Numerical Simulations of the Circularized Accretion Flow in Population III Star Tidal Disruption Events. I. The Accretion Flow and the Wind

TL;DR

This study investigates the circularized accretion flow and wind in Population III star tidal disruption events (TDEs) around a $M_{ m BH}=10^{6}M_ot$ black hole, using 2D radiative-hydrodynamic simulations to capture extreme, super-Eddington accretion. The authors employ the PLUTO code with flux-limited diffusion, a pseudo-Newtonian potential, and a viscous angular-momentum transport model, comparing two metallicities, $Z=10^{-9}Z_ot$ and $Z=10^{-5}Z_ot$. They find that a radiation-pressure–driven wind carries away a majority of the fallback, with only about $25$–$35\%$ accreted (approximately $0.25-0.35$ of the fallback for the two models), wind velocities reaching up to $\\sim0.9c$ and kinetic powers up to $\\sim10^{46}$–$10^{47}\\,\\text{erg s}^{-1}$, and a photosphere that starts vertically elongated and later becomes horizontally extended, effectively obscuring the inner regions in early phases. These winds can reprocess hard photons into infrared/optical wavelengths and potentially drive radio emission via wind–CNM interactions, highlighting observational signatures for Pop III TDEs and informing reprocessing models, while also underscoring limitations such as the neglect of magnetic fields and relativistic effects in the current framework.

Abstract

Tidal Disruption Events (TDEs) have recently been proposed as potential probes for Population III stars. However, the properties of the accretion flow and the wind from the Pop III star TDE system are not clear. By performing radiative hydrodynamic simulations, we study the 'circularized' accretion flow of the Pop III star TDE system. The masses of the black hole (BH) and the disrupted star are $10^6$ and $300$ solar masses, respectively. We focus on the properties of the wind. We find that the black hole accretion rate is highly super-Eddington. A strong wind is driven by radiation pressure. Due to the presence of a strong wind, only $25\%$--$35\%$ of the fallback debris is accreted by the BH. The remaining part is taken away by the wind. The kinetic power of the wind can be as high as $10^{46} {\rm \ erg \ s^{-1}}$. The properties of the wind obtained in this paper may be useful for understanding the radiation properties of Pop III star TDEs in the context of the wind 'reprocessing' model.

Figures (21)

• Figure 1: Accretion rate for model M300-9. Left panel: time evolution of the black hole accretion rate (blue line) and stellar debris fallback rate (red dotted line) in Eddington units. Right panel: time evolution of black hole accretion in the unit of the stellar debris fallback rate.
• Figure 2: Snapshots for gas density (colour scale) for model M300-9 with fluid velocity (streamlines). We illustrate the system state at $t = 10.0\,\mathrm{days}$ (top-first and top-second panels), $t = 60.0\,\mathrm{days}$ (top-third and top-fourth panels), $t = 150.0\,\mathrm{days}$ (bottom-first and bottom-second panels), and $t = 400.0\,\mathrm{days}$ (bottom-third and bottom-fourth panels). For each time snapshot, we present two panels to show the properties of a zoom-out large domain and a zoom-in smaller domain of the system. The red lines in the top-first, top-third, bottom-first, bottom-third and bottom-fourth panels are the electron scattering photosphere.
• Figure 3: Snapshots for the Bernoulli parameter (colour scale) with fluid velocity (streamlines) for model M300-9 at $t = 10.0\mathrm{\ days}$ (top-left panel), $t = 60.0\mathrm{\ days}$ (top-right panel), $t = 150.0\mathrm{\ days}$ (bottom-left panel) and $t = 400.0\mathrm{\ days}$ (bottom-right panel). The Bernoulli parameter is calculated in the code unit with $GM_{\rm BH} = R_{\rm s} = 1$. The white lines are the contour for $Be=0$. The black dashed lines in the two bottom figures depict the electron scattering photosphere.
• Figure 4: Radial profiles of Bernoulli parameter along the mid-plane at $t = \mathrm{60.0\ days}$ for model M300-9 . The blue solid line shows the Bernoulli parameter. The orange solid line, green solid line, red dashed line, purple dash-dotted line and black dotted line represent the rotation kinetic energy, the outflow kinetic energy, the gas enthalpy, the radiation energy enthalpy and the gravitational potential energy, respectively.
• Figure 5: Radial profile of radial velocity of the wind for model M300-9 at $t = 10.0\,\mathrm{\ days}$ (top-left panel),$t = 60.0\,\mathrm{\ days}$ (top-right panel), $t = 150.0\,\mathrm{\ days}$ (bottom-left panel) and $t = 400.0\,\mathrm{\ days}$ (bottom-right panel). In each panel we plot the velocity along six different viewing angles.