arXiv subjects

Hao-Qiang Zhang

Publications and source records attributed to Hao-Qiang Zhang.

3 recordsLinked to original sources

arXiv2026

Could the interaction of jet and SN ejecta be the cause of X-ray knots observed in a radio galaxy?

We investigate the interaction between relativistic jets and supernova (SN) ejecta as a potential origin of X-ray knots in radio galaxies, employing knot A in M 87 as a test case. By modeling the dynamical evolution of the interaction, we evaluate this scenario based on particle acceleration efficiency and spatial morphology. Our modeling indicates that the ejecta shock expands to only ~ 30 pc, which is inconsistent with the observed spatial scale of knot A (~ 60 pc). In contrast, the jet shock can successfully reproduce the observed scale after approximately 3000 yr, with the ejecta being accelerated to a bulk velocity of β~ 0.43. We fit the multi-wavelength spectral energy distribution (SED) using a one-zone leptonic framework, attributing the X-rays to synchrotron radiation from electrons accelerated up to~1 PeV at the jet shock. The derived magnetic field is approximately 70 uG in the SN ejecta rest frame, which is significantly below the equipartition value. Protons may be accelerated up to ~ EeV, supporting the hypothesis that the jets of radio galaxies (RGs) may be the potential site for ultra-high-energy cosmic-ray (UHECR) acceleration within the framework of the jet-ejecta interaction.

astro-ph.HE↗

arXiv2025

SN2023syz and SN2025cbj: Two Type IIn Supernovae Associated with IceCube High-energy Neutrinos

Type IIn supernovae (SNe IIn) are a subclass of core-collapse SNe in which strong interactions occur between the ejecta and dense circumstellar material, creating ideal conditions for the production of high-energy neutrinos. This makes them promising candidate sources of neutrinos. In this work, we conduct an association study between 163 SNe IIn observed by the Zwicky Transient Facility and 138 neutrino alert events detected by the IceCube neutrino observatory. After excluding alerts with poor localization, we find two SNe that are spatiotemporally coincident with neutrino events. IC231027A and IC250421A coincide with the positions of SN2023syz and SN2025cbj, respectively, within their localization uncertainties, and the neutrino arrival times are delayed by 38 days and 61 days relative to the discovery times of the corresponding SNe. Using Monte Carlo simulations, we estimate that the probability of such two coincidences occurring by chance in our sample is $p \sim 0.67\%$, suggesting that they may originate from genuine physical associations, though the result is not yet statistically significant. Our model calculations, however, indicate that the likelihood of a neutrino originating from IC231027A is low, implying that the association between IC231027A and SN2023syz is likely coincidental. Nevertheless, under optimistic parameters, the probability of detecting a neutrino from the whole SNe IIn sample could reach $\gtrsim6\%$, indicating that detecting neutrino emission from the SNe population may be possible. Our study provides a systematic analysis, combining statistical analysis and model calculations, to assess whether interacting supernovae can serve as potential sources of neutrino emission.

astro-ph.HE↗

arXiv2024

Revisit the Emission Polarization of the Internal-shock for the blazars' Jet

Recent Imaging X-ray Polarimetry Explorer (IXPE) observations of blazars tend to support the shock model for the X-ray emission, but report a low polarization degree ($Π\sim 10\%$) in X-rays compared with the previous theoretical expectations in the shock model. In order to reconcile the theoretical expectations with observations, we revisit the polarization of the shock emission by considering different kind of direction distribution for the shock-generated magnetic fields (sgMFs). Here, $w'_{\rm sg}\propto(\sinθ')^{ζ_{\rm sg}}$ with $θ'=0$ along the shock normal direction is used to describe the direction distribution of the sgMFs in the shock co-moving frame. It is found that the polarization in the X-ray and radio emission for a general jet in blazars can be described as $Π\sim 44.5[1-\exp(-ζ_{\rm sg}/2.6)]\%$ and $Π\sim 20[1-\exp(-ζ_{\rm sg}/2.4)]\%$, respectively. Correspondingly, one can have $ζ_{\rm sg}\sim 1-1.5$ according to the IXPE observations. Besides the sgMFs, the magnetic fields generated by the Richmyer-Meshkov instability (rmMFs) is supposed to present in the jets. The direction of the rmMFs is mainly distributed along the shock normal in the simulations and thus $w'_{\rm rm}\propto(\cos θ')^{ζ_{\rm rm}}$ is adopted to describe the direction distribution of rmMFs. We find that the rmMFs is likely to significantly affect the polarization properties at the low-frequency emission, especially when the sgMFs decay rapidly. Based on the contemporaneous radio and X-ray observations, we find the the emission of the electrons in the rmMFs make a significant contribution in the low-frequency emission and the the ordered background magnetic fields (obMFs) can be neglected.

astro-ph.HE↗