Polarization and Multiwavelength Observations of Mrk 501 Reveal Polarization Variability across Different Energies and Fluxes
Xin-Ke HuGXU, Yu-Wei YuBIT, Jin ZhangBIT, Xiang-Gao WangGXU, Kishore C. PatraUC, Thomas G. BrinkUC, Wei-Kang ZhengUC, Qi WangGXU, De-Feng KongGXU, Liang-Jun ChenGXU, Ji-Wang ZhouGXU, Jia-Xin CaoGXU, Ming-Xuan LuGXU, Zi-Min ZhouGXU, Yi-Ning WeiGXU, Xin-Bo HuangGXU, Xing-Lin LiGXU, Hao LouGXU, Fei XieGXU, Ji-Rong MaoNYO, En-Wei LiangGXU, Alexei V. FilippenkoUC
arXiv:2402.11949v1 Announce Type: new
Abstract: Mrk 501 is a prototypical high-synchrotron-peaked blazar (HBL) and serves as one of the primary targets for the Imaging X-ray Polarimetry Explorer (IXPE). In this study, we report X-ray polarization measurements of Mrk 501 based on six IXPE observations. The $>99%$ confidence detection of X-ray polarization is obtained in four out of six observations in the entire energy band (2–8 keV) of IXPE, with a maximum polarization degree ($Pi_{rm X}$) of $15.8%pm2.8%$ and a polarization angle ($psi_{rm X}$) of $98.0^{circ}pm5.1^{circ}$ at a confidence level of $5.2sigma$. During the other two observations, the source only exhibits the $>99%$ confidence detection of X-ray polarization within an energy bin of 1 keV. Interestingly, both the second and sixth IXPE observations present energy-dependent variability in X-ray polarization, which is also observed in our optical spectropolarimetry. The chromatic behavior of $Pi$ and the consistent values of $psi$ across different frequencies, along with the agreement between $psi$ and jet position angle, strongly support the interpretation of the energy-stratified model with shock-accelerated particles in the jet of Mrk 501. Additionally, the possibility of the presence of a global helical magnetic field in the jet of Mrk 501 is discussed.arXiv:2402.11949v1 Announce Type: new
Abstract: Mrk 501 is a prototypical high-synchrotron-peaked blazar (HBL) and serves as one of the primary targets for the Imaging X-ray Polarimetry Explorer (IXPE). In this study, we report X-ray polarization measurements of Mrk 501 based on six IXPE observations. The $>99%$ confidence detection of X-ray polarization is obtained in four out of six observations in the entire energy band (2–8 keV) of IXPE, with a maximum polarization degree ($Pi_{rm X}$) of $15.8%pm2.8%$ and a polarization angle ($psi_{rm X}$) of $98.0^{circ}pm5.1^{circ}$ at a confidence level of $5.2sigma$. During the other two observations, the source only exhibits the $>99%$ confidence detection of X-ray polarization within an energy bin of 1 keV. Interestingly, both the second and sixth IXPE observations present energy-dependent variability in X-ray polarization, which is also observed in our optical spectropolarimetry. The chromatic behavior of $Pi$ and the consistent values of $psi$ across different frequencies, along with the agreement between $psi$ and jet position angle, strongly support the interpretation of the energy-stratified model with shock-accelerated particles in the jet of Mrk 501. Additionally, the possibility of the presence of a global helical magnetic field in the jet of Mrk 501 is discussed.