High-resolution hydrodynamic simulation of tidal detonation of a helium white dwarf by an intermediate mass black hole

TL;DR

This study uses extremely high-resolution simulations to demonstrate that tidal disruption of a helium white dwarf by an intermediate mass black hole can cause tidal detonation, producing elements like nickel-56 and silicon, potentially observable as luminous transients.

Contribution

The paper presents the first convergence-tested, high-resolution 3D SPH and 1D mesh simulations confirming tidal detonation in white dwarf disruptions, avoiding unphysical heating issues of prior studies.

Findings

Tidal detonation occurs during white dwarf disruption by an IMBH.

Detonation produces large amounts of $^{56}$Ni and Si group elements.

Results are converged across different simulation resolutions.

Abstract

We demonstrate tidal detonation during a tidal disruption event (TDE) of a helium (He) white dwarf (WD) with $0.45M_\odot$ by an intermediate mass black hole (IMBH) by extremely high-resolution simulations. Tanikawa et al. (2017) have showed tidal detonation in previous studies results from unphysical heating due to low-resolution simulations, and such unphysical heating occurs in 3-dimensional (3D) smoothed particle hydrodynamics (SPH) simulations even with $10$ million SPH particles. In order to avoid such unphysical heating, we perform 3D SPH simulations up to $300$ million SPH particles, and 1D mesh simulations using flow structure in the 3D SPH simulations for 1D initial conditions. The 1D mesh simulations have higher resolution than the 3D SPH simulations. We show tidal detonation occurs, and confirm this result is perfectly converged with different space resolution in both 3D SPH and 1D mesh simulations. We find detonation waves independently arises in leading parts of the WD, and yield large amounts of $^{56}$Ni. Although detonation waves are not generated in trailing parts of the WD, the trailing parts receive detonation waves generated in the leading parts, and leave large amounts of Si group elements. Eventually, this He WD TDE would synthesize $^{56}$Ni of $0.30M_\odot$ and Si group elements of $0.08M_\odot$, and could be observed as a luminous thermonuclear transient comparable to type Ia supernovae.