X-Ray Polarization Variability of High Spectral Peak BL Lacertaes: Cases of 1ES 1959+650 and PKS 2155–304

Abstract The high-energy-peaked BL Lacertae objects (HBLs) are the main targets of the Imaging X-ray Polarimetry Explorer (IXPE) for investigating the mechanisms of radiation and particle acceleration in jets. In this Letter, we report the first IXPE observations of two HBLs, 1ES 1959+650 and PKS 21...

Full description

Saved in:
Bibliographic Details
Published in:Astrophysical journal. Letters 2024-03, Vol.963 (2), p.L41
Main Authors: Hu, Xin-Ke, Yu, Yu-Wei, Zhang, Jin, Wu, Tan-Zheng, Lian, Ji-Shun, Wang, Xiang-Gao, Zhang, Hai-Ming, Liang, En-Wei
Format: Article
Language:English
Subjects:
Active galactic nuclei
BL Lacertae objects
Blazars
Confidence intervals
Energy bands
Particle acceleration
Polarimetry
Polarization
X ray imagery
X-ray active galactic nuclei
X-rays
Citations: Items that this one cites
Items that cite this one
Online Access:Get full text
Tags: Add Tag
No Tags, Be the first to tag this record!
Description
Summary:Abstract The high-energy-peaked BL Lacertae objects (HBLs) are the main targets of the Imaging X-ray Polarimetry Explorer (IXPE) for investigating the mechanisms of radiation and particle acceleration in jets. In this Letter, we report the first IXPE observations of two HBLs, 1ES 1959+650 and PKS 2155–304. Both sources exhibit X-ray polarization with a confidence level exceeding 99%, as well as significant variability in polarization across different time intervals and energy ranges. Notably, PKS 2155–304 demonstrates the highest X-ray polarization among all blazars detected by IXPE within its entire energy band (2–8 keV), with a polarization degree of Π X = 21.9% ± 1.9% (MDP 99 ∼ 6.0%). An even higher polarization is observed in the 3–4 keV band, reaching Π X = 28.6% ± 2.7% (MDP 99 ∼ 8.1%) with a confidence level of 10.8 σ . Furthermore, no polarization is detected above the 5 keV energy band. For 1ES 1959+650, the highest detected polarization degree in the 2–8 keV band is Π X = 12.4% ± 0.7% (MDP 99 ∼ 2.2%), with an electric vector position angle (EVPA) of ψ X = 19.°7 ± 1.°6. The X-ray polarization of 1ES 1959+650 exhibits evident variability, accompanied by the variations of ψ X , flux, spectrum, and energy bin. We discuss possible implications of these observational findings, including the variability in polarization, rotation of EVPA, and transition between synchrotron and synchrotron–self-Compton. We speculate that the X-rays observed during different IXPE observations originate from distinct regions in the jet and may involve diverse mechanisms for particle acceleration.
ISSN:2041-8205
2041-8213
DOI:10.3847/2041-8213/ad2a4f