X-Ray Polarization of BL Lacertae in Outburst
: Peirson Abel L., Negro Michela, Liodakis Ioannis, Middei Riccardo, Kim Dawoon E., Marscher Alan P., Marshall Herman L., Pacciani Luigi, Romani Roger W., Wu Kinwah, Di Marco Alessandro, Di Lalla Niccoló, Omodei Nicola, Jorstad Svetlana G., Agudo Iván, Kouch Pouya M., Lindfors Elina, Aceituno Francisco José, Bernardos Maria I., Bonnoli Giacomo, Casanova Víctor, García-Comas Maya, Agís-González Beatriz, Husillos César, Marchini Alessandro, Sota Alfredo, Casadio Carolina, Escudero Juan, Myserlis Ioannis, Sievers Albrecht, Gurwell Mark, Rao Ramprasad, Imazawa Ryo, Sasada Mahito, Fukazawa Yasushi, Kawabata Koji S., Uemura Makoto, Mizuno Tsunefumi, Nakaoka Tatsuya, Akitaya Hiroshi, Cheong Yeon, Jeong Hyeon-Woo, Kang Sincheol, Kim Sang-Hyun, Lee Sang-Sung, Angelakis Emmanouil, Kraus Alexander, Cibrario Nicoló, Donnarumma Immacolata, Poutanen Juri, Tavecchio Fabrizio, Antonelli Lucio A., Bachetti Matteo, Baldini Luca, Baumgartner Wayne H., Bellazzini Ronaldo, Bianchi Stefano, Bongiorno Stephen D., Bonino Raffaella, Brez Alessandro, Bucciantini Niccoló, Capitanio Fiamma, Castellano Simone, Cavazzuti Elisabetta, Chen Chien-Ting, Ciprini Stefano, Costa Enrico, De Rosa Alessandra, Del Monte Ettore, Di Gesu Laura, Doroshenko Victor, Dovčiak Michal, Ehlert Steven R., Enoto Teruaki, Evangelista Yuri, Fabiani Sergio, Ferrazzoli Riccardo, Garcia Javier A., Gunji Shuichi, Hayashida Kiyoshi, Heyl Jeremy, Iwakiri Wataru, Kaaret Philip, Karas Vladimir, Kitaguchi Takao, Kolodziejczak Jeffery J., Krawczynski Henric, La Monaca Fabio, Latronico Luca, Madejski Grzegorz, Maldera Simone, Manfreda Alberto, Marin Frédéric, Marinucci Andrea, Massaro Francesco, Matt Giorgio, Mitsuishi Ikuyuki, Muleri Fabio, Ng C.-Y., O'Dell Stephen L., Oppedisano Chiara, Papitto Alessandro, Pavlov George G., Perri Matteo, Pesce-Rollins Melissa, Petrucci Pierre-Olivier, Pilia Maura, Possenti Andrea, Puccetti Simonetta, Ramsey Brian D., Rankin John, Ratheesh Ajay, Roberts Oliver J., Sgró Carmelo, Slane Patrick, Soffitta Paolo, Spandre Gloria, Swartz Douglas A., Tamagawa Toru, Taverna Roberto, Tawara Yuzuru, Tennant Allyn F., Thomas Nicholas E., Tombesi Francesco, Trois Alessio, Tsygankov Sergey, Turolla Roberto, Vink Jacco, Weisskopf Martin C., Xie Fei, Zane Silvia
Publisher: Institute of Physics Publishing
: 2023
: Astrophysical Journal Letters
: Astrophysical Journal Letters
: L25
: 948
: 2
: 2041-8213
DOI: https://doi.org/10.3847/2041-8213/acd242(external)
: https://iopscience.iop.org/article/10.3847/2041-8213/acd242(external)
: https://research.utu.fi/converis/portal/detail/Publication/179844827(external)
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 π2-4KeV = 21.7-7.9+5.6 % and electric vector polarization angle ψ2–4keV = −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.
