Accelerating Compact Object Mergers in Triple Systems with the Kozai
  Resonance: A Mechanism for "Prompt" Type Ia Supernovae, Gamma-Ray Bursts, and
  Other Exotica
  White dwarf-white dwarf (WD-WD) and neutron star-neutron star (NS-NS) mergers
may produce Type Ia supernovae and gamma-ray bursts (GRBs), respectively. A
general problem is how to produce binaries with semi-major axes small enough to
in significantly less than the Hubble time (t_H), and thus accommodate the
observation that these events closely follow episodes of star formation. I
explore the possibility that such systems are not binaries at all, but actually
coeval, or dynamical formed, triple systems. The tertiary induces Kozai
oscillations in the inner binary, driving it to high eccentricity, and reducing
its gravitational wave (GW) merger timescale. This effect significantly
increases the allowed range of binary period P such that the merger time is
t_merge < t_H. In principle, Chandrasekhar-mass binaries with P ~ 300 days can
merge in < t_H if they contain a prograde solar-mass tertiary at high enough
inclination. For retrograde tertiaries, the maximum P such that t_merge < t_H
is yet larger. In contrast, P < 0.3 days is required in the absence of a
tertiary. I discuss implications of these findings for the production of
transients formed via compact object binary mergers. Based on the statistics of
solar-type binaries, I argue that many such binaries should be in triple
systems affected by the Kozai resonance. If true, expectations for the mHz GW
signal from individual sources, the diffuse background, and the foreground for
GW experiments like LISA are modified. This work motivates future studies of
triples systems of A, B,and O stars, and new types of searches for WD-WD
binaries in triple systems.
