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Universe
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Multimessenger Studies of Active Galactic Nucleus
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Multimessenger Studies of Active Galactic Nucleus

A special issue of Universe (ISSN 2218-1997). This special issue belongs to the section "Galaxies and Clusters".

Deadline for manuscript submissions: closed (15 November 2023) | Viewed by 2548

Special Issue Editors

Dr. Yuhai Yuan

E-Mail Website
Guest Editor
School of Physics and Materials Science, Guangzhou University, Guangzhou, China
Interests: optical variabilities of blazars
Dr. Jingmeng Hao

E-Mail Website
Guest Editor
School of Physics and Materials Science, Guangzhou University, Guangzhou, China
Interests: galaxies and cosmology
Dr. Zhiyuan Pei

E-Mail Website
Guest Editor
School of Physics and Materials Science, Guangzhou University, Guangzhou, China
Interests: accretion and jet

Special Issue Information

Dear Colleagues,

Active galactic nuclei (AGNs) are a special type of galaxy. Depending on their emission origins, these galaxies possess special properties, including violent optical variability, core dominance, non-thermal emission, the jet phenomenon, and more. Multimessenger studies of active galactic nuclei (AGN) can aid us in developing methods that can be used to study the origins of AGNs. For example, violent optical variability is a typical property of AGNs. This variability can affect all the electromagnetic bands and help us to determine the emission structures, constrain the emission region, develop emission models, etc. Optical variabilities can reflect timescales ranging from minutes to years and can be divided into three types: microvariability, for timescales within 1 day; short-term variability, for timescales ranging from days to months; and long-term variability, for timescales encompassing multiple years. Some variabilities are periodic/quasi-periodic, such as long-term variability, but most display non-periodicity.

This Special Issue aims to showcase multimessenger studies of active galactic nuclei and to elucidate the emission origins and variable properties of AGNs.

Dr. Yuhai Yuan
Dr. Jingmeng Hao
Dr. Zhiyuan Pei
Guest Editors

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All submissions that pass pre-check are peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Universe is an international peer-reviewed open access monthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Published Papers (2 papers)

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Research

17 pages, 2169 KiB  
Article
Unveiling the Emission and Variation Mechanism of Mrk 501: Using the Multi-Wavelength Data at Different Time Scale
by Lizhi Liu, Yunguo Jiang, Junhao Deng, Zhaohao Chen and Chenli Ma
Universe 2024, 10(3), 114; https://doi.org/10.3390/universe10030114 - 1 Mar 2024
Viewed by 903
Abstract
Variability study at multi-frequency provides us with rich information of the emission and variation mechanism for blazars. In this work, we present a comprehensive multi-frequency analysis of the high-synchrotron-peaked (HSP) blazar Mrk 501, using γ-ray, X-ray, optical, optical polarization, and radio data. [...] Read more.
Variability study at multi-frequency provides us with rich information of the emission and variation mechanism for blazars. In this work, we present a comprehensive multi-frequency analysis of the high-synchrotron-peaked (HSP) blazar Mrk 501, using γ-ray, X-ray, optical, optical polarization, and radio data. The multiple-wavelength light curves are analyzed by using the localized cross-correlation function to derive locations of their emitting regions. The X-ray, γ-ray, and optical emitting regions are found to be upstream of the radio core region, while the X-ray and γ-ray emitting regions likely coincide. We studied the variation behaviors for three long-term (years), five relatively short-term (months) periods. We find a positive correlation between the optical and X-ray fluxes, and conclude that the variable of Doppler factor is not favored for the one-zone SSC scenario. The study also identifies the existence of a soft γ-ray background in the low-activity state, which could be explained by the spine/layer jet model. Our study on Mrk 501 provides valuable insights to understand the emission processes and variation mechanism for HSP blazars. Full article
(This article belongs to the Special Issue Multimessenger Studies of Active Galactic Nucleus)
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20 pages, 629 KiB  
Article
Why Are Some Radio Galaxies Detected by Fermi, but Others Not?
by Danyi Huang, Xuhong Ye, Xiao Ye, Xiulin Huang, Yanjun Qian, Ziyan Li, Chengfeng Li, Jiru Liao, Hengji Zhang, Zhiyuan Pei, Jianghe Yang and Junhui Fan
Universe 2023, 9(11), 479; https://doi.org/10.3390/universe9110479 - 8 Nov 2023
Viewed by 1246
Abstract
Aiming to answer an interesting question on why some radio sources can be detected by Fermi-LAT but others cannot, we compare several parameters of Fermi-detected Fanaroff-Riley radio galaxies (FFRs) and non-Fermi-detected sources (NFFRs), including the optical absolute magnitude, 1.4 GHz [...] Read more.
Aiming to answer an interesting question on why some radio sources can be detected by Fermi-LAT but others cannot, we compare several parameters of Fermi-detected Fanaroff-Riley radio galaxies (FFRs) and non-Fermi-detected sources (NFFRs), including the optical absolute magnitude, 1.4 GHz radio luminosity, radio loudness, core dominance parameter, Doppler factor, and the mass of the central black hole. Significant differences are ascertained within these parameters between FFRs and NFFRs. Our findings suggest that FFRs are jet-dominant while NFFRs are disk-dominant sources, and NFFRs have a weaker beaming effect. Additionally, we predict the observed γ-ray flux for NFFRs, establishing that the reason why some NFFRs are not detectable arises from their γ-ray flux being below the sensitivity detection threshold of Fermi. We also discuss two sub-types of Fanaroff-Riley galaxies, namely FR I and FR II sources. We first propose a “changing-look” phenomenon in these radio sources and also investigate why FR IIs seem to be exclusive in γ-ray emission. Full article
(This article belongs to the Special Issue Multimessenger Studies of Active Galactic Nucleus)
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