Magnetic Field Properties inside the Jet of Mrk 421: Multiwavelength Polarimetry Including the Imaging X-ray Polarimetry Explorer
Creators: name: Kim, Dawoon E.
name: Di Gesu, Laura
name: Liodakis, Ioannis
name: Marscher, Alan P.
name: Jorstad, Svetlana G.
name: Midde, Riccardo
name: Marshall, Herman L.
name: Pacciani, Luigi
name: Agudo, Iván
name: Tavecchio, Fabrizio
name: Cibrario, Nicolò
name: Tugliani, Stefano
name: Bonino, Raffaella
name: Negro, Michela
name: Puccetti, Simonetta
name: Tombesi, Francesco
name: Costa, Enrico
name: Donnarumma, Immacolata
name: Soffitta, Paolo
name: Mizuno, Tsunefumi
name: Fukazawa, Yasushi
name: Kawabata, Koji S.
name: Nakaoka, Tatsuya
name: Uemura, Makoto
name: Imazawa, Ryo
name: Sasada, Mahito
name: Akitaya, Hiroshi
name: Aceituno, Francisco Josè
name: Bonnoli, Giacomo
name: Casanova, Vìctor
name: Myserlis, Ioannis
name: Sievers, Albrecht
name: Angelakis, Emmanouil
name: Kraus, Alexander
name: Cheong, Whee Yeon
name: Jeong, Hyeon-Woo
name: Kang, Sincheol
name: Kim, Sang-Hyun
name: Lee, Sang-Sung
name: Agìs-Gonzàlez, Beatriz
name: Sota, Alfredo
name: Escudero, Juan
name: Gurwell, Mark
name: Keating, Garrett K.
name: Rao, Ramprasad
name: Kouch, Pouya M.
name: Lindfors, Elina
name: Bourbah, Ioakeim G.
name: Kiehlmann, Sebastian
name: Kontopodis, Evangelos
name: Mandarakas, Nikos
name: Romanopoulos, Stylianos
name: Skalidis, Raphael
name: Vervelaki, Anna
name: Savchenko, Sergey S.
name: Antonelli, Lucio A.
name: Bachetti, Matteo
name: Baldini, Luca
name: Baumgartner, Wayne H.
name: Bellazzini, Ronaldo
name: Bianchi, Stefano
name: Bongiorno, Stephen D.
name: Brez, Alessandro
name: Bucciantini, Niccolò
name: Capitanio, Fiamma
name: Castellano, Simone
name: Cavazzuti, Elisabetta
name: Chen, Chien-Ting
name: Ciprini, Stefano
name: De Rosa, Alessandra
name: Del Monte, Ettore
name: Di Lalla, Niccolò
name: Di Marco, Alessandro
name: Doroshenko, Victor
name: Dovčiak, Michal
name: Ehlert, Steven R.
name: Enoto, Teruaki
name: Evangelista, Yuri
name: Fabiani, Sergio
name: Ferrazzoli, Riccardo
name: Garcia, Javier A.
name: Gunji, Shuichi
name: Hayashida, Kiyoshi
name: Heyl, Jeremy
name: Iwakiri, Wataru
name: Kaaret, Philip
name: Karas, Vladimir
name: Kislat, Fabian
name: Kitaguchi, Takao
name: Kolodziejczak, Jeffery J.
name: Krawczynski, Henric
name: La Monaca, Fabio
name: Latronico, Luca
name: Maldera, Simone
name: Manfreda, Alberto
name: Marin, Frédéric
name: Marinucci, Andrea
name: Massaro, Francesco
name: Matt, Giorgio
name: Mitsuishi, Ikuyuki
name: Muleri, Fabio
name: Ng, C. -Y.
name: O'Dell, Stephen L.
name: Omodei, Nicola
name: Oppedisano, Chiara
name: Papitto, Alessandro
name: Pavlov, George G.
name: Peirson, Abel L.
name: Perri, Matteo
name: Pesce-Rollins, Melissa
name: Petrucci, Pierre-Olivier
name: Pilia, Maura
name: Possenti, Andrea
name: Poutanen, Juri
name: Ramsey, Brian D.
name: Rankin, John
name: Ratheesh, Ajay
name: Roberts, Oliver
name: Romani, Roger W.
name: Sgrò, Carmelo
name: Slane, Patrick
name: Spandre, Gloria
name: Swartz, Doug
name: Tamagawa, Toru
name: Taverna, Roberto
name: Tawara, Yuzuru
name: Tennant, Allyn F.
name: Thomas, Nicholas E.
name: Trois, Alessio
name: Tsygankov, Sergey S.
name: Turolla, Roberto
name: Vink, Jacco
name: Weisskopf, Martin C.
name: Wu, Kinwah
name: Xie, Fei
name: Zane, Silvia
Publisher: name: arXiv
Year: 2023
Subjects: subject: High Energy Astrophysical Phenomena (astro-ph.HE)
subject: FOS: Physical sciences
subject: FOS: Physical sciences

description: 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) measurements on 2022 December 6-8. We detected X-ray polarization of Mrk 421 with a degree of $Π_{\rm X}$=14$\pm$1$\%$ and an electric-vector position angle $ψ_{\rm X}$=107$\pm$3$^{\circ}$ in the 2-8 keV band. From the time variability analysis, we find a significant episodic variation in $ψ_{\rm X}$. During 7 months from the first IXPE pointing of Mrk 421 in 2022 May, $ψ_{\rm X}$ varied across the range of 0$^{\circ}$ to 180$^{\circ}$, while $Π_{\rm X}$ maintained similar values within $\sim$10-15$\%$. Furthermore, a swing in $ψ_{\rm X}$ in 2022 June was accompanied by simultaneous spectral variations. The results of the multiwavelength polarimetry show that the X-ray polarization degree was generally $\sim$2-3 times greater than that at longer wavelengths, while the polarization angle fluctuated. Additionally, based on radio, infrared, and optical polarimetry, we find that rotation of $ψ$ occurred in the opposite direction with respect to the rotation of $ψ_{\rm X}$ over longer timescales at similar epochs. The polarization behavior observed across multiple wavelengths is consistent with previous IXPE findings for HSP blazars. This result favors the energy-stratified shock model developed to explain variable emission in relativistic jets. The accompanying spectral variation during the $ψ_{\rm X}$ rotation can be explained by a fluctuation in the physical conditions, e.g., in the energy distribution of relativistic electrons. The opposite rotation direction of $ψ$ between the X-ray and longer-wavelength polarization accentuates the conclusion that the X-ray emitting region is spatially separated from that at longer wavelengths.
description: 17 pages, 13 figures, 4 tables; Accepted for publication in A&amp;A