Nuclear Ignition of White Dwarf Stars by Relativistic Encounters with Rotating Intermediate Mass Black Holes

TL;DR

This study uses general relativistic calculations to show how encounters between white dwarf stars and rotating intermediate mass black holes can trigger thermonuclear explosions similar to Type Ia supernovae, with black hole spin having a modest effect.

Contribution

It provides the first detailed analysis of nuclear ignition in white dwarfs caused by relativistic encounters with rotating black holes, highlighting the role of black hole spin and orbit alignment.

Findings

Black hole spin has a weak influence on nucleosynthesis outcomes.

Prograde trajectories lead to closer encounters and more iron group elements.

The resulting debris contains radioisotopes like Ni56, producing observable supernova-like light curves.

Abstract

We present results from general relativistic calculations of nuclear ignition in white dwarf stars triggered by near encounters with rotating intermediate mass black holes with different spin and alignment parameters. These encounters create thermonuclear environments characteristic of Type Ia supernovae capable of producing both calcium and iron group elements in arbitrary ratios, depending primarily on the proximity of the interaction which acts as a strong moderator of nucleosynthesis. We explore the effects of black hole spin and spin-orbital alignment on burn product synthesis to determine whether they might also be capable of moderating reactive flows. When normalized to equivalent impact penetration, accounting for frame dragging corrections, the influence of spin is weak, no more than 25% as measured by nuclear energy release and mass of burn products, even for near maximally rotating black holes. Stars on prograde trajectories approach closer to the black hole and produce significantly more unbound debris and iron group elements than is possible by encounters with nonrotating black holes or by retrograde orbits, at more than 50% mass conversion efficiency. The debris contains several radioisotopes, most notably Ni56, made in amounts that produce sub-luminous (but still observable) light curves compared to branch-normal SNe Ia.