Looking into the Jet Cone of the Neutrino-Associated Very High Energy Blazar PKS 1424+240
arXiv:2504.09287 · doi:10.1051/0004-6361/202555400
Abstract
The acceleration process of massive particles as well as the production of very high energy (VHE) photons and neutrinos remains a fundamental challenge in astrophysics. We investigate the parsec-scale jet structure and magnetic field of the blazar PKS 1424+240, that has been selected on the basis of strong VHE gamma-ray emission and identified with one of the highest peaks in the IceCube 9-year neutrino sky. We analyze 15 GHz VLBA observations of this BL Lac object, stacking 42 polarization-sensitive images collected in 2009-2025 to enhance the signal and reveal persistent parsec-scale structure. Our observations uncover a rare scenario. The object is viewed inside the jet cone, very close to the axis of its relativistic jet, with a viewing angle of <0.6 deg. This effectively maximizes Doppler boosting to values ~30 and enhances both electromagnetic and neutrino emission in the observer's direction. Based on polarimetric observations, we unambiguously detect a net toroidal component of the jet's magnetic field, indicating a current carrying jet flowing almost directly towards our line of sight. Blazars with very small jet viewing angles offer a solution to the longstanding mismatch between Doppler factors inferred from low VLBI apparent jet speed and those derived from VHE observations -- the so-called "Doppler factor crisis". We show that relativistic beaming plays the critical role in the gamma-ray and neutrino emission of blazars, with direct implications for models of their multi-messenger emission.
5 pages, 5 figures; accepted by A&A Letters
References in corpus (15)
- Five-Year Wilkinson Microwave Anisotropy Probe (WMAP) Observations: Cosmological Interpretation
- Evidence for neutrino emission from the nearby active galaxy NGC 1068
- Magnetic acceleration of relativistic AGN jets
- MOJAVE: XV. VLBA 15 GHz Total Intensity and Polarization Maps of 437 Parsec-Scale AGN Jets From 1996-2017
- MOJAVE. XVII. Jet Kinematics and Parent Population Properties of Relativistically Beamed Radio-Loud Blazars
- MOJAVE: XVIII. Kinematics and Inner Jet Evolution of Bright Radio-Loud Active Galaxies
- Directional association of TeV to PeV astrophysical neutrinos with radio blazars
- MOJAVE XIX: Brightness Temperatures and Intrinsic Properties of Blazar Jets
- On the redshift of TeV BL Lac objects
- The Radio Fundamental Catalogue. I. Astrometry
- MOJAVE. XX. Persistent Linear Polarization Structure in Parsec-scale AGN Jets
- PKS 1424+240: yet another masquerading BL Lac object as a possible IceCube neutrino source
- Luminous and high-frequency peaked blazars: the origin of the -ray emission from PKS 1424+240
- MOJAVE XXI. Decade-long linear polarization variability in AGN jets at parsec scales
- Neutrino production in blazar radio cores