Numerical Simulations of the Circularized Accretion Flow in Population III Star Tidal Disruption Events. II. Radiative Properties

Abstract

Tidal Disruption Events (TDEs) release enormous amounts of energy, offering a promising avenue for detecting Population III (Pop III) stars. However, the radiative properties of TDEs of Pop III stars have so far been studied only analytically, relying on many assumptions. Based on our radiative hydrodynamic simulations that follow the evolution of the accretion system for Pop III star TDEs where a $300\ M_{\odot}$ ($M_{\odot}$ is the solar mass) star is disrupted by a $10^{6}\ M_{\odot}$ black hole (BH), we compute the emission properties of the event in rest frame and find that the spectrum peaks in the optical/UV waveband. After accounting for redshift ($z \sim 10$) and extinction effects, we find the observed spectral peak shifts to the infrared, with fluxes exceeding $10^{2}\mathrm{nJy}$-making such events detectable with both the James Webb Space Telescope (JWST) and the Nancy Grace Roman Space Telescope (Roman). The dependence of the observed spectrum on viewing angle is suppressed due to dust extinction. Using our simulation results, we also calculate the radio emission generated by the interaction between the wind and the circumnuclear medium (CNM) and find that a Pop III star TDE can produce an unusually long-lasting, continuously increasing radio flare with a duration greater than $10^4$ days and thus has the potential to be detected in radio wavebands. These results may be helpful to the detection of Pop III stars.

Figures (21)

• Figure 1: Snapshots of gas density (colour scale) and fluid velocity streamlines (black arrows are used for the panels in the first row, and white arrows for the other panels.) for model M300-9 at 15 evolutionary stages: from $t = 0.5\,\mathrm{days}$ (top-left panel), to $t = 499.0\,\mathrm{days}$ (bottom-right panel). The electron scattering photosphere is indicated by the red contour and the funnel region is denoted as purple shade in corresponding panels. The first two panels in the top row concentrate the zoom-in region $0\le r\le500 R_{\rm s}$; the third panel in the same row covers $0\le r\le10000 R_{\rm s}$, and the remaining panels extend to $0\le r\le90000 R_{\rm s}$.
• Figure 2: Photoionization cross section per atom at different photon energy for the WHIM at a temperature of $10^6$ K and a metallicity of $Z = 0.5 Z_{\odot}$, calculated using the parameters and formalism of the xspec model ABSORI.
• Figure 3: The extinction curve for SMC-type calculated by the model proposed by 1992ApJ...395..130P. This extinction curve is normalized by $\xi(5500 \ \mathring{\mathrm{A}})=1$.
• Figure 4: Temporal evolution of the apparent specific luminosity for model M300-9, shown for 15 discrete snapshots from $t = 0.5$ to $499.0\,\mathrm{days}$. The coloured background bands indicate different spectral wavebands: radio (gray), far-infrared (FIR; red), near-infrared (NIR; orange), optical (yellow), near-ultraviolet (NUV; green), far-ultraviolet (FUV; blue), extreme ultraviolet (EUV; purple), and X-ray (pink). Spectra are shown for different viewing angles: $\theta = 1^\circ$ (solid orange line), $30^\circ$ (dotted purple line), $45^\circ$ (dash-dotted green line), $60^\circ$ (dashed blue line), and $90^\circ$ (solid red line).
• Figure 5: Temporal evolution of the flux density for model M300-9, displayed at 15 discrete snapshots from $t_{\rm obs} = 5.5$ to $5489.0\,\mathrm{days}$, where $t_{\rm obs}$ is the observer frame time. The calculation assumes a cosmological redshift of $z = 10$ and does not include extinction effects. The horizontal red and blue dashed lines indicate the detection limits of JWST and the Roman Space Telescope, respectively. The color bands (denoting spectral wavebands) and line styles (representing different viewing angles) follow the same convention as in Fig. \ref{['fig4']}.