Tracking Down the Broadband Polarimetric Properties of PG 1553+113

Middei R, Jorstad SG, Marscher AP, Liodakis I, Perri M, Maselli A, Ciprini S, Nardini E, Puccetti S, Di Gesu L, Agudo I, Kim DE, Myserlis I, Trindade Falcão A, Król D, Antonelli LA, Aniello T, Kouch PM, Nilsson K, Lindfors E, Pursimo T, Aceituno FJ, Casanova V, Emery G, Pedrosa JE, Otero-Santos J, Sota A, Piirola V, Borman GA, Grishina TS, Hagen-Thorn VA, Kopatskaya EN, Larionova EG, Morozova DA, Savchenko SS, Shishkina EV, Troitskiy IS, Troitskaya YV, Vasilyev AA, Zhovtan AV, Benke P, Debbrecht L, Eich J, Eppel F, Gokus A, Hämmerich S, Hessdörfer J, Kadler M, Kirchner D, Paraschos GF, Rösch F, Schulga W, Gurwell M, Keating G, Rao R, Angelakis E, Kraus A, Agís-González B, Blinov D, Glykopoulou A, Capecchiacci S, Floris A, Fotis P, Koukoutsi A, Kypriotakis JA, Langis DA, Rompogiannakis D, Polychronakis A, Tsioupli V, Vogiatzis S, Zoumpoulakis O, Tochihara S, Imazawa R, Sasada M, Fukazawa Y, Kawabata KS, Uemura M, Mizuno T, Nakaoka T, Akitaya H, Akai T (2026)

Publication Type: Journal article

Publication year: 2026

Journal

Book Volume: 1004

Article Number: 130

Journal Issue: 1

DOI: 10.3847/1538-4357/ae6cf0

Abstract

We report on a nine-month monitoring campaign of the blazar PG 1553+113, relying on three observations carried out in 2025 with the Imaging X-ray Polarimetry Explorer (IXPE) and supported by multiwavelength facilities. The source displayed pronounced variability across the electromagnetic spectrum, with X-ray flux changes by up to a factor of ∼5 and complex evolution of the optical polarization properties, including one of the largest (exceeding 150°) and fastest rotations in the electric vector position angle (EVPA) ever recorded. This swing of the EVPA was also accompanied by a temporary drop of the optical polarization degree to nearly zero. Significant X-ray polarization was observed during the third IXPE pointing, with a polarization degree ΠX  = (18.4 ± 5.8)% and ΨX  =  74° ± 9° in the 2–8 keV band, while only upper limits were obtained in the first two epochs. The optical data show that the second IXPE observation occurred shortly after a dramatic optical polarization event characterized by a rapid EVPA swing and strong depolarization. Two possible scenarios may explain the broadband polarimetric behavior: (i) the superposition of two emitting regions with nearly orthogonal magnetic field configurations and variable relative contributions, and (ii) the interaction of a single emitting region with a shock that temporarily reorders the magnetic field. In both cases, the data support a picture in which the X-ray and optical emissions arise from closely related but not strictly cospatial regions within a dynamically evolving, magnetically structured jet.

Authors with CRIS profile

Involved external institutions

Max-Planck-Institut für Radioastronomie / Max Planck Institute for Radio Astronomy Germany (DE) Foundation for Research and Technology-Hellas (FORTH) / Ίδρυμα Τεχνολογίας και Έρευνας Greece (GR) University of Crete / Πανεπιστήμιο Κρήτης Greece (GR) Hiroshima University / 広島大学 Japan (JP) Institute of Science Tokyo (ISCT) / 東京科学大学 Japan (JP) Saint Petersburg State University (SPbU) / Санкт-Петербургский государственный университет (СПбГУ) Russian Federation (RU) Institute of Astrophysics of Andalusia / Instituto de Astrofísica de Andalucía (IAA-CSIC) Spain (ES) Smithsonian Institution United States (USA) (US) Chiba Institute of Technology / 千葉工業大学 Japan (JP) Turku University Hospital / Turun yliopistollinen keskussairaala (TYKS) Finland (FI) Crimean Astrophysical Observatory (CrAO) Ukraine (UA) National Institute for Astrophysics / Istituto Nazionale Astrofisica (INAF) Italy (IT) Boston University United States (USA) (US) Italian Space Agency / Agenzia Spaziale Italiana (ASI) Italy (IT) IRAM : Institut de Radioastronomie Millimétrique France (FR) National Aeronautics and Space Administration (NASA) United States (USA) (US) Nordic Optical Telescope Spain (ES) Julius-Maximilians-Universität Würzburg Germany (DE) Washington University in St. Louis United States (USA) (US) National and Kapodistrian University of Athens Greece (GR)

How to cite

APA:

Middei, R., Jorstad, S.G., Marscher, A.P., Liodakis, I., Perri, M., Maselli, A.,... Akai, T. (2026). Tracking Down the Broadband Polarimetric Properties of PG 1553+113. Astrophysical Journal, 1004(1). https://doi.org/10.3847/1538-4357/ae6cf0

MLA:

Middei, Riccardo, et al. "Tracking Down the Broadband Polarimetric Properties of PG 1553+113." Astrophysical Journal 1004.1 (2026).

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