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arXiv · 2603.22403

Where within the 3C 84 jet are $\gamma$-rays produced?

Georgios F. Paraschos·Ioannis Liodakis·Svetlana Jorstad·Yuri Y. Kovalev·Sudip Chakraborty·Frederic Marin·Steven R. Ehlert·Efthalia Traianou·Lena C. Debbrecht·Ivan Agudo·Thibault Barnouin·Jacob J. Casey·Laura Di Gesu·Philip Kaaret·Dawoon E. Kim·Fabian Kislat·Ajay Ratheesh·M. Lynne Saade·Francesco Tombesi·Alan Marscher·Jose-Luis Gomez·Alexander B. Pushkarev·Tuomas Savolainen·Ioannis Myserlis·Mark Gurwell·Garrett Keating·Ramprasad Rao·Sincheol Kang·Sang-Sung Lee·Sanghyun Kim·Whee Yeon Cheong·Hyeon-Woo Jeong·Chanwoo Song·Shan Li·Myeong-Seok Nam·Diego Alvarez-Ortega·Carolina Casadio·Chien-Ting Chen·Enrico Costa·Eugene Churazov·Riccardo Ferrazzoli·Giorgio Galanti·Ildar Khabibullin·Stephen L. O'Dell·Luigi Pacciani·Marco Roncadelli·Oliver J. Roberts·Paolo Soffitta·Douglas A. Swartz·Fabrizio Tavecchio·Martin C. Weisskopf·Irina Zhuravleva
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Abstract

The location of $\gamma$-ray creation and emission within extra-galactic jets is a matter of active debate. One particularly well-suited source to pinpoint the location is the nearby, bright radio galaxy 3C 84, harbouring a powerful jet. Here we investigate the origin of $\gamma$-rays measured during a recent $\gamma$-ray flare, by analysing the linear polarisation signal of close-in-time very long baseline interferometry (VLBI) observations at centimetre and millimetre wavelengths. While 3C 84 is overall almost unpolarised, we find that close-in-time to the $\gamma$-ray flare peak regions at parsec-scale distances from the central engine shows a fractional linear polarisation increase. Under the physically well-motivated assumption of a causal relation between this polarisation enhancement and the $\gamma$-ray flare, and combined with insights from concurrent X-ray polarisation measurements, the $\gamma$-rays being created in this region is a physically motivated scenario, in a process consistent with synchrotron self-Compton.

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Georgios F. Paraschos, Ioannis Liodakis, Svetlana Jorstad, Yuri Y. Kovalev, Sudip Chakraborty, Frederic Marin, Steven R. Ehlert, Efthalia Traianou, Lena C. Debbrecht, Ivan Agudo, Thibault Barnouin, Jacob J. Casey, Laura Di Gesu, Philip Kaaret, Dawoon E. Kim, Fabian Kislat, Ajay Ratheesh, M. Lynne Saade, Francesco Tombesi, Alan Marscher, Jose-Luis Gomez, Alexander B. Pushkarev, Tuomas Savolainen, Ioannis Myserlis, Mark Gurwell, Garrett Keating, Ramprasad Rao, Sincheol Kang, Sang-Sung Lee, Sanghyun Kim, Whee Yeon Cheong, Hyeon-Woo Jeong, Chanwoo Song, Shan Li, Myeong-Seok Nam, Diego Alvarez-Ortega, Carolina Casadio, Chien-Ting Chen, Enrico Costa, Eugene Churazov, Riccardo Ferrazzoli, Giorgio Galanti, Ildar Khabibullin, Stephen L. O'Dell, Luigi Pacciani, Marco Roncadelli, Oliver J. Roberts, Paolo Soffitta, Douglas A. Swartz, Fabrizio Tavecchio, Martin C. Weisskopf, Irina Zhuravleva. 2026-03-23. Where within the 3C 84 jet are $\gamma$-rays produced?. https://doi.org/10.1051/0004-6361%2F202659250

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