY 10016, USA), AE(Jet Propulsion Laboratory, California Institute of Technology, 4800 Oak Grove Drive, Mail Stop 169-221, Pasadena, CA 91109, USA), AF(Lawrence Berkeley National Laboratory, 1 Cyclotron Road, Berkeley, CA 92420, USA; Berkeley Center for Cosmological Physics, Berkeley, CA 94720, USA), AG(Núcleo de Astronomía de la Facultad de Ingeniería y Ciencias, Universidad Diego Portales, Av. Ejército Libertador 441, Santiago, Chile), AH(National Optical Astronomy Observatory, 950 N. Cherry Ave, Tucson, AZ 85719, USA), AI(Center for Advanced Computing Research, California Institute of Technology, 1200 E California Blvd, Pasadena, CA 91125, USA), AJ(School of Physics, Korea Institute for Advanced Study, 85 Hoegiro, Dongdaemun-gu, Seoul 02455, Korea), AK(Dunlap Institute, University of Toronto, Toronto, ON M5S 3H4, Canada; Department of Astronomy & Astrophysics, University of Toronto, Toronto, ON M5S 3H4, Canada; Perimeter Institute for Theoretical Physics, Waterloo, ON N2L 2Y5, Canada)
Publication:
Monthly Notices of the Royal Astronomical Society, Volume 480, Issue 4, p.4468-4479 (MNRAS Homepage)
Publication Date:
11/2018
Origin:
OUP
Astronomy Keywords:
accretion, accretion discs, surveys, quasars: general, quasars: individual: J1100-0053
Abstract Copyright:
2018 The Author(s) Published by Oxford University Press on behalf of the Royal Astronomical Society
DOI:
10.1093/mnras/sty2002
Bibliographic Code:
2018MNRAS.480.4468R

Abstract

Changing-look quasars are a recently identified class of active galaxies in which the strong UV continuum and/or broad optical hydrogen emission lines associated with unobscured quasars either appear or disappear on time-scales of months to years. The physical processes responsible for this behaviour are still debated, but changes in the black hole accretion rate or accretion disc structure appear more likely than changes in obscuration. Here, we report on four epochs of spectroscopy of SDSS J110057.70-005304.5, a quasar at a redshift of z = 0.378 whose UV continuum and broad hydrogen emission lines have faded, and then returned over the past ≈20 yr. The change in this quasar was initially identified in the infrared, and an archival spectrum from 2010 shows an intermediate phase of the transition during which the flux below rest frame ≈3400 Å has decreased by close to an order of magnitude. This combination is unique compared to previously published examples of changing-look quasars, and is best explained by dramatic changes in the innermost regions of the accretion disc. The optical continuum has been rising since mid-2016, leading to a prediction of a rise in hydrogen emission-line flux in the next year. Increases in the infrared flux are beginning to follow, delayed by a ˜3 yr observed time-scale. If our model is confirmed, the physics of changing-look quasars are governed by processes at the innermost stable circular orbit around the black hole, and the structure of the innermost disc. The easily identifiable and monitored changing-look quasars would then provide a new probe and laboratory of the nuclear central engine.
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