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Title: Extreme Variability Quasars from the Sloan Digital Sky Survey and the Dark Energy Survey

Journal Article · · The Astrophysical Journal (Online)
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Here, we perform a systematic search for long-term extreme variability quasars (EVQs) in the overlapping Sloan Digital Sky Survey (SDSS) and 3-Year Dark Energy Survey (DES) imaging, which provide light curves spanning more than 15 years. We also identified 1000 EVQs with a maximum g band magnitude change of more than 1 mag over this period, about 10% of all quasars searched. The EVQs have Lbol 1045 - 1047 erg s-1 and L=LEdd 0:01-1. Accounting for selection effects, we estimate an intrinsic EVQ fraction of 30-50% among all g.22 quasars over a baseline of 15 years. These EVQs are good candidates for so-called “changing-look quasars”, where a spectral transition between the two types of quasars (broad-line and narrow-line) is observed between the dim and bright states. We performed detailed multi-wavelength, spectral and variability analyses for the EVQs and compared to their parent quasar sample. We found that EVQs are distinct from a control sample of quasars matched in redshift and optical luminosity: (1) their UV broad emission lines have larger equivalent widths; (2) their Eddington ratios are systematically lower; and (3) they are more variable on all timescales. The intrinsic difference in quasar properties for EVQs suggest that internal processes associated with accretion are the main driver for the observed extreme long-term variability. In spit of their different properties, EVQs seem to be in the tail of a continuous distribution of quasar properties, rather than standing out as a distinct population. We speculate that EVQs are normal quasars accreting at relatively low accretion rates, where the accretion flow is more likely to experience instabilities that drive the factor of few changes in flux on multi-year timescales.

Research Organization:
SLAC National Accelerator Laboratory (SLAC), Menlo Park, CA (United States); Brookhaven National Laboratory (BNL), Upton, NY (United States); Fermi National Accelerator Laboratory (FNAL), Batavia, IL (United States); Oak Ridge National Laboratory (ORNL), Oak Ridge, TN (United States)
Sponsoring Organization:
USDOE Office of Science (SC), High Energy Physics (HEP)
Contributing Organization:
DES Collaboration
Grant/Contract Number:
AC02-76SF00515; AST-1138766; AYA2012-39559; ESP2013-48274; FPA2013-47986; 240672; 291329; 306478; SC0012704; AC02-07CH11359; AC05-00OR22725
OSTI ID:
1425676
Alternate ID(s):
OSTI ID: 1389253; OSTI ID: 1409080; OSTI ID: 1435204
Report Number(s):
BNL-114280-2017-JA; FERMILAB-PUB-17-211-AE; arXiv:1706.07875; TRN: US1802147
Journal Information:
The Astrophysical Journal (Online), Vol. 854, Issue 2; ISSN 1538-4357
Publisher:
Institute of Physics (IOP)Copyright Statement
Country of Publication:
United States
Language:
English
Citation Metrics:
Cited by: 59 works
Citation information provided by
Web of Science

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A Population of X-ray Weak Quasars: PHL 1811 Analogs at High Redshift text January 2011
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X-ray Insights into the Nature of PHL 1811 Analogs and Weak Emission-Line Quasars: Unification with a Geometrically Thick Accretion Disk? text January 2015
A tidal disruption flare in a massive galaxy? Implications for the fuelling mechanisms of nuclear black holes text January 2015
Revisiting the Unified Model of Active Galactic Nuclei text January 2015
The 31 Deg$^2$ Release of the Stripe 82 X-ray Survey: The Point Source Catalog text January 2015
The optical variability of SDSS quasars from multi-epoch spectroscopy. II. color variation text January 2016
Revisiting Stochastic Variability of AGNs with Structure Functions text January 2016
The detection and X-ray view of the changing look AGN HE 1136-2304 text January 2016
The Close AGN Reference Survey (CARS) - What is causing Mrk1018's return to the shadows after 30 years? text January 2016
iPTF Discovery of the Rapid "Turn On" of a Luminous Quasar text January 2016
Insight Into "Changing-Look" AGN Mrk 1018 from the Fe K$α$ Line: The Reprocessing Gas Has Yet to Fully Respond to the Fading of the AGN text January 2017
Mid-infrared variability of changing-look AGN text January 2017
A photometricity and extinction monitor at the Apache Point Observatory text January 2001
The Ensemble Photometric Variability of ~25000 Quasars in the Sloan Digital Sky Survey text January 2003
SDSS Data Management and Photometric Quality Assessment text January 2004
The 2.5 m Telescope of the Sloan Digital Sky Survey text January 2006
The Sloan Digital Sky Survey Photometric Camera text January 1998
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Cited By (33)

A model for AGN variability on multiple time-scales journal February 2018
The Ensemble Photometric Variability of Over 10 5 Quasars in the Dark Energy Camera Legacy Survey and the Sloan Digital Sky Survey journal June 2018
The Sloan Digital Sky Survey Reverberation Mapping Project: Accretion and Broad Emission Line Physics from a Hypervariable Quasar journal October 2019
Initial Results from a Systematic Search for Changing-look Active Galactic Nuclei Selected via Mid-infrared Variability journal January 2020
A new physical interpretation of optical and infrared variability in quasars journal July 2018
A New Class of Changing-look LINERs journal September 2019
Discovery of an Mg ii Changing-look Active Galactic Nucleus and Its Implications for a Unification Sequence of Changing-look Active Galactic Nuclei journal October 2019
Spectral energy distributions of candidate periodically variable quasars: testing the binary black hole hypothesis journal December 2019
HST/COS observations of the newly discovered obscuring outflow in NGC 3783 journal December 2018
Understanding Broad Mg ii Variability in Quasars with Photoionization: Implications for Reverberation Mapping and Changing-look Quasars journal January 2020
Changing-look Quasar Candidates: First Results from Follow-up Spectroscopy of Highly Optically Variable Quasars journal March 2019
A Forward Modeling Approach to AGN Variability--Method Description and Early Applications journal September 2019
WISE view of narrow-line Seyfert 1 galaxies: mid-infrared colour and variability journal November 2018
Discovery of 21 New Changing-look AGNs in the Northern Sky journal July 2018
Extreme AGN variability: evidence of magnetically elevated accretion? journal November 2018
NuSTAR Perspective on High-redshift MeV Blazars journal February 2020
Observational Nonstationarity of AGN Variability: The Only Way to Go Is Down! journal January 2020
The ‘Big Dipper’: the nature of the extreme variability of the AGN SDSS J2232−0806 journal February 2019
Two New “Turn-off” Changing-look Active Galactic Nuclei and Implication on “Partially Obscured” AGNs journal December 2019
An Unusual Mid-infrared Flare in a Type 2 AGN: An Obscured Turning-on AGN or Tidal Disruption Event? journal November 2019
NuSTAR perspective on high-redshift MeV blazars text January 2020
A model for AGN variability on multiple timescales text January 2018
A new physical interpretation of optical and infrared variability in quasars text January 2018
The ensemble photometric variability of over $10^5$ quasars in the Dark Energy Camera Legacy Survey and the Sloan Digital Sky Survey text January 2018
Changing-Look Quasar Candidates: First Results from Follow-up Spectroscopy of Highly Optically Variable Quasars text January 2018
HST/COS observations of the newly discovered obscuring outflow in NGC 3783 text January 2018
WISE view of Narrow-Line Seyfert 1 galaxies: mid-infrared color and variability text January 2018
Initial results from a systematic search for changing-look active galactic nuclei selected via mid-infrared variability text January 2019
The Sloan Digital Sky Survey Reverberation Mapping Project: Accretion and Broad Emission Line Physics from a Hypervariable Quasar text January 2019
Understanding Broad Mg II Variability in Quasars with Photoionization: Implications for Reverberation Mapping and Changing-Look Quasars text January 2019
Spectral Energy Distributions of Candidate Periodically-Variable Quasars: Testing the Binary Black Hole Hypothesis text January 2019
A forward modelling approach to AGN variability -- Method description and early applications text January 2019
Observational nonstationarity of AGN variability: The only way to go is down! text January 2020

Linked Research (1)

Figures / Tables (17)

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Related Subjects

79 ASTRONOMY AND ASTROPHYSICS
black hole physics
galaxies: active
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quasars: general
surveys