White Dwarf Bounds on CHAMPs
  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.
