Simulations of Tidal Disruption of Supernova in Galaxy Nuclear Region: A Novel Model for Ambiguous Nuclear Transients

TL;DR

This paper addresses the origin of ambiguous nuclear transients in low-luminosity AGNs by proposing tidal disruption of a supernova (TDS) by a supermassive black hole as a viable mechanism. Using 3D hydrodynamic simulations with Athena++, the authors show SN ejecta captured by an SMBH can self-intersect and circularize into an accretion disk, producing TDE-like luminosities (\sim10^{45} erg s^{-1}) and slow evolution, even for SMBHs with $M_{\rm BH}$ well above the standard TDE limit. Key findings include a fiducial accretion rate of about $0.4\,M_\odot\ \,\mathrm{yr^{-1}}$ and a rise time of $\tau_{\rm rise}\sim316$ days, with circularization completing around $\tau_{\rm circ}\approx256$ days; different ejecta energies and launch radii yield plateau-like or power-law decay accretion histories. The work suggests TDSs can explain energetic, long-lived nuclear transients in LLAGNs and may link to ENTs and turn-on CLAGN phenomena, though radiation, magnetic fields, and GR effects need future treatment.

Abstract

An increasing number of ambiguous nuclear transients, including some extreme nuclear transients with very shallow light-curve declines and weak AGN activity in their host galaxies, have been reported. Stars form in or are captured by AGN disks will grow and migrate inward, potentially exploding as supernovae once the inner cold accretion disk disappears in low-luminosity AGNs. We propose that the tidal disruption of a supernova (TDS) by a supermassive black hole (SMBH) can produce nuclear transients that are more energetic and evolve more slowly than typical tidal disruption events (TDEs), without the black hole mass limit as in TDEs. In this scenario, the SMBH capture the supernova ejecta, which subsequently self-intersects and circularizes into an accretion disk. Based on hydrodynamical simulations, we find that the accretion rate of the TDS disk exhibits a slow decline that can last for months to decades. The peak accretion rate of a typical core-collapse SN scenario can exceed the Eddington limit for SMBHs with $M_{\rm BH} \lesssim 10^{7.5}\,M_\odot$, while it remains sub-Eddington for more massive SMBHs. This model provides a mechanism for triggering an energetic TDE-like flare with luminosity \(\gtrsim10^{45}\,\mathrm{erg\,s^{-1}}\) in weak AGNs even with SMBH mass much larger than $10^{8}\,M_\odot$ or triggering turn-on changing-look AGNs.

Figures (4)

• Figure 1: Schematic diagram of tidal disruption of a supernova (TDS). (a) Stars embedded in AGN disk accrete and grow during their inward migration. The massive disk stars will roughly stop accretion, quickly evolve and eventually explode as SN after the star migrate into inner low-density ADAF region. (b) After the SN explosion, part of the ejecta is captured by the central supermassive BH. The resulting bound streams undergo self-intersection and eventually circularize to form an accretion disk.
• Figure 2: Temporal evolution of the density distribution for the TDS in Model-0 at several typical snapshots. The time is measured since the SN explosion. The black lines indicate the photon trapping radius $R_{\rm trap}$.
• Figure 3: Temporal evolution of the accretion rate (top) and the photon trapping radius (bottom) in Model-0. In the top panel, colored solid lines denote the net mass flux at different radii, while the black solid line shows the weekly averaged accretion rate at $R = 6\,R_{\rm g}$. The vertical dashed line and dotted line mark the circularization timescale $\tau_{\rm cir}$ and rise timescale $\tau_{\rm rise}$ (time of peak accretion), respectively. The bottom panel shows the mid-plane photon trapping region equivalent radius (black solid line), with its maximum ($R_{\rm trap,mid-max}$) and minimum ($R_{\rm trap,mid-min}$) azimuthal boundary indicated by gray dash-dotted lines. We define the circularization timescale $\tau_{\rm cir}$ as the time after which the condition $|R_{\rm trap,mid-max}-R_{\rm trap,mid-min}|/R_{\rm trap,mid-max}<5\%$ is satisfied in the mid-plane (vertical gray dashed line).
• Figure 4: Same as Figure \ref{['fig:massdot_cc']} but for SN ejecta with $E_{\rm ej}=10^{52}$ erg, $R_{\rm ej}=100 R_{\rm g}$ (Model-1) and $R_{\rm ej}=300 R_{\rm g}$ (Model-2), respectively. The semi-transparent grey lines indicate power-law declines of the accretion rate.