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1. Effect of laser irradiation on thermal conductivity of ZnO nanofluids

Author

Sang Hyun Kim, Jonggan Hong, and Dongsik Kim

Subjects
History, Materials science, Nanostructure, Absorption spectroscopy, Analytical chemistry, Laser, Computer Science Applications, Education, law.invention, Nanofluid, Thermal conductivity, Transmission electron microscopy, law, Irradiation, Composite material, Spectroscopy
Abstract

This work examines a laser particle fragmentation process to enhance the thermal conductivity of nanofluids. A Q-switched Nd:YAG laser is employed to change the size of the suspended ZnO nanoparticles in water. The influence of laser irradiation on the suspended particles is analyzed by transmission electron microscopy and absorption spectroscopy. The thermal conductivity of the nanofluid is measured by the transient hot-wire method. The results show that laser irradiation leads to partial fragmentation of some particles. However, the partial size reduction results in substantial enhancement of the thermal conductivity.

Published
2007
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2. Methodology for using residual stresses for self-assembly during deposition and etching of microstructures under external load

Author

Sathyanarayanan Mani, Sang-Hyun Kim, and James G. Boyd

Subjects
Cantilever, Materials science, business.industry, Mechanical Engineering, Structural engineering, Microstructure, Computer Science::Other, Electronic, Optical and Magnetic Materials, Mechanics of Materials, Residual stress, Spring (device), Etching (microfabrication), Physics::Accelerator Physics, Deposition (phase transition), Electrical and Electronic Engineering, Composite material, Electroplating, business, Beam (structure)
Abstract

A methodology is presented for using intrinsic (or residual) stresses as a means of self-assembling microstructures under external loading during material deposition and etching. Assembly of two components is considered: one component is subjected to deposition or etching and is modeled as an Euler?Bernoulli beam and the other component is neither deposited nor etched and is modeled as a linear spring. For the purposes of this paper, the definition of assembly requires that the beam does work on the spring. It is shown that, during deposition, the beam deflection and the work performed by the beam on the spring are monotonic. During etching, however, the beam deflection and the work can be nonmonotonic, thus complicating the design of self-assembly processes. The deposition analysis is experimentally verified by electroplating nickel onto an AFM cantilever beam in contact with a second AFM beam (serving as the spring) that does not undergo deposition.

Published
2007
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3. A new technique for measuring Young's modulus of electroplated nickel using AFM

Author

James G. Boyd and Sang-Hyun Kim

Subjects
Cantilever, Materials science, Applied Mathematics, Modulus, chemistry.chemical_element, Laminar flow, Young's modulus, Nickel, symbols.namesake, chemistry, Spring (device), Plating, symbols, Composite material, Electroplating, Instrumentation, Engineering (miscellaneous)
Abstract

This paper addresses a relatively simple method of measuring Young's modulus of electroplated nickel using an atomic force microscope. The thin layer of nickel to be measured is electroplated onto the tip side of an AFM silicon cantilever, whose Young's modulus and geometric dimensions are well defined from the manufacturer. The resonant frequency and quality factor of the electroplated AFM cantilever are measured by the tapping mode of the AFM and its spring constant is calculated using Sader's method. The spring constant of the electroplated cantilever is also calculated by using the laminar composite beam theory. Comparing two spring constants, Young's modulus of electroplated nickel is determined. The measured Young's modulus of nickel at the end of each plating step ranged between 148.04 GPa and 159.90 GPa with a relative uncertainty of 4.21%.

Published
2006
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4. Dielectric Properties of 22.9 kV Class Prototype High-TcSuperconducting Cable

Author

Hae-Jong Kim, Young Seok Kim, Dong-Soon Kwag, and Sang-Hyun Kim

Subjects
Superconductivity, Power transmission, Materials science, Physics and Astronomy (miscellaneous), Partial discharge, General Engineering, General Physics and Astronomy, Breakdown voltage, Dielectric loss, High current, Dielectric, Engineering physics, Power (physics)
Abstract

Based on the increasing power demands of power transmission in major cities, high-Tc superconductivity (HTS) power cables which have high current capacity and low power loss will be demanded. Electrical insulation is required to realize the HTS cable system with low power loss as well as high current capacity of cable. For this reason, we manufactured a 22.9 kV class prototype HTS cable and measured the dielectric loss tangent (tan δ) which is one of the parameters of electrical insulation. From the experimental results, the tan δ of the prototype cable was 1.16×10-3 when the electric stress was low. However, when the electric stress was high, the tan δ suddenly increased because partial discharge occurred inside the butt gap of prototype cable.

Published
2003
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5. Sensitivity of Electroplating Conditions on Young's Modulus of Thin Film

Author

Sang-Wook Kang and Sang-Hyun Kim

Subjects
Materials science, Cantilever, Physics and Astronomy (miscellaneous), Physics::Instrumentation and Detectors, General Engineering, Analytical chemistry, General Physics and Astronomy, chemistry.chemical_element, Modulus, Young's modulus, Physics::Fluid Dynamics, Nickel, symbols.namesake, chemistry, Plating, symbols, Thin film, Composite material, Electroplating, Current density
Abstract

We address a relatively simple method to investigate the sensitivity of Young's modulus to the plating conditions such as the plating temperature and applied current density. This method uses the resonance method of atomic force microscope, which does not require specially microfabricated cantilevers and additional experimental set-up. The measured Young's modulus is as high as that of bulk nickel at low plating temperature between 40–60 °C and at low applied current density (J=8.6 mA/cm2), but drastically drops at high temperature or current density. The dependence of Young's modulus on the plating thickness is negligible in thin film less than few microns.

Published
2008
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6. Phase transitions of 2D triangular antiferromagnetic Ising model in a uniform magnetic field near h=0 and T=0

Author

Chi-Ok Hwang, Wooseop Kwak, and Sang-Hyun Kim

Subjects
Physics, History, Phase transition, Phase boundary, Condensed matter physics, Quantum mechanics, Diagram, Antiferromagnetism, Condensed Matter::Strongly Correlated Electrons, Ising model, Computer Science Applications, Education, Magnetic field
Abstract

Using a microcanonical magnetization-energy (ME) diagram, this paper describes all the possible phase transitions of a 2D triangular antiferromagnetic (TAFM) Ising model in a uniform external magnetic field. In particular, we investigate the detailed phase boundary shape of the TAFM near h = 0 and T = 0 using staggered susceptibility.

Published
2016
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7. Parametric study of electroplating conditions on mismatch strain of thin film for self-positioning of MEMS

Author

Sang-Hyun Kim

Subjects
Microelectromechanical systems, Materials science, Cantilever, Mechanical Engineering, Detector, Analytical chemistry, Laser, Computer Science::Other, Electronic, Optical and Magnetic Materials, law.invention, Mechanics of Materials, Deflection (engineering), law, Electrical and Electronic Engineering, Composite material, Thin film, Electroplating, Current density
Abstract

In this paper, we report a detailed investigation of mismatch strain profiles taking account of the effects of process conditions, specifically the electrodeposition current density and temperature. This concept is demonstrated using the standard AFM (atomic force microscope) optical method. First, the thin layer of nickel to be measured is electrodeposited onto the tip side of the AFM cantilever at various current densities and temperatures. Then the cantilever deflections are measured by detecting the position change of the laser on the detector shifts and converted into the quantitative mismatch strain by appropriate mechanics. For a given deposition thickness, the magnitude of the mismatch strain increases with an elevation of the current density or plating temperature. The maximum deflection rate and mismatch strain happen on the interface when two different materials are connected. Next, the determined mismatch strain is further assessed experimentally by comparing its predictions for the self-deformed shape and the measured deflections of the AFM cantilever.

Published
2015
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8. Electric-field induced ferromagnetic domain changes in exchange biased Co–BiFeO3composites

Author

Sang-hyun Kim, Hyunwoo Choi, Sung-Chul Shin, and Kwangsoo No

Subjects
Acoustics and Ultrasonics, Magnetic domain, Condensed matter physics, Chemistry, Magnetism, Exchange interaction, Condensed Matter Physics, Ferroelectricity, Surfaces, Coatings and Films, Electronic, Optical and Magnetic Materials, Magnetic field, Condensed Matter::Materials Science, Ferromagnetism, Electric field, Magnetic force microscope
Abstract

We present direct observations of electric-field induced changes in the local ferromagnetic (F) domain structure in films formed from inclusions of F cobalt in an antiferromagnetic host of BiFeO3. Piezoelectric force microscopy was used to demonstrate that the composite Co–BiFeO3 films display ferroelectricity. Strikingly, magnetic contrast changes in magnetic force microscopic images were found with the application of a perpendicular electric field. These are the results of an exchange interaction between Co and BiFeO3.

Published
2010
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9. Mismatch Strain and Residual Stress of Freestanding Electroplated Ni Thin Film

Author

Sang-Hyun Kim

Subjects
Cantilever, Materials science, Thin layers, Physics and Astronomy (miscellaneous), Metallurgy, General Engineering, General Physics and Astronomy, chemistry.chemical_element, Nickel, chemistry, Residual stress, Plating, Thin film, Electroplating, Current density
Abstract

In this paper, we report the detailed investigation into the effects of plating temperature and applied current density upon the residual stress of plated nickel film. Thin layers of nickel are electroplated onto the tip surface of atomic force microscope (AFM) cantilevers and quantitative residual stress of plated nickel film is determined by detecting the self-deformation of the released AFM cantilever. The residual stress was a strong function of the process conditions, and decreased with the elevation of the current density and plating temperature. And the intrinsic and extrinsic stresses of plated nickel are separated from the measured residual stress, and correlated with plating conditions. Dependence of the plated thickness on the residual stress is also considered. Through-thickness variation of residual stress is also experimentally investigated and compared to the analytical values.

Published
2010
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10. Substrate Temperature Dependence of ZnO Films Prepared by Ultrasonic Spray Pyrolysis

Author

Sang-Hyun Kim, Hyun Yul Moon, Young-Jin Kim, Gi Cheol Park, Tae Young Ma, and Ki–Wan Kim

Subjects
Materials science, Scanning electron microscope, General Engineering, General Physics and Astronomy, Mineralogy, chemistry.chemical_element, Crystal growth, Substrate (electronics), Zinc, Crystallinity, chemistry, Chemical engineering, Electrical resistivity and conductivity, Wafer, Pyrolysis
Abstract

Strongly c-axis oriented zinc oxide (ZnO) films were deposited on silicon wafers coated with SiO2 or 7059 corning glass substrates from a solution containing zinc acetate. The films were deposited in a hot wall reactor by the pyrolysis of an aerosol produced by an ultrasonic generator. The crystallinity, surface morphology and composition of the films were studied using X-ray diffraction analysis (XRD), scanning electron microscopy (SEM) and Rutherford back-scattering spectrometry (RBS), respectively. The influences of the concentration of zinc acetate in the solution and the substrate temperature on the crystallinity of the films were studied. The films grown at a substrate temperature of 350–450° C from a 0.03 M/ l solution exhibited strong (002) orientation with a very smooth surface. The resistivity of the films was around 10 Ω· cm. Oxidation resulted in a 10,000-fold increase in the resistivity.

Published
1996
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11. Luminescent Properties of Ca-α--SiAlON:Eu2+ Phosphors Synthesized by Gas-Pressured Sintering.

Author

Jeong Ho Ryu, Youn-Gon Park, Hyong Sik Won, Sang Hyun Kim, Suzuki, Hideo, Jong Myeon Lee, Chulsoo Yoon, Nazarov, Mihail, Do Young Noh, and Tsukerblat, Boris

Subjects
PHOSPHORS, CALCIUM, SILICON nitride, EUROPIUM, SINTERING, PHOTOLUMINESCENCE, INORGANIC synthesis
Abstract

Rare-earth-doped oxynitride or nitride compounds have been reported to be photoluminescent and may then serve as new phosphors with good thermal and chemical stabilities. In this work, Ca-α-SiAlON:Eu2+ based yellow and orange oxynitride phosphors with compositions of Ca0.485Eu0.015Si9.2Al2.8O1.8N14.2 and Ca0.94Eu0.06Si9Al3ON15 were prepared using the gas-pressured sintering method. The crystallinity and particle morphology of the prepared phosphors were characterized. The temperature dependence of photoluminescence properties was investigated from 25 to 150°C. The Stokes shift and zero-phonon line was calculated mathematically and estimated from the spectral data. The prepared Ca-α-SiAlON:Eu2+ phosphors showed superior thermal quenching properties compared to commercially used YAG:Ce3+ phosphors. In addition, the activation energies (ΔE) for thermal quenching of the prepared Ca-α-SiAlON:Eu2+ phosphors were determined by Arrhenius fitting. [ABSTRACT FROM AUTHOR]

Published
2008
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12. Electrical Breakdown Properties in Liquid-Gas Composite N2

Author

Sang-Hyun Kim, Hyun-Hee Kim, Daeyoung Ma, and Kang-Sik Ryu

Subjects
Liquid gas, Composite number, General Engineering, Electrical breakdown, Analytical chemistry, General Physics and Astronomy, chemistry.chemical_element, Corona, Nitrogen, chemistry, Electrode, Breakdown voltage, Composite material, Voltage
Abstract

Electrical breakdown characteristics of composite insulators consisting of cryogenic gas and liquid in a non-uniform field have been investigated. The breakdown voltage increases slightly as the electrode distance of gas layer, d ′, increases. After the breakdown voltage decreases abruptly with increasing d ′, it again increases slightly with further increase of d ′. These results observed at both AC and DC voltages were interpreted as the Sumoto effect and corona wind.

Published
1994
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13. The effect of electrodeposition process parameters on residual stress-induced self-assembly under external load.

Author

Sang-Hyun Kim, Yoonhwan Woo, and James G Boyd

Subjects
*ELECTROPLATING, *RESIDUAL stresses, *MOLECULAR self-assembly, *ATOMIC force microscopes, *YOUNG'S modulus, *EULER-Bernoulli beam theory
Abstract

The authors (Boyd et al 2007 J. Micromech. Microeng.17 452–61http://iopscience.iop.org/0960-1317/17/3/006/) presented a methodology for using residual stresses due to mismatch strains as a means of self-assembling microstructures under external loading during material deposition. Assembly of two components was considered: one component was subjected to deposition and was modeled as an Euler–Bernoulli beam, and the other component was not deposited and was modeled as a linear spring. This work experimentally extends Boyd et al (2007 J. Micromech. Microeng.17 452–61http://iopscience.iop.org/0960-1317/17/3/006/) to account for the effects of process conditions, specifically the electrodeposition current density and temperature, which affect both the Young’s modulus and the mismatch strain. First, nickel was electrodeposited onto an atomic force microscope (AFM) cantilever, and the cantilever deflections at various current densities and temperatures were measured by using the resonance method of AFM and the measured deformation of the cantilever was converted into the quantitative mismatch strain by appropriate mechanics. For a given deposition thickness, the magnitude of the mismatch strain increased with increasing current density or plating temperature. The Young’s modulus decreased with increasing current density and increased slightly with increasing temperature. Next, the self-assembly model was experimentally verified by electrodepositing nickel onto an AFM cantilever beam in contact with a second AFM beam, serving as the spring, that does not undergo deposition. For a given deposition thickness, the spring deflection increased with increasing current density and increasing deposition temperature. [ABSTRACT FROM AUTHOR]

Published
2014
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14. Observations of Low and Intermediate Spectral Peak Blazars with the Imaging X-Ray Polarimetry Explorer

Author

Herman L. Marshall, Ioannis Liodakis, Alan P. Marscher, Niccolò Di Lalla, Svetlana G. Jorstad, Dawoon E. Kim, Riccardo Middei, Michela Negro, Nicola Omodei, Abel L. Peirson, Matteo Perri, Simonetta Puccetti, Marco Laurenti, Iván Agudo, Giacomo Bonnoli, Andrei V. Berdyugin, Elisabetta Cavazzuti, Nicole Rodriguez Cavero, Immacolata Donnarumma, Laura Di Gesu, Jenni Jormanainen, Henric Krawczynski, Elina Lindfors, Greg Madjeski, Frédéric Marin, Francesco Massaro, Luigi Pacciani, Juri Poutanen, Fabrizio Tavecchio, Pouya M. Kouch, Francisco José Aceituno, Maria I. Bernardos, Víctor Casanova, Maya García-Comas, Beatriz Agís-González, César Husillos, Alessandro Marchini, Alfredo Sota, Dmitry Blinov, Ioakeim G. Bourbah, Sebastian Kielhmann, Evangelos Kontopodis, Nikos Mandarakas, Stylianos Romanopoulos, Raphael Skalidis, Anna Vervelaki, George A. Borman, Evgenia N. Kopatskaya, Elena G. Larionova, Daria A. Morozova, Sergey S. Savchenko, Andrey A. Vasilyev, Alexey V. Zhovtan, Carolina Casadio, Juan Escudero, Joana Kramer, Ioannis Myserlis, Efthalia Trainou, Ryo Imazawa, Mahito Sasada, Yasushi Fukazawa, Koji S. Kawabata, Makoto Uemura, Tsunefumi Mizuno, Tatsuya Nakaoka, Hiroshi Akitaya, Joseph R. Masiero, Dimitri Mawet, Georgia V. Panopoulou, Samaporn Tinyanont, Masato Kagitani, Vadim Kravtsov, Takeshi Sakanoi, Matthew Dattolo, Mark Gurwell, Garrett Keating, Ramprasad Rao, Whee Yeon Cheong, Hyeon-Woo Jeong, Sincheol Kang, Sang-Hyun Kim, Sang-Sung Lee, Emmanouil Angelakis, Alexander Kraus, Antonio Hales, Seiji Kameno, Ruediger Kneissl, Hugo Messias, Hiroshi Nagai, Lucio A. Antonelli, Matteo Bachetti, Luca Baldini, Wayne H. Baumgartner, Ronaldo Bellazzini, Stefano Bianchi, Stephen D. Bongiorno, Raffaella Bonino, Alessandro Brez, Niccolò Bucciantini, Fiamma Capitanio, Simone Castellano, Chen-Ting Chen, Stefano Ciprini, Enrico Costa, Alessandra De Rosa, Ettore Del Monte, Alessandro Di Marco, Victor Doroshenko, Michal Dovčiak, Steven R. Ehlert, Teruaki Enoto, Yuri Evangelista, Sergio Fabiani, Riccardo Ferrazzoli, Javier A. Garcia, Shuichi Gunji, Kiyoshi Hayashida, Jeremy Heyl, Wataru Iwakiri, Philip Kaaret, Vladimir Karas, Fabian Kislat, Takao Kitaguchi, Jeffery J. Kolodziejczak, Fabio La Monaca, Luca Latronico, Simone Maldera, Alberto Manfreda, Andrea Marinucci, Giorgio Matt, Ikuyuki Mitsuishi, Fabio Muleri, C.-Y. Ng, Stephen L. O’Dell, Chiara Oppedisano, Alessandro Papitto, George G. Pavlov, Melissa Pesce-Rollins, Pierre-Olivier Petrucci, Maura Pilia, Andrea Possenti, Brian D. Ramsey, John Rankin, Ajay Ratheesh, Oliver J. Roberts, Roger W. Romani, Carmelo Sgrò, Patrick Slane, Paolo Soffitta, Gloria Spandre, Douglas A. Swartz, Toru Tamagawa, Roberto Taverna, Yuzuru Tawara, Allyn F. Tennant, Nicholas E. Thomas, Francesco Tombesi, Alessio Trois, Sergey S. Tsygankov, Roberto Turolla, Jacco Vink, Martin C. Weisskopf, Kinwah Wu, Fei Xie, and Silvia Zane

Subjects
X-ray astronomy, Polarimetry, Spectropolarimetry, Radio loud quasars, X-ray quasars, Blazars, Astrophysics, QB460-466
Abstract

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, 3C 279, 3C 454.3, and S5 0716+714. For none of these objects was IXPE able to detect X-ray polarization at the 3 σ level. However, we placed upper limits on the polarization degree at ∼10%–30%. The undetected polarizations favor models where the X-ray band is dominated by unpolarized photons upscattered by relativistic electrons in the jets of blazars, although hadronic models are not completely eliminated. We discuss the X-ray polarization upper limits in the context of our contemporaneous multiwavelength polarization campaigns.

Published
2024
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15. X-Ray and Multiwavelength Polarization of Mrk 501 from 2022 to 2023

Author

Chien-Ting J. Chen, Ioannis Liodakis, Riccardo Middei, Dawoon E. Kim, Laura Di Gesu, Alessandro Di Marco, Steven R. Ehlert, Manel Errando, Michela Negro, Svetlana G. Jorstad, Alan P. Marscher, Kinwah Wu, Iván Agudo, Juri Poutanen, Tsunefumi Mizuno, Pouya M. Kouch, Elina Lindfors, George A. Borman, Tatiana S. Grishina, Evgenia N. Kopatskaya, Elena G. Larionova, Daria A. Morozova, Sergey S. Savchenko, Ivan S. Troitsky, Yulia V. Troitskaya, Andrey A. Vasilyev, Alexey V. Zhovtan, Francisco José Aceituno, Giacomo Bonnoli, Víctor Casanova, Juan Escudero, Beatriz Agís-González, César Husillos, Jorge Otero Santos, Alfredo Sota, Vilppu Piirola, Ioannis Myserlis, Emmanouil Angelakis, Alexander Kraus, Mark Gurwell, Garrett Keating, Ramprasad Rao, Sincheol Kang, Sang-Sung Lee, Sang-Hyun Kim, Whee Yeon Cheong, Hyeon-Woo Jeong, Chanwoo Song, Andrei V. Berdyugin, Masato Kagitani, Vadim Kravtsov, Anagha P. Nitindala, Takeshi Sakanoi, Ryo Imazawa, Mahito Sasada, Yasushi Fukazawa, Koji S. Kawabata, Makoto Uemura, Tatsuya Nakaoka, Hiroshi Akitaya, Carolina Casadio, Albrecht Sievers, Lucio Angelo Antonelli, Matteo Bachetti, Luca Baldini, Wayne H. Baumgartner, Ronaldo Bellazzini, Stefano Bianchi, Stephen D. Bongiorno, Raffaella Bonino, Alessandro Brez, Niccoló Bucciantini, Fiamma Capitanio, Simone Castellano, Elisabetta Cavazzuti, Stefano Ciprini, Enrico Costa, Alessandra De Rosa, Ettore Del Monte, Niccoló Di Lalla, Immacolata Donnarumma, Victor Doroshenko, Michal Dovčiak, Teruaki Enoto, Yuri Evangelista, Sergio Fabiani, Riccardo Ferrazzoli, Javier A. Garcia, Shuichi Gunji, Kiyoshi Hayashida, Jeremy Heyl, Wataru Iwakiri, Philip Kaaret, Vladimir Karas, Fabian Kislat, Takao Kitaguchi, Jeffery J. Kolodziejczak, Henric Krawczynski, Fabio La Monaca, Luca Latronico, Simone Maldera, Alberto Manfreda, Frédéric Marin, Andrea Marinucci, Herman L. Marshall, Francesco Massaro, Giorgio Matt, Ikuyuki Mitsuishi, Fabio Muleri, C.-Y. Ng, Stephen L. O’Dell, Nicola Omodei, Chiara Oppedisano, Alessandro Papitto, George G. Pavlov, Abel Lawrence Peirson, Matteo Perri, Melissa Pesce-Rollins, Pierre-Olivier Petrucci, Maura Pilia, Andrea Possenti, Simonetta Puccetti, Brian D. Ramsey, John Rankin, Ajay Ratheesh, Oliver J. Roberts, Roger W. Romani, Carmelo Sgró, Patrick Slane, Paolo Soffitta, Gloria Spandre, Douglas A. Swartz, Toru Tamagawa, Fabrizio Tavecchio, Roberto Taverna, Yuzuru Tawara, Allyn F. Tennant, Nicholas E. Thomas, Francesco Tombesi, Alessio Trois, Sergey S. Tsygankov, Roberto Turolla, Jacco Vink, Martin C. Weisskopf, Fei Xie, and Silvia Zane

Subjects
Blazars, Active galaxies, Black holes, Relativistic jets, Spectropolarimetry, Polarimetry, Astrophysics, QB460-466
Abstract

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 Polarimetry Explorer (IXPE) with six 100 ks observations spanning from 2022 March to 2023 April. Each IXPE observation was accompanied by simultaneous X-ray data from NuSTAR, Swift/XRT, and/or XMM-Newton. Complementary optical–infrared polarization measurements were also available in the B , V , R , I , and J bands, as were radio polarization measurements from 4.85 GHz to 225.5 GHz. Among the first five IXPE observations, we did not find significant variability in the X-ray polarization degree and angle with IXPE. However, the most recent sixth observation found an elevated polarization degree at >3 σ above the average of the other five observations. The optical and radio measurements show no apparent correlations with the X-ray polarization properties. Throughout the six IXPE observations, the X-ray polarization degree remained higher than, or similar to, the R -band optical polarization degree, which remained higher than the radio value. This is consistent with the energy-stratified shock scenario proposed to explain the first two IXPE observations, in which the polarized X-ray, optical, and radio emission arises from different regions.

Published
2024
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16. X-Ray Polarization of BL Lacertae in Outburst

Author

Abel L. Peirson, Michela Negro, Ioannis Liodakis, Riccardo Middei, Dawoon E. Kim, Alan P. Marscher, Herman L. Marshall, Luigi Pacciani, Roger W. Romani, Kinwah Wu, Alessandro Di Marco, Niccoló Di Lalla, Nicola Omodei, Svetlana G. Jorstad, Iván Agudo, Pouya M. Kouch, Elina Lindfors, Francisco José Aceituno, Maria I. Bernardos, Giacomo Bonnoli, Víctor Casanova, Maya García-Comas, Beatriz Agís-González, César Husillos, Alessandro Marchini, Alfredo Sota, Carolina Casadio, Juan Escudero, Ioannis Myserlis, Albrecht Sievers, Mark Gurwell, Ramprasad Rao, Ryo Imazawa, Mahito Sasada, Yasushi Fukazawa, Koji S. Kawabata, Makoto Uemura, Tsunefumi Mizuno, Tatsuya Nakaoka, Hiroshi Akitaya, Yeon Cheong, Hyeon-Woo Jeong, Sincheol Kang, Sang-Hyun Kim, Sang-Sung Lee, Emmanouil Angelakis, Alexander Kraus, Nicoló Cibrario, Immacolata Donnarumma, Juri Poutanen, Fabrizio Tavecchio, Lucio A. Antonelli, Matteo Bachetti, Luca Baldini, Wayne H. Baumgartner, Ronaldo Bellazzini, Stefano Bianchi, Stephen D. Bongiorno, Raffaella Bonino, Alessandro Brez, Niccoló Bucciantini, Fiamma Capitanio, Simone Castellano, Elisabetta Cavazzuti, Chien-Ting Chen, Stefano Ciprini, Enrico Costa, Alessandra De Rosa, Ettore Del Monte, Laura Di Gesu, Victor Doroshenko, Michal Dovčiak, Steven R. Ehlert, Teruaki Enoto, Yuri Evangelista, Sergio Fabiani, Riccardo Ferrazzoli, Javier A. Garcia, Shuichi Gunji, Kiyoshi Hayashida, Jeremy Heyl, Wataru Iwakiri, Philip Kaaret, Vladimir Karas, Takao Kitaguchi, Jeffery J. Kolodziejczak, Henric Krawczynski, Fabio La Monaca, Luca Latronico, Grzegorz Madejski, Simone Maldera, Alberto Manfreda, Frédéric Marin, Andrea Marinucci, Francesco Massaro, Giorgio Matt, Ikuyuki Mitsuishi, Fabio Muleri, C.-Y. Ng, Stephen L. O’Dell, Chiara Oppedisano, Alessandro Papitto, George G. Pavlov, Matteo Perri, Melissa Pesce-Rollins, Pierre-Olivier Petrucci, Maura Pilia, Andrea Possenti, Simonetta Puccetti, Brian D. Ramsey, John Rankin, Ajay Ratheesh, Oliver J. Roberts, Carmelo Sgró, Patrick Slane, Paolo Soffitta, Gloria Spandre, Douglas A. Swartz, Toru Tamagawa, Roberto Taverna, Yuzuru Tawara, Allyn F. Tennant, Nicholas E. Thomas, Francesco Tombesi, Alessio Trois, Sergey Tsygankov, Roberto Turolla, Jacco Vink, Martin C. Weisskopf, Fei Xie, and Silvia Zane

Subjects
Astrophysical black holes, Black hole physics, Supermassive black holes, Active galactic nuclei, Active galaxies, Jets, Astrophysics, QB460-466
Abstract

We report the first >99% confidence detection of X-ray polarization in BL Lacertae. During a recent X-ray/ γ -ray outburst, a 287 ks observation (2022 November 27–30) was taken using the Imaging X-ray Polarimetry Explorer (IXPE), together with contemporaneous multiwavelength observations from the Neil Gehrels Swift observatory and XMM-Newton in soft X-rays (0.3–10 keV), NuSTAR in hard X-rays (3–70 keV), and optical polarization from the Calar Alto and Perkins Telescope observatories. Our contemporaneous X-ray data suggest that the IXPE energy band is at the crossover between the low- and high-frequency blazar emission humps. The source displays significant variability during the observation, and we measure polarization in three separate time bins. Contemporaneous X-ray spectra allow us to determine the relative contribution from each emission hump. We find >99% confidence X-ray polarization ${{\rm{\Pi }}}_{2\mbox{--}4\mathrm{keV}}={21.7}_{-7.9}^{+5.6} \% $ and electric vector polarization angle ψ _2–4keV = −28.°7 ± 8.°7 in the time bin with highest estimated synchrotron flux contribution. We discuss possible implications of our observations, including previous IXPE BL Lacertae pointings, tentatively concluding that synchrotron self-Compton emission dominates over hadronic emission processes during the observed epochs.

Published
2023
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17. IXPE and Multiwavelength Observations of Blazar PG 1553+113 Reveal an Orphan Optical Polarization Swing

Author

Riccardo Middei, Matteo Perri, Simonetta Puccetti, Ioannis Liodakis, Laura Di Gesu, Alan P. Marscher, Nicole Rodriguez Cavero, Fabrizio Tavecchio, Immacolata Donnarumma, Marco Laurenti, Svetlana G. Jorstad, Iván Agudo, Herman L. Marshall, Luigi Pacciani, Dawoon E. Kim, Francisco José Aceituno, Giacomo Bonnoli, Víctor Casanova, Beatriz Agís-González, Alfredo Sota, Carolina Casadio, Juan Escudero, Ioannis Myserlis, Albrecht Sievers, Pouya M. Kouch, Elina Lindfors, Mark Gurwell, Garrett K. Keating, Ramprasad Rao, Sincheol Kang, Sang-Sung Lee, Sang-Hyun Kim, Whee Yeon Cheong, Hyeon-Woo Jeong, Emmanouil Angelakis, Alexander Kraus, Lucio A. Antonelli, Matteo Bachetti, Luca Baldini, Wayne H. Baumgartner, Ronaldo Bellazzini, Stefano Bianchi, Stephen D. Bongiorno, Raffaella Bonino, Alessandro Brez, Niccolò Bucciantini, Fiamma Capitanio, Simone Castellano, Elisabetta Cavazzuti, Chien-Ting Chen, Stefano Ciprini, Enrico Costa, Alessandra De Rosa, Ettore Del Monte, Niccolò Di Lalla, Alessandro Di Marco, Victor Doroshenko, Michal Dovčiak, Steven R. Ehlert, Teruaki Enoto, Yuri Evangelista, Sergio Fabiani, Riccardo Ferrazzoli, Javier A. García, Shuichi Gunji, Kiyoshi Hayashida, Jeremy Heyl, Wataru Iwakiri, Philip Kaaret, Vladimir Karas, Fabian Kislat, Takao Kitaguchi, Jeffery J. Kolodziejczak, Henric Krawczynski, Fabio La Monaca, Luca Latronico, Simone Maldera, Alberto Manfreda, Frédéric Marin, Andrea Marinucci, Francesco Massaro, Giorgio Matt, Ikuyuki Mitsuishi, Tsunefumi Mizuno, Fabio Muleri, Michela Negro, Chi-Yung Ng, Stephen L. O’Dell, Nicola Omodei, Chiara Oppedisano, Alessandro Papitto, George G. Pavlov, Abel L. Peirson, Melissa Pesce-Rollins, Pierre-Olivier Petrucci, Maura Pilia, Andrea Possenti, Juri Poutanen, Brian D. Ramsey, John Rankin, Ajay Ratheesh, Oliver J. Roberts, Roger W. Romani, Carmelo Sgrò, Patrick Slane, Paolo Soffitta, Gloria Spandre, Douglas A. Swartz, Toru Tamagawa, Roberto Taverna, Yuzuru Tawara, Allyn F. Tennant, Nicholas E. Thomas, Francesco Tombesi, Alessio Trois, Sergey S. Tsygankov, Roberto Turolla, Jacco Vink, Martin C. Weisskopf, Kinwah Wu, Fei Xie, and Silvia Zane

Subjects
BL Lacertae objects, Spectropolarimetry, Polarimetry, Active galactic nuclei, Jets, X-ray active galactic nuclei, Astrophysics, QB460-466
Abstract

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 consensus regarding jet emission processes, the particle acceleration mechanism is still debated. Here, we present the first X-ray polarization observations of PG 1553+113, a high-synchrotron-peak blazar observed by the Imaging X-ray Polarimetry Explorer (IXPE). We detect an X-ray polarization degree of (10 ± 2)% along an electric-vector position angle of ψ _X = 86° ± 8°. At the same time, the radio and optical polarization degrees are lower by a factor of ∼3. During our IXPE pointing, we observed the first orphan optical polarization swing of the IXPE era, as the optical angle of PG 1553+113 underwent a smooth monotonic rotation by about 125°, with a rate of ∼17° day ^–1 . We do not find evidence of a similar rotation in either radio or X-rays, which suggests that the X-ray and optically emitting regions are separate or, at most, partially cospatial. Our spectropolarimetric results provide further evidence that the steady-state X-ray emission in blazars originates in a shock-accelerated and energy-stratified electron population.

Published
2023
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