Interferometric monitoring of gamma-ray bright AGNs: Measuring the magnetic field strength of 4C+29.45?

Kang, S. and Lee, S. -S. and Hodgson, J. and Algaba, J. -C. and Lee, J. W. and Kim, J. -Y. and Park, J. and Kino, M. and Kim, D. and Trippe, S. (2021) Interferometric monitoring of gamma-ray bright AGNs: Measuring the magnetic field strength of 4C+29.45? Astronomy & Astrophysics, 651. ISSN 0004-6361, DOI

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Aims. We present the results of multi-epoch, multifrequency monitoring of blazar 4C +29.45, which was regularly monitored as part of the Interferometric Monitoring of GAmma-ray Bright Active Galactic Nuclei (iMOGABA) program - a key science program of the Korean Very long baseline interferometry Network (KVN).Methods. Observations were conducted simultaneously at 22, 43, 86, and 129 GHz over the 4 years from 5 December 2012 to 28 December 2016. We also used additional data from the 15 GHz Owens Valley Radio Observatory (OVRO) monitoring program.Results. From the 15 GHz light curve, we estimated the variability timescales of the source during several radio flux enhancements. We found that the source experienced six radio flux enhancements with variability timescales of 9-187 days during the observing period, yielding corresponding variability Doppler factors of 9-27. From the simultaneous multifrequency KVN observations, we were able to obtain accurate radio spectra of the source and hence to more precisely measure the turnover frequencies nu(r), of synchrotron self-absorption (SSA) emission with a mean value of GHz. Using jet geometry assumptions, we estimated the size of the emitting region at the turnover frequency. We found that the equipartition magnetic field strength is up to two orders of magnitude higher than the SSA magnetic field strength (0.001-0.1 G). This is consistent with the source being particle dominated. We performed a careful analysis of the systematic errors related to the making of these estimations.Conclusions. From the results, we concluded that the equipartition region is located upstream from the SSA region.

Item Type: Article
Funders: Malaysian Fundamental Research Grant Scheme (FRGS) [FRGS/1/2019/STG02/UM/02/6 ], National Research Foundation of Korea (NRF) - Korea government (MIST) [2020R1A2C2009003 ], KREONET (Korea Research Environment Open NETwork), OVRO 40-m monitoring program (ApJS) [194] [29], ational Aeronautics & Space Administration (NASA) [NNX08AW31G] [NNX11A043G] [NNX14AQ89G], National Science Foundation (NSF) [AST-0808050] [AST-1109911], NASA through the Fermi Guest Investigator Program, Korean National Research Foundation (NRF) via Global PhD Fellowship [2014H1A2A1018695], EACOA Fellowship - East Asia Core Observatories Association, Academia Sinica Institute of Astronomy and Astrophysics, the National Astronomical Observatory of Japan, Center for Astronomical Mega-Science, Chinese Academy of Sciences, Korea Astronomy and Space Science Institute, ational Research Foundation of Korea [2021R1C1C1009973] [2019R1F1A1059721 ]
Uncontrolled Keywords: Galaxies: active; Galaxies: jets; BL Lacertae objects: individual: J1159+2914
Subjects: Q Science > QB Astronomy
Divisions: Faculty of Science > Department of Physics
Depositing User: Ms Zaharah Ramly
Date Deposited: 09 Jun 2022 06:29
Last Modified: 09 Jun 2022 06:29

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