TY - JOUR

T1 - Magnetic field properties inside the jet of Mrk 421. Multiwavelength polarimetry, including the Imaging X-ray Polarimetry Explorer

AU - Kim, Dawoon E.

AU - Di Gesu, Laura

AU - Liodakis, Ioannis

AU - Marscher, Alan P.

AU - Jorstad, Svetlana G.

AU - Middei, Riccardo

AU - Marshall, Herman L.

AU - Pacciani, Luigi

AU - Agudo, Ivan

AU - Tavecchio, Fabrizio

AU - Cibrario, Nicoló

AU - Tugliani, Stefano

AU - Bonino, Raffaella

AU - Negro, Michela

AU - Puccetti, Simonetta

AU - Tombesi, Francesco

AU - Costa, Enrico

AU - Donnarumma, Immacolata

AU - Soffitta, Paolo

AU - Mizuno, Tsunefumi

AU - Fukazawa, Yasushi

AU - Kawabata, Koji S.

AU - Nakaoka, Tatsuya

AU - Uemura, Makoto

AU - Imazawa, Ryo

AU - Sasada, Mahito

AU - Akitaya, Hiroshi

AU - Josè Aceituno, Francisco

AU - Bonnoli, Giacomo

AU - Casanova, Vìctor

AU - Myserlis, Ioannis

AU - Sievers, Albrecht

AU - Angelakis, Emmanouil

AU - Kraus, Alexander

AU - Yeon Cheong, Whee

AU - Jeong, Hyeon-Woo

AU - Kang, Sincheol

AU - Kim, Sang-Hyun

AU - Lee, Sang-Sung

AU - Agìs-Gonzàlez, Beatriz

AU - Sota, Alfredo

AU - Escudero, Juan

AU - Gurwell, Mark

AU - Keating, Garrett K.

AU - Rao, Ramprasad

AU - Kouch, Pouya M.

AU - Lindfors, Elina

AU - Bourbah, Ioakeim G.

AU - Kiehlmann, Sebastian

AU - Kontopodis, Evangelos

AU - Mandarakas, Nikos

AU - Romanopoulos, Stylianos

AU - Skalidis, Raphael

AU - Vervelaki, Anna

AU - Savchenko, Sergey S.

AU - Antonelli, Lucio A.

AU - Bachetti, Matteo

AU - Baldini, Luca

AU - Baumgartner, Wayne H.

AU - Bellazzini, Ronaldo

AU - Bianchi, Stefano

AU - Bongiorno, Stephen D.

AU - Brez, Alessandro

AU - Bucciantini, Niccoló

AU - Capitanio, Fiamma

AU - Castellano, Simone

AU - Cavazzuti, Elisabetta

AU - Chen, Chien-Ting

AU - Ciprini, Stefano

AU - De Rosa, Alessandra

AU - Del Monte, Ettore

AU - Di Lalla, Niccoló

AU - Di Marco, Alessandro

AU - Doroshenko, Victor

AU - Dovčiak, Michal

AU - Ehlert, Steven R.

AU - Enoto, Teruaki

AU - Evangelista, Yuri

AU - Fabiani, Sergio

AU - Ferrazzoli, Riccardo

AU - Garcia, Javier A.

AU - Gunji, Shuichi

AU - Hayashida, Kiyoshi

AU - Heyl, Jeremy

AU - Iwakiri, Wataru

AU - Kaaret, Philip

AU - Karas, Vladimir

AU - Kislat, Fabian

AU - Kitaguchi, Takao

AU - Kolodziejczak, Jeffery J.

AU - Krawczynski, Henric

AU - La Monaca, Fabio

AU - Latronico, Luca

AU - Maldera, Simone

AU - Manfreda, Alberto

AU - Marin, Frédéric

AU - Marinucci, Andrea

AU - Massaro, Francesco

AU - Matt, Giorgio

AU - Mitsuishi, Ikuyuki

AU - Muleri, Fabio

AU - Ng, C. -Y.

AU - O'Dell, Stephen L.

AU - Omodei, Nicola

AU - Oppedisano, Chiara

AU - Papitto, Alessandro

AU - Pavlov, George G.

AU - Peirson, Abel L.

AU - Perri, Matteo

AU - Pesce-Rollins, Melissa

AU - Petrucci, Pierre-Olivier

AU - Pilia, Maura

AU - Possenti, Andrea

AU - Poutanen, Juri

AU - Ramsey, Brian D.

AU - Rankin, John

AU - Ratheesh, Ajay

AU - Roberts, Oliver

AU - Romani, Roger W.

AU - Sgró, Carmelo

AU - Slane, Patrick

AU - Spandre, Gloria

AU - Swartz, Doug

AU - Tamagawa, Toru

AU - Taverna, Roberto

AU - Tawara, Yuzuru

AU - Tennant, Allyn F.

AU - Thomas, Nicholas E.

AU - Trois, Alessio

AU - Tsygankov, Sergey S.

AU - Turolla, Roberto

AU - Vink, Jacco

AU - Weisskopf, Martin C.

AU - Wu, Kinwah

AU - Xie, Fei

AU - Zane, Silvia

PY - 2024/1/1

Y1 - 2024/1/1

N2 - Aims. We aim to probe the magnetic field geometry and particle acceleration mechanism in the relativistic jets of supermassive black holes. Methods. 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 from 2022 December 6-8. During the IXPE observation, we also monitored Mrk 421 using Swift-XRT and obtained a single observation with XMM-Newton to improve the X-ray spectral analysis. The time-averaged X-ray polarization was determined consistently using the event-by-event Stokes parameter analysis, spectropolarimetric fit, and maximum likelihood methods. We examined the polarization variability over both time and energy, the former via analysis of IXPE data obtained over a time span of 7 months. Results. We detected X-ray polarization of Mrk 421 with a degree of ΠX = 14 ± 1% and an electric-vector position angle ΨX = 107 ± 3 in the 2-8 keV band. From the time variability analysis, we find a significant episodic variation in ΨX. During the 7 months from the first IXPE pointing of Mrk 421 in 2022 May, ΨX varied in the range 0 to 180, while ΠX remained relatively constant within ∼10-15%. Furthermore, a swing in ΨX in 2022 June was accompanied by simultaneous spectral variations. The results of the multiwavelength polarimetry show that ΠX was generally ∼2-3 times greater than Π at longer wavelengths, while Ψfluctuated. Additionally, based on radio, infrared, and optical polarimetry, we find that the rotation of Ψoccurred in the opposite direction with respect to the rotation of ΨX and over longer timescales at similar epochs. Conclusions. 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. We considered two versions of the model, one with linear and the other with radial stratification geometry, to explain the rotation of ΨX. The accompanying spectral variation during the ΨX rotation can be explained by a fluctuation in the physical conditions, for example in the energy distribution of relativistic electrons. The opposite rotation direction of Ψbetween the X-ray and longer wavelength polarization accentuates the conclusion that the X-ray emitting region is spatially separated from that at longer wavelengths. Moreover, we identify a highly polarized knot of radio emission moving down the parsec-scale jet during the episode of ΨX rotation, although it is unclear whether there is any connection between the two events.

AB - Aims. We aim to probe the magnetic field geometry and particle acceleration mechanism in the relativistic jets of supermassive black holes. Methods. 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 from 2022 December 6-8. During the IXPE observation, we also monitored Mrk 421 using Swift-XRT and obtained a single observation with XMM-Newton to improve the X-ray spectral analysis. The time-averaged X-ray polarization was determined consistently using the event-by-event Stokes parameter analysis, spectropolarimetric fit, and maximum likelihood methods. We examined the polarization variability over both time and energy, the former via analysis of IXPE data obtained over a time span of 7 months. Results. We detected X-ray polarization of Mrk 421 with a degree of ΠX = 14 ± 1% and an electric-vector position angle ΨX = 107 ± 3 in the 2-8 keV band. From the time variability analysis, we find a significant episodic variation in ΨX. During the 7 months from the first IXPE pointing of Mrk 421 in 2022 May, ΨX varied in the range 0 to 180, while ΠX remained relatively constant within ∼10-15%. Furthermore, a swing in ΨX in 2022 June was accompanied by simultaneous spectral variations. The results of the multiwavelength polarimetry show that ΠX was generally ∼2-3 times greater than Π at longer wavelengths, while Ψfluctuated. Additionally, based on radio, infrared, and optical polarimetry, we find that the rotation of Ψoccurred in the opposite direction with respect to the rotation of ΨX and over longer timescales at similar epochs. Conclusions. 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. We considered two versions of the model, one with linear and the other with radial stratification geometry, to explain the rotation of ΨX. The accompanying spectral variation during the ΨX rotation can be explained by a fluctuation in the physical conditions, for example in the energy distribution of relativistic electrons. The opposite rotation direction of Ψbetween the X-ray and longer wavelength polarization accentuates the conclusion that the X-ray emitting region is spatially separated from that at longer wavelengths. Moreover, we identify a highly polarized knot of radio emission moving down the parsec-scale jet during the episode of ΨX rotation, although it is unclear whether there is any connection between the two events.

KW - BL Lacertae objects: individual: HSP

KW - galaxies: jets

KW - polarization

KW - relativistic processes

KW - magnetic fields

KW - Astrophysics - High Energy Astrophysical Phenomena

KW - BL Lacertae objects: individual: HSP

KW - Galaxies: jets

KW - Magnetic fields

KW - Polarization

KW - Relativistic processes

UR - https://www.mendeley.com/catalogue/edf0d4df-230f-3a0b-8938-41e32afd735f/

U2 - 10.1051/0004-6361/202347408

DO - 10.1051/0004-6361/202347408

M3 - Article

VL - 681

JO - ASTRONOMY & ASTROPHYSICS

JF - ASTRONOMY & ASTROPHYSICS

SN - 0004-6361

M1 - A12

ER -