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Multi-messenger flare in the quasar PKS 0446+11

Y. Y. Kovalev, M. F. Aller, A. K. Erkenov, J. L. Gómez, D. C. Homan, P. I. Kivokurtseva, Yu. A. Kovalev, M. L. Lister, P. V. de la Parra, A. V. Plavin, A. V. Popkov, A. B. Pushkarev, A. C. S. Readhead, E. Shablovinskaia, Yu. V. Sotnikova, O. I. Spiridonova, S. V. Troitsky, V. V. Vlasyuk

TL;DR

The study investigates a multi-messenger flare in the blazar PKS 0446+11 that coincides with the IceCube-240105A high-energy neutrino. Using contemporaneous gamma-ray, X-ray, optical, and radio data plus MOJAVE VLBA polarization, the authors fit a single-zone leptohadronic SED with proton injection and a Doppler-boost increase from $\delta=18$ to $\delta=24$, placing the neutrino-emitting region beyond the BLR. A $\sim90^{\circ}$ EVPA flip and a sub-degree viewing angle $\theta$ imply extreme beaming near the jet base, supporting a shock-formation scenario during the flare. The results bolster the case that blazars are efficient hadron accelerators and notable contributors to the high-energy neutrino flux, underscoring the importance of rapid multi-messenger observations to constrain jet physics.

Abstract

The physical mechanisms driving neutrino and electromagnetic flares in blazars remain poorly understood. We investigate a prominent multi-messenger flare in the quasar PKS 0446+11 to identify the processes responsible for its high-energy emission. We analyze the IceCube-240105A high-energy neutrino event together with contemporaneous observations in the gamma-ray, X-ray, optical, and radio bands. The on- and off-flare spectral energy distributions (SEDs) are modeled within a single-zone leptohadronic framework. Multi-epoch VLBA observations from the MOJAVE program provide parsec-scale polarization data that complement the multi-wavelength light curves. No significant time delay is detected between the neutrino arrival and the flares in different energy bands. This is consistent with an extremely small jet viewing angle below 1 deg, inferred from the parsec-scale polarization structure. The flare can be reproduced by the injection of a proton population and an increase of the Doppler factor from 18 to 24. We also detect an approximately 90 deg rotation of the EVPA in the parsec-scale core during the initial phase of the flare, indicating the emergence of a shock formed by the change in the bulk plasma speed. Our comprehensive multi-messenger analysis demonstrates that the extreme beaming and sub-degree viewing angle of this distant blazar can account for the observed neutrino and electromagnetic activity. These findings strengthen the case for blazars as efficient accelerators of hadrons and as significant contributors to the observed high-energy neutrino flux.

Multi-messenger flare in the quasar PKS 0446+11

TL;DR

The study investigates a multi-messenger flare in the blazar PKS 0446+11 that coincides with the IceCube-240105A high-energy neutrino. Using contemporaneous gamma-ray, X-ray, optical, and radio data plus MOJAVE VLBA polarization, the authors fit a single-zone leptohadronic SED with proton injection and a Doppler-boost increase from to , placing the neutrino-emitting region beyond the BLR. A EVPA flip and a sub-degree viewing angle imply extreme beaming near the jet base, supporting a shock-formation scenario during the flare. The results bolster the case that blazars are efficient hadron accelerators and notable contributors to the high-energy neutrino flux, underscoring the importance of rapid multi-messenger observations to constrain jet physics.

Abstract

The physical mechanisms driving neutrino and electromagnetic flares in blazars remain poorly understood. We investigate a prominent multi-messenger flare in the quasar PKS 0446+11 to identify the processes responsible for its high-energy emission. We analyze the IceCube-240105A high-energy neutrino event together with contemporaneous observations in the gamma-ray, X-ray, optical, and radio bands. The on- and off-flare spectral energy distributions (SEDs) are modeled within a single-zone leptohadronic framework. Multi-epoch VLBA observations from the MOJAVE program provide parsec-scale polarization data that complement the multi-wavelength light curves. No significant time delay is detected between the neutrino arrival and the flares in different energy bands. This is consistent with an extremely small jet viewing angle below 1 deg, inferred from the parsec-scale polarization structure. The flare can be reproduced by the injection of a proton population and an increase of the Doppler factor from 18 to 24. We also detect an approximately 90 deg rotation of the EVPA in the parsec-scale core during the initial phase of the flare, indicating the emergence of a shock formed by the change in the bulk plasma speed. Our comprehensive multi-messenger analysis demonstrates that the extreme beaming and sub-degree viewing angle of this distant blazar can account for the observed neutrino and electromagnetic activity. These findings strengthen the case for blazars as efficient accelerators of hadrons and as significant contributors to the observed high-energy neutrino flux.

Paper Structure

This paper contains 15 sections, 5 figures, 1 table.

Table of Contents

  1. Introduction
  2. Observational data
  3. The radio-to-gamma light curve and VLBA observations
  4. A collection of calibrated data for SED
  5. Neutrino
  6. A single-zone SED model
  7. The 90-deg EVPA flip in the parsec-scale core
  8. The jet viewing angle and Lorentz factor
  9. Multi-messenger flare coincidence and the gamma-ray-to-radio delay
  10. Summary
  11. Electromagnetic observations of PKS 0446+11, data processing and calibration
  12. Radio band
  13. Optical band
  14. X-ray band
  15. Gamma-ray band

Figures (5)

  • Figure 1: Multi-band light curve for PKS 0446+11, shown for the time range around the high energy neutrino arrival time. From top to bottom: gamma-ray, X-ray, optical, radio light curves. They are supplemented by RATAN spectral index $\alpha$, calculated for $S\propto\nu^{+\alpha}$ between 5 and 22 GHz, and electric vector position angle (EVPA) of the parsec-scale core at 15 GHz, with a gray stripe of a $90^\circ$ width. Uncertainties are shown as $1\sigma$ values. The IceCube-240105A neutrino event epoch is shown by the vertical red dashed line. See details in \ref{['s:data']} and \ref{['sa:obs']}.
  • Figure 2: A set of polarization MOJAVE images, observed by the VLBA at 15 GHz. The images are reconstructed using the CLEAN method and the same circular restoring beam, its FWHM size of 0.7 mas is shown in the bottom left corner. Stokes I is indicated by contours, with fractional polarization superimposed in false color. Stokes I contours start from a $4\sigma$ rms level. The EVPA is indicated by sticks. Drastic changes in the polarization direction around the neutrino arrival (5 January 2024) are readily apparent, see also \ref{['f:lc']}.
  • Figure 3: Top: Combined Spectral Energy Distribution (SED) for the quasar PKS 0446+11, bottom left: the off flare period, bottom right: the on flare period. The total photon spectrum is shown as a thick red curve. The pink dashed line represents the neutrino spectrum (all flavors). The orange curve gives the sum of synchrotron and Compton emissions from injected electrons, while the black one is the synchrotron emission from injected protons. The green and blue curves present the synchrotron emission from $e^+e^-$ pairs generated via the Bethe–Heitler process and $\gamma \gamma$ annihilation, respectively. See the text for discussion of the observational data points.
  • Figure 4: MOJAVE 15 GHz VLBA epoch with the weakest core emission. Stokes I is shown by contours, while fractional linear polarization by false color and EVPA direction by sticks. Stokes I contours start from a $2.5\sigma$ level. The beam is presented at the Full Width at Half Maximum (FWHM) level as an elliptical Gaussian in the bottom left corner. A radial pattern of EVPA directions is readily apparent, indicating close to a face-on viewing angle, see \ref{['s:eye']}. This effect clearly seen in epochs with low core dominance because of dynamic range limitations: compare to \ref{['f:MOJAVE_pol']}. Note that \ref{['f:MOJAVE_pol']} color bar has a different scale, reflecting changes in the core polarization fraction over time.
  • Figure 5: The full multi-band light curve for PKS 0446+11. See detailed comments in \ref{['f:lc']}.