The Nature of Transition Blazars

Abstract

Blazars are classically divided into the BL Lac (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 (BEL). 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 SDSS, 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 add credence to claims of a negative BLL redshift evolution.

arXiv comment14 pages, 11 Figures, ApJ accepted

References in corpus (58)

• Maps of Dust IR Emission for Use in Estimation of Reddening and CMBR Foregrounds
• The Sloan Digital Sky Survey: Technical Summary
• Nine-Year Wilkinson Microwave Anisotropy Probe (WMAP) Observations: Cosmological Parameter Results
• Unified Schemes for Radio-Loud Active Galactic Nuclei
• The Large Area Telescope on the Fermi Gamma-ray Space Telescope Mission
• The 2.5 m Telescope of the Sloan Digital Sky Survey
• Advection-Dominated Accretion: A Self-Similar Solution
• SDSS-III: Massive Spectroscopic Surveys of the Distant Universe, the Milky Way Galaxy, and Extra-Solar Planetary Systems
• The Baryon Oscillation Spectroscopic Survey of SDSS-III
• Composite Quasar Spectra From the Sloan Digital Sky Survey
• A Catalog of Quasar Properties from SDSS DR7
• Fermi Large Area Telescope Second Source Catalog
• A Unifying View of the Spectral Energy Distributions of Blazars
• First Results from the Catalina Real-time Transient Survey
• Spectral Energy Distributions and Multiwavelength Selection of Type 1 Quasars
• The Multi-Object, Fiber-Fed Spectrographs for SDSS and the Baryon Oscillation Spectroscopic Survey
• The Spectral Energy Distribution of Fermi bright blazars
• The Tenth Data Release of the Sloan Digital Sky Survey: First Spectroscopic Data from the SDSS-III Apache Point Observatory Galactic Evolution Experiment
• Estimating Black Hole Masses in Active Galaxies Using the Halpha Emission Line
• Modeling the Time Variability of SDSS Stripe 82 Quasars as a Damped Random Walk
• Spectral Classification and Redshift Measurement for the SDSS-III Baryon Oscillation Spectroscopic Survey
• The Second Catalog of Active Galactic Nuclei Detected by the Fermi Large Area Telescope
• The cosmological evolution of quasar black-hole masses
• Biases in Virial Black Hole Masses: An SDSS Perspective
• Unification of Luminous Type 1 Quasars through CIV Emission
• Roma-BZCAT: A multifrequency catalogue of Blazars
• Quantifying Quasar Variability As Part of a General Approach To Classifying Continuously Varying Sources
• Broad Emission Line Shifts in Quasars: An Orientation Measure for Radio-Quiet Quasars?
• The transition between BL Lac objects and Flat Spectrum Radio Quasars
• The SDSS-III Baryon Oscillation Spectroscopic Survey: Quasar Target Selection for Data Release Nine
• A simplified view of blazars: clearing the fog around long-standing selection effects
• The blazar sequence: a new perspective
• Jets and accretion processes in Active Galactic Nuclei: further clues
• The Sloan Digital Sky Survey quasar catalog: tenth data release
• Spectroscopy of The Largest Ever Gamma-ray Selected BL Lac Sample
• The Jet-Disk Connection and Blazar Unification
• Spectroscopy of Broad Line Blazars from 1LAC
• Klein-Nishina Effects in the Spectra of Non-Thermal Sources Immersed in External Radiation Fields
• The Fermi-LAT high-latitude Survey: Source Count Distributions and the Origin of the Extragalactic Diffuse Background
• An evolutionary scenario for blazar unification
• A Sample-oriented Catalogue of BL Lacertae Objects
• The relation between broad lines and gamma--ray luminosities in Fermi blazars
• Optically Selected BL Lacertae Candidates from the Sloan Digital Sky Survey Data Release Seven
• The Properties of the X-Ray-Selected EMSS Sample of BL Lac Objects
• The Deep X-Ray Radio Blazar Survey (DXRBS). III. Radio Number Counts, Evolutionary Properties, and Luminosity Function of Blazars
• Orientation dependency of broad-line widths in quasars and consequences for black-hole mass estimation
• The HRX-BL Lac sample - evolution of BL Lac objects
• Characterizing the Optical Variability of Bright Blazars: Variability-Based Selection of Fermi AGN
• The Accretion Rates and Spectral Energy Distributions of BL Lacertae Objects
• Photometrically Triggered Keck Spectroscopy of Fermi BL Lac Objects
• A Time Resolved Study of the Broad Line Region in Blazar 3C 454.3
• Implications of Gamma-Ray Transparency Constraints in Blazars: Minimum Distances and Gamma-Ray Collimation
• The orientation dependence of quasar single-epoch black hole mass scaling relationships
• Orientation effects in quasar spectra: The broad- and narrow-line regions
• On the cosmological evolution of BL Lacs
• The CLASS BL Lac sample: The Radio Luminosity Function
• Highly Variable Objects in the Palomar-QUEST Survey: A Blazar Search using Optical Variability
• Implications of the Anomalous Outburst in the Blazar PKS 0208-512

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