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X-ray Polarization Observations of BL Lacertae

Middei, R; Liodakis, I; Perri, M; Puccetti, S; Cavazzuti, E; Di Gesu, L; Ehlert, SR; ... Zane, S; + view all (2023) X-ray Polarization Observations of BL Lacertae. The Astrophysical Journal Letters , 942 (1) , Article L10. 10.3847/2041-8213/aca281. Green open access

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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 ΠX < 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.

Type: Article
Title: X-ray Polarization Observations of BL Lacertae
Open access status: An open access version is available from UCL Discovery
DOI: 10.3847/2041-8213/aca281
Publisher version: https://doi.org/10.3847/2041-8213/aca281
Language: English
Additional information: Original content from this work may be used under the terms of the Creative Commons Attribution 4.0 licence. Any further distribution of this work must maintain attribution to the author(s) and the title of the work, journal citation and DOI.
UCL classification: UCL
UCL > Provost and Vice Provost Offices > UCL BEAMS
UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences
UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences > Dept of Space and Climate Physics
URI: https://discovery.ucl.ac.uk/id/eprint/10159306
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