Neutrino Emission from Gamma-ray Burst Jet Propagating inside the Cavity within Active Galactic Nucleus Accretion Disks

TL;DR

This work investigates neutrino emission from short GRB jets propagating inside cavities of AGN accretion disks, emphasizing how the ambient disk photon field alters proton cooling and pγ interactions in the jet's internal-dissipation region. A two-component, on-axis jet is modeled, incorporating Band prompt photons and external disk photon fields from SG03 and TQM05, along with gamma-gamma attenuation; neutrino spectra and detection prospects are computed across SMBH masses and GRB locations. The authors find that the disk photon field suppresses high-energy (PeV–EeV) neutrinos while enhancing TeV–PeV neutrinos, producing a two-bump spectrum with the narrow core dominating at high energies. They show that next-generation detectors (IceCube-Gen2, KM3NeT, Baikal-GVD) could detect neutrinos from such events out to ~100–200 Mpc, enabling constraints on jet parameters and offering a multi-messenger pathway to identify sGRBs in AGN disks and study their central engines.

Abstract

Short gamma-ray bursts (sGRBs) from the merger of binary compact objects (BCOs) could occur in the accretion disks of the active galactic nucleus (AGN). Before merging, the BCO will inevitably form a low-density cavity. The sGRB jet will interact with the AGN disk photons during its propagation through the cavity, leading to unique electromagnetic and neutrino signatures. In this work, we investigate the influence of the AGN disk photon field on neutrino emission within the internal dissipation regions of a two-component sGRB jet (a narrow core and a wide wing). We find that, due to the strong AGN disk photon field, the neutrino flux at high-energy part (e.g., PeV to EeV) will be suppressed, while the relatively lower-energy part (e.g., TeV to PeV) will be enhanced. Such a conclusion can enhance the constraints on GRB parameters (e.g., baryonic loading factor and bulk Lorentz factor) based on the future detection or non-detection of high-energy neutrinos from GRBs. Besides, the two-component jet can display two-bump structure at higher and lower energy in the neutrino spectrum. Therefore, the joint observations of electromagnetic and neutrinos emission can help us identify the sGRB jet and its structure in the AGN disk.

Figures (5)

• Figure 1: A schematic picture of the jet launched by the BCO merger embedded in the AGN disk. The cavity will be created by the powerful outflow during the BCO evolution. The area of the AGN disk and the cavity are presented by the light blue and the light gray shadows, respectively. The sGRB jet contains two components, a narrow core (dark green cone) and a wide wing (light green cone). The red rays represent the AGN disk photons, which can enter the jet and affect the cooling of protons and electrons. The yellow area is the internal dissipation region of the jet. The AGN disk photons (red solid rays) may undergo two distinct experiences: one is directly reacting with protons (dark filled circle), and the other is being scattered by electrons (grey filled circle) and then reacting with protons. The red dashed ray represents the scattered AGN disk photons, and the green ray is the photons from electron cooling processes, e.g., synchrotron emissions and synchrotron self-Compton. The blue rays are the neutrino emission from the p$\gamma$ reactions.
• Figure 2: AGN disk profile for the half-thickness $H$ (top row) and effective temperature $T_{\rm d, eff}$ (bottom row) with $M_\bullet=10^6M_\odot$ (left column), $10^7M_\odot$ (middle column) and $10^8 M_\odot$ (right column). The red and blue lines represent the SG03 and TQM05 models, respectively. The vertical lines from left to right in each panel are the distance from the central BH for $10R_{\rm s}$, $100R_{\rm s}$, and $1000R_{\rm s}$, where $R_{\rm s}=2GM_\bullet/c^2$ is the Schwarzschild radius.
• Figure 3: The seed photon number density in the comoving frame for the p$\gamma$ reaction. The green and magenta lines present the number density in the narrow and wide component jets, respectively. The dotted lines are the Band photons for narrow (green) and wide (magenta) components. Similarly, the thin solid lines are the AGN disk photons of SG03, the thick solid lines are the AGN disk photons of TQM05, the thin dashed lines are the EIC of SG03, and the thick dashed lines are the EIC of TQM05. Additionally, each panel title lists the SMBH mass $M_\bullet$ and sGRB location $R_{\rm GRB}$ used in the calculation.
• Figure 4: The observable fluence of muon neutrino at $d_{\rm L}=300$ Mpc with different seed photon sources. The green, magenta, and black lines are the contributions of the narrow, wide and total components, respectively. Similarly, the dotted lines are the only Band photons ingredient, the thin solid lines are the Band and SG03 AGN disk photons ingredients and the thick solid lines are the Band and TQM05 AGN disk photons ingredients.
• Figure 5: The probability of neutrino detection. The dotted lines only contain the influence of Band photons, and the solid lines consider both the Band and AGN disk photons (thin: SG03, thick: TQM05). The black and red lines represent the probability for IceCube and Gen2, respectively. In the up (middle, or bottom) row, we fix $M_\bullet=10^6M_\odot$, $R_{\rm GRB}=10R_{\rm s}$ ($M_\bullet=10^6M_\odot$, $R_{\rm GRB}=1000R_{\rm s}$, or $M_\bullet=10^8M_\odot$$R_{\rm GRB}=10R_{\rm s}$) and change $\delta$ in each panel.