X-Ray Polarization Observations of BL Lacertae

Riccardo Middei , Ioannis Liodakis , Matteo Perri , Simonetta Puccetti , Elisabetta Cavazzuti , Laura Di Gesu , Steven R. Ehlert , Grzegorz Madejski , Alan P. Marscher , Herman L. Marshall , Fabio Muleri , Michela Negro , Svetlana G. Jorstad , Beatriz Agís-González , Iván Agudo , Giacomo Bonnoli , Maria I. Bernardos , Víctor Casanova , Maya García-Comas , César Husillos , Alessandro Marchini , Alfredo Sota , Pouya M. Kouch , Elina Lindfors , George A. Borman , Evgenia N. Kopatskaya , Elena G. Larionova , Daria A. Morozova , Sergey S. Savchenko , Andrey A. Vasilyev , Alexey V. Zhovtan , Carolina Casadio , Juan Escudero , Ioannis Myserlis , Antonio Hales , Seiji Kameno , Ruediger Kneissl , Hugo Messias , Hiroshi Nagai , Dmitry Blinov , Ioakeim G. Bourbah , Sebastian Kiehlmann , Evangelos Kontopodis , Nikos Mandarakas , Stylianos Romanopoulos , Raphael Skalidis , Anna Vervelaki , Joseph R. Masiero , Dimitri Mawet , Maxwell A. Millar-Blanchaer , Georgia V. Panopoulou , Samaporn Tinyanont , Andrei V. Berdyugin , Masato Kagitani , Vadim Kravtsov , Takeshi Sakanoi , Ryo Imazawa , Mahito Sasada , Yasushi Fukazawa , Koji S. Kawabata , Makoto Uemura , Tsunefumi Mizuno , Tatsuya Nakaoka , Hiroshi Akitaya , Mark Gurwell , Ramprasad Rao , Niccoló Di Lalla , Nicoló Cibrario , Immacolata Donnarumma , Dawoon E. Kim , Nicola Omodei , Luigi Pacciani , Juri Poutanen , Fabrizio Tavecchio , Lucio A. Antonelli , Matteo Bachetti , Luca Baldini , Wayne H. Baumgartner , Ronaldo Bellazzini , Stefano Bianchi , Stephen D. Bongiorno , Raffaella Bonino , Alessandro Brez , Niccoló Bucciantini , Fiamma Capitanio , Simone Castellano , Stefano Ciprini , Enrico Costa , Alessandra de Rosa , Ettore del Monte , Alessandro Di Marco , Victor Doroshenko , Michal Dovčiak , 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 (1) , Andrea Marinucci , Francesco Massaro , Giorgio Matt , Ikuyuki Mitsuishi , C. -Y. Ng , Stephen L. O'Dell , Chiara Oppedisano , Alessandro Papitto , George G. Pavlov , Abel L. Peirson , Melissa Pesce-Rollins , Pierre-Olivier Petrucci (2) , Maura Pilia , Andrea Possenti , Brian D. Ramsey , John Rankin , Ajay Ratheesh , Roger W. Romani , Carmelo Sgró , Patrick Slane , Paolo Soffitta , Gloria Spandre , Toru Tamagawa , Roberto Taverna , Yuzuru Tawara , Allyn F. Tennant , Nicholas E. Thomas , Francesco Tombesi , Alessio Trois , Sergey Tsygankov , Roberto Turolla , Jacco Vink , Martin C. Weisskopf , Kinwah Wu , Fei Xie , Silvia Zane

1 ObAS - Observatoire astronomique de Strasbourg
2 IPAG - Institut de Planétologie et d'Astrophysique de Grenoble

Blazars are a class of jet-dominated active galactic nuclei with a typical double-humped spectral energy distribution. It is of common consensus that the synchrotron emission is responsible for the low frequency peak, while the origin of the high frequency hump is still debated. The analysis of X-rays and their polarization can provide a valuable tool to understand the physical mechanisms responsible for the origin of high-energy emission of blazars. We report the first observations of BL Lacertae (BL Lac) performed with the Imaging X-ray Polarimetry Explorer, from which an upper limit to the polarization degree Π _X < 12.6% was found in the 2-8 keV band. We contemporaneously measured the polarization in radio, infrared, and optical wavelengths. Our multiwavelength polarization analysis disfavors a significant contribution of proton-synchrotron radiation to the X-ray emission at these epochs. Instead, it supports a leptonic origin for the X-ray emission in BL Lac.

Keywords: Relativistic jets; X-ray active galactic nuclei; Active galactic nuclei; Blazars; Spectropolarimetry; Astrophysics - High Energy Astrophysical Phenomena; Astrophysics - Astrophysics of Galaxies

Domains: Sciences of the Universe [physics]

Riccardo Middei, Ioannis Liodakis, Matteo Perri, Simonetta Puccetti, Elisabetta Cavazzuti, et al.. X-Ray Polarization Observations of BL Lacertae. The Astrophysical journal letters, 2023, 942, ⟨10.3847/2041-8213/aca281⟩. ⟨insu-03920568⟩