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    The nature of transition blazars

    251729.pdf (1.576Mb)
    Access Status
    Open access
    Authors
    Ruan, J.
    Anderson, S.
    Plotkin, Richard
    Brandt, W.
    Burnett, T.
    Myers, A.
    Schneider, D.
    Date
    2014
    Type
    Journal Article
    
    Metadata
    Show full item record
    Citation
    Ruan, J. and Anderson, S. and Plotkin, R. and Brandt, W. and Burnett, T. and Myers, A. and Schneider, D. 2014. The nature of transition blazars. Astrophysical Journal. 797: 19.
    Source Title
    Astrophysical Journal
    DOI
    10.1088/0004-637X/797/1/19
    ISSN
    0004-637X
    School
    Department of Physics and Astronomy
    Remarks

    Copyright © 2014 The American Astronomical Society. All rights reserved..

    URI
    http://hdl.handle.net/20.500.11937/52594
    Collection
    • Curtin Research Publications
    Abstract

    Blazars are classically divided into the BL Lacertae (BLL) and flat-spectrum radio quasar (FSRQ) subclasses, corresponding to radiatively inefficient and efficient accretion regimes, respectively, largely based on the equivalent width (EW) of their optical broad emission lines (BELs). However, EW-based classification criteria are not physically motivated, and a few blazars have previously "transitioned" from one subclass to the other. We present the first systematic search for these transition blazars in a sample of 602 unique pairs of repeat spectra of 354 blazars in the Sloan Digital Sky Survey, finding six clear cases. These transition blazars have bolometric Eddington ratios of ~0.3 and low-frequency synchrotron peaks, and are thus FSRQ-like. We show that the strong EW variability (up to an unprecedented factor of >60) is due to swamping of the BELs from variability in jet continuum emission, which is stronger in amplitude and shorter in timescale than typical blazars. Although these transition blazars appear to switch between FSRQ and BLL according to the phenomenologically based EW scheme, we show that they are most likely rare cases of FSRQs with radiatively efficient accretion flows and especially strongly beamed jets. These results have implications for the decrease of the apparent BLL population at high redshifts, and may lend credence to claims of a negative BLL redshift evolution.

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