Optical variability of blazars

Using the SDSS spectroscopy, we have carried out fine optical spectral classification for activity types for 710 AGN candidates. These objects come from a larger sample of some 2,500 candidate AGN using pre-selection by various samples; bright objects of the Catalog of Quasars and Active Galactic Nuclei, AGN candidates among X-ray sources, optically variable radio sources, IRAS extragalactic objects, etc. A number of papers have been published with the results of this spectral classification. More than 800 QSOs have been identified and classified, including 710 QSOs, Seyferts and Composites. The fine classification shows that many QSOs show the same features as Seyferts, i.e., subtypes between S1 and S2 (S1.2, S1.5, S1.8 and S1.9). We have introduced subtypes for the QSOs: QSO1.2, QSO1.5, QSO1.8, QSO1.9, though the last subtype does not appear in SDSS wavelength range due to mostly highly redshifted Hα (the main line for identification of the 1.9 subtype). Thus, independent of the luminosity (which serves as a separator between QSOs and Seyferts), AGN show the same features. We also have classified many objects as Composites, spectra having composite characteristics between Sy and LINERs, Sy and HII or LINERs and HII; in some cases all three characteristics appear together resulting as Sy/LINER/HII subtype. The QSOs subtypes together with Seyfert ones allow to follow AGN properties along larger redshift range expanding our knowledge on the evolution of AGN to more distant Universe represented by QSOs.

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“…Having the absolute magnitude, we calculated luminosities for blazars using Eq. 3 (Abrahamyan et al 2019b).…”

Section: Average Characteristics Of Objects By Subtypesmentioning

confidence: 99%

Fine Classification of QSOs and Seyferts for Activity Types Based on SDSS Spectroscopy

Mickaelian

Abrahamyan

Paronyan

et al. 2021

Front. Astron. Space Sci.

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“…Aiming at understanding some optical properties and the way they can be connected with radio properties, we have computed absolute magnitudes and luminosities for our objects (Abrahamyan et al 2019). For our absolute magnitude computation, we have used V‐band from VCV‐13 (Véron‐Cetty & Véron 2010) and taken redshift from SDSS DR15 (Aguado et al 2019) if there is spectroscopic identification.…”

Section: Absolute Magnitude and Luminositymentioning

confidence: 99%

“…Having absolute magnitude, we have counted the luminosities using Formula (3) (Abrahamyan et al 2019).

L = L_{⊙} \times {2.512}^{M_{⊙} - M}

where L ⊙ and M ⊙ are luminosity and absolute magnitude of Sun, respectively ( L ⊙ = 3.83 × 10 33 erg/s, M ⊙ = 4.83).…”

Section: Absolute Magnitude and Luminositymentioning

confidence: 99%

The nature of active galaxies based on their radio properties

Abrahamyan

2020

Astron Nachr

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In this paper, we investigate radio properties of active galaxies taken from the reference [Véron‐Cetty & Véron (2010)] catalog. The galaxies are limited to magnitudes in the range of 12m − 19m. We have cross‐correlated the list with radio catalogs and selected those galaxies that have data on six or more radio fluxes at different wavelengths. As a result, we have 198 galaxies that satisfy these conditions. Using SDSS DR15, we have obtained 96 spectroscopic identifications of the 198 objects. After the classification, 85% of the 96 objects have changed their types. Available data on the classification of these objects and our classification showed that 56.7% of them are Seyfert galaxies. For all the objects, we have built radio spectra and estimated radio spectral indices. As a result, we obtain αtrue‾=−0.6089±0.056(trueα‾Seyfert=−0.6013±0.027, trueα‾LINER=−0.5955±0.025, trueα‾normalHII=−0.6672±0.039, trueα‾Comp.=−0.7128±0.043). We discuss the radio properties of active galaxies based on their radio spectral indices.

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“…For understanding some physical properties of blazars we use the paper Abrahamyan et al (2019). In this paper calculated absolute magnitude for all blazars.…”

Section: Observational Datamentioning

confidence: 99%

“…But information about variability is not complete in this catalogue. Information for optical variability of blazars is given by Abrahamyan et al (2019).…”

Section: Introductionmentioning

confidence: 99%