The X-Ray Polarization View of Mrk 421 in an Average Flux State as Observed by the Imaging X-Ray Polarimetry Explorer

Laura Di Gesu; Immacolata Donnarumma; Fabrizio Tavecchio; Iván Agudo; Thibault Barnounin; Nicolò Cibrario; Niccolò Di Lalla; Alessandro Di Marco; Juan Escudero; Manel Errando; Svetlana G. Jorstad; Dawoon E. Kim; Pouya M. Kouch; Ioannis Liodakis; Elina Lindfors; Grzegorz Madejski; Herman L. Marshall; Alan P. Marscher; Riccardo Middei; Fabio Muleri; Ioannis Myserlis; Michela Negro; Nicola Omodei; Luigi Pacciani; Alessandro Paggi; Matteo Perri; Simonetta Puccetti; 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; Stefano Ciprini; Enrico Costa; Alessandra De Rosa; Ettore Del Monte; 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; Vladimir Karas; 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; C. Y. Ng; Stephen L. O’Dell; 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; Roger W. Romani; Carmelo Sgrò; Patrick Slane; Paolo Soffitta; Gloria Spandre; Toru Tamagawa; Roberto Taverna; Yuzuru Tawara; Allyn F. Tennant; Nicolas E. Thomas; Francesco Tombesi; Alessio Trois; Sergey Tsygankov; Roberto Turolla; Jacco Vink; Martin C. Weisskopf; Kinwah Wu; Fei Xie; Silvia Zane

doi:10.3847/2041-8213/ac913a

The X-Ray Polarization View of Mrk 421 in an Average Flux State as Observed by the Imaging X-Ray Polarimetry Explorer

Laura Di Gesu, Immacolata Donnarumma, Fabrizio Tavecchio, Iván Agudo, Thibault Barnounin, Nicolò Cibrario, Niccolò Di Lalla, Alessandro Di Marco, Juan Escudero, Manel Errando, Svetlana G. Jorstad, Dawoon E. Kim, Pouya M. Kouch, Ioannis Liodakis, Elina Lindfors, Grzegorz Madejski, Herman L. Marshall, Alan P. Marscher, Riccardo Middei, Fabio MuleriIoannis Myserlis, Michela Negro, Nicola Omodei, Luigi Pacciani, Alessandro Paggi, Matteo Perri, Simonetta Puccetti, 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, Stefano Ciprini, Enrico Costa, Alessandra De Rosa, Ettore Del Monte, 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, Vladimir Karas, 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, C. Y. Ng, Stephen L. O’Dell, 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, Roger W. Romani, Carmelo Sgrò, Patrick Slane, Paolo Soffitta, Gloria Spandre, Toru Tamagawa, Roberto Taverna, Yuzuru Tawara, Allyn F. Tennant, Nicolas E. Thomas, Francesco Tombesi, Alessio Trois, Sergey Tsygankov, Roberto Turolla, Jacco Vink, Martin C. Weisskopf, Kinwah Wu, Fei Xie, Silvia Zane

Research output: Contribution to journal › Article › peer-review

3 Citations (SciVal)

Abstract

Particle acceleration mechanisms in supermassive black hole jets, such as shock acceleration, magnetic reconnection, and turbulence, are expected to have observable signatures in the multiwavelength polarization properties of blazars. The recent launch of the Imaging X-Ray Polarimetry Explorer (IXPE) enables us, for the first time, to use polarization in the X-ray band (2-8 keV) to probe the properties of the jet synchrotron emission in high-synchrotron-peaked BL Lac objects (HSPs). We report the discovery of X-ray linear polarization (degree Π_x = 15% ± 2% and electric vector position angle ψ _x = 35° ± 4°) from the jet of the HSP Mrk 421 in an average X-ray flux state. At the same time, the degree of polarization at optical, infrared, and millimeter wavelengths was found to be lower by at least a factor of 3. During the IXPE pointing, the X-ray flux of the source increased by a factor of 2.2, while the polarization behavior was consistent with no variability. The higher level of Π_x compared to longer wavelengths, and the absence of significant polarization variability, suggest a shock is the most likely X-ray emission site in the jet of Mrk 421 during the observation. The multiwavelength polarization properties are consistent with an energy-stratified electron population, where the particles emitting at longer wavelengths are located farther from the acceleration site, where they experience a more disordered magnetic field.

Original language	English (US)
Article number	L7
Journal	Astrophysical Journal Letters
Volume	938
Issue number	1
DOIs	https://doi.org/10.3847/2041-8213/ac913a
State	Published - Oct 1 2022

All Science Journal Classification (ASJC) codes

Astronomy and Astrophysics
Space and Planetary Science

Access to Document

10.3847/2041-8213/ac913a

Cite this

Di Gesu, L., Donnarumma, I., Tavecchio, F., Agudo, I., Barnounin, T., Cibrario, N., Di Lalla, N., Di Marco, A., Escudero, J., Errando, M., Jorstad, S. G., Kim, D. E., Kouch, P. M., Liodakis, I., Lindfors, E., Madejski, G., Marshall, H. L., Marscher, A. P., Middei, R., ... Zane, S. (2022). The X-Ray Polarization View of Mrk 421 in an Average Flux State as Observed by the Imaging X-Ray Polarimetry Explorer. Astrophysical Journal Letters, 938(1), [L7]. https://doi.org/10.3847/2041-8213/ac913a

@article{e2e5efd9c82d402782415720b7cf9f99,

title = "The X-Ray Polarization View of Mrk 421 in an Average Flux State as Observed by the Imaging X-Ray Polarimetry Explorer",

abstract = "Particle acceleration mechanisms in supermassive black hole jets, such as shock acceleration, magnetic reconnection, and turbulence, are expected to have observable signatures in the multiwavelength polarization properties of blazars. The recent launch of the Imaging X-Ray Polarimetry Explorer (IXPE) enables us, for the first time, to use polarization in the X-ray band (2-8 keV) to probe the properties of the jet synchrotron emission in high-synchrotron-peaked BL Lac objects (HSPs). We report the discovery of X-ray linear polarization (degree Πx = 15% ± 2% and electric vector position angle ψ x = 35° ± 4°) from the jet of the HSP Mrk 421 in an average X-ray flux state. At the same time, the degree of polarization at optical, infrared, and millimeter wavelengths was found to be lower by at least a factor of 3. During the IXPE pointing, the X-ray flux of the source increased by a factor of 2.2, while the polarization behavior was consistent with no variability. The higher level of Πx compared to longer wavelengths, and the absence of significant polarization variability, suggest a shock is the most likely X-ray emission site in the jet of Mrk 421 during the observation. The multiwavelength polarization properties are consistent with an energy-stratified electron population, where the particles emitting at longer wavelengths are located farther from the acceleration site, where they experience a more disordered magnetic field.",

author = "{Di Gesu}, Laura and Immacolata Donnarumma and Fabrizio Tavecchio and Iv{\'a}n Agudo and Thibault Barnounin and Nicol{\`o} Cibrario and {Di Lalla}, Niccol{\`o} and {Di Marco}, Alessandro and Juan Escudero and Manel Errando and Jorstad, {Svetlana G.} and Kim, {Dawoon E.} and Kouch, {Pouya M.} and Ioannis Liodakis and Elina Lindfors and Grzegorz Madejski and Marshall, {Herman L.} and Marscher, {Alan P.} and Riccardo Middei and Fabio Muleri and Ioannis Myserlis and Michela Negro and Nicola Omodei and Luigi Pacciani and Alessandro Paggi and Matteo Perri and Simonetta Puccetti and Antonelli, {Lucio A.} and Matteo Bachetti and Luca Baldini and Baumgartner, {Wayne H.} and Ronaldo Bellazzini and Stefano Bianchi and Bongiorno, {Stephen D.} and Raffaella Bonino and Alessandro Brez and Niccol{\`o} Bucciantini and Fiamma Capitanio and Simone Castellano and Elisabetta Cavazzuti and Stefano Ciprini and Enrico Costa and {De Rosa}, Alessandra and {Del Monte}, Ettore and Victor Doroshenko and Michal Dov{\v c}iak and Ehlert, {Steven R.} and Teruaki Enoto and Yuri Evangelista and Sergio Fabiani and Riccardo Ferrazzoli and Garcia, {Javier A.} and Shuichi Gunji and Kiyoshi Hayashida and Jeremy Heyl and Wataru Iwakiri and Vladimir Karas and Takao Kitaguchi and Kolodziejczak, {Jeffery J.} and Henric Krawczynski and {La Monaca}, Fabio and Luca Latronico and Simone Maldera and Alberto Manfreda and Fr{\'e}d{\'e}ric Marin and Andrea Marinucci and Francesco Massaro and Giorgio Matt and Ikuyuki Mitsuishi and Tsunefumi Mizuno and Ng, {C. Y.} and O{\textquoteright}Dell, {Stephen L.} and Chiara Oppedisano and Alessandro Papitto and Pavlov, {George G.} and Peirson, {Abel L.} and Melissa Pesce-Rollins and Petrucci, {Pierre Olivier} and Maura Pilia and Andrea Possenti and Juri Poutanen and Ramsey, {Brian D.} and John Rankin and Ajay Ratheesh and Romani, {Roger W.} and Carmelo Sgr{\`o} and Patrick Slane and Paolo Soffitta and Gloria Spandre and Toru Tamagawa and Roberto Taverna and Yuzuru Tawara and Tennant, {Allyn F.} and Thomas, {Nicolas E.} and Francesco Tombesi and Alessio Trois and Sergey Tsygankov and Roberto Turolla and Jacco Vink and Weisskopf, {Martin C.} and Kinwah Wu and Fei Xie and Silvia Zane",

note = "Funding Information: IXPE is a joint US and Italian mission. The US contribution is supported by the National Aeronautics and Space Administration (NASA) and led and managed by its Marshall Space Flight Center (MSFC), with industry partner Ball Aerospace (contract NNM15AA18C). The Italian contribution is supported by the Italian Space Agency (Agenzia Spaziale Italiana, ASI), through contract ASI-OHBI-2017-12-I.0, agreements ASI-INAF-2017-12-H0 and ASI-INFN-2017.13-H0, and its Space Science Data Center (SSDC) with agreements ASI-INAF-2022-14-HH.0 and ASI-INFN 2021-43-HH.0, and by Istituto Nazionale di Astrofisica (INAF) and Istituto Nazionale di Fisica Nucleare (INFN) in Italy. This research used data products provided by the IXPE Team (MSFC, SSDC, INAF, and INFN) and distributed with additional software tools by the High-energy Astrophysics Science Archive Research Center (HEASARC), at NASA{\textquoteright}s Goddard Space Flight Center (GSFC). The Instituto de Astrofisica de Andalucia (IAA)-CSIC group acknowledges financial support from the Spanish “Ministerio de Ciencia e Innovaci{\'o}n” (MCINN) through the “Center of Excellence Severo Ochoa” award for IAA-CSIC (SEV-2017-0709) and through grants AYA2016-80889-P and PID2019-107847RB-C44. The Polarimetric Monitoring of AGN at Millimeter Wavelengths (POLAMI) observations were carried out at the IRAM 30 m Telescope. IRAM is supported by INSU/CNRS (France), MPG (Germany), and IGN (Spain). Some of the data reported here are based on observations made with the NOT, owned in collaboration by the University of Turku and Aarhus University, and operated jointly by Aarhus University, the University of Turku, and the University of Oslo, representing Denmark, Finland, and Norway; the University of Iceland; and Stockholm University at Observatorio del Roque de los Muchachos, La Palma, Spain, of Instituto de Astrofisica de Canarias. E.L. was supported by Academy of Finland projects 317636 and 320045. The data presented here were obtained (in part) with the Alhambra Faint Object Spectrograph and Camera (ALFOSC), which is provided by IAA under a joint agreement with the University of Copenhagen and NOT. Part of the French contribution is supported by the Scientific Research National Center (CNRS) and the French space agency (CNES). The research at Boston University was supported in part by National Science Foundation (NSF) grant AST-2108622, NASA Fermi Guest Investigator grant 80NSSC21K1917, and NASA Swift Guest Investigator grant 80NSSC22K0537. This research was conducted in part using the Mimir instrument, jointly developed at Boston University and Lowell Observatory and supported by NASA, NSF, and the W. M. Keck Foundation. We thank D. Clemens for guidance in the analysis of the Mimir data. Funding Information: IXPE is a joint US and Italian mission. The US contribution is supported by the National Aeronautics and Space Administration (NASA) and led and managed by its Marshall Space Flight Center (MSFC), with industry partner Ball Aerospace (contract NNM15AA18C). The Italian contribution is supported by the Italian Space Agency (Agenzia Spaziale Italiana, ASI), through contract ASI-OHBI-2017-12-I.0, agreements ASI-INAF-2017-12-H0 and ASI-INFN-2017.13-H0, and its Space Science Data Center (SSDC) with agreements ASI-INAF-2022-14-HH.0 and ASI-INFN 2021-43-HH.0, and by Istituto Nazionale di Astrofisica (INAF) and Istituto Nazionale di Fisica Nucleare (INFN) in Italy. This research used data products provided by the IXPE Team (MSFC, SSDC, INAF, and INFN) and distributed with additional software tools by the High-energy Astrophysics Science Archive Research Center (HEASARC), at NASA{\textquoteright}s Goddard Space Flight Center (GSFC). The Instituto de Astrofisica de Andalucia (IAA)-CSIC group acknowledges financial support from the Spanish “Ministerio de Ciencia e Innovaci{\'o}n” (MCINN) through the “Center of Excellence Severo Ochoa” award for IAA-CSIC (SEV-2017-0709) and through grants AYA2016-80889-P and PID2019-107847RB-C44. The Polarimetric Monitoring of AGN at Millimeter Wavelengths (POLAMI) observations were carried out at the IRAM 30 m Telescope. IRAM is supported by INSU/CNRS (France), MPG (Germany), and IGN (Spain). Some of the data reported here are based on observations made with the NOT, owned in collaboration by the University of Turku and Aarhus University, and operated jointly by Aarhus University, the University of Turku, and the University of Oslo, representing Denmark, Finland, and Norway; the University of Iceland; and Stockholm University at Observatorio del Roque de los Muchachos, La Palma, Spain, of Instituto de Astrofisica de Canarias. E.L. was supported by Academy of Finland projects 317636 and 320045. The data presented here were obtained (in part) with the Alhambra Faint Object Spectrograph and Camera (ALFOSC), which is provided by IAA under a joint agreement with the University of Copenhagen and NOT. Part of the French contribution is supported by the Scientific Research National Center (CNRS) and the French space agency (CNES). The research at Boston University was supported in part by National Science Foundation (NSF) grant AST-2108622, NASA Fermi Guest Investigator grant 80NSSC21K1917, and NASA Swift Guest Investigator grant 80NSSC22K0537. This research was conducted in part using the Mimir instrument, jointly developed at Boston University and Lowell Observatory and supported by NASA, NSF, and the W. M. Keck Foundation. We thank D. Clemens for guidance in the analysis of the Mimir data. Publisher Copyright: {\textcopyright} 2022. The Author(s). Published by the American Astronomical Society.",

year = "2022",

month = oct,

day = "1",

doi = "10.3847/2041-8213/ac913a",

language = "English (US)",

volume = "938",

journal = "Astrophysical Journal Letters",

issn = "2041-8205",

publisher = "IOP Publishing Ltd.",

number = "1",

}

Di Gesu, L, Donnarumma, I, Tavecchio, F, Agudo, I, Barnounin, T, Cibrario, N, Di Lalla, N, Di Marco, A, Escudero, J, Errando, M, Jorstad, SG, Kim, DE, Kouch, PM, Liodakis, I, Lindfors, E, Madejski, G, Marshall, HL, Marscher, AP, Middei, R, Muleri, F, Myserlis, I, Negro, M, Omodei, N, Pacciani, L, Paggi, A, Perri, M, Puccetti, S, Antonelli, LA, Bachetti, M, Baldini, L, Baumgartner, WH, Bellazzini, R, Bianchi, S, Bongiorno, SD, Bonino, R, Brez, A, Bucciantini, N, Capitanio, F, Castellano, S, Cavazzuti, E, Ciprini, S, Costa, E, De Rosa, A, Del Monte, E, Doroshenko, V, Dovčiak, M, Ehlert, SR, Enoto, T, Evangelista, Y, Fabiani, S, Ferrazzoli, R, Garcia, JA, Gunji, S, Hayashida, K, Heyl, J, Iwakiri, W, Karas, V, Kitaguchi, T, Kolodziejczak, JJ, Krawczynski, H, La Monaca, F, Latronico, L, Maldera, S, Manfreda, A, Marin, F, Marinucci, A, Massaro, F, Matt, G, Mitsuishi, I, Mizuno, T, Ng, CY, O’Dell, SL, Oppedisano, C, Papitto, A, Pavlov, GG, Peirson, AL, Pesce-Rollins, M, Petrucci, PO, Pilia, M, Possenti, A, Poutanen, J, Ramsey, BD, Rankin, J, Ratheesh, A, Romani, RW, Sgrò, C, Slane, P, Soffitta, P, Spandre, G, Tamagawa, T, Taverna, R, Tawara, Y, Tennant, AF, Thomas, NE, Tombesi, F, Trois, A, Tsygankov, S, Turolla, R, Vink, J, Weisskopf, MC, Wu, K, Xie, F & Zane, S 2022, 'The X-Ray Polarization View of Mrk 421 in an Average Flux State as Observed by the Imaging X-Ray Polarimetry Explorer', Astrophysical Journal Letters, vol. 938, no. 1, L7. https://doi.org/10.3847/2041-8213/ac913a

TY - JOUR

T1 - The X-Ray Polarization View of Mrk 421 in an Average Flux State as Observed by the Imaging X-Ray Polarimetry Explorer

AU - Di Gesu, Laura

AU - Donnarumma, Immacolata

AU - Tavecchio, Fabrizio

AU - Agudo, Iván

AU - Barnounin, Thibault

AU - Cibrario, Nicolò

AU - Di Lalla, Niccolò

AU - Di Marco, Alessandro

AU - Escudero, Juan

AU - Errando, Manel

AU - Jorstad, Svetlana G.

AU - Kim, Dawoon E.

AU - Kouch, Pouya M.

AU - Liodakis, Ioannis

AU - Lindfors, Elina

AU - Madejski, Grzegorz

AU - Marshall, Herman L.

AU - Marscher, Alan P.

AU - Middei, Riccardo

AU - Muleri, Fabio

AU - Myserlis, Ioannis

AU - Negro, Michela

AU - Omodei, Nicola

AU - Pacciani, Luigi

AU - Paggi, Alessandro

AU - Perri, Matteo

AU - Puccetti, Simonetta

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 - Bonino, Raffaella

AU - Brez, Alessandro

AU - Bucciantini, Niccolò

AU - Capitanio, Fiamma

AU - Castellano, Simone

AU - Cavazzuti, Elisabetta

AU - Ciprini, Stefano

AU - Costa, Enrico

AU - De Rosa, Alessandra

AU - Del Monte, Ettore

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 - Karas, Vladimir

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 - Mizuno, Tsunefumi

AU - Ng, C. Y.

AU - O’Dell, Stephen L.

AU - Oppedisano, Chiara

AU - Papitto, Alessandro

AU - Pavlov, George G.

AU - Peirson, Abel L.

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 - Romani, Roger W.

AU - Sgrò, Carmelo

AU - Slane, Patrick

AU - Soffitta, Paolo

AU - Spandre, Gloria

AU - Tamagawa, Toru

AU - Taverna, Roberto

AU - Tawara, Yuzuru

AU - Tennant, Allyn F.

AU - Thomas, Nicolas E.

AU - Tombesi, Francesco

AU - Trois, Alessio

AU - Tsygankov, Sergey

AU - Turolla, Roberto

AU - Vink, Jacco

AU - Weisskopf, Martin C.

AU - Wu, Kinwah

AU - Xie, Fei

AU - Zane, Silvia

N1 - Funding Information: IXPE is a joint US and Italian mission. The US contribution is supported by the National Aeronautics and Space Administration (NASA) and led and managed by its Marshall Space Flight Center (MSFC), with industry partner Ball Aerospace (contract NNM15AA18C). The Italian contribution is supported by the Italian Space Agency (Agenzia Spaziale Italiana, ASI), through contract ASI-OHBI-2017-12-I.0, agreements ASI-INAF-2017-12-H0 and ASI-INFN-2017.13-H0, and its Space Science Data Center (SSDC) with agreements ASI-INAF-2022-14-HH.0 and ASI-INFN 2021-43-HH.0, and by Istituto Nazionale di Astrofisica (INAF) and Istituto Nazionale di Fisica Nucleare (INFN) in Italy. This research used data products provided by the IXPE Team (MSFC, SSDC, INAF, and INFN) and distributed with additional software tools by the High-energy Astrophysics Science Archive Research Center (HEASARC), at NASA’s Goddard Space Flight Center (GSFC). The Instituto de Astrofisica de Andalucia (IAA)-CSIC group acknowledges financial support from the Spanish “Ministerio de Ciencia e Innovación” (MCINN) through the “Center of Excellence Severo Ochoa” award for IAA-CSIC (SEV-2017-0709) and through grants AYA2016-80889-P and PID2019-107847RB-C44. The Polarimetric Monitoring of AGN at Millimeter Wavelengths (POLAMI) observations were carried out at the IRAM 30 m Telescope. IRAM is supported by INSU/CNRS (France), MPG (Germany), and IGN (Spain). Some of the data reported here are based on observations made with the NOT, owned in collaboration by the University of Turku and Aarhus University, and operated jointly by Aarhus University, the University of Turku, and the University of Oslo, representing Denmark, Finland, and Norway; the University of Iceland; and Stockholm University at Observatorio del Roque de los Muchachos, La Palma, Spain, of Instituto de Astrofisica de Canarias. E.L. was supported by Academy of Finland projects 317636 and 320045. The data presented here were obtained (in part) with the Alhambra Faint Object Spectrograph and Camera (ALFOSC), which is provided by IAA under a joint agreement with the University of Copenhagen and NOT. Part of the French contribution is supported by the Scientific Research National Center (CNRS) and the French space agency (CNES). The research at Boston University was supported in part by National Science Foundation (NSF) grant AST-2108622, NASA Fermi Guest Investigator grant 80NSSC21K1917, and NASA Swift Guest Investigator grant 80NSSC22K0537. This research was conducted in part using the Mimir instrument, jointly developed at Boston University and Lowell Observatory and supported by NASA, NSF, and the W. M. Keck Foundation. We thank D. Clemens for guidance in the analysis of the Mimir data. Funding Information: IXPE is a joint US and Italian mission. The US contribution is supported by the National Aeronautics and Space Administration (NASA) and led and managed by its Marshall Space Flight Center (MSFC), with industry partner Ball Aerospace (contract NNM15AA18C). The Italian contribution is supported by the Italian Space Agency (Agenzia Spaziale Italiana, ASI), through contract ASI-OHBI-2017-12-I.0, agreements ASI-INAF-2017-12-H0 and ASI-INFN-2017.13-H0, and its Space Science Data Center (SSDC) with agreements ASI-INAF-2022-14-HH.0 and ASI-INFN 2021-43-HH.0, and by Istituto Nazionale di Astrofisica (INAF) and Istituto Nazionale di Fisica Nucleare (INFN) in Italy. This research used data products provided by the IXPE Team (MSFC, SSDC, INAF, and INFN) and distributed with additional software tools by the High-energy Astrophysics Science Archive Research Center (HEASARC), at NASA’s Goddard Space Flight Center (GSFC). The Instituto de Astrofisica de Andalucia (IAA)-CSIC group acknowledges financial support from the Spanish “Ministerio de Ciencia e Innovación” (MCINN) through the “Center of Excellence Severo Ochoa” award for IAA-CSIC (SEV-2017-0709) and through grants AYA2016-80889-P and PID2019-107847RB-C44. The Polarimetric Monitoring of AGN at Millimeter Wavelengths (POLAMI) observations were carried out at the IRAM 30 m Telescope. IRAM is supported by INSU/CNRS (France), MPG (Germany), and IGN (Spain). Some of the data reported here are based on observations made with the NOT, owned in collaboration by the University of Turku and Aarhus University, and operated jointly by Aarhus University, the University of Turku, and the University of Oslo, representing Denmark, Finland, and Norway; the University of Iceland; and Stockholm University at Observatorio del Roque de los Muchachos, La Palma, Spain, of Instituto de Astrofisica de Canarias. E.L. was supported by Academy of Finland projects 317636 and 320045. The data presented here were obtained (in part) with the Alhambra Faint Object Spectrograph and Camera (ALFOSC), which is provided by IAA under a joint agreement with the University of Copenhagen and NOT. Part of the French contribution is supported by the Scientific Research National Center (CNRS) and the French space agency (CNES). The research at Boston University was supported in part by National Science Foundation (NSF) grant AST-2108622, NASA Fermi Guest Investigator grant 80NSSC21K1917, and NASA Swift Guest Investigator grant 80NSSC22K0537. This research was conducted in part using the Mimir instrument, jointly developed at Boston University and Lowell Observatory and supported by NASA, NSF, and the W. M. Keck Foundation. We thank D. Clemens for guidance in the analysis of the Mimir data. Publisher Copyright: © 2022. The Author(s). Published by the American Astronomical Society.

PY - 2022/10/1

Y1 - 2022/10/1

N2 - Particle acceleration mechanisms in supermassive black hole jets, such as shock acceleration, magnetic reconnection, and turbulence, are expected to have observable signatures in the multiwavelength polarization properties of blazars. The recent launch of the Imaging X-Ray Polarimetry Explorer (IXPE) enables us, for the first time, to use polarization in the X-ray band (2-8 keV) to probe the properties of the jet synchrotron emission in high-synchrotron-peaked BL Lac objects (HSPs). We report the discovery of X-ray linear polarization (degree Πx = 15% ± 2% and electric vector position angle ψ x = 35° ± 4°) from the jet of the HSP Mrk 421 in an average X-ray flux state. At the same time, the degree of polarization at optical, infrared, and millimeter wavelengths was found to be lower by at least a factor of 3. During the IXPE pointing, the X-ray flux of the source increased by a factor of 2.2, while the polarization behavior was consistent with no variability. The higher level of Πx compared to longer wavelengths, and the absence of significant polarization variability, suggest a shock is the most likely X-ray emission site in the jet of Mrk 421 during the observation. The multiwavelength polarization properties are consistent with an energy-stratified electron population, where the particles emitting at longer wavelengths are located farther from the acceleration site, where they experience a more disordered magnetic field.

AB - Particle acceleration mechanisms in supermassive black hole jets, such as shock acceleration, magnetic reconnection, and turbulence, are expected to have observable signatures in the multiwavelength polarization properties of blazars. The recent launch of the Imaging X-Ray Polarimetry Explorer (IXPE) enables us, for the first time, to use polarization in the X-ray band (2-8 keV) to probe the properties of the jet synchrotron emission in high-synchrotron-peaked BL Lac objects (HSPs). We report the discovery of X-ray linear polarization (degree Πx = 15% ± 2% and electric vector position angle ψ x = 35° ± 4°) from the jet of the HSP Mrk 421 in an average X-ray flux state. At the same time, the degree of polarization at optical, infrared, and millimeter wavelengths was found to be lower by at least a factor of 3. During the IXPE pointing, the X-ray flux of the source increased by a factor of 2.2, while the polarization behavior was consistent with no variability. The higher level of Πx compared to longer wavelengths, and the absence of significant polarization variability, suggest a shock is the most likely X-ray emission site in the jet of Mrk 421 during the observation. The multiwavelength polarization properties are consistent with an energy-stratified electron population, where the particles emitting at longer wavelengths are located farther from the acceleration site, where they experience a more disordered magnetic field.

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U2 - 10.3847/2041-8213/ac913a

DO - 10.3847/2041-8213/ac913a

M3 - Article

AN - SCOPUS:85140007890

SN - 2041-8205

VL - 938

JO - Astrophysical Journal Letters

JF - Astrophysical Journal Letters

IS - 1

M1 - L7

ER -

The X-Ray Polarization View of Mrk 421 in an Average Flux State as Observed by the Imaging X-Ray Polarimetry Explorer

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