IXPE observation of the low-synchrotron peaked blazar S4 0954+65 during an optical-X-ray flare

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 from blazars. Here, we report the first X-ray polarization observation of the blazar S4 0954+65 in a high optical and X-ray state. During our multi-wavelength (MWL) campaign of the source, we detected an optical flare whose peak coincided with the peak of an X-ray flare. This optical-X-ray flare most likely took place in a feature moving along the parsec-scale jet, imaged at 43 GHz by the Very Long Baseline Array (VLBA). The 43 GHz polarization angle of the moving component underwent a rotation near the time of the flare. In the optical band, prior to the IXPE observation, we measured the polarization angle to be aligned with the jet axis. In contrast, during the optical flare, the optical polarization angle was perpendicular to the jet axis; after the flare, it reverted to being parallel to the jet axis. Due to the smooth behavior of the optical polarization angle during the flare, we favor shocks as the main acceleration mechanism. We also infer that the ambient magnetic field lines in the jet were parallel to the jet position angle. The average degree of optical polarization during the IXPE observation was (14.3 ± 4.1)%. Despite the flare, we only detected an upper limit of 14% (at 3 σ level) on the X-ray polarization degree; however, a reasonable assumption on the X-ray polarization angle results in an upper limit of 8.8% (3 σ ). We modeled the spectral energy distribution (SED) and spectral polarization distribution (SPD) of S4 0954+65 with leptonic (synchrotron self-Compton) and hadronic (proton and pair synchrotron) models. Our combined MWL polarization observations and SED modeling tentatively disfavor the use of hadronic models for the X-ray emission in S4 0954+65.

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Journal
Astronomy and Astrophysics
Published
2025-02-12
DOI
https://doi.org/10.1051/0004-6361/202453127
Citations
10
Primary Topic
Astrophysics and Cosmic Phenomena
Type
article
Field-Weighted Citation Impact
18.70

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article

IXPE observation of the low-synchrotron peaked blazar S4 0954+65 during an optical-X-ray flare

Niccolò Di Lalla, Fabian Kislat, F. Massaro, H. C. Zhang et al.
10 citations
Astronomy and Astrophysics
Astrophysics and Cosmic Phenomena
18.70
article

IXPE observation of the low-synchrotron peaked blazar S4 0954+65 during an optical-X-ray flare

Niccolò Di Lalla, Fabian Kislat, F. Massaro, H. C. Zhang, Jeffery J. Kolodziejczak, Juri Poutanen, R. Bonino, A. Brez, I. S. Troitskiy, Ekaterina V. Shishkina, Laura Di Gesu, Simonetta Puccetti, Michal Dovčiak, Y. Evangelista, S. Ciprini, Dawoon E. Kim, A. A. Vasilyev, Silvia Zane, M. Pilia, Jeremy Heyl, Andrea Possenti, Victor Doroshenko, Chien‐Ting Chen, C. Husillos, Jacco Vink, A. Sota, Herman L. Marshall, A. Kraus, Stella Boula, Ioannis Liodakis, А. В. Жовтан, Francesco Fenu, Pouya M. Kouch, E. Costa, Garrett K. Keating, R. Turolla, F. Tavecchio, E. Angelakis, G. Matt, Pierre-Olivier Petrucci, Svetlana G. Jorstad, Alessandro Di Marco, P. Soffitta, Alberto Manfreda, W. H. Baumgartner, Alessandra De Rosa, D. Blinov, Jorge Otero-Santos, Kinwah Wu, M. Perri, Martin C. Weisskopf, Beatriz Agı́s-González, Е. Г. Ларионова, E. Del Monte, G. Spandre, O. J. Roberts, I. Myserlis, Fei Xie, T. S. Grishina, George G. Pavlov, Roger W. Romani, I. Agudo, Francesco Tombesi, Ramprasad Rao, M. Pesce-Rollins, Frédéric Marin, Patrick Slane, Toru Tamagawa, S. Kiehlmann, Yuzuru Tawara, Fiamma Capitanio, Steven R. Ehlert, Stephen L. O’Dell, Stephen D. Bongiorno, S. Maldera, C. Sgrò, V. Karas, John Rankin, Alessandro Papitto, F. J. Aceituno, A. Trois, Sergey S. Tsygankov, E. N. Kopatskaya, Riccardo Ferrazzoli, W. Iwakiri, Fabio Muleri, N. Mandarakas, G. Bonnoli, Brian D. Ramsey, E. Lindfors, V. Casanova, Tsunefumi Mizuno, Ikuyuki Mitsuishi, Roberto Taverna, Teruaki Enoto, R. Bellazzini, Javier Agüero García, Г. А. Борман, С. С. Савченко, E. Cavazzuti, Sergio Fabiani, Douglas A. Swartz, H. Krawczynski, Shuichi Gunji, Michela Negro, Georgios Filippos Paraschos, Andrea Marinucci, R. Middei, Daria A. Morozova, Mark Gurwell, Abel L. Peirson, Matteo Bachetti, C. Oppedisano, Nikolaos Triantafyllou, Simone Castellano, P. Kaaret, L. Baldini, Ajay Ratheesh, M. Errando, N. Bucciantini, Fabio La Monaca, L. Latronico, I. Donnarumma, L. A. Antonelli, S. Bianchi, V. Piirola, Anna Vervelaki, Allyn F. Tennant, Kun Hu, Juan Escudero, Nicholas E. Thomas, Alan P. Marscher, N. Omodei, C.‐Y. Ng, Kiyoshi Hayashida, Takao Kitaguchi, Anastasia Gourni, Angelos Kourtidis
article en
10 citations

Abstract

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 from blazars. Here, we report the first X-ray polarization observation of the blazar S4 0954+65 in a high optical and X-ray state. During our multi-wavelength (MWL) campaign of the source, we detected an optical flare whose peak coincided with the peak of an X-ray flare. This optical-X-ray flare most likely took place in a feature moving along the parsec-scale jet, imaged at 43 GHz by the Very Long Baseline Array (VLBA). The 43 GHz polarization angle of the moving component underwent a rotation near the time of the flare. In the optical band, prior to the IXPE observation, we measured the polarization angle to be aligned with the jet axis. In contrast, during the optical flare, the optical polarization angle was perpendicular to the jet axis; after the flare, it reverted to being parallel to the jet axis. Due to the smooth behavior of the optical polarization angle during the flare, we favor shocks as the main acceleration mechanism. We also infer that the ambient magnetic field lines in the jet were parallel to the jet position angle. The average degree of optical polarization during the IXPE observation was (14.3 ± 4.1)%. Despite the flare, we only detected an upper limit of 14% (at 3 σ level) on the X-ray polarization degree; however, a reasonable assumption on the X-ray polarization angle results in an upper limit of 8.8% (3 σ ). We modeled the spectral energy distribution (SED) and spectral polarization distribution (SPD) of S4 0954+65 with leptonic (synchrotron self-Compton) and hadronic (proton and pair synchrotron) models. Our combined MWL polarization observations and SED modeling tentatively disfavor the use of hadronic models for the X-ray emission in S4 0954+65.

Astronomy and AstrophysicsVol. 695
University of Pisa (IT), Boston University (US), Yamagata University (JP), Hiroshima University (JP), University of Rome Tor Vergata (IT), Roma Tre University (IT), Louisiana State University (US), United States Naval Research Laboratory (US), Marshall Space Flight Center (US), Centre National de la Recherche Scientifique (FR), Goddard Space Flight Center (US), Pennsylvania State University (US), Universities Space Research Association (US), University of Padua (IT), University of British Columbia (CA), University of Crete (GR), Guangxi University (CN), University of Turku (FI), Chiba University (JP), Istituto Nazionale di Fisica Nucleare (IT), University of New Hampshire (US), St Petersburg University (RU), Washington University in St. Louis (US), Arcetri Astrophysical Observatory (IT), Astronomical Observatory of Rome (IT), Czech Academy of Sciences, Astronomical Institute (CZ), Agenzia Spaziale Italiana (IT), Pulkovo Observatory (RU), Instituto Geológico y Minero de España (ES), Observatoire astronomique de Strasbourg (FR), Brera Astronomical Observatory (IT), Kavli Institute for Particle Astrophysics and Cosmology (US), Istituto Nazionale di Fisica Nucleare, Sezione di Torino (IT), Institute for Space Astrophysics and Planetology (IT), Pioneer (Japan) (JP), Istituto Nazionale di Fisica Nucleare, Sezione di Napoli (IT), RIKEN (JP), Istituto Nazionale di Fisica Nucleare, Roma Tor Vergata (IT), Center for Astrophysics Harvard & Smithsonian (US), FORTH Institute of Electronic Structure and Laser (GR), Istituto Nazionale di Fisica Nucleare, Sezione di Firenze (IT), Instituto de Radioastronomía Milimétrica (ES), Osservatorio Astronomico di Cagliari (IT), Max Planck Institute for Radio Astronomy (DE), Instituto de Astrofísica de Andalucía (ES), Istituto Nazionale di Fisica Nucleare, Sezione di Pisa (IT), Ordem dos Médicos (PT), Crimean Astrophysical Observatory (UA), University of Florence (IT), University College London (GB), University of Turin (IT), Nagoya University (JP), Massachusetts Institute of Technology (US), University of Maryland, College Park (US), Université de Strasbourg (FR), University of Maryland, Baltimore County (US), University of Tübingen (DE), Sapienza University of Rome (IT), University of Amsterdam (NL), University of Hong Kong (HK), Université Grenoble Alpes (FR), Stanford University (US), The University of Osaka (JP)
National Science Foundation, Smithsonian Institution, National Aeronautics and Space Administration, Oak Ridge Associated Universities, California Institute of Technology, University of Hawai'i, Space Telescope Science Institute, UK Research and Innovation, National Radio Astronomy Observatory, Associated Universities, European Commission, Queen's University Belfast, National Research Foundation, Trinity College Dublin, Ministry of Education, Culture, Sports, Science and Technology, Academia Sinica, Aalto-Yliopisto, Queen's University, Bulgarian National Science Fund, Nuclear Safety and Security Commission, Korea Institute of Science and Technology, Korea Institute of Science and Technology Information, Korea Astronomy and Space Science Institute, National Research Foundation of Korea, Agenzia Spaziale Italiana, Liverpool John Moores University, Ministerio de Ciencia e Innovación, Istituto Nazionale di Astrofisica, Stockholms Universitet, Junta de Andalucía, Istituto Nazionale di Fisica Nucleare, Instituto de Astrofísica de Andalucía, Korea Research Environment Open Network, Marshall Space Flight Center, Goddard Space Flight Center, Smithsonian Astrophysical Observatory, Science and Technology Facilities Council, Deutsches Elektronen-Synchrotron, Japan Society for the Promotion of Science, Consejo Superior de Investigaciones Científicas, Agencia Estatal de Investigación, Institut National de Physique Nucléaire et de Physique des Particules
Openalex Percentile: Top 1%
Astrophysics and Cosmic Phenomena
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