Confirming new changing--look AGNs discovered through optical variability using a random-forest based light curve classifier

Abstract

Determining the frequency and duration of changing--look (CL) active galactic nuclei (AGNs) phenomena, where the optical broad emission lines appear or disappear, is crucial to understand the evolution of the accretion flow around supermassive black holes. We present a strategy to select new CL candidates starting from a spectroscopic type 2 AGNs sample and searching for current type 1 photometric variability. We use the publicly available Zwicky Transient Facility (ZTF) alert stream and the Automatic Learning for the Rapid Classification of Events (ALeRCE) light curve classifier to produce a list of CL candidates with a highly automated algorithm, resulting in 60 candidates. Visual inspection reduced the sample to 30. We performed new spectroscopic observations of six candidates of our clean sample, without further refinement, finding the appearance of clear broad Balmer lines in four of them and tentative evidence of type changes in the remaining two, which suggests a promising success rate of $\ge 66$ per cent for this CL selection method.

arXiv comment5 pages

References in corpus (29)

• The SIMBAD astronomical database
• The Zwicky Transient Facility: System Overview, Performance, and First Results
• The Sixteenth Data Release of the Sloan Digital Sky Surveys: First Release from the APOGEE-2 Southern Survey and Full Release of eBOSS Spectra
• Improving the full spectrum fitting method: accurate convolution with Gauss-Hermite functions
• Revisiting the Unified Model of Active Galactic Nuclei
• Evolutionary Stellar Population Synthesis with MILES. Part I: The Base Models and a New Line Index System
• Automated data reduction workflows for astronomy
• Dwarf Galaxies with Optical Signatures of Active Massive Black Holes
• The evolution of black hole states
• The Discovery of the First "Changing Look" Quasar: New Insights into the Physics & Phenomenology of AGN
• A Systematic Search for Changing-Look Quasars in SDSS
• Explaining changing-look AGN with state transition triggered by rapid mass accretion rate drop
• Discovery of 21 New Changing-look AGNs in Northern Sky
• The Automatic Learning for the Rapid Classification of Events (ALeRCE) Alert Broker
• 1ES 1927+654: An AGN Caught Changing Look on a Timescale of Months
• Hidden Broad Line Seyfert 2 Galaxies in the CfA and 12micron Samples
• Bolometric correction factors for Active Galactic Nuclei
• Changing-Look Quasar Candidates: First Results from Follow-up Spectroscopy of Highly Optically Variable Quasars
• Alert Classification for the ALeRCE Broker System: The Light Curve Classifier
• A possible mechanism for multiple changing look phenomenon in Active Galactic Nuclei
• A new physical interpretation of optical and infrared variability in quasars
• Understanding extreme quasar optical variability with CRTS: II. Changing-state quasars
• A New Class of Changing-Look LINERs
• Polarization of changing-look quasars
• Searching for changing-state AGNs in massive datasets -- I: applying deep learning and anomaly detection techniques to find AGNs with anomalous variability behaviours
• Near Infrared Variability of obscured and unobscured X-ray selected AGN in the COSMOS field
• Polarization of the changing-look quasar J1011+5442
• The Eddington ratio-dependent changing look events in NGC 2992
• X-ray binary accretion states in Active Galactic Nuclei? Sensing the accretion disc of supermassive black holes with mid-infrared nebular lines

Cited by in corpus (15)

• Exploring Changing-look Active Galactic Nuclei with the Sloan Digital Sky Survey V: First Year Results
• BASS XXXIX: Swift-BAT AGN with changing-look optical spectra
• Probing the Origin of Changing-look Quasar Transitions with Chandra
• The rise and fall of the iron-strong nuclear transient PS16dtm
• Improving the selection of changing-look AGNs through multi-wavelength photometric variability
• Accretion disks, quasars and cosmology: meandering towards understanding
• The Type 1 and Type 2 AGN dichotomy according to their ZTF optical variability
• Persistent and occasional: searching for the variable population of the ZTF/4MOST sky using ZTF data release 11
• SDSS1335+0728: The awakening of a $\sim 10^6{M}_{\odot }$ black hole
• Unveiling the quasar main sequence: illuminating the complexity of active galactic nuclei and their evolution
• Extreme Variability Quasars in Their Various States. II: Spectral Variation Revealed with Multi-epoch Spectra
• The Success of Optical Variability in Uncovering AGNs in Low-stellar Mass Galaxies
• Modeling Star Formation Histories of Changing-Look AGN Host Galaxies with Prospector
• Identifying Changing-Look AGN Transitions in Light Curve Data with the Zwicky Transient Facility
• Seeing through the dust: Unraveling near-infrared variability in type 2 active galactic nuclei