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Published February 2020 | Supplemental Material + Submitted + Published
Journal Article Open

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

Abstract

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.

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 (https://academic.oup.com/journals/pages/open_access/funder_policies/chorus/standard_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 http://www.sdss3.org/. 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.

Attached Files

Published - stz3244.pdf

Submitted - 1905.02262.pdf

Supplemental Material - stz3244_supplemental_file.pdf

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Additional details

Created:
August 22, 2023
Modified:
October 20, 2023