X-ray Polarization Observations of BL Lacertae
Creators: name: Middei, Riccardo
name: Liodakis, Ioannis
name: Perri, Matteo
name: Puccetti, Simonetta
name: Cavazzuti, Elisabetta
name: Di Gesu, Laura
name: Ehlert, Steven R.
name: Madejski, Grzegorz
name: Marscher, Alan P.
name: Marshall, Herman L.
name: Muleri, Fabio
name: Negro, Michela
name: Jorstad, Svetlana G.
name: Agís-González, Beatriz
name: Agudo, Iván
name: Bonnoli, Giacomo
name: Bernardos, Maria I.
name: Casanova, Víctor
name: García-Comas, Maya
name: Husillos, César
name: Marchini, Alessandro
name: Sota, Alfredo
name: Kouch, Pouya M.
name: Borman, George A.
name: Kopatskaya, Evgenia N.
name: Larionova, Elena G.
name: Morozova, Daria A.
name: Savchenko, Sergey S.
name: Vasilyev, Andrey A.
name: Zhovtan, Alexey V.
name: Casadio, Carolina
name: Escudero, Juan
name: Myserlis, Ioannis
name: Hales, Antonio
name: Kameno, Seiji
name: Kneissl, Ruediger
name: Messias, Hugo
name: Nagai, Hiroshi
name: Blinov, Dmitry
name: Bourbah, Ioakeim G.
name: Kiehlmann, Sebastian
name: Kontopodis, Evangelos
name: Mandarakas, Nikos
name: Romanopoulos, Stylianos
name: Skalidis, Raphael
name: Vervelaki, Anna
name: Masiero, Joseph R.
name: Mawet, Dimitri
name: Millar-Blanchaer, Maxwell A.
name: Panopoulou, Georgia V.
name: Tinyanont, Samaporn
name: Berdyugin, Andrei V.
name: Kagitani, Masato
name: Kravtsov, Vadim
name: Sakanoi, Takeshi
name: Imazawa, Ryo
name: Sasada, Mahito
name: Fukazawa, Yasushi
name: Kawabata, Koji S.
name: Uemura, Makoto
name: Mizuno, Tsunefumi
name: Nakaoka, Tatsuya
name: Akitaya, Hiroshi
name: Gurwell, Mark
name: Rao, Ramprasad
name: Di Lalla, Niccoló
name: Cibrario, Nicoló
name: Donnarumma, Immacolata
name: Kim, Dawoon E.
name: Omodei, Nicola
name: Pacciani, Luigi
name: Poutanen, Juri
name: Tavecchio, Fabrizio
name: Antonelli, Lucio A.
name: Bachetti, Matteo
name: Baldini, Luca
name: Baumgartner, Wayne H.
name: Bellazzini, Ronaldo
name: Bianchi, Stefano
name: Bongiorno, Stephen D.
name: Bonino, Raffaella
name: Brez, Alessandro
name: Bucciantini, Niccoló
name: Capitanio, Fiamma
name: Castellano, Simone
name: Ciprini, Stefano
name: Costa, Enrico
name: De Rosa, Alessandra
name: Del Monte, Ettore
name: Di Marco, Alessandro
name: Doroshenko, Victor
name: Dovčiak, Michal
name: Enoto, Teruaki
name: Evangelista, Yuri
name: Fabiani, Sergio
name: Ferrazzoli, Riccardo
name: Garcia, Javier A.
name: Gunji, Shuichi
name: Hayashida, Kiyoshi
name: Heyl, Jeremy
name: Iwakiri, Wataru
name: Karas, Vladimir
name: Kitaguchi, Takao
name: Kolodziejczak, Jeffery J.
name: Krawczynski, Henric
name: La Monaca, Fabio
name: Latronico, Luca
name: Maldera, Simone
name: Manfreda, Alberto
name: Marin, Frédéric
name: Marinucci, Andrea
name: Massaro, Francesco
name: Matt, Giorgio
name: Mitsuishi, Ikuyuki
name: Ng, C. -Y.
name: O'Dell, Stephen L.
name: Oppedisano, Chiara
name: Papitto, Alessandro
name: Pavlov, George G.
name: Peirson, Abel L.
name: Pesce-Rollins, Melissa
name: Petrucci, Pierre-Olivier
name: Pilia, Maura
name: Possenti, Andrea
name: Ramsey, Brian D.
name: Rankin, John
name: Ratheesh, Ajay
name: Romani, Roger W.
name: Sgró, Carmelo
name: Slane, Patrick
name: Soffitta, Paolo
name: Spandre, Gloria
name: Tamagawa, Toru
name: Taverna, Roberto
name: Tawara, Yuzuru
name: Tennant, Allyn F.
name: Thomas, Nicholas E.
name: Tombesi, Francesco
name: Trois, Alessio
name: Tsygankov, Sergey
name: Turolla, Roberto
name: Vink, Jacco
name: Weisskopf, Martin C.
name: Wu, Kinwah
name: Xie, Fei
name: Zane, Silvia
Publisher: name: arXiv
Year: 2022
Subjects: subject: High Energy Astrophysical Phenomena (astro-ph.HE)
subject: Astrophysics of Galaxies (astro-ph.GA)
subject: FOS: Physical sciences
subject: FOS: Physical sciences

description: Blazars are a class of jet-dominated active galactic nuclei with a typical double-humped spectral energy distribution. It is of common consensus the Synchrotron emission to be 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 performed with the Imaging X-ray Polarimetry Explorer ({IXPE}), from which an upper limit to the polarization degree $Π_X&lt;$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.
description: 17 pages, 5 figures, accepted for publication in ApJL