43 citations · 176 across the 25 of their papers we have counts for
25 papers
Cosmological Distance Measurements of High Redshift Blazars: OJ 248 (z=0.939) and 4C +38.41 (z=1.814)
Young-Bin Shin, Sang-Sung Lee, Sincheol Kang +3
In this study, we estimated the angular diameter distances to two high-redshift active galactic nuclei (AGNs), OJ 248 (z = 0.939) and 4C +38.41 (z = 1.814), using 43 GHz radio ligh…
The Celestial Reference Frame at K Band: The CRF-K-2025 Catalog
David Gordon, Aletha de Witt, Christopher S. Jacobs +10
We present an updated K band (24 GHz) celestial reference frame (CRF) constructed from 3.5 million Very Long Baseline Interferometry (VLBI) observations collected during 211 observ…
Constraining the magnetic field strength of a flaring radio core in the compact steep spectrum source 3C 138
Shan Li, Sang-Sung Lee, Whee Yeon Cheong +3
Compact steep spectrum (CSS) sources generally show weak Doppler boosting, yet some exceptions show multi-year-scale radio flux variability and high-energy activity. Since 2022, th…
Verification of the Polarimetric Capability of the East Asia VLBI Network
Yunjeong Lee, Jongho Park, Do-Young Byun +10
The East Asia VLBI Network (EAVN) has recently enabled dual-polarization observations at and . We present the first systematic verification of its polarimetr…
Where within the 3C 84 jet are -rays produced?
Georgios F. Paraschos, Ioannis Liodakis, Svetlana Jorstad +49
The location of -ray creation and emission within extra-galactic jets is a matter of active debate. One particularly well-suited source to pinpoint the location is the nearby, b…
A distance measurement for blazar TXS 0506+056 using its radio variability and very long baseline images
Chanwoo Song, Sang-Sung Lee, Sincheol Kang +1
We present the results of constraining the angular diameter distance to blazar TXS 0506+056. We used data obtained with the 15 GHz VLBA in MJD 54838-60262 and data from the 15 GHz…
Unveiling blazar synchrotron emission: a multiwavelength polarimetric study of HSP and LSP populations
Sara Capecchiacci, Ioannis Liodakis, Riccardo Middei +96
Polarimetric properties of blazars allow us to put constraints on the acceleration mechanisms that fuel their powerful jets. By studying the multiwavelength polarimetric behaviour…
Determining the origin of the X-ray emission in blazars through multiwavelength polarization
Ioannis Liodakis, Haocheng Zhang, Stella Boula +48
The origin of the high-energy emission in astrophysical jets from black holes is a highly debated issue. This is particularly true for jets from supermassive black holes that are a…
High optical to X-ray polarization ratio reveals Compton scattering in BL Lacertae's jet
Ivan Agudo, Ioannis Liodakis, Jorge Otero-Santos +147
Blazars, supermassive black hole systems (SMBHs) with highly relativistic jets aligned with the line of sight, are the most powerful long-lived emitters of electromagnetic emission…
Polarization flare of 3C 454.3 in millimeter wavelengths seen from decadal polarimetric observations
Hyeon-Woo Jeong, Sang-Sung Lee, Sincheol Kang +6
This study investigates polarimetric characteristics of the blazar 3C~454.3 at 22-129~GHz using decadal~(2011-2022) data sets. In addition, we also delve into the origin of the pol…
Gamma-ray flares from the jet of the blazar CTA 102 in 2016-2018
Sanghyun Kim, Sang-Sung Lee, Juan Carlos Algaba +16
CTA 102 is a -ray bright blazar that exhibited multiple flares in observations by the Large Area Telescope on board the Fermi Gamma-Ray Space Telescope during the period of 2016…
A Two-Week Monitoring Campaign on Mrk 421
W. Peter Maksym, Ioannis Liodakis, M. Lynne Saade +153
X-ray polarization is a unique new probe of the particle acceleration in astrophysical jets made possible through the Imaging X-ray Polarimetry Explorer. Here we report on the firs…
X-ray and multiwavelength polarization of Mrk 501 from 2022 to 2023
Chien-Ting J. Chen, Ioannis Liodakis, Riccardo Middei +143
We present multiwavelength polarization measurements of the luminous blazar Mrk~501 over a 14-month period. The 2--8 keV X-ray polarization was measured with the Imaging X-ray Pola…
IXPE observation of PKS 2155-304 reveals the most highly polarized blazar
Pouya M. Kouch, Ioannis Liodakis, Riccardo Middei +133
We report the X-ray polarization properties of the high-synchrotron-peaked (HSP) blazar PKS 2155304 based on observations with the Imaging X-ray Polarimetry Explorer (IXPE). We…
A Multi-wavelength Study on A Gamma-ray Bright AGN 1308+326 Using KVN at 22 and 43 GHz
Shan Li, Sang-Sung Lee, Whee Yeon Cheong
In this paper, we conduct a multi-frequency analysis of the gamma-ray bright blazar 1308+326 from February 2013 to March 2020, using the Korean VLBI Network at 22 and 43 GHz and ga…
Broadband Multi-wavelength Properties of M87 during the 2018 EHT Campaign including a Very High Energy Flaring Episode
J. C. Algaba, M. Balokovic, S. Chandra +738
The nearby elliptical galaxy M87 contains one of the only two supermassive black holes whose emission surrounding the event horizon has been imaged by the Event Horizon Telescope (…
A study of the radio spectrum of Mrk 421
Jee Won Lee, Sang-Sung Lee, Jeffrey Hodgson +5
We present the results of a spectral analysis using simultaneous multifrequency (22, 43, 86, and 129 GHz) very long baseline interferometry (VLBI) observations of the Korean VLBI N…
Interferometric Monitoring of Gamma-ray Bright AGNs: 4C +28.07 and its Synchrotron Self-absorption Spectrum
Myoung-Seok Nam, Sang-Sung Lee, Whee Yeon Cheong
We present the analysis results of the simultaneous multifrequency observations of the blazar 4C +28.07. The observations were conducted by the Interferometric Monitoring of Gamma-…
A Near Magnetic-to-kinetic Energy Equipartition Flare from the Relativistic Jet in AO 0235+164 during 2013-2019
Whee Yeon Cheong, Sang-Sung Lee, Sang-Hyun Kim +17
We present the multiwavelength flaring activity of the blazar AO 0235+164 during its recent active period from 2013 to 2019. From a discrete correlation function (DCF) analysis, we…
Observations of Low and Intermediate Spectral Peak Blazars with the Imaging X-ray Polarimetry Explorer
Herman L. Marshall, Ioannis Liodakis, Alan P. Marscher +145
We present X-ray polarimetry observations from the Imaging X-ray Polarimetry Explorer (IXPE) of three low spectral peak and one intermediate spectral peak blazars, namely 3C 273, 3…
Magnetic Field Properties inside the Jet of Mrk 421: Multiwavelength Polarimetry Including the Imaging X-ray Polarimetry Explorer
Dawoon E. Kim, Laura Di Gesu, Ioannis Liodakis +133
We conducted a polarimetry campaign from radio to X-ray wavelengths of the high-synchrotron-peak (HSP) blazar Mrk 421, including Imaging X-ray Polarimetry Explorer (IXPE) measureme…
IXPE and multi-wavelength observations of blazar PG 1553+113 reveal an orphan optical polarization swing
Riccardo Middei, Matteo Perri, Simonetta Puccetti +119
The lower energy peak of the spectral energy distribution of blazars has commonly been ascribed to synchrotron radiation from relativistic particles in the jets. Despite the consen…
Double SSA Spectrum and Magnetic Field Strength of the FSRQ 3C 454.3
Hyeon-Woo Jeong, Sang-Sung Lee, Whee Yeon Cheong +7
We present the results of a radio multi-frequency () study of the blazar 3C~454.3. After subtracting the quiescent spectrum corresponding to optically thin emission,…
Monitoring the Size and Flux Density of Sgr A* during the Active State in 2019 with East Asian VLBI Network
Xiaopeng Cheng, Ilje Cho, Tomohisa Kawashima +9
In this work, we studied the Galactic Center supermassive black hole (SMBH), Sagittarius A* (Sgr A*), with the KVN and VERA Array (KaVA)/East Asian VLBI Network (EAVN) monitoring o…