X-Ray Polarization of BL Lacertae in Outburst

Abel L. Peirson, Michela Negro, Ioannis Liodakis, Riccardo Middei, Dawoon E. Kim, Alan P. Marscher, Herman L. Marshall, Luigi Pacciani, Roger W. Romani, Kinwah Wu, Alessandro Di Marco, Niccoló Di Lalla, Nicola Omodei, Svetlana G. Jorstad, Iván Agudo, Pouya M. Kouch, Elina Lindfors, Francisco José Aceituno, Maria I. Bernardos, Giacomo BonnoliVíctor Casanova, Maya García-Comas, Beatriz Agís-González, César Husillos, Alessandro Marchini, Alfredo Sota, Carolina Casadio, Juan Escudero, Ioannis Myserlis, Albrecht Sievers, Mark Gurwell, Ramprasad Rao, Ryo Imazawa, Mahito Sasada, Yasushi Fukazawa, Koji S. Kawabata, Makoto Uemura, Tsunefumi Mizuno, Tatsuya Nakaoka, Hiroshi Akitaya, Yeon Cheong, Hyeon Woo Jeong, Sincheol Kang, Sang Hyun Kim, Sang Sung Lee, Emmanouil Angelakis, Alexander Kraus, Nicoló Cibrario, Immacolata Donnarumma, 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, Elisabetta Cavazzuti, Chien Ting Chen, Stefano Ciprini, Enrico Costa, Alessandra De Rosa, Ettore Del Monte, Laura Di Gesu, 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, Philip Kaaret, Vladimir Karas, Takao Kitaguchi, Jeffery J. Kolodziejczak, Henric Krawczynski, Fabio La Monaca, Luca Latronico, Grzegorz Madejski, Simone Maldera, Alberto Manfreda, Frédéric Marin, Andrea Marinucci, Francesco Massaro, Giorgio Matt, Ikuyuki Mitsuishi, Fabio Muleri, C. Y. Ng, Stephen L. O’Dell, Chiara Oppedisano, Alessandro Papitto, George G. Pavlov, Matteo Perri, Melissa Pesce-Rollins, Pierre Olivier Petrucci, Maura Pilia, Andrea Possenti, Simonetta Puccetti, Brian D. Ramsey, John Rankin, Ajay Ratheesh, Oliver J. Roberts, Carmelo Sgró, Patrick Slane, Paolo Soffitta, Gloria Spandre, Douglas A. Swartz, 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, Fei Xie, Silvia Zane

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Abstract

We report the first >99% confidence detection of X-ray polarization in BL Lacertae. During a recent X-ray/γ-ray outburst, a 287 ks observation (2022 November 27-30) was taken using the Imaging X-ray Polarimetry Explorer (IXPE), together with contemporaneous multiwavelength observations from the Neil Gehrels Swift observatory and XMM-Newton in soft X-rays (0.3-10 keV), NuSTAR in hard X-rays (3-70 keV), and optical polarization from the Calar Alto and Perkins Telescope observatories. Our contemporaneous X-ray data suggest that the IXPE energy band is at the crossover between the low- and high-frequency blazar emission humps. The source displays significant variability during the observation, and we measure polarization in three separate time bins. Contemporaneous X-ray spectra allow us to determine the relative contribution from each emission hump. We find >99% confidence X-ray polarization Π 2 - 4 keV = 21.7 − 7.9 + 5.6 % and electric vector polarization angle ψ 2-4keV = −28.°7 ± 8.°7 in the time bin with highest estimated synchrotron flux contribution. We discuss possible implications of our observations, including previous IXPE BL Lacertae pointings, tentatively concluding that synchrotron self-Compton emission dominates over hadronic emission processes during the observed epochs.

Original languageEnglish (US)
Article numberL25
JournalAstrophysical Journal Letters
Volume948
Issue number2
DOIs
StatePublished - May 1 2023

All Science Journal Classification (ASJC) codes

  • Astronomy and Astrophysics
  • Space and Planetary Science

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