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Understanding extreme quasar optical variability with CRTS: II. Changing-state quasars

Graham, Matthew J. and Ross, Nicholas P. and Stern, Daniel and Drake, Andrew J. and McKernan, Barry and Ford, K. E. Saavik and Djorgovski, S. G. and Mahabal, Ashish A. and Glikman, Eilat and Larson, Steve and Christensen, Eric (2020) Understanding extreme quasar optical variability with CRTS: II. Changing-state quasars. Monthly Notices of the Royal Astronomical Society, 491 (4). pp. 4925-4948. ISSN 0035-8711. doi:10.1093/mnras/stz3244.

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We present the results of a systematic search for quasars in the Catalina Real-time Transient Survey exhibiting both strong photometric variability and spectroscopic variability over a decadal baseline. We identify 111 sources with specific patterns of optical and mid-infrared photometric behaviour and a defined spectroscopic change. These ‘changing-state’ quasars (CSQs) form a higher luminosity sample to complement existing sets of ‘changing-look’ AGNs and quasars in the literature. The CSQs (by selection) exhibit larger photometric variability than the changing-look quasars (CLQs). The spectroscopic variability is marginally stronger in the CSQs than CLQs as defined by the change in H β/[OIIIOIII] ratio. We find 48 sources with declining H β flux and 63 sources with increasing H β flux, and discover 8 sources with z > 0.8, further extending the redshift arm. Our CSQ sample compares to the literature CLQ objects in similar distributions of H β flux ratios and differential Eddington ratios between high (bright) and low (dim) states. Taken as a whole, we find that this population of extreme varying quasars is associated with changes in the Eddington ratio and the time-scales imply cooling/heating fronts propagating through the disc.

Item Type:Article
Related URLs:
URLURL TypeDescription Paper
Graham, Matthew J.0000-0002-3168-0139
Ross, Nicholas P.0000-0003-1830-6473
Stern, Daniel0000-0003-2686-9241
McKernan, Barry0000-0002-9726-0508
Djorgovski, S. G.0000-0002-0603-3087
Mahabal, Ashish A.0000-0003-2242-0244
Glikman, Eilat0000-0003-0489-3750
Larson, Steve0000-0002-0057-8211
Additional Information:© 2019 The Author(s) Published by Oxford University Press on behalf of the Royal Astronomical Society. This article is published and distributed under the terms of the Oxford University Press, Standard Journals Publication Model ( Accepted 2019 November 6. Received 2019 October 10; in original form 2019 May 6. Published: 20 November 2019. We thank Chelsea MacLeod for useful discussions. This work was supported in part by the NSF grants AST-1313422, AST-1413600, AST-1518308, and AST-1815034, and the NASA grant 16-ADAP16-0232. The work of DS was carried out at the Jet Propulsion Laboratory, California Institute of Technology, under a contract with NASA. NPR acknowledges support from the STFC and the Ernest Rutherford Fellowship scheme. This work made use of the Million Quasars Catalogue. Funding for SDSS-III has been provided by the Alfred P. Sloan Foundation, the Participating Institutions, the National Science Foundation, and the U.S. Department of Energy Office of Science. The SDSS-III web site is This publication makes use of data products from the Near-Earth Object Wide-field Infrared Survey Explorer (NEOWISE), which is a project of the Jet Propulsion Laboratory/California Institute of Technology. NEOWISE is funded by the National Aeronautics and Space Administration. SDSS-III is managed by the Astrophysical Research Consortium for the Participating Institutions of the SDSS-III Collaboration including the University of Arizona, the Brazilian Participation Group, Brookhaven National Laboratory, Carnegie Mellon University, University of Florida, the French Participation Group, the German Participation Group, Harvard University, the Instituto de Astrofisica de Canarias, the Michigan State/Notre Dame/JINA Participation Group, Johns Hopkins University, Lawrence Berkeley National Laboratory, Max Planck Institute for Astrophysics, Max Planck Institute for Extraterrestrial Physics, New Mexico State University, New York University, Ohio State University, Pennsylvania State University, University of Portsmouth, Princeton University, the Spanish Participation Group, University of Tokyo, University of Utah, Vanderbilt University, University of Virginia, University of Washington, and Yale University.
Funding AgencyGrant Number
Science and Technology Facilities Council (STFC)UNSPECIFIED
Alfred P. Sloan FoundationUNSPECIFIED
Participating InstitutionsUNSPECIFIED
Department of Energy (DOE)UNSPECIFIED
Subject Keywords:methods: data analysis – techniques: photometric – surveys – quasars: general
Issue or Number:4
Record Number:CaltechAUTHORS:20190722-112841141
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Official Citation:Matthew J Graham, Nicholas P Ross, Daniel Stern, Andrew J Drake, Barry McKernan, K E Saavik Ford, S G Djorgovski, Ashish A Mahabal, Eilat Glikman, Steve Larson, Eric Christensen, Understanding extreme quasar optical variability with CRTS – II. Changing-state quasars, Monthly Notices of the Royal Astronomical Society, Volume 491, Issue 4, February 2020, Pages 4925–4948,
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:97324
Deposited By: Tony Diaz
Deposited On:22 Jul 2019 20:51
Last Modified:16 Nov 2021 17:30

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