On the resonant detonation of sub-Chandrasekhar mass white dwarfs during binary inspiral

TL;DR

This paper explores how resonant tidal interactions in white dwarf binaries could trigger early detonations, potentially altering supernova rates and gravitational wave signals, with implications for understanding Type Ia supernovae and binary evolution.

Contribution

It introduces the concept that resonant mode excitation in tidally locked white dwarf binaries can lead to premature detonations, a mechanism not previously emphasized in supernova models.

Findings

Resonant tidal forcing can raise core temperatures above fusion thresholds.

Mode energy thermalization may cause rapid Helium burning and core detonation.

Energy transfer during resonance can shorten binary merger timescales.

Abstract

White dwarfs (WDs) are believed to detonate via explosive Carbon-fusion in a Type Ia Supernova when their temperature and/or density reach the point where Carbon is ignited in a runaway reaction. Observations of the Type Ia supernova (SN) rate imply all WD binaries that merge through the emission of gravitational radiation within a Hubble time should result in SNe, regardless of total mass. Here we investigate the conditions under which a single WD in a binary system might extract energy from its orbit, depositing enough energy into a resonant mode such that it detonates before merger. We show that, ignoring non-linear effects, in a WD binary in tidal lock at small binary separations, the sustained tidal forcing of a low-order quadrupolar g-mode or a harmonic of a low-order quadrupolar p-mode could in principle drive the average temperature of Carbon nuclei in the mode over the runaway fusion threshold. If growing mode energy is thermalized at a core/atmosphere boundary, rapid Helium burning and inward-travelling p-waves may result in core detonation. Thermalization at a boundary in the core can also result in detonation. If energy can be efficiently transferred from the orbit to modes as the WD binary passes through resonances, the WD merger timescale will be shortened by Myr-Gyr compared to expected timescales from GW-emission alone and GW detectors will observe deviations from predicted chirp profiles in resolved WD binaries. Future work in this area should focus on whether tidal locking in WD binaries is naturally driven towards low-order mode frequencies.