Hyperaccretion-driven relativistic jets from massive collapsars in active galactic nucleus disks

TL;DR

This paper investigates gamma-ray bursts embedded in active galactic nucleus disks arising from massive collapsars. By coupling a self-consistent SG AGN disk model with progenitor density profiles across metallicities, it links envelope accretion to central-engine activity and jet breakout, using a Blandford-Znajek jet luminosity L_j = η \dot{M} c^2 with η = 6.2×10^−4. For jets that break out, it predicts prompt emission via E_{γ,iso} = (2/θ_j^2) ∫ ζ L_j dt and afterglows from external shocks in an ISM-like environment, evaluating detectability with Swift BAT and Einstein Probe; metallicity strongly affects breakout likelihood and observed brightness. The results imply that AGN disks can host observable, long-duration GRBs whose signatures depend on disk location, SMBH mass, and embedded stellar properties, offering a window into AGN disk structure and massive-star evolution in dense galactic environments.

Abstract

The observable characteristics of gamma-ray bursts (GRBs) embedded in the accretion disk of active galactic nuclei (AGNs) are mainly determined by the jet propagation within the disk. In the massive collapsar scenario, we consider that the mass and metallicity of progenitor stars can significantly affect the jet durations and luminosities, which in turn influence whether the jet can break out from AGN disks. For the cases with low metallicity, massive stars tend to keep their massive envelopes. Thus the hyperaccretion of these envelopes onto the newborn black holes (BHs) can prolong the activity duration of the central engine, thereby allowing the jets to potentially break out from the disks. For successful jets, we further study their prompt emission and afterglows for different supermassive BHs and locations and discuss the detectability of these signals by instruments such as \emph{Swift} and Einstein Probe. Future related observations will help constrain the structure, components, and evolutionary history of AGN disks and the massive stars embedded within them.

Figures (11)

• Figure 1: Density profiles of the progenitor stars investigated, with different masses and metallicities. The black, red, and blue curves correspond to progenitor metallicities of $Z/Z_{\odot}=0, ~0.01$, and $1$, respectively. The solid, dashed, and dotted lines represent the progenitor masses of $M_{\rm{pro}}/M_{\odot}=20, ~30$, and $40$, respectively.
• Figure 2: Time evolution of the mass accretion rate onto the newborn BH. The black, red, and blue curves correspond to the cases of progenitors with metallicities of $Z/Z_{\odot}=0$, $0.01$, and $1$, respectively. For each color, the dotted lines represent the jet propagation inside the star, the solid lines indicate the jet propagation inside the AGN disk, and the dashed lines indicate the phase after the jet breaks out from the AGN disk. The dashed lines give the information of the duration and energetics of AGN GRBs. The left, middle, and right panels correspond to progenitor masses of $M_{\rm{pro}}/M_{\odot}$ = 20, 30, and 40, respectively, with an SMBH mass of $10^{6} M_{\odot}$. In top panels and bottom panels, the radial locations from the SMBH are $10^{4} R_{g}$ and $10^{5} R_{g}$, respectively.
• Figure 3: Same as Figure \ref{['fig2']}, but for an SMBH mass of $10^{7} M_{\odot}$. The top and bottom panels correspond to radial locations of $10^{3} R_{g}$ and $10^{4} R_{g}$ from the SMBH, respectively.
• Figure 4: Same as Figure \ref{['fig2']}, but for an SMBH mass of $10^{8} M_{\odot}$. The radial location from the SMBH is $10^{3} R_{g}$.
• Figure 5: Light curves of the prompt emission of AGN GRBs with different progenitors. The flux is calculated at the Swift BAT energy range ($15-150$ keV). The black, red, and blue curves correspond to the cases of progenitors with metallicity of $Z/Z_{\odot}=0$, $0.01$, and $1$, respectively. The solid, dashed, and dotted lines represent the progenitor masses of $M_{\rm{pro}}/M_{\odot}$=20, 30, and 40, respectively. The gray dotted lines indicates the BAT sensitivities $f_{\rm sen} (\Delta t_{\rm obs})$ with the integration times of $\Delta t_{\rm obs}=10^{4}$ s. The SMBH mass is $10^{6} M_{\odot}$. In panels (a) and (b), the radial locations from the SMBH are $10^{4} R_{g}$ and $10^{5} R_{g}$, respectively.