153 citations · 1.2k across the 44 of their papers we have counts for
47 papers
Discriminating blazar emission models with high-energy polarimetry: Multi-band predictions and detectability
Sara Capecchiacci, Ioannis Liodakis, Haocheng Zhang +2
Polarimetric properties of blazars provide key constraints on the acceleration mechanisms powering their relativistic jets, the high-energy emission processes involved, and the com…
Detectability of Polarized Gamma-ray Emission from Blazar Flares with COSI
Garrett A. Latiolais, Jorge Otero-Santos, Michela Negro +18
We investigate the detectability of polarized gamma-ray emission from blazar flares with the Compton Spectrometer and Imager (COSI). Using 17 years of Fermi Large Area Telescope ob…
Energy-Dependent Polarization Angle Variability as a Robust Diagnostic for Blazar Flaring Mechanisms
Haocheng Zhang, Benjamin de Jonge, Manel Errando +2
Identifying the physical mechanism driving blazar flares remains a central challenge in high-energy astrophysics. We show that the energy dependence of the standard deviation of th…
A minimalist approach to BL Lacertae: explaining gamma-ray spectral and temporal variability with a single physical parameter
Raniere de Menezes, Francesco Massaro, Elisa Visentin +2
The eponymous BL Lac object BL Lacertae is one of the most well-monitored active galactic nuclei, frequently observed from radio to gamma rays. Its relatively soft -ray spectrum…
Polarization Dynamics of X-Ray Synchrotron Emission from a Multi-Zone Blazar Jet
Benjamin de Jonge, Haocheng Zhang, Manel Errando +2
The polarization of X-ray synchrotron emission in blazars directly probes the magnetic field geometry and particle acceleration processes in relativistic jets. We use particle-in-c…
Testing Magnetic Field Configurations in Spider Pulsar PSR J1723-2837 with IXPE
Michela Negro, Haocheng Zhang, Niccolò Di Lalla +4
We present the first X-ray polarimetry observations of a redback millisecond pulsar binary, PSR J1723-2837, with the Imaging X-ray Polarimetry Explorer (IXPE). We conduct a spectro…
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…
Multi-wavelength observations of a jet launch in real time from the post-changing-look Active Galaxy 1ES 1927+654
Sibasish Laha, Eileen T. Meyer, Dev R. Sadaula +34
We present results from a high cadence multi-wavelength observational campaign of the enigmatic changing look AGN 1ES 1927+654 from May 2022- April 2024, coincident with an unprece…
IXPE Observation of the Low-Synchrotron Peaked Blazar S4 0954+65 During An Optical-X-ray Flare
Pouya M. Kouch, Ioannis Liodakis, Francesco Fenu +134
The X-ray polarization observations made possible with the Imaging X-ray Polarimetry Explorer (IXPE) offer new ways of probing high-energy emission processes in astrophysical jets…
Testing particle acceleration in blazar jets with continuous high-cadence optical polarization observations
Ioannis Liodakis, Sebastian Kiehlmann, Alan P. Marscher +44
Variability can be the pathway to understanding the physical processes in astrophysical jets, however, the high-cadence observations required to test particle acceleration models a…
Radiative Properties of Plasmoids and Plasmoid Mergers in Magnetic Reconnection
Haocheng Zhang, Lingyi Dong, Dimitrios Giannios
Magnetic reconnection is often considered as the primary particle acceleration mechanism in a magnetized blazar zone environment. The majority of radiation in the reconnection laye…
Late-time radio brightening and emergence of a radio jet in the changing-look AGN 1ES 1927+654
Eileen T. Meyer, Sibasish Laha, Onic I. Shuvo +32
We present multi-frequency (5-345 GHz) and multi-resolution radio observations of 1ES 1927+654, widely considered one of the most unusual and extreme changing-look active galactic…
Revisiting High-Energy Polarization from Leptonic and Hadronic Blazar Scenarios
Haocheng Zhang, Markus Böttcher, Ioannis Liodakis
X-ray and MeV polarization can be powerful diagnostics for leptonic and hadronic blazar models. Previous predictions are mostly based on a one-zone framework. However, recent IXPE…
The High Energy X-ray Probe (HEX-P): the most powerful jets through the lens of a superb X-ray eye
Lea Marcotulli, Marco Ajello, Markus Böttcher +20
A fraction of the active supermassive black holes at the centers of galaxies in our Universe are capable of launching extreme kiloparsec-long relativistic jets. These jets are know…
Jets with a Twist: Emergence of FR0 Jets in 3D GRMHD Simulation of Zero Angular Momentum Black Hole Accretion
Aretaios Lalakos, Alexander Tchekhovskoy, Omer Bromberg +4
Spinning supermassive black holes (BHs) in active galactic nuclei (AGN) magnetically launch relativistic collimated outflows, or jets. Without angular momentum supply, such jets ar…
A comparison of co-temporal vector magnetograms obtained with HMI/SDO and SP/Hinode
Mei Zhang, Haocheng Zhang, Chengqing Jiang
An accurate measurement of magnetic field is very important for understanding the formation and evolution of solar magnetic fields. Currently there are two types of solar magnetic…
The force-freeness of the solar photosphere: Revisit with new approach and large datasets
Mei Zhang, Haocheng Zhang
Although it is generally believed that the solar photosphere is not magnetically force-free owning to its high plasma , the estimations of force-freeness using observed magnetog…
The peculiar variable X-ray spectrum of the active galactic nucleus PKS 2005-489
Owen Chase, Felicia McBride, Andrea Gokus +4
PKS 2005-489 is a well-known, bright southern BL Lac object that has been detected up to TeV energies. In a low-flux state it exhibits the expected multiwavelength double-peaked sp…
First-Principle-Integrated Study of Blazar Synchrotron Radiation and Polarization Signatures from Magnetic Turbulence
Haocheng Zhang, Alan Marscher, Fan Guo +3
Blazar emission is dominated by nonthermal radiation processes that are highly variable across the entire electromagnetic spectrum. Turbulence, which can be a major source of nonth…
Radiation and Polarization Signatures from Magnetic Reconnection in Relativistic Jets--II. Connection with -rays
Haocheng Zhang, Xiaocan Li, Dimitrios Giannios +5
It is commonly believed that blazar jets are relativistic magnetized plasma outflows from supermassive black holes. One key question is how the jets dissipate magnetic energy to ac…
First-Principle Prediction of X-ray Polarization from Magnetic Reconnection in High-Frequency BL Lacs
Haocheng Zhang, Xiaocan Li, Dimitrios Giannios +1
Relativistic magnetic reconnection is a potential particle acceleration mechanism for high-frequency BL Lacs (HBLs). The {\it Imaging X-ray Polarimetry Explorer} ({\it IXPE}) sched…
Radiation Signatures From Striped Blazar Jet
Haocheng Zhang, Dimitrios Giannios
Relativistic jets from supermassive black holes are among the most powerful and luminous astrophysical systems in Universe. We propose that the open magnetic field lines through th…
Radiation and Polarization Signatures from Magnetic Reconnection in Relativistic Jets--I. A Systematic Study
Haocheng Zhang, Xiaocan Li, Dimitrios Giannios +3
Blazars are relativistic magnetized plasma outflows from supermassive black holes that point very close to our line of sight. Their emission is nonthermal dominated and highly vari…