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Table · dataset · 2024

Changing-look AGN. I. Main sequence transition

Listed in IVOA Registry (Virtual Observatory)

This paper is the first in a series of papers that prepare and analyze spectral and other properties for a database of already-discovered changing-look active galactic nuclei (CL AGNs).

Description

Here we focus on the spectral fitting and analysis of broad emission lines in a sample of 93 CL AGNs collected from the literature with existing Sloan Digital Sky Survey (SDSS)/Baryon Oscillation Spectroscopic Survey (BOSS)/extended-BOSS spectroscopy where the H{beta} emission-line profile does not completely disappear in any epochs.

Additionally, we have gathered older/newer spectral epochs from all the available SDSS data releases to make the database more complete. We use PyQSOFit and perform a homogeneous spectral decomposition of all of our SDSS spectra and tabulate the AGN continuum and emission-line properties per epoch per source, chronologically. This further allows us to categorize the sources in our sample as Turn-On or Turn-Off and subsequently check for repeated occurrences of such phases.

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We then estimate the black hole mass (M_BH_) and the Eddington ratio ({lambda}_Edd_) per epoch per source where the required parameters are available and well estimated. We demonstrate the movement of the source in the M_BH_-{lambda}_Edd_ plane, allowing us to check for systematic changes in the source's fundamental properties. We then track their transition along the optical plane of the Eigenvector 1 schema and categorize sources that either stay within the same population (A or B) or make an interpopulation movement as a function of spectral epoch.

We also test the Balmer decrement (H{alpha}/H{beta}) of a subset of our sample of CL AGNs as a function of time and AGN luminosity.

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