35 citations · 64 across the 23 of their papers we have counts for
24 papers
The 2015-2017 Large EVPA Rotation in OJ 287: Dominant Propagating Component in a Helical Magnetic Field with Time-Dependent Viewing Geometry
Wanchaloem Khwammai, Minchul Kam, Motoki Kino +11
We present high-cadence, multi-frequency monitoring of the blazar OJ 287 using KVN (22--129 GHz), ALMA (91.5--343.5 GHz), and Metsähovi (37 GHz), covering 2012--2023, together with…
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…
A Universal Physics Defining the Radiation Spectra of Blazars and Gamma-Ray Bursts
Z. Lucas Uhm, Sang-Sung Lee, Bing Zhang +5
Blazars and gamma-ray bursts (GRBs) are both cosmic beacons of extreme energy release powered by relativistic jets. However, they originate from tremendously different environments…
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…
Magnetic field strength constraints on -ray flaring regions in the flat spectrum radio quasar PKS 1222+216
Yeji Jo, Sang-Sung Lee
We present a multi-wavelength study of the Flat Spectrum Radio Quasar PKS 1222+216, analyzing its long-term variability of radio data obtained in 2013-2020 from the iMOGABA, MOJAVE…
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…
Detection of Compton scattering in the jet of 3C 84
Ioannis Liodakis, Sudip Chakraborty, Frédéric Marin +77
3C 84 is the brightest cluster galaxy in the Perseus Cluster. It is among the closest radio-loud active galaxies and among the very few that can be detected from low frequency radi…
The variability angular diameter distance and the intrinsic brightness temperature of active galactic nuclei
Whee Yeon Cheong, Sang-Sung Lee, Chanwoo Song +5
Context. It has recently been suggested that angular diameter distances derived from comparing the variability timescales of blazars to angular size measurements with very long bas…
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…
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-…
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…
Multiple simultaneous Gamma-ray emission sites in 3C 84
Jeffrey A. Hodgson, S. S. Lee, B. Rani +1
The mis-aligned active galactic nuclei (AGN), 3C\,84, has been observed approximately monthly at four frequencies simultaneously (22\,GHz -- 129\,GHz) on the Korean VLBI Network (K…