White Dwarf Bounds on CHAMPs

TL;DR

This paper investigates how CHAMPs could induce supernova explosions in white dwarfs, providing new constraints on their abundance and suggesting possible links to unusual supernovae.

Contribution

It introduces novel mechanisms by which CHAMPs can trigger white dwarf explosions, significantly tightening abundance constraints for high-mass CHAMPs.

Findings

White dwarfs can constrain high-mass CHAMP abundance by many orders of magnitude.

CHAMP-induced supernova mechanisms include core collapse, fusion, and black hole formation.

Potential connection between CHAMPs and calcium-rich gap transients.

Abstract

White dwarfs (WD) effectively act as high-gain amplifiers for relatively small energy deposits within their volume via their supernova instability. In this paper, we consider the ways a galactic abundance of $\mathcal{O}(1)$-charged massive relics (i.e., CHAMPs) could trigger this instability, thereby destroying old WD. The dense central core structure formed inside the WD when heavy CHAMPs sink to its center can trigger a supernova via injection of energy during collapse phases, via direct density-enhanced (pycnonuclear) fusion processes of carbon nuclei dragged into the core by the CHAMPs, or via the formation of a black hole (BH) at the center of the WD. In the latter scenario, Hawking radiation from the BH can ignite the star if the BH forms with a sufficiently small mass; if the BH instead forms at large enough mass, heating of carbon nuclei that accrete onto the BH as it grows in size may be able to achieve the same outcome (with the conservative alternative being simply that the WD is devoured by the BH). The known existence of old WD that have not been destroyed by these mechanisms allows us to improve by many orders of magnitude on the existing CHAMP abundance constraints in the regime of large CHAMP mass, $m_X \sim 10^{11}$-$10^{18}\,$GeV. Additionally, in certain regions of parameter space, we speculate that this setup could provide a trigger mechanism for the calcium-rich gap transients: a class of anomalous, sub-luminous supernova events that occur far outside of a host galaxy.